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1
Ghazi, Haneen H., and Aseel M. Aljeboree. "Synthetic Water-Gel Crystals (Orbeez Balls) as Environmentally Friendly Adsorbent for Removal of Toxic Brilliant Green Dye From Aqueous Solutions." Asian Journal of Water, Environment and Pollution 21, no. 3 (2024): 53–60. http://dx.doi.org/10.3233/ajw240034.
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Water pollution caused by dyes is a major threat to marine organisms. Hydrogels (decorative balls), called water-gel crystals, are widely used to treat wastewater pollution caused from toxic dyes. This study aims to remove Brilliant Green (BG), a toxic harmful pigment that can cause widespread biota and environmental damage, from the aqueous solution. Water-Gel Crystals efficiently eliminate BG in a short time frame. Furthermore, several variables, such as counting equilibrium time, pH solution, the concentration of BG dye and adsorbent dosage were investigated. The results of this study exhibited that the adsorption equilibrium increased as BG dye concentration increased at pH = 7 after an equilibrium time of 2h, with 0.1 g of water-gel crystals having the top adsorption efficiency at 95.567 mg/g. This water-gel crystals adsorbent is regarded as an effective candidate that can be utilised for water treatment because the re-usability method of produced beads can successfully complete four cycles, and the adsorbent maintained its ability to remove BG dye. The water-gel crystals are therefore excellent candidates to be used as potent BG dye adsorbents from aqueous solutions. The water-gel crystals regeneration and re-usability investigation for the removal of BG dye was completed in at least four cycles successfully. This indicates that the Water-Gel Crystals produced have a high adsorption value. The (ΔG) was negative for the adsorption processes, indicating that the process was spontaneous. In addition, (ΔH) was determined for the adsorption method utilising water-gel crystals at 5.146 KJ/mol. ΔH Positive indicates that the method is endothermic in the range of 15-35 °C, using water-gel crystals.
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Mulyono, Shodiq Syamsul, Abiyyu Ristio Cahyo Anggoro, and Suyatno. "Development of Digital Media with CapCut, Canva, and Remove-BG to Improve Students' Digital Competence in Innovative Learning Course for BIPA." International Journal of Social Science and Human Research 08, no. 03 (2025): 1884–93. https://doi.org/10.5281/zenodo.15111238.
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This study aims to describe the process of developing learning media based on CapCut, Canva, and Remove-BG applications, the quality of learning media produced, and the effectiveness of learning media in supporting learning improvement. This research uses the Research and Development (R&D) method with the 4-D model (Define, Design, Develop, Disseminate). The validation process was carried out by material and media experts, followed by a trial on 10 students. Data collection techniques in this study include interviews, observations, validation questionnaires, pretests, and posttests. Data analysis techniques in this study used quantitative and qualitative approaches. The learning media developed obtained an average feasibility score of 85.34% (Very Feasible) based on expert validation. The effectiveness of the learning media reached 86% (Very Good), which was indicated by an increase in student learning outcomes. In addition, all students participating in the trial produced 10 works recognized with Intellectual Property Rights (HAKI), reflecting success in developing creativity and technological skills. This research shows that CapCut, Canva, and Remove-BG application-based learning media can improve the quality of learning and encourage students to produce innovative works that are relevant to the needs of the digital era.
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Gul, Salma, Azra Gul, Hajera Gul, et al. "Removal of Brilliant Green Dye from Water Using Ficus benghalensis Tree Leaves as an Efficient Biosorbent." Materials 16, no. 2 (2023): 521. http://dx.doi.org/10.3390/ma16020521.
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The presence of dyes in water stream is a major environmental problem that affects aquatic and human life negatively. Therefore, it is essential to remove dye from wastewater before its discharge into the water bodies. In this study, Banyan (Ficus benghalensis, F. benghalensis) tree leaves, a low-cost biosorbent, were used to remove brilliant green (BG), a cationic dye, from an aqueous solution. Batch model experiments were carried out by varying operational parameters, such as initial concentration of dye solution, contact time, adsorbent dose, and pH of the solution, to obtain optimum conditions for removing BG dye. Under optimum conditions, maximum percent removal of 97.3% and adsorption capacity (Qe) value of 19.5 mg/g were achieved (at pH 8, adsorbent dose 0.05 g, dye concentration 50 ppm, and 60 min contact time). The Langmuir and Freundlich adsorption isotherms were applied to the experimental data. The linear fit value, R2 of Freundlich adsorption isotherm, was 0.93, indicating its best fit to our experimental data. A kinetic study was also carried out by implementing the pseudo-first-order and pseudo-second-order kinetic models. The adsorption of BG on the selected biosorbent follows pseudo-second-order kinetics (R2 = 0.99), indicating that transfer of internal and external mass co-occurs. This study surfaces the excellent adsorption capacity of Banyan tree leaves to remove cationic BG dye from aqueous solutions, including tap water, river water, and filtered river water. Therefore, the selected biosorbent is a cost-effective and easily accessible approach for removing toxic dyes from industrial effluents and wastewater.
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Adzali, Nur Maizatul Shima, Nur Farahin Dahlan, Banjuraizah Johar, and Nor Akmah Baharom. "The Microstructural and Bioactivity Behavior of Magnesium Alloy Filled with Bioglass For Biomedical Application." Journal of Physics: Conference Series 2169, no. 1 (2022): 012011. http://dx.doi.org/10.1088/1742-6596/2169/1/012011.
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Abstract Magnesium alloy have known as degradable implant material due to biodegradable properties. However, by developed Mg alloy matrix composites containing a bioceramic will produced more biodegradable and does not need second surgical to remove the implants in body. Powder metallurgy route was used to fabricate the AZ91/BG composite by mixing, compacting and sintering. Mg alloy (AZ91) was reinforced with 0, 3, 6, and 9 wt% of bioglass (BG) before compact and sintered at 400°C for 2 hours. The Vickers hardness, scanning electron microscope, and x-ray diffraction are used to investigate the effect of BG particles addition on the mechanical properties and microstructure of the composite AZ91/BG. Bioactivity behaviour was studied by immersion test of AZ91/BG composite into phosphate buffered saline (PBS) solution for 72 hours. The results showed that as the addition of BG increases from 3 to 9 wt%, the hardness of AZ91/BG decrease from 43.3HV to 27.9HV. The result also showed the formation of protective layers or apatite layer on the surface of AZ91/BG composite after immersed in PBS solution for 72 hours. Phase analysis by XRD shows the presence of peak Ca10(OH)2(PO4)6 as the BG increased from 3 to 9 wt%. As a conclusion, AZ91/3BG shows the optimum composite for biomedical application based on its properties and bioactivity behaviour.
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Abbas, Moussa. "Removal of brilliant green (BG) by activated carbon derived from medlar nucleus (ACMN) – Kinetic, isotherms and thermodynamic aspects of adsorption." Adsorption Science & Technology 38, no. 9-10 (2020): 464–82. http://dx.doi.org/10.1177/0263617420957829.
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Experimental investigations were undertaken to adsorb Brilliant Green (BG) a toxic dye from aqueous medium using activated carbon derived from the medlar nucleus (ACMN). The adsorption was used to remove BG using ACMN as bio-adsorbent to replace activated carbon still expensive. The prepared adsorbent was characterized by the BET surface area measurement, FTIR spectroscopy and X-ray diffraction. Various parameters such as the initial dye concentration (110–200 mg/L), adsorbent dose (1–6 mg/L), initial pH (2–9) and temperature (298–318 K) were studied to observe their effects on the BG adsorption. Batch studies were conducted in order to determine the optimal parameters required to reach the adsorption equilibrium. The maximum adsorption capacity of ACMN for the BG adsorption at 298 K was found to be 833.15 mg/g. The adsorption kinetic data were analyzed by using several kinetic models namely the pseudo-first-order, pseudo-second-order, Elovich equation, intraparticules diffusion model. It was established that the adsorption obeys the pseudo-second-order kinetic model. The evaluation of thermodynamics parameters such as the free energy ΔG° (−10.584 to −6.413 kJ/mol), enthalpy ΔH° (36.439 kJ/mol) and the change of entropy (0.1438 kJ/mol K) indicated a spontaneous and endothermic nature of the reaction with a chemisorption process. The present adsorbent may be considered as an alternative for the better performance of the BG removal from aqueous medium.
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Basharat, Sumaira, Rabia Rehman, and Liviu Mitu. "Adsorptive Separation of Brilliant Green Dye from Water by Tartaric Acid-Treated Holarrhena antidysenterica and Citrullus colocynthis Biowaste." Journal of Chemistry 2021 (March 18, 2021): 1–18. http://dx.doi.org/10.1155/2021/6636181.
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Holarrhena antidysenterica (Ha) and Citrullus colocynthis (Cc) biowaste from indigenous Pakistan resources was used to remove toxic brilliant green (BG) dye from aqueous solutions in a batch mode. Tartaric acid chemical modification gave promising results than the nonmodified forms of biowaste. Surface characterization was carried out by FT-IR and SEM. The optimum conditions for (BG) dye elimination by Ha-tartaric acid modified (Ha-Ta) were 1.8 g, 45 minutes, 4.0 pH; 40°C, and 100 rpm and with Cc-tartaric acid modified (Cc-Ta) were 1.6 g, 45 minutes, 6.0 pH; 40°C, and 150 rpm dye solution shaking rate, which gave optimum results. Equilibrium data of raw and chemically modified biowaste followed the Langmuir model indicating monolayer chemisorption. Qmax values were found to be 55.24 mg/g, 112.35 mg/g, 50.50 mg/g, and 79.36 mg/g for Ha, Ha-Ta, Cc, and Cc-Ta. Kinetics followed the pseudo-second-order kinetic model. Dye removal involved surface and intraparticle mode of diffusion. Thermodynamic studies proved the process to be spontaneous and exothermic one. The adsorbents can be effectively utilized for the removal of toxic basic dyes, such as BG from wastewaters.
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Yu, Ze, Wenxuan Wang, He Gao, and Daxin Liang. "Properties Analysis and Preparation of Biochar–Graphene Composites Under a One-Step Dip Coating Method in Water Treatment." Applied Sciences 10, no. 11 (2020): 3689. http://dx.doi.org/10.3390/app10113689.
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In order to improve the adsorption efficiency of biochar in water treatment, biochar–graphene (BG) composites were prepared by the one-step dip coating method and applied to remove phthalates from water. Firstly, the materials and equipment needed for the experiment are introduced. The steps of preparing graphene oxide (GO) by the improved Hummers method and BG composites by one-step dip coating are discussed. Then, the morphology characterization, adsorption performance measurement, and isothermal model of BG composites are introduced. Finally, the structure characterization, adsorption kinetics, and adsorption isotherms of BG composites are analyzed. The results show that the properties of biochar could be changed by one-step dip coating, and the biochar could form composites with graphene. Compared with biochar, biochar–graphene composites have greater surface area and porosity. When the pyrolysis temperature was 600 °C, the specific surface area of biochar was 8.4 m2g−1, and the specific surface area of the biochar–graphene composite was 221.3 m2g−1. When the temperature was 300 °C, the specific surface area of biochar was 11.01 m2g−1, and the specific surface area of biochar–graphene composite was 251.82 m2g−1. The formation of graphene on the surface of biochar can increase the stability of the composite and acts as a very high potential active site. The porous structure and surface properties of biochar–graphene composites regulate the adsorption rate of pollutant molecules, thereby improving the adsorption performance. When the adsorption equilibrium was reached, the adsorption effect of phthalate esters on the biochar/graphene composite at the pyrolysis temperature of 600 °C was the best, and the adsorption capacity of Dimethyl phthalate (DMP)was 35.2 mg/g, that of Diethyl phthalate (DEP) was 26.4 mg/g, and that of Dibutyl phthalate (DBP) was 25.1 mg/g. The adsorption effect of DMP was the best. The results of the isotherm study indicate that the adsorption of phthalates by BG composites has great potential, which provides a good theoretical basis for the application of BG composites in environmental protection in China.
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Hicham, Zaitan, Zineb Bencheqroun, Imane El Mrabet, Mohammed Kachabi, Mostafa Nawdali, and Isabel Neves. "Removal of Basic Dyes from Aqueous Solutions by Adsorption onto Moroccan Clay (Fez City)." Mediterranean Journal of Chemistry 8, no. 3 (2019): 158–67. http://dx.doi.org/10.13171/mjc8319050803hz.
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The main objective of this study was to investigate the potential of natural clay obtained (from Fez city, Morocco) as an adsorbent for the removal of basic dyes (Astrazon Blue BG and Astrazon Yellow 7GLL) from liquid effluents. Natural clay was characterised using different physical-chemical methods, including nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), pH of the point of zero charge (pHPZC) and Boehm titration method. The clay was tested to remove various textile dyes from the aqueous solution at room temperature. Parameters such as initial dye concentration, solution pH, adsorbent dosages and contact time were performed in a batch system for controlling the operating conditions. Experimental results data indicated that the adsorption process is a fast and spontaneous reaction. A pseudo-second-order kinetic model provides the best fit to the experimental data of BG and YL adsorption onto the natural clay. Theadsorption isotherm data of both the dyes onto the natural clay were fitted well to the Langmuir model. A maximum monolayer adsorption capacity of 101 mg.g-1 for BG and 127 mg.g-1 for YL are obtained at 298.15 K.The results suggest that the natural clay could be used as an inexpensive adsorbent for the removal of the textile dyes from aqueous solutions.
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Mohwes, Mithal N., Khawla K. Jassm, and Ayad F. Alkaim. "Photocatalytic Degradation of Pollutants by Using Highly Surface Pd Doped on ZnO/CdS Nanocomposite: As a Model of Water Treatment." Asian Journal of Water, Environment and Pollution 20, no. 5 (2023): 79–86. http://dx.doi.org/10.3233/ajw230068.
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In the last few decades, more attention has been focussed on water treatment. In this study, an advanced catalyst Pd-doped ZnO-CdS nanocomposite was prepared using the photo deposition method. The structure and morphology of the obtained material were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), examining optical properties using UV-visible spectroscopy. Results of absorption show broader bands with moderated energy band gaps and improved photocatalytic properties. The photocatalytic applications show that the increase in amount of pd/ZnO-CdS nanocomposites up to 0.4 g/L increase the number of active site, but beyond 0.4 g/L there is little increase in % degradation. Therefore, the best catalyst at 0.4 g/L was used to remove BG dye. Photo catalytic activity increase was observed for Pd/ZnO-CdS nanocomposites which is about 86.6%. Photocatalytic degradation efficiency (PDE%) increases as the dye concentration decreases from 86.66% to 26.9 %. It was observed that the photo-catalytic degradation of BG dye was 86.6%–95.8% for the first four cycles. This indicates the good stability of ZnO-CdS/Pd nano-composites and could be potentially applied in the practical batch degradation.
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Chauhan, Harshvardhan, Mohd Saquib Tanweer, and Masood Alam. "Efficient Removal of Cationic and Anionic Dyes from Synthetic and Real Wastewater by Plant-mediated Nickel Nanoparticles." Oriental Journal Of Chemistry 39, no. 3 (2023): 703–11. http://dx.doi.org/10.13005/ojc/390321.
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In this study, Ni NPs were produced by biosynthesis method with the help of phytoconstituents present in the Sahadevi plant (Vernonia cinerea) ethanoic extract namely Sahadevi nickel nanoparticles (SNPs). SNPs were characterized using XRD, FT-IR, HR-FESEM. XRD study shows crystalline nature of SNPs. SNPs were employed as bioadsorbent for the elimination of dyes like cationic (BG) and anionic (CR) dyes from aqueous media. Adsorption capacity of SNPs was analyzed in batch modes at various pH, initial dye concentration, contact time, isotherm, and kinetics. The maximum adsorption capacity (qm) shown in Langmuir isotherm was obtained as 1666.7 mg g-1 in case of BG dye and 666.7 mg g-1 in CR dye, respectively. The higher value of coefficient of Langmuir isotherm recommended monolayer adsorption. Adsorption kinetics information was valuable suited to pseudo-second order kinetics with R2 > 0.99 for both dyes. SNPs proved to be an efficient sorbent for the elimination of dyes from aqueous media and can be employed to remove textile and tannery discharges. Overall, this study suggests that the use of SNPs is safe and secure, eco-friendly, cost-effective, which can be used as bioadsorbent removing colored organic effluents as dyes from water bodies.
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Hicham, Zaitan, Zineb Bencheqroun, Imane El Mrabet, Mohammed Kachabi, Mostafa Nawdali, and Isabel Neves. "Removal of Basic Dyes from Aqueous Solutions by Adsorption onto Moroccan Clay (Fez City)." Mediterranean Journal of Chemistry 8, no. 3 (2019): 158. http://dx.doi.org/10.13171/10.13171/mjc8319050803hz.
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<p class="Mabstract">The main objective of this study was to investigate the potential of natural clay obtained <span style="text-decoration: line-through;">(</span>from Fez city, Morocco<span style="text-decoration: line-through;">)</span> as an adsorbent for the removal of basic dyes (Astrazon Blue BG and Astrazon Yellow 7GLL) from liquid effluents. Natural clay was characterised using different physical-chemical methods, including nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), pH of the point of zero charge (pH<sub>PZC</sub>) and Boehm titration method. The clay was tested to remove various textile dyes from the aqueous solution at room temperature. Parameters such as initial dye concentration, solution pH, adsorbent dosages and contact time were performed in a batch system for controlling the operating conditions. Experimental results <span style="text-decoration: line-through;">data</span> indicated that the adsorption process is a fast and spontaneous reaction. A pseudo-second-order kinetic model provides the best fit to the experimental data of BG and YL adsorption onto the natural clay. Theadsorption isotherm data of both the dyes onto the natural clay were fitted well to the Langmuir model. A maximum monolayer adsorption capacity of 101 mg.g<sup>-1</sup> for BG and 127 mg.g<sup>-1</sup> for YL are obtained at 298.15 K.</p><p class="Mabstract">The results suggest that the natural clay could be used as an inexpensive adsorbent for the removal of the textile dyes from aqueous solutions.</p>
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Haimberger, Leopold, Christina Tavolato, and Stefan Sperka. "Toward Elimination of the Warm Bias in Historic Radiosonde Temperature Records—Some New Results from a Comprehensive Intercomparison of Upper-Air Data." Journal of Climate 21, no. 18 (2008): 4587–606. http://dx.doi.org/10.1175/2008jcli1929.1.
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Abstract The apparent cooling trend in observed global mean temperature series from radiosonde records relative to Microwave Sounding Unit (MSU) radiances has been a long-standing problem in upper-air climatology. It is very likely caused by a warm bias of radiosonde temperatures in the 1980s, which has been reduced over time with better instrumentation and correction software. The warm bias in the MSU-equivalent lower stratospheric (LS) layer is estimated as 0.6 ± 0.3 K in the global mean and as 1.0 ± 0.3 K in the tropical (20°S–20°N) mean. These estimates are based on comparisons of unadjusted radiosonde data, not only with MSU data but also with background forecast (BG) temperature time series from the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and with two new homogenized radiosonde datasets. One of the radiosonde datasets [Radiosonde Observation Correction using Reanalyses (RAOBCORE) version 1.4] employs the BG as reference for homogenization, which is not strictly independent of MSU data. The second radiosonde dataset uses the dates of the breakpoints detected by RAOBCORE as metadata for homogenization. However, it relies only on homogeneous segments of neighboring radiosonde data for break-size estimation. Therefore, adjustments are independent of satellite data. Both of the new adjusted radiosonde time series are in better agreement with satellite data than comparable published radiosonde datasets, not only for zonal means but also at most single stations. A robust warming maximum of 0.2–0.3K (10 yr)−1 for the 1979–2006 period in the tropical upper troposphere could be found in both homogenized radiosonde datasets. The maximum is consistent with mean temperatures of a thick layer in the upper troposphere and upper stratosphere (TS), derived from M3U3 radiances. Inferred from these results is that it is possible to detect and remove most of the mean warm bias from the radiosonde records, and thus most of the trend discrepancy compared to MSU LS and TS temperature products. The comprehensive intercomparison also suggests that the BG is temporally quite homogeneous after 1986. Only in the early 1980s could some inhomogeneities in the BG be detected and quantified.
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Larabi, Oussama, Afaf Amara-Rekkab, Mohamed Amine Didi, Amel Didi, and Souad Feddane. "Experimental Studies to Optimize Process Parameters for the Removal of Cationic and Anionic Dyes by Natural Cypress Leaves." Journal of the Mexican Chemical Society 68, no. 3 (2024): 469–93. http://dx.doi.org/10.29356/jmcs.v68i3.2037.
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Abstract. In this study, cypress leaves were used for the preparation of a biosorbent to remove brilliant green (BG) and black lanasyn (LB) from aqueous solutions. The influence of several experimental factors, such as time of contact, pH, initial concentration, ionic strength, temperature, stirring speed, and particle size, on the adsorption of these dyes was studied. Contact time s'effect has showed that balance was reached at 30 min with adsorption capacities 9.24 and 4.08 mg/g and elimination rates of 95.97 % and 34 % for BG and LB, respectively. Moreover, the study has shown that the adsorption of the two dyes can be described by pseudo-second-order kinetics. The adsorption isotherms demonstrated that the Freundlich model was satisfactory compared with the Langmuir model for describing the process of adsorption of the two dyes on the cypress. The results showed that the adsorption process is spontaneous, feasible, and endothermic for BG and non-spontaneous and exothermic for LB. Multi-docking reflecting the biosorption of brilliant green and Lanasyn black on the adsorbant surface is proposed. On the fundamental plane, the fractional orthogonal Taguchi plane L16 (45) was used to optimize the conditions for brilliant green adsorption on the cypress. In conclusion, the results showed that cypress leaves could be advantageously used as a low-cost biosorbent for the removal of brilliant green and lanasyn black in wastewater treatment. Resumen. En este estudio se usaron hojas de ciprés para preparar un biosorbente que remueve los colorantes verde brillante (BG) y lanasyn negro (LB) de soluciones acuosas. En la adsorción de estos colorantes se estudió la influencia de varios factores experimentales como tiempo de contacto, pH, concentración inicial, fuerza iónica, temperatura, velocidad de agitación y tamaño de partícula. El efecto del tiempo de contacto mostró que el balance se alcanzó a los 30 min con capacidades de adsorción de 9.24 y 4.08 mg/g y velocidades de eliminación de 95.97 % y 34 % para BG y LB, respectivamente. El estudio mostró que la adsorción de los dos colorantes se puede describir por una cinética de pseudo segundo orden. Para describir el proceso de adsorción de los dos colorantes en las hojas de ciprés, las isotermas de adsorción demostraron que el modelo de Freundlich es satisfactorio comparado con el modelo de Langmuir. Los resultados muestran que el proceso de adsorción es espontáneo, factible y endotérmico para BG, y no espontáneo y exotérmico para LB. Se propone un acoplamiento múltiple reflejando la biosorción del verde brillante y el lanasyn negro sobre la superficie del adsorbente. En el aspecto fundamental, la fracción ortogonal del plano de Taguchi L16 (45) se utilizó para optimizar las condiciones de adsorción del verde brillante en las hojas de ciprés. En conclusión, los resultados muestran que las hojas de ciprés pueden utilizarse como biosorbentes de bajo costo para la remoción de verde brillante y lanasyn negro en el tratamiento de aguas residuales.
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Meetiyagoda, Thenuwara Arachchige Omila Kasun, and Takeshi Fujino. "Comparison of Different Anode Materials to Remove Microcystis aeruginosa Cells Using Electro-Coagulation–Flotation Process at Low Current Inputs." Water 12, no. 12 (2020): 3528. http://dx.doi.org/10.3390/w12123528.
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Cyanobacterial blooms are a threat to the drinking water supply owing to their potential toxicity. Microcystins which are the most widespread cyanotoxins, are mainly produced by Microcystis spp. In this study, we cultured Microcystis aeruginosa cells in BG-11 medium at 25 °C to investigate the efficiency of the electro-coagulation–flotation process to remove them. Different anode materials (Fe, Al, Cu, and Zn) along with a graphite cathode were compared separately in the 10–100 mA current range in a 0.025 M Na2SO4 electrolyte. Turbidity, optical density at 684 nm (OD684), OD730, Chl-a concentration, and DOC concentration were analyzed to clarify the mechanism by which M. aeruginosa cells are removed. The Al anode indicated the highest removal efficiencies in terms of turbidity (90%), OD684 and OD730 (98%), and Chl-a concentration (96%) within 30 min at 4.0 mA/cm2 current density and the lowest average electrode consumption of 0.120 ± 0.023 g/L. The energy consumption of the Al electrode was 0.80 Wh/L. From these results, we found that Al was the best among the anode materials evaluated to remove M. aeruginosa cells. However, further studies are required to optimize the Al anode in terms of pH, treatment time, electrode distance, and electrolyte concentration to enhance the removal of M. aeruginosa cells.
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Ukeje, Okanta, Sunday. "Effect of Information and Communication Technology on the Nigerian Economy: Evidence from the Banking Sector." American International Journal of Economics and Finance Research 1, no. 1 (2019): 1–20. http://dx.doi.org/10.46545/aijefr.v1i1.45.
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This paper investigated the impact of information and communication technology on the Nigerian economy, taking evidence from the banking sector. Ordinary least squares method of regression for the period 2004-2017 was employed. Generally, the paper found that there was positive relationship between bank related information and communication technology components used and economic growth, except the automated teller machine component, under a fixed effect modeling. However, using the Breusch Godfrey (BG) dynamic modeling to remove serial autocorrelation, the paper revealed that only the mobile banking payment component positively and significantly affected the gross domestic product. On the basis of the findings, the researcher recommended that the Central Bank of Nigeria, banks and stakeholders should collaborate to strengthen the information and communication infrastructures and security systems in the country to reduce frauds, make the environment user friendly and improve public confidence.
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Ahmed, Arfan, Sarah Aziz, Alaa Abd-alrazaq, Faisal Farooq, Mowafa Househ, and Javaid Sheikh. "The Effectiveness of Wearable Devices Using Artificial Intelligence for Blood Glucose Level Forecasting or Prediction: Systematic Review." Journal of Medical Internet Research 25 (March 14, 2023): e40259. http://dx.doi.org/10.2196/40259.
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Background In 2021 alone, diabetes mellitus, a metabolic disorder primarily characterized by abnormally high blood glucose (BG) levels, affected 537 million people globally, and over 6 million deaths were reported. The use of noninvasive technologies, such as wearable devices (WDs), to regulate and monitor BG in people with diabetes is a relatively new concept and yet in its infancy. Noninvasive WDs coupled with machine learning (ML) techniques have the potential to understand and conclude meaningful information from the gathered data and provide clinically meaningful advanced analytics for the purpose of forecasting or prediction. Objective The purpose of this study is to provide a systematic review complete with a quality assessment looking at diabetes effectiveness of using artificial intelligence (AI) in WDs for forecasting or predicting BG levels. Methods We searched 7 of the most popular bibliographic databases. Two reviewers performed study selection and data extraction independently before cross-checking the extracted data. A narrative approach was used to synthesize the data. Quality assessment was performed using an adapted version of the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Results From the initial 3872 studies, the features from 12 studies were reported after filtering according to our predefined inclusion criteria. The reference standard in all studies overall (n=11, 92%) was classified as low, as all ground truths were easily replicable. Since the data input to AI technology was highly standardized and there was no effect of flow or time frame on the final output, both factors were categorized in a low-risk group (n=11, 92%). It was observed that classical ML approaches were deployed by half of the studies, the most popular being ensemble-boosted trees (random forest). The most common evaluation metric used was Clarke grid error (n=7, 58%), followed by root mean square error (n=5, 42%). The wide usage of photoplethysmogram and near-infrared sensors was observed on wrist-worn devices. Conclusions This review has provided the most extensive work to date summarizing WDs that use ML for diabetic-related BG level forecasting or prediction. Although current studies are few, this study suggests that the general quality of the studies was considered high, as revealed by the QUADAS-2 assessment tool. Further validation is needed for commercially available devices, but we envisage that WDs in general have the potential to remove the need for invasive devices completely for glucose monitoring in the not-too-distant future. Trial Registration PROSPERO CRD42022303175; https://tinyurl.com/3n9jaayc
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Sinaga, Luhut Tumpal Parulian. "Experimental Analysis on Sinking Time of Littoral Submarine in Various Trim Angle." Applied Mechanics and Materials 874 (January 2018): 128–33. http://dx.doi.org/10.4028/www.scientific.net/amm.874.128.
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A submarine must conform to Archimedes’ Principle, which states that a body immersed in a fluid has an upward force on it (buoyancy) equal to the weight of the displaced fluid, (displacement). Submarines are ships capable of being submerged. The history of submarines and their operation have largely revolved around being able to alter the density of the vessel so that it may dive below the surface, maintain a depth, and return to the surface as needed. The way modern submarines accomplish this task is to bring in and remove water from tanks in the submarine called ballast tanks. Ballast tanks fit into two categories: those used for major adjustment of mass (main ballast tanks); and those used for minor adjustments (trim tanks). The effect of each tank is plotted and this is compared with the changes in mass and trimming moment possible during operations using a trim polygon to determine whether the ballast tanks are adequate. On the water surface, metacentric height (GM) is important, whereas below the surface it is the distance between the centre of buoyancy and the centre of gravity (BG) which governs the transverse stability of a submarine.
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Silva-Stenico, Maria Estela, Jucirlene Santos Azevedo, Renata Beatriz Cruz, and Marli Fátima Fiore. "Application of cyanobacteria in radioactive waste." Brazilian Journal of Development 10, no. 1 (2024): 1293–309. http://dx.doi.org/10.34117/bjdv10n1-084.
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The extremely toxic radioactive wastes whose radioactivity persists for thousands of years are accumulated through nuclear power plants, mining companies, industries, and research centers, among others. However, the lack of technology for the treatment and removal of radioactivity from radioactive waste becomes a bottleneck for research. Currently, there are temporary solutions, and the radioactive waste continues to increase. Given this scenario it is necessary to seek alternatives for the treatment of radioactive waste with efficiency and low cost, without polluting the environment, and that is not harmful to human health. One way to reduce this type of pollution is to use microorganisms, especially cyanobacteria, which comprise one of the largest, most ecologically diverse, successful, and important group of bacteria on Earth. These bacteria have a great ability to remove pollutants, such as heavy metals, textile dyes, pesticides, etc., but their role in the degradation of recalcitrant and radioactive compounds is still scarce. The present work aimed to investigate the potential of cyanobacteria isolated from different environments to remove radiolabeled molecules from radioactive waste (containing 14C radioisotopes). Seven cyanobacteria, Synechococcus sp. CENA136 (isolated from the Mangrove of Cardoso Island), Phormidium autumnale UTEX 1580 (collection of UTEX cultures - fish aquarium), Nostoc sp CENA420 (Antarctica), Limnothrix sp. CENA458 (isolated from the reservoir), Oscillatoria acuminata CENA525 (isolated from the Pantanal), Nodularia sp CENA215 (isolated from Caatinga), and Trichormus SP UFV-56 (isolated from the Federal University of Viçosa-MG) were used in the present study. Cyanobacteria were maintained in Z8, BG-11, and SWBG-11 liquid culture medium under constant fluorescent lighting of 40 µmol photons·m-2·s-1 and a controlled temperature of 23 ± 1°C. Radioactive waste containing several 14C organic molecules, solubilized in organic solvents was used. The inoculums were obtained from 50 mL of culture medium. The radioactive waste was added at concentrations of 0, 5, 10 and 15%. To investigate the removal of the radioactivity present in the waste, analysis was performed by Liquid Scintillation Counting (LSC) in the beginning and final cultivation and HPLC (coupled to a flow scintillation analyzer) in order to evaluate the profile of radioactive molecules present in the waste. Intracellularly accumulated radioactivity was also assessed by LSC after cell disruption. The ability to accumulate radioactive molecules intracellularly was observed in all cyanobacteria, but Nostoc sp CENA420 accumulated 43% and Trichormus sp UFV-56 accumulated 68%, both cultivated with 15% of radioactive waste. These results showed that the cyanobacteria Nostoc sp CENA420 and Trichormus sp UFV-56 consumed 87 and 86% of radioactive molecules, respectively, being of great potential for the removal of radiolabeled radioactive waste molecules. Research using cyanobacteria to remove radiolabeled molecules from radioactive waste is still at an early stage but is a promising alternative to biological treatment.
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Saama, Peter M., Osman V. Patel, Anilkumar Bettegowda, James J. Ireland, and George W. Smith. "Novel algorithm for transcriptome analysis." Physiological Genomics 28, no. 1 (2006): 62–66. http://dx.doi.org/10.1152/physiolgenomics.00108.2006.
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A growing body of evidence implicates the oocyte as a key regulator of ovarian folliculogenesis and early embryonic development. We have screened bovine cDNA microarrays (containing expressed sequence tags representing >15,000 unique genes) with Cy3- and Cy5-labeled cDNA derived from bovine oocyte samples collected at two different stages of meiotic maturation (germinal vesicle vs. metaphase II; n = 3 samples per group). Here, we present a novel data analysis approach that uses all available information from above experiments to obtain and index the transcriptome of bovine oocytes and changes in transcriptome composition in response to meiotic maturation. Signal intensities (Fg) for all housekeeping genes were omitted prior to analysis. A local threshold for gene expression was computed as background intensity (Bg) plus 2 times the standard deviation of background and foreground signals. Within each array, data were normalized by the LOWESS procedure. Subsequently, a two-stage mixed model was fitted to remove systematic variations. In the first stage, the response was the LOWESS normalized Fg with treatment as a fixed effect. In stage 2, the residuals from stage 1 were analyzed in a gene-specific model that included treatment group and spots nested within patch and array. A test for the difference between least squares means for the treatment effect was performed. A false discovery rate (FDR) adjustment on the p values for the difference was carried out. This novel algorithm was compared with approaches that ignore the FDR and the threshold described herein and stark differences obtained.
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SHAIK, Reehana, and Ibrahim SIDDIQUE. "NOVEL MULTI-MODAL OBSTRUCTION MODULE FOR DIABETES MELLITUS CLASSIFICATION USING EXPLAINABLE MACHINE LEARNING." Applied Computer Science 20, no. 4 (2024): 39–62. https://doi.org/10.35784/acs-2024-39.
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Diabetes Mellitus (DM) is a persistent metabolic disorder which is characterized by increased blood glucose level in the blood stream. Initially, DM occurs while the insulin secretion in the pancreas has a disability to secrete or to use hormone for the metabolic process. Moreover, there are different types of DM depending on the physiological process, and the types include Type1 DM, Type2 DM and Gestational DM. Electrocardiography (ECG) waves are used to detect the abnormal heartbeats and cannot directly detect DM, but the wave abnormality can indicate the possibility and presence of DM. Whereas the Photoplethysmography (PPG) signals are a non-invasive method used to detect changes in blood volume that can monitor BG changes. Furthermore, the detection and classification of DM using PPG and ECG can involve analyzing the functional performance of these modalities. By extracting the features like R wave (W1) and QRS complex (W2) in the ECG signals and Pulse Width (S1) and Pulse Amplitude Variation (S2) can detect DM and can be classified into DM and Non-DM. The authors propose a Novel architecture in the basis of Encoder Decoder structure named as Obstructive Encoder Decoder module. This module extracts the specific features and the proposed novel Obstructive Erasing Module remove the remaining artifacts and then the extracted features are fed into the Multi-Uni-Net for the fusion of the two modalities and the fused image is classified using EXplainable Machine Learning (EX-ML). From this classification the performance metrics like Accuracy, Precision, Recall, F1-Score and AUC can be determined.
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Kenyon, Jonathan, Emily Thomas, Karen Lingas, and Stanton L. Gerson. "Differential hMLH1 Gene Expression after Temozolomide Selection Linked to Microsatellite Instability in a Subset of Hematopoietic Stem/Progenitor Cells in Old Versus Young and Cancer Versus Normal Patient Samples." Blood 110, no. 11 (2007): 509. http://dx.doi.org/10.1182/blood.v110.11.509.509.
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Abstract The etiology of hematologic pathologies such as leukemia, myelodysplasia, anemia, bone marrow failure, altered immune function, and how they are associated with aging, remains unclear. Our hypothesis is that these diseases are caused or aggravated by a subset of hematopoietic stem/progenitor cells (HSC) lacking effective mismatch repair (MMR) and therefore exhibiting a hypermutator phenotype. Microsatellite instability (MSI) is a marker of MMR deficiency. We used cord blood, bone marrow, and bone core samples to isolate and then clonally expand HSC for MSI analysis. Five microsatellite loci previously used in the diagnosis of the MMR defective disease HNPCC (BAT 25, BAT 26, D2S123, D5S346, and D17S250) were analyzed for insertions and deletions. We have analyzed 38 patient samples between the ages of 0 and 86 years, including 8 cancer patients. These data show an age-dependent increase in the frequency of high grade microsatellite instability (MSI-H), i.e. those CFU with microsatellite instability at >20% of loci tested. Additionally, samples obtained from individuals older than 50 years were 6 times more likely to have a > 10% frequency of MSI-H CFU than samples obtained from younger individuals, suggesting an inflection point for the onset of hematopoietic diseases. In all instances this instability is seen only within a subset of human HSC clones. To further characterize the origin of this deficiency, a method to select for MMR deficient hematopoietic cells was developed that first selected for survival of MMR deficient HSC, and then allowed for the examination of expression status of key MMR pathway genes hMLH1 and hMSH2 and their protein products. First, CD34+ HSC were isolated from various aged patient samples. To avoid possible effects of other repair pathways, the cells were treated with O6-Benzylguanine (BG) to remove O6-methylguanine DNA-methyltransferase (MGMT) activity and prevent removal of O6-methylguanine lesions. Next, temozolomide (TMZ) at concentrations of 50–125 μM was used to induce O6-methylguanine (O6-mG) lesions that persist in the presence of BG. These O6-mG lesions mispair with cytosine and are recognized as DNA mismatches by the mismatch repair (MMR) pathway inducing apoptotic cell death. TMZ selected cells that fail to recognize the mispair due to a lack of MMR survive this selection. In these TMZ resistant clones, RT-PCR amplification of hMLH1 transcripts from total RNA isolated reveal a defect in hMLH1 but not hMSH2 expression. In the one AML sample obtained thus far HSC treated with 200 uM TMZ we have observed 0 to 30% of hMLH1 expression within TMZ resistant CFU was observed when compared to untreated controls. Together this data links MSI to MMR defects of a subpopulation of hematopoietic precursors in older individuals. This is the first examination of MMR gene expression in clones of HSC that has shown specific MMR functional deficiencies. Our study suggests that a MMR pathway deficiency in a subset of stem cells could contribute to age related hematopoietic disease processes including stem cell failure and malignant transformation.
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Melhaoui, R., Y. Miyah, S. Kodad, et al. "On the Suitability of Almond Shells for the Manufacture of a Natural Low-Cost Bioadsorbent to Remove Brilliant Green: Kinetics and Equilibrium Isotherms Study." Scientific World Journal 2021 (January 29, 2021): 1–13. http://dx.doi.org/10.1155/2021/6659902.
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Almond production generates a large number of coproducts, but the farmer’s interest mainly focuses on the nutritional and commercial aspects of the kernel for getting the best return from their harvests. Thus, almond coproducts such as almond shells that represent more than 70% of biomass remain underexplored. In this work, the suitability of almond shell powder (ASP) as a natural low-cost adsorbent was evaluated in the adsorption of brilliant green dye (BG), which is known as a chemical pollutant. Brunauer–Emmett–Teller (BET) method, for the determination of specific surface area, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) techniques were performed to characterize the ASP adsorbent. The batch adsorption kinetic study for the removal of BG dye was carried out by varying pH, temperature, initial concentration of the dye, bioadsorbent dose, and contact time. It was found that 98% of BG dye is removed under the following optimal experimental conditions: ASP bioadsorbent dose of 1 g/L at T = 25°C, pH = 6.8, and C0 = 1 g/L, which proves that ASP can be used as an excellent low-cost bioadsorbent for the removal of BG dye from wastewater. The experimental isotherm data were analyzed using Freundlich and Langmuir models. The results show the best correlation with single-layer adsorption, and the adsorption kinetics seems to follow a pseudo-second-order model.
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Gutierrez Becker, B., E. Giuffrida, M. Mangia, et al. "P069 Artificial intelligence (AI)-filtered Videos for Accelerated Scoring of Colonoscopy Videos in Ulcerative Colitis Clinical Trials." Journal of Crohn's and Colitis 15, Supplement_1 (2021): S173—S174. http://dx.doi.org/10.1093/ecco-jcc/jjab076.198.
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Abstract Background Endoscopic assessment is a critical procedure to assess the improvement of mucosa and response to therapy, and therefore a pivotal component of clinical trial endpoints for IBD. Central scoring of endoscopic videos is challenging and time consuming. We evaluated the feasibility of using an Artificial Intelligence (AI) algorithm to automatically produce filtered videos where the non-readable portions of the video are removed, with the aim of accelerating the scoring of endoscopic videos. Methods The AI algorithm was based on a Convolutional Neural Network trained to perform a binary classification task. This task consisted of assigning the frames in a colonoscopy video to one of two classes: “readable” or “unreadable.” The algorithm was trained using annotations performed by two data scientists (BG, FA). The criteria to consider a frame “readable” were: i) the colon walls were within the field of view; ii) contrast and sharpness of the frame were sufficient to visually inspect the mucosa, and iii) no presence of artifacts completely obstructing the visibility of the mucosa. The frames were extracted randomly from 351 colonoscopy videos of the etrolizumab EUCALYPTUS (NCT01336465) Phase II ulcerative colitis clinical trial. Evaluation of the performance of the AI algorithm was performed on colonoscopy videos obtained as part of the etrolizumab HICKORY (NCT02100696) and LAUREL (NCT02165215) Phase III ulcerative colitis clinical trials. Each video was filtered using the AI algorithm, resulting in a shorter video where the sections considered unreadable by the AI algorithm were removed. Each of three annotators (EG, MM and MD) was randomly assigned an equal number of AI-filtered videos and raw videos. The gastroenterologist was tasked to score temporal segments of the video according to the Mayo Clinic Endoscopic Subscore (MCES). Annotations were performed by means of an online annotation platform (Virgo Surgical Video Solutions, Inc). Results We measured the time it took the annotators to score raw and AI-filtered videos. We observed a statistically significant reduction (Mann Whitney U test p-value=0.039) in the median time spent by the annotators scoring raw videos (10.59∓ 0.94 minutes) with respect to the time spent scoring AI-filtered videos (9.51 ∓ 0.92 minutes), with a substantial intra-rater agreement when evaluating highlight and raw videos (Cohen’s kappa 0.92 and 0.55 for experienced and junior gastroenterologists respectively). Conclusion Our analysis shows that AI can be used reliably as an assisting tool to automatically remove non-readable time segments from full colonoscopy videos. The use of our proposed algorithm can lead to reduced annotation times in the task of centrally reading colonoscopy videos.
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Abdellaoui, Karima, Ivana Pavlovic, and Cristobalina Barriga. "Nanohybrid Layered Double Hydroxides Used to Remove Several Dyes from Water." ChemEngineering 3, no. 2 (2019): 41. http://dx.doi.org/10.3390/chemengineering3020041.
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For the preparation and characterization of several layer double hydroxides (LDH) with inorganic interlayer anions (carbonate and nitrate) and nanohybrids, two organo-LDHs were studied in detail. The dodecylbenzene sulfonate (DBS) was used as an organic interlayer anion to modify the hydrophilic nature of the interlayer. The aim of the modification of the layered double hydroxides (LDH) was to change the hydrophilic character of the interlayer to hydrophobic with the purpose of improving its ability to adsorb several (anionic and cationic) dyes from water. These compounds have been used as adsorbents of amaranth (Am), diamine green B (DGB) and brilliant green (BG) dyes. Adsorption tests were conducted using variable pH values, contact times and initial dye concentrations (adsorption isotherms) to identify the optimum conditions for the intended purpose. Adsorbents and adsorption products were characterized by several physicochemical techniques. The results of the adsorption tests showed that the organo-LDH nanohybrids could be efficient adsorbents in the removal of studied dyes from water. Thus, it can be concluded that nanohybrids studied in this work might act as suitable supports in the design of adsorbents for the removal of a wide spectrum of dyes with the aim of reducing the adverse effects on water resources.
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Hajri, Amira K., Ifat Alsharif, Marzough A. Albalawi, Shareefa A. Alshareef, Raghad K. Albalawi, and Bassem Jamoussi. "Utilizing Mixed Cultures of Microalgae to Up-Cycle and Remove Nutrients from Dairy Wastewater." Biology 13, no. 8 (2024): 591. http://dx.doi.org/10.3390/biology13080591.
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This study explores the novel use of mixed cultures of microalgae—Spirulina platensis, Micractinium, and Chlorella—for nutrient removal from dairy wastewater (DW). Microalgae were isolated from a local wastewater treatment plant and cultivated under various light conditions. The results showed significant biomass production, with mixed cultures achieving the highest biomass (2.51 g/L), followed by Spirulina (1.98 g/L) and Chlorella (1.92 g/L). Supplementing DW (75%) with BG medium (25%) significantly enhanced biomass and pH levels, improving pathogenic bacteria removal. Spirulina and mixed cultures exhibited high nitrogen removal efficiencies of 92.56% and 93.34%, respectively, while Chlorella achieved 86.85% nitrogen and 83.45% phosphorus removal. Although growth rates were lower under phosphorus-limited conditions, the microalgae adapted well to real DW, which is essential for effective algal harvesting. Phosphorus removal efficiencies ranged from 69.56% to 86.67%, with mixed cultures achieving the highest removal. Microbial and coliform removal efficiencies reached 97.81%, with elevated pH levels contributing to significant reductions in fecal E. coli and coliform levels. These findings suggest that integrating microalgae cultivation into DW treatment systems can significantly enhance nutrient and pathogen removal, providing a sustainable solution for wastewater management.
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Alexandrov, Georgii A., Victor A. Brovkin, Thomas Kleinen, and Zicheng Yu. "The capacity of northern peatlands for long-term carbon sequestration." Biogeosciences 17, no. 1 (2020): 47–54. http://dx.doi.org/10.5194/bg-17-47-2020.
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Abstract. Northern peatlands have been a persistent natural carbon sink since the Last Glacial Maximum. The continued growth and expansion of these carbon-rich ecosystems could offset a large portion of anthropogenic carbon emissions before the end of the present interglacial period. Here we used an impeded drainage model and gridded data on the depth to bedrock and the fraction of histosol-type soils to evaluate the limits to the growth of northern peatland carbon stocks. Our results show that the potential carbon stock in northern peatlands could reach a total of 875±125 Pg C before the end of the present interglacial, which could, as a result, remove 330±200 Pg C of carbon from the atmosphere. We argue that northern peatlands, together with the oceans, will potentially play an important role in reducing the atmospheric carbon dioxide concentration over the next 5000 years.
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Jalal, Aveen F., and Nabil A. Fakhre. "Removal of dyes (BG, MG, and SA) from aqueous solution using a novel adsorbent macrocyclic compound." PLOS ONE 17, no. 10 (2022): e0275330. http://dx.doi.org/10.1371/journal.pone.0275330.
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The use of macrocyclic compounds to remove organic dyes is fascinating because they have a wide surface area range and can be used for different things. new (14E, 34E)-7-Hydroxy-7, 8, 22, 23, 24, 25, 26, 27-Octahydro-6H, 16H, 33H Tetrabenzo[f,k,u,z][1,5,13,20]Tetraoxacycloheptacosine-16,33-Dione (HOTTD) was obtained by a simple high-dilution method, and characterized by FTIR, 1H-NMR, FESEM, EDX, and XRD. It worked well in removing organic dyes from aqueous solutions. Contact time, pH, dosage, initial concentration and temperature were studied. The optimum conditions were achieved by using 20 mg/L dye concentration, 50 mg dose of adsorbent and pH 9.0 at room temperature. The adsorption process was remarkably fast and reached equilibrium within 10 min for both Brilliant Green and Malachite Green while 70 min for Safranin. The batch adsorption experiments followed a pseudo 2nd order and Langmuir model with maximum adsorption capacity 19.26 mg/g, 18.28 mg/g, and 14.35 mg/g for Brilliant Green, Malachite green and Safranin respectively. The process was endothermic and spontaneous in nature. Adsorbent regeneration test provides an excellent value 5 times.
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Xue, D., P. Boeckx та Z. Wang. "Nitrate sources and dynamics in a salinized river and estuary – a δ<sup>15</sup>N–NO<sub>3</sub><sup>−</sup> and δ<sup>18</sup>O–NO<sub>3</sub><sup>−</sup> isotope approach". Biogeosciences 11, № 20 (2014): 5957–67. http://dx.doi.org/10.5194/bg-11-5957-2014.
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Abstract. To trace NO3− sources and assess NO3− dynamics in salinized rivers and estuaries, three rivers (Haihe River: HH River, Chaobaixin River: CB River and Jiyun River: JY River) and two estuaries (HH Estuary and CJ Estuary) along the Bohai Bay (China) have been selected to determine dissolved inorganic nitrogen (DIN: NH4+, NO2− and NO3−. Upstream of the HH River, NO3− was removed 30.9 ± 22.1% by denitrification, resulting from effects of the floodgate: limiting water exchange with downstream and prolonging water residence time to remove NO3−. Downstream of the HH River NO3− was removed 2.5 ± 13.3% by NO3− turnover processes. Conversely, NO3− was increased 36.6 ± 25.2% by external N source addition in the CB River and 34.6 ± 35.1% by in-stream nitrification in the JY River. The HH and CY Estuaries behaved mostly conservatively excluding the sewage input in the CJ Estuary. Hydrodynamics in estuaries has been changed by the ongoing reclamation projects, aggravating the loss of the attenuation function of NO3− in the estuary.
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van Helmond, Niels A. G. M., Elizabeth K. Robertson, Daniel J. Conley, et al. "Removal of phosphorus and nitrogen in sediments of the eutrophic Stockholm archipelago, Baltic Sea." Biogeosciences 17, no. 10 (2020): 2745–66. http://dx.doi.org/10.5194/bg-17-2745-2020.
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Abstract. Coastal systems can act as filters for anthropogenic nutrient input into marine environments. Here, we assess the processes controlling the removal of phosphorus (P) and nitrogen (N) for four sites in the eutrophic Stockholm archipelago. Bottom water concentrations of oxygen (O2) and P are inversely correlated. This is attributed to the seasonal release of P from iron-oxide-bound (Fe-oxide-bound) P in surface sediments and from degrading organic matter. The abundant presence of sulfide in the pore water and its high upward flux towards the sediment surface (∼4 to 8 mmol m−2 d−1), linked to prior deposition of organic-rich sediments in a low-O2 setting (“legacy of hypoxia”), hinder the formation of a larger Fe-oxide-bound P pool in winter. This is most pronounced at sites where water column mixing is naturally relatively low and where low bottom water O2 concentrations prevail in summer. Burial rates of P are high at all sites (0.03–0.3 mol m−2 yr−1), a combined result of high sedimentation rates (0.5 to 3.5 cm yr−1) and high sedimentary P at depth (∼30 to 50 µmol g−1). Sedimentary P is dominated by Fe-bound P and organic P at the sediment surface and by organic P, authigenic Ca-P and detrital P at depth. Apart from one site in the inner archipelago, where a vivianite-type Fe(II)-P mineral is likely present at depth, there is little evidence for sink switching of organic or Fe-oxide-bound P to authigenic P minerals. Denitrification is the major benthic nitrate-reducing process at all sites (0.09 to 1.7 mmol m−2 d−1) with rates decreasing seaward from the inner to outer archipelago. Our results explain how sediments in this eutrophic coastal system can remove P through burial at a relatively high rate, regardless of whether the bottom waters are oxic or (frequently) hypoxic. Our results suggest that benthic N processes undergo annual cycles of removal and recycling in response to hypoxic conditions. Further nutrient load reductions are expected to contribute to the recovery of the eutrophic Stockholm archipelago from hypoxia. Based on the dominant pathways of P and N removal identified in this study, it is expected that the sediments will continue to remove part of the P and N loads.
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Amann, Thorben, and Jens Hartmann. "Ideas and perspectives: Synergies from co-deployment of negative emission technologies." Biogeosciences 16, no. 15 (2019): 2949–60. http://dx.doi.org/10.5194/bg-16-2949-2019.
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Abstract. Numerous publications propose the deployment of negative emission technologies, which intend to actively remove CO2 from the atmosphere with the goal to reach the 1.5∘ target as discussed by the IPCC. The increasing number of scientific studies on the individual potential of different envisaged technologies and methods indicates that no single method has enough capacities to mitigate the issue by itself. It is thus expected that technology portfolios are deployed. As some of them utilize the same environmental compartment, co-deployment effects are expected. Those effects are particularly important to evaluate with respect to additional CO2 uptake. Considering soils as one of the main affected compartments, we see a plethora of processes which can positively benefit from each other, canceling out negative side effects or increasing overall CO2 sequestration potentials. To derive more reliable estimates of negative emission potentials and to evaluate common effects on global carbon pools, it is now necessary to intensively study interrelated effects of negative emission technology deployment while minimizing negative side effects.
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Fallico, C., S. Troisi, A. Molinari, and M. F. Rivera. "Characterization of broom fibers for PRB in the remediation of aquifers contaminated by heavy metals." Biogeosciences 7, no. 8 (2010): 2545–56. http://dx.doi.org/10.5194/bg-7-2545-2010.
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Abstract. The present level of pollution, increasingly involving ground waters, constitutes a serious risk to the environment and also to human health. Therefore the remediation of saturated and unsaturated soils to remove pollutant materials is more and more frequently required. In the present paper, the possibility of removing heavy metals by permeable reactive barrier (PRB) from the groundwater carried out specifically with broom fibers, is investigated. Once shown the economic benefits deriving from the use of this plant, a hydraulic characterization of the broom fiber mass was performed, determining the permeability and the porosity in correspondence to different levels of compactness of the fibers. Having verified the effectiveness of removal of some heavy metals by these fibers, the results of some experiments, carried out in the laboratory for this purpose, are shown. These experiments were carried out utilizing broom fibers obtained in different ways and, limitedly to the considered pollutants, showed the high capability of these fibers to reduce their concentrations. The best results were obtained for the broom fibers extracted by a particular chemical-physical process. Moreover, the behaviour of this fiber with time was investigated, determining the kinetic constant of degradation.
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Terhaar, Jens. "Composite model-based estimate of the ocean carbon sink from 1959 to 2022." Biogeosciences 22, no. 6 (2025): 1631–49. https://doi.org/10.5194/bg-22-1631-2025.
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Abstract. The ocean takes up around one-quarter of anthropogenically emitted carbon and is projected to remain the main carbon sink once global temperatures stabilize. Despite the importance of this natural carbon sink, estimates of its strength over the last decades remain uncertain, mainly due to too few and unevenly sampled observations and shortcomings in ocean models and their setups. Here, I present a composite model-based estimate of the annually averaged ocean carbon sink from 1959 to 2022 by combining the higher-frequency variability of the annually averaged estimates of the carbon sink from ocean models in hindcast mode and the long-term trends from fully coupled Earth system models. Ocean models in hindcast mode reproduce the observed climate variability, but their spin-up strategy likely leads to long-term trends that are too weak, whereas fully coupled Earth system models simulate their own internal climate variability but better represent long-term trends. By combining these two modelling approaches, I keep the strength of each approach and remove the respective weaknesses. This composite model-based estimate of the ocean carbon sink from 1959 to 2022 is 125±8 Pg C and is similar in magnitude to the best estimate of the Global Carbon Budget but 70 % less uncertain.
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Letscher, Robert T., and Tracy A. Villareal. "Evaluation of the seasonal formation of subsurface negative preformed nitrate anomalies in the subtropical North Pacific and North Atlantic." Biogeosciences 15, no. 21 (2018): 6461–80. http://dx.doi.org/10.5194/bg-15-6461-2018.
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Abstract. Summertime mixed-layer drawdown of dissolved inorganic carbon in the absence of measurable nutrients in the ocean's subtropical gyres and non-Redfieldian oxygen : nitrate relationships in the underlying subsurface waters are two biogeochemical phenomena that have thus far eluded complete description. Many processes are thought to contribute to one or both, including lateral nutrient transport, carbon overconsumption or non-Redfield C:N:P organic matter cycling, heterotrophic nutrient uptake, and the actions of vertically migrating phytoplankton. To obtain insight into the likely magnitude of potential contributing mechanisms that can remove nitrate from the nutricline while supporting dissolved inorganic carbon (DIC) drawdown tens of meters higher in the water column, we investigated the seasonal formation rates for negative preformed nitrate (preNO3) anomalies (oxygen consumption without stoichiometric nitrate release) in the subsurface and positive preformed nitrate anomalies (oxygen production without stoichiometric nitrate drawdown) in the euphotic zone at the subtropical ocean time series stations ALOHA (A Long-Term Oligotrophic Habitat Assessment) in the North Pacific and BATS (Bermuda Atlantic Time-series Study) in the North Atlantic. Non-Redfield -O2:N stoichiometry for dissolved organic matter (DOM) remineralization accounts for up to ∼15 mmol N m−2 yr−1 of negative preNO3 anomaly formation at both stations. We present a new formulation for calculating preNO3 (residual preNO3) that includes components resulting from non-Redfield DOM cycling. Residual negative preNO3 anomalies in excess of that which can be accounted for by non-Redfield DOM cycling are found to accumulate at a rate of ∼32–46 mmol N m−2 yr−1 at Station ALOHA and ∼46–87 mmol N m−2 yr−1 at the BATS station. These negative anomaly formation rates are in approximate balance with residual positive preNO3 anomaly formation rates from the euphotic zone located immediately above the nutricline in the water column. We evaluate three mechanisms to explain these anomalies, calculating that transparent exopolymer particle (TEP) cycling and heterotrophic nitrate uptake can contribute to the formation of both residual preNO3 anomalies. However, a significant fraction, estimated at ∼50 %–95 %, is unexplained by the sum of these processes. Vertically migrating phytoplankton possess the necessary distribution, nutrient acquisition strategy, and biogeochemical signature to simultaneously remove nitrate at depth and transport it above the nutricline. Reported transport rates by known migrators equal or exceed the residual preNO3 anomaly formation rates and potentially explain both the negative and positive residual preNO3 anomalies as well as the mixed-layer DIC drawdown at the stations ALOHA and BATS within the limits of scarce detailed abundance profiles. However, the three processes examined are not independent and mutually exclusive. The model Rhizosolenia mat system (and perhaps other migrators) produces TEPs, suggesting that migration could provide accelerated vertical transport of TEPs and provide labile carbon for heterotrophic nitrate uptake. These results based on geochemical distributions suggest that, in the absence of additional mechanisms and rates, phytoplankton vertical migrators, although rare and easily overlooked, play a larger role in subtropical ocean nutrient cycling and the biological pump than generally recognized.
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Wang, Feng, Dominique Arseneault, Étienne Boucher, et al. "Chemical destaining and the delta correction for blue intensity measurements of stained lake subfossil trees." Biogeosciences 17, no. 18 (2020): 4559–70. http://dx.doi.org/10.5194/bg-17-4559-2020.
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Abstract. The stain of wood samples from lake subfossil trees (LSTs) is challenging the wide application of the blue intensity (BI) technique for millennial dendroclimatic reconstructions. In this study, we used seven chemical destaining reagents to treat samples of subfossil black spruce (Picea mariana (Mill.) B.S.P.) trees from two lakes in the eastern Canadian boreal forest. We subsequently compared latewood BI (LBI) and delta BI (DBI) time series along with conventional maximum latewood density (MXD) measured from the stained and destained samples. Results showed that the stain of our samples is most likely caused by postsampling oxidation of dissolved ferrous iron in lake sediments that penetrated into wood. Three reagents (ascorbic acid, sodium ascorbate, and sodium dithionite all mixed with ethylenediaminetetraacetic acid) could remove >90 % of Fe. However, even for the best chemical protocol, a discrepancy of about +2 ∘C compared to MXD data remained in the LBI-based temperature reconstruction due to incomplete destaining. On the contrary, the simple mathematical delta correction, DBI, was unaffected by the Fe stain and showed very similar results compared to MXD data (r>0.82) from annual to centennial timescales over the past ∼360 years. This study underlines the difficulty of completely destaining lake subfossil samples while confirming the robustness of the DBI approach. DBI data measured from stained LSTs can be used to perform robust millennial temperature reconstructions.
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Liu, W., L. Yao, Z. Wang, Z. Xiong, and G. Liu. "Human land uses enhance sediment denitrification and N<sub>2</sub>O production in Yangtze lakes primarily by influencing lake water quality." Biogeosciences 12, no. 20 (2015): 6059–70. http://dx.doi.org/10.5194/bg-12-6059-2015.
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Abstract. Sediment denitrification in lakes alleviates the effects of eutrophication through the removal of nitrogen to the atmosphere as N2O and N2. However, N2O contributes notably to the greenhouse effect and global warming. Human land uses (e.g. agricultural and urban areas) strongly affect lake water quality and sediment characteristics, which, in turn, may regulate lake sediment denitrification and N2O production. In this study, we investigated sediment denitrification and N2O production and their relationships to within-lake variables and watershed land uses in 20 lakes from the Yangtze River basin in China. The results indicated that both lake water quality and sediment characteristics were significantly influenced by watershed land uses. N2O production rates increased with increasing background denitrification rates. Background denitrification and N2O production rates were positively related to water nitrogen concentrations but were not significantly correlated with sediment characteristics and plant community structure. A significant positive relationship was observed between background denitrification rate and percentage of human-dominated land uses (HDL) in watersheds. Structural equation modelling revealed that the indirect effects of HDL on sediment denitrification and N2O production in Yangtze lakes were mediated primarily through lake water quality. Our findings also suggest that although sediments in Yangtze lakes can remove large quantities of nitrogen through denitrification, they may also be an important source of N2O, especially in lakes with high nitrogen content.
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Jin, X., N. Gruber, H. Frenzel, S. C. Doney, and J. C. McWilliams. "The impact on atmospheric CO<sub>2</sub> of iron fertilization induced changes in the ocean's biological pump." Biogeosciences 5, no. 2 (2008): 385–406. http://dx.doi.org/10.5194/bg-5-385-2008.
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Abstract. Using numerical simulations, we quantify the impact of changes in the ocean's biological pump on the air-sea balance of CO2 by fertilizing a small surface patch in the high-nutrient, low-chlorophyll region of the eastern tropical Pacific with iron. Decade-long fertilization experiments are conducted in a basin-scale, eddy-permitting coupled physical/biogeochemical/ecological model. In contrast to previous studies, we find that most of the dissolved inorganic carbon (DIC) removed from the euphotic zone by the enhanced biological export is replaced by uptake of CO2 from the atmosphere. Atmospheric uptake efficiencies, the ratio of the perturbation in air-sea CO2 flux to the perturbation in export flux across 100 m, integrated over 10 years, are 0.75 to 0.93 in our patch size-scale experiments. The atmospheric uptake efficiency is insensitive to the duration of the experiment. The primary factor controlling the atmospheric uptake efficiency is the vertical distribution of the enhanced biological production and export. Iron fertilization at the surface tends to induce production anomalies primarily near the surface, leading to high efficiencies. In contrast, mechanisms that induce deep production anomalies (e.g. altered light availability) tend to have a low uptake efficiency, since most of the removed DIC is replaced by lateral and vertical transport and mixing. Despite high atmospheric uptake efficiencies, patch-scale iron fertilization of the ocean's biological pump tends to remove little CO2 from the atmosphere over the decadal timescale considered here.
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Amaro, T., S. Bianchelli, D. S. M. Billett, M. R. Cunha, A. Pusceddu, and R. Danovaro. "The trophic biology of the holothurian <i>Molpadia musculus</i>: implications for organic matter cycling and ecosystem functioning in a deep submarine canyon." Biogeosciences 7, no. 8 (2010): 2419–32. http://dx.doi.org/10.5194/bg-7-2419-2010.
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Abstract. Megafaunal organisms play a key role in ecosystem functioning in the deep-sea through bioturbation, bioirrigation and organic matter cycling. At 3500 m water depth in the Nazaré Canyon, NE Atlantic, very high abundances of the infaunal holothurian Molpadia musculus were observed. To quantify the role of M. musculus in sediment cycling, sediment samples and holothurians were collected using an ROV and in situ experiments were conducted with incubation chambers. The biochemical composition of the sediment (in terms of proteins, carbohydrates and lipids), the holothurians' gut contents and holothurians' faecal material were analysed. In the sediments, proteins were the dominant organic compound, followed by carbohydrates and lipids. In the holothurian's gut contents, protein concentrations were higher than the other compounds, decreasing significantly as the material passed through the digestive tract. Approximately 33±1% of the proteins were digested by the time sediment reached the mid gut, with a total digestion rate equal to 67±1%. Carbohydrates and lipids were ingested in smaller amounts and digested with lower efficiencies (23±11% and 50±11%, respectively). As a result, the biopolymeric C digestion rate was on average 62±3%. We estimated that the population of M. musculus could remove approximately 0.49±0.13 g biopolymeric C and 0.13±0.03 g N m−2 d−1 from the sediments. These results suggest that M. musculus plays a key role in the benthic tropho-dynamics and biogeochemical processes in the Nazaré Canyon.
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Dean, Joshua F., Jurgen R. van Hal, A. Johannes Dolman, Rien Aerts, and James T. Weedon. "Filtration artefacts in bacterial community composition can affect the outcome of dissolved organic matter biolability assays." Biogeosciences 15, no. 23 (2018): 7141–54. http://dx.doi.org/10.5194/bg-15-7141-2018.
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Abstract. Inland waters are large contributors to global carbon dioxide (CO2) emissions, in part due to the vulnerability of dissolved organic matter (DOM) to microbial decomposition and respiration to CO2 during transport through aquatic systems. To assess the degree of this vulnerability, aquatic DOM is often incubated in standardized biolability assays. These assays isolate the dissolved fraction of aquatic OM by size filtration prior to incubation. We test whether this size selection has an impact on the bacterial community composition and the consequent dynamics of DOM degradation using three different filtration strategies: 0.2 µm (filtered and inoculated), 0.7 µm (generally the most common DOM filter size) and 106 µm (unfiltered). We found that bacterial community composition, based on 16S rRNA amplicon sequencing, was significantly affected by the different filter sizes. At the same time, the filtration strategy also affected the DOM degradation dynamics, including the δ13C signature. However, the dynamics of these two responses were decoupled, suggesting that filtration primarily influences biolability assays through bacterial abundance and the presence of their associated predators. By the end of the 41-day incubations all treatments tended to converge on a common total DOM biolability level, with the 0.7 µm filtered incubations reaching this point the quickest. These results suggest that assays used to assess the total biolability of aquatic DOM should last long enough to remove filtration artefacts in the microbial population. Filtration strategy should also be taken into account when comparing results across biolability assays.
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Molari, Massimiliano, Felix Janssen, Tobias R. Vonnahme, Frank Wenzhöfer, and Antje Boetius. "The contribution of microbial communities in polymetallic nodules to the diversity of the deep-sea microbiome of the Peru Basin (4130–4198 m depth)." Biogeosciences 17, no. 12 (2020): 3203–22. http://dx.doi.org/10.5194/bg-17-3203-2020.
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Abstract. Industrial-scale mining of deep-sea polymetallic nodules will remove nodules in large areas of the sea floor. The regrowth of the nodules by metal precipitation is estimated to take millions of years. Thus, for future mining impact studies, it is crucial to understand the role of nodules in shaping microbial diversity and function in deep-sea environments. Here we investigated microbial-community composition based on 16S rRNA gene sequences retrieved from sediments and nodules of the Peru Basin (4130–4198 m water depth). The nodule field of the Peru Basin showed a typical deep-sea microbiome, with dominance of the classes Gammaproteobacteria, Alphaproteobacteria, Deltaproteobacteria, and Acidimicrobiia. Nodules and sediments host distinct bacterial and archaeal communities, with nodules showing lower diversity and a higher proportion of sequences related to potential metal-cycling Bacteria (i.e. Magnetospiraceae, Hyphomicrobiaceae), bacterial and archaeal nitrifiers (i.e. AqS1, unclassified Nitrosomonadaceae, Nitrosopumilus, Nitrospina, Nitrospira), and bacterial sequences found in the oceanic crust, nodules, hydrothermal deposits, and sessile fauna. Sediment and nodule communities overall shared a low proportion of operational taxonomic units (OTUs; 21 % for Bacteria and 19 % for Archaea). Our results show that nodules represent a specific ecological niche (i.e. hard substrate, high metal concentrations, and sessile fauna), with a potentially relevant role in organic-carbon degradation. Differences in nodule community composition (e.g. Mn-cycling bacteria, nitrifiers) between the Clarion–Clipperton Fracture Zone (CCZ) and the Peru Basin suggest that changes in environmental setting (e.g. sedimentation rates) also play a significant role in structuring the nodule microbiome.
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Ritson, Jonathan P., Richard E. Brazier, Nigel J. D. Graham, Chris Freeman, Michael R. Templeton, and Joanna M. Clark. "The effect of drought on dissolved organic carbon (DOC) release from peatland soil and vegetation sources." Biogeosciences 14, no. 11 (2017): 2891–902. http://dx.doi.org/10.5194/bg-14-2891-2017.
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Abstract. Drought conditions are expected to increase in frequency and severity as the climate changes, representing a threat to carbon sequestered in peat soils. Downstream water treatment works are also at risk of regulatory compliance failures and higher treatment costs due to the increase in riverine dissolved organic carbon (DOC) often observed after droughts. More frequent droughts may also shift dominant vegetation in peatlands from Sphagnum moss to more drought-tolerant species. This paper examines the impact of drought on the production and treatability of DOC from four vegetation litters (Calluna vulgaris, Juncus effusus, Molinia caerulea and Sphagnum spp.) and a peat soil. We found that mild droughts caused a 39.6 % increase in DOC production from peat and that peat DOC that had been exposed to oxygen was harder to remove by conventional water treatment processes (coagulation/flocculation). Drought had no effect on the amount of DOC production from vegetation litters; however large variation was observed between typical peatland species (Sphagnum and Calluna) and drought-tolerant grassland species (Juncus and Molinia), with the latter producing more DOC per unit weight. This would therefore suggest the increase in riverine DOC often observed post-drought is due entirely to soil microbial processes and DOC solubility rather than litter layer effects. Long-term shifts in species diversity may, therefore, be the most important impact of drought on litter layer DOC flux, whereas pulses related to drought may be observed in peat soils and are likely to become more common in the future. These results provide evidence in support of catchment management which increases the resilience of peat soils to drought, such as ditch blocking to raise water tables.
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Hensen, A., E. Nemitz, M. J. Flynn, et al. "Inter-comparison of ammonia fluxes obtained using the Relaxed Eddy Accumulation technique." Biogeosciences 6, no. 11 (2009): 2575–88. http://dx.doi.org/10.5194/bg-6-2575-2009.
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Abstract. The exchange of Ammonia (NH3) between grassland and the atmosphere was determined using Relaxed Eddy Accumulation (REA) measurements. The use of REA is of special interest for NH3, since the determination of fluxes at one height permits multiple systems to be deployed to quantify vertical flux divergence (either due to effects of chemical production or advection). During the Braunschweig integrated experiment four different continuous-sampling REA systems were operated during a period of about 10 days and were compared against a reference provided by independent application of the Aerodynamic Gradient Method (AGM). The experiment covered episodes before and after both cutting and fertilizing and provided a wide range of fluxes −60–3600 ng NH3 m−2 s−1 for testing the REA systems. The REA systems showed moderate to good correlation with the AGM estimates, with r2 values for the linear regressions between 0.3 and 0.82. For the period immediately after fertilization, the REA systems showed average fluxes 20% to 70% lower than the reference. At periods with low fluxes REA and AGM can agree within a few %. Overall, the results show that the continuous REA technique can now be used to measure NH3 surface exchange fluxes. While REA requires greater analytical precision in NH3 measurement than the AGM, a key advantage of REA is that reference sampling periods can be introduced to remove bias between sampling inlets. However, while the data here indicate differences consistent with advection effects, significant improvements in sampling precision are essential to allow robust determination of flux divergence in future studies. Wet chemical techniques will be developed further since they use the adsorptive and reactive properties of NH3 that impedes development of cheaper optical systems.
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Poulter, B., D. C. Frank, E. L. Hodson, and N. E. Zimmermann. "Impacts of land cover and climate data selection on understanding terrestrial carbon dynamics and the CO<sub>2</sub> airborne fraction." Biogeosciences 8, no. 8 (2011): 2027–36. http://dx.doi.org/10.5194/bg-8-2027-2011.
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Abstract. Terrestrial and oceanic carbon cycle processes remove ~55 % of global carbon emissions, with the remaining 45 %, known as the "airborne fraction", accumulating in the atmosphere. The long-term dynamics of the component fluxes contributing to the airborne fraction are challenging to interpret, but important for informing fossil-fuel emission targets and for monitoring the trends of biospheric carbon fluxes. Climate and land-cover forcing data for terrestrial ecosystem models are a largely unexplored source of uncertainty in terms of their contribution to understanding airborne fraction dynamics. Here we present results using a single dynamic global vegetation model forced by an ensemble experiment of climate (CRU, ERA-Interim, NCEP-DOE II), and diagnostic land-cover datasets (GLC2000, GlobCover, MODIS). For the averaging period 1996–2005, forcing uncertainties resulted in a large range of simulated global carbon fluxes, up to 13 % for net primary production (52.4 to 60.2 Pg C a−1) and 19 % for soil respiration (44.2 to 54.8 Pg C a−1). The sensitivity of contemporary global terrestrial carbon fluxes to climate strongly depends on forcing data (1.2–5.9 Pg C K−1 or 0.5 to 2.7 ppmv CO2 K−1), but weakening carbon sinks in sub-tropical regions and strengthening carbon sinks in northern latitudes are found to be robust. The climate and land-cover combination that best correlate to the inferred carbon sink, and with the lowest residuals, is from observational data (CRU) rather than reanalysis climate data and with land-cover categories that have more stringent criteria for forest cover (MODIS). Since 1998, an increasing positive trend in residual error from bottom-up accounting of global sinks and sources (from 0.03 (1989–2005) to 0.23 Pg C a−1 (1998–2005)) suggests that either modeled drought sensitivity of carbon fluxes is too high, or that carbon emissions from net land-cover change is too large.
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Minet, J., E. Laloy, B. Tychon, and L. François. "Bayesian inversions of a dynamic vegetation model at four European grassland sites." Biogeosciences 12, no. 9 (2015): 2809–29. http://dx.doi.org/10.5194/bg-12-2809-2015.
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Abstract. Eddy covariance data from four European grassland sites are used to probabilistically invert the CARAIB (CARbon Assimilation In the Biosphere) dynamic vegetation model (DVM) with 10 unknown parameters, using the DREAM(ZS) (DiffeRential Evolution Adaptive Metropolis) Markov chain Monte Carlo (MCMC) sampler. We focus on comparing model inversions, considering both homoscedastic and heteroscedastic eddy covariance residual errors, with variances either fixed a priori or jointly inferred together with the model parameters. Agreements between measured and simulated data during calibration are comparable with previous studies, with root mean square errors (RMSEs) of simulated daily gross primary productivity (GPP), ecosystem respiration (RECO) and evapotranspiration (ET) ranging from 1.73 to 2.19, 1.04 to 1.56 g C m−2 day−1 and 0.50 to 1.28 mm day−1, respectively. For the calibration period, using a homoscedastic eddy covariance residual error model resulted in a better agreement between measured and modelled data than using a heteroscedastic residual error model. However, a model validation experiment showed that CARAIB models calibrated considering heteroscedastic residual errors perform better. Posterior parameter distributions derived from using a heteroscedastic model of the residuals thus appear to be more robust. This is the case even though the classical linear heteroscedastic error model assumed herein did not fully remove heteroscedasticity of the GPP residuals. Despite the fact that the calibrated model is generally capable of fitting the data within measurement errors, systematic bias in the model simulations are observed. These are likely due to model inadequacies such as shortcomings in the photosynthesis modelling. Besides the residual error treatment, differences between model parameter posterior distributions among the four grassland sites are also investigated. It is shown that the marginal distributions of the specific leaf area and characteristic mortality time parameters can be explained by site-specific ecophysiological characteristics.
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Thomas, Zahra, Benjamin W. Abbott, Olivier Troccaz, Jacques Baudry, and Gilles Pinay. "Proximate and ultimate controls on carbon and nutrient dynamics of small agricultural catchments." Biogeosciences 13, no. 6 (2016): 1863–75. http://dx.doi.org/10.5194/bg-13-1863-2016.
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Abstract. Direct and indirect effects from human activity have dramatically increased nutrient loading to aquatic inland and estuarine ecosystems. Despite an abundance of studies investigating the impact of agricultural activity on water quality, our understanding of what determines the capacity of a watershed to remove or retain nutrients remains limited. The goal of this study was to identify proximate and ultimate controls on dissolved organic carbon and nutrient dynamics in small agricultural catchments by investigating the relationship between catchment characteristics, stream discharge, and water chemistry. We analyzed a 5-year, high-frequency water chemistry data set from three catchments in western France ranging from 2.3 to 10.8 km2. The relationship between hydrology and solute concentrations differed between the three catchments and was associated with hedgerow density, agricultural activity, and geology. The catchment with thicker soil and higher surface roughness had relatively invariant carbon and nutrient chemistry across hydrologic conditions, indicating high resilience to human disturbance. Conversely, the catchments with smoother, thinner soils responded to both intra- and interannual hydrologic variation with high concentrations of phosphate (PO43−) and ammonium (NH4+) in streams during low flow conditions and strong increases in dissolved organic carbon (DOC), sediment, and particulate organic matter during high flows. Despite contrasting agricultural activity between catchments, the physical context (geology, topography, and land-use configuration) appeared to be the most important determinant of catchment solute dynamics based on principle components analysis. The influence of geology and accompanying topographic and geomorphological factors on water quality was both direct and indirect because the distribution of agricultural activity in these catchments is largely a consequence of the geologic and topographic context. This link between inherent catchment buffering capacity and the probability of human disturbance provides a useful perspective for evaluating vulnerability of aquatic ecosystems and for managing systems to maintain agricultural production while minimizing leakage of nutrients.
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Isaac, Peter, James Cleverly, Ian McHugh, Eva van Gorsel, Cacilia Ewenz, and Jason Beringer. "OzFlux data: network integration from collection to curation." Biogeosciences 14, no. 12 (2017): 2903–28. http://dx.doi.org/10.5194/bg-14-2903-2017.
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Abstract. Measurement of the exchange of energy and mass between the surface and the atmospheric boundary-layer by the eddy covariance technique has undergone great change in the last 2 decades. Early studies of these exchanges were confined to brief field campaigns in carefully controlled conditions followed by months of data analysis. Current practice is to run tower-based eddy covariance systems continuously over several years due to the need for continuous monitoring as part of a global effort to develop local-, regional-, continental- and global-scale budgets of carbon, water and energy. Efficient methods of processing the increased quantities of data are needed to maximise the time available for analysis and interpretation. Standardised methods are needed to remove differences in data processing as possible contributors to observed spatial variability. Furthermore, public availability of these data sets assists with undertaking global research efforts. The OzFlux data path has been developed (i) to provide a standard set of quality control and post-processing tools across the network, thereby facilitating inter-site integration and spatial comparisons; (ii) to increase the time available to researchers for analysis and interpretation by reducing the time spent collecting and processing data; (iii) to propagate both data and metadata to the final product; and (iv) to facilitate the use of the OzFlux data by adopting a standard file format and making the data available from web-based portals. Discovery of the OzFlux data set is facilitated through incorporation in FLUXNET data syntheses and the publication of collection metadata via the RIF-CS format. This paper serves two purposes. The first is to describe the data sets, along with their quality control and post-processing, for the other papers of this Special Issue. The second is to provide an example of one solution to the data collection and curation challenges that are encountered by similar flux tower networks worldwide.
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Smith, Helen E. K., Alex J. Poulton, Rebecca Garley, et al. "The influence of environmental variability on the biogeography of coccolithophores and diatoms in the Great Calcite Belt." Biogeosciences 14, no. 21 (2017): 4905–25. http://dx.doi.org/10.5194/bg-14-4905-2017.
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Abstract. The Great Calcite Belt (GCB) of the Southern Ocean is a region of elevated summertime upper ocean calcite concentration derived from coccolithophores, despite the region being known for its diatom predominance. The overlap of two major phytoplankton groups, coccolithophores and diatoms, in the dynamic frontal systems characteristic of this region provides an ideal setting to study environmental influences on the distribution of different species within these taxonomic groups. Samples for phytoplankton enumeration were collected from the upper mixed layer (30 m) during two cruises, the first to the South Atlantic sector (January–February 2011; 60° W–15° E and 36–60° S) and the second in the South Indian sector (February–March 2012; 40–120° E and 36–60° S). The species composition of coccolithophores and diatoms was examined using scanning electron microscopy at 27 stations across the Subtropical, Polar, and Subantarctic fronts. The influence of environmental parameters, such as sea surface temperature (SST), salinity, carbonate chemistry (pH, partial pressure of CO2 (pCO2), alkalinity, dissolved inorganic carbon), macronutrients (nitrate + nitrite, phosphate, silicic acid, ammonia), and mixed layer average irradiance, on species composition across the GCB was assessed statistically. Nanophytoplankton (cells 2–20 µm) were the numerically abundant size group of biomineralizing phytoplankton across the GCB, with the coccolithophore Emiliania huxleyi and diatoms Fragilariopsis nana, F. pseudonana, and Pseudo-nitzschia spp. as the most numerically dominant and widely distributed. A combination of SST, macronutrient concentrations, and pCO2 provided the best statistical descriptors of the biogeographic variability in biomineralizing species composition between stations. Emiliania huxleyi occurred in silicic acid-depleted waters between the Subantarctic Front and the Polar Front, a favorable environment for this species after spring diatom blooms remove silicic acid. Multivariate statistics identified a combination of carbonate chemistry and macronutrients, covarying with temperature, as the dominant drivers of biomineralizing nanoplankton in the GCB sector of the Southern Ocean.
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Santos, G. M., A. Alexandre, J. R. Southon, K. K. Treseder, R. Corbineau, and P. E. Reyerson. "Possible source of ancient carbon in phytolith concentrates from harvested grasses." Biogeosciences 9, no. 5 (2012): 1873–84. http://dx.doi.org/10.5194/bg-9-1873-2012.
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Abstract. Plants absorb and transport silicon (Si) from soil, and precipitation of Si within the living plants results in micrometric amorphous biosilica particles known as phytoliths. During phytolith formation, a small amount of carbon (<2%) can become occluded in the silica structure (phytC) and therefore protected from degradation by the environment after plant tissue decomposition. Since the major C source within plants is from atmospheric carbon dioxide (CO2) via photosynthesis, the current understanding is that the radiocarbon (14C) content of phytC should reflect the 14C content of atmospheric CO2 at the time the plant is growing. This assumption was recently challenged by 14C data from phytoliths extracted from living grasses that yielded ages of several thousand years (2–8 kyr BP; in radiocarbon years "Before Present" (BP), "Present" being defined as 1950). Because plants can take up small amounts of C of varying ages from soils (e.g., during nutrient acquisition), we hypothesized that this transported C within the plant tissue could be attached to or even embedded in phytoliths. In this work, we explore this hypothesis by reviewing previously published data on biosilica mineralization and plant nutrient acquisition as well as by evaluating the efficiency of phytolith extraction protocols from scanning electron microscope (SEM) images and energy dispersive spectrometer (EDS) analyses from harvested grasses phytolith concentrates. We show that current extraction protocols are inefficient since they do not entirely remove recalcitrant forms of C from plant tissue. Consequently, material previously measured as "phytC" may contain at least some fraction of soil-derived C (likely radiocarbon-old) taken up by roots. We also suggest a novel interpretation for at least some of the phytC – which enters via the root pathway during nutrient acquisition – that may help to explain the old ages previously obtained from phytolith concentrates.
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King, A. L., S. A. Sañudo-Wilhelmy, P. W. Boyd, et al. "A comparison of biogenic iron quotas during a diatom spring bloom using multiple approaches." Biogeosciences 9, no. 2 (2012): 667–87. http://dx.doi.org/10.5194/bg-9-667-2012.
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Abstract. Biogenic Fe quotas were determined using three distinct techniques on samples collected concurrently in the subtropical Pacific Ocean east of New Zealand. Fe quotas were measured using radioisotope uptake experiments (24 h incubation), bulk filtration and analysis by inductively-coupled plasma mass spectrometer (ICPMS), and single-cell synchrotron x-ray fluorescence (SXRF) analysis over a sixteen-day period (year days 263 to 278 of 2008) during a quasi-Lagrangian drifter experiment that tracked the evolution of the annual spring diatom bloom within a counter-clockwise open-ocean eddy. Overall, radioisotope uptake-determined Fe quotas (washed with oxalate reagent to remove extracellular Fe) were the lowest (0.5–1.0 mmol Fe:mol P; 4–8 μmol Fe:mol C), followed by single-cell Fe quotas (2.3–7.5 mmol Fe:mol P; 17–57 μmol Fe:mol C), and the highest and most variable quotas were from the bulk filtration ICPMS approach that used the oxalate reagent wash, corrected for lithogenic Fe using Al (0.8–21 mmol Fe:mol P; 4–136 μmol Fe:mol C). During the evolution of the spring bloom within the eddy (year days 263 to 272), the surface mixed layer inventories of particulate biogenic elements (C, N, P, Si) and chlorophyll increased while Fe quotas estimated from all three approaches exhibited a general decline. After the onset of the bloom decline, the drogued buoys exited the eddy center (days 273 to 277). Fe quotas returned to pre-bloom values during this part of the study. Our standardized and coordinated sampling protocols reveal the general observed trend in Fe quotas: ICPMS > SXRF > radioisotope uptake. We discuss the inherent differences between the techniques and argue that each technique has its individual merits and uniquely contributes to the characterization of the oceanic particulate Fe pool.
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Amann, Thorben, Jens Hartmann, Eric Struyf, et al. "Enhanced Weathering and related element fluxes – a cropland mesocosm approach." Biogeosciences 17, no. 1 (2020): 103–19. http://dx.doi.org/10.5194/bg-17-103-2020.
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Abstract. The weathering of silicates is a major control on atmospheric CO2 at geologic timescales. It was proposed to enhance this process to actively remove CO2 from the atmosphere. While there are some studies that propose and theoretically analyze the application of rock powder to agricultural land, results from field experiments are still scarce. In order to evaluate the efficiency and side effects of Enhanced Weathering (EW), a mesocosm experiment was set up and agricultural soil from Belgium was amended with olivine-bearing dunite ground to two different grain sizes, while distinguishing setups with and without crops. Based on measurements of Mg, Si, pH, and DIC, the additional weathering effect of olivine could be confirmed. Calculated weathering rates are up to 3 orders of magnitude lower than found in other studies. The calculated CO2 consumption by weathering based on the outlet water of the mesocosm systems was low with 2.3–4.9 tCO2km-2a-1 if compared with previous theoretical estimates. Suspected causes were the removal or dilution of Mg as a weathering product by processes like adsorption, mineralization, plant uptake, evapotranspiration, and/or preferential flow, not specifically addressed in previous EW experiments for CO2 consumption. The observation that Mg concentrations in the upper soil layers were about 1 order of magnitude higher than in the outlet water indicates that a careful tracking of weathering indicators like Mg in the field is essential for a precise estimate of the CO2 consumption potential of EW, specifically under global deployment scenarios with a high diversity of ecosystem settings. Porewater Mg∕Si molar ratios suggest that dissolved Si is reprecipitating, forming a cation-depleted Si layer on the reactive mineral surface of freshly ground rocks. The release of potentially harmful trace elements is an acknowledged side effect of EW. Primarily Ni and Cr are elevated in the soil solution, while Ni concentrations exceed the limits of drinking water quality. The use of olivine, rich in Ni and Cr, is not recommended, and alternative rock sources are suggested for the application.
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Krause, Andreas, Thomas A. M. Pugh, Anita D. Bayer, et al. "Global consequences of afforestation and bioenergy cultivation on ecosystem service indicators." Biogeosciences 14, no. 21 (2017): 4829–50. http://dx.doi.org/10.5194/bg-14-4829-2017.
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Abstract. Land management for carbon storage is discussed as being indispensable for climate change mitigation because of its large potential to remove carbon dioxide from the atmosphere, and to avoid further emissions from deforestation. However, the acceptance and feasibility of land-based mitigation projects depends on potential side effects on other important ecosystem functions and their services. Here, we use projections of future land use and land cover for different land-based mitigation options from two land-use models (IMAGE and MAgPIE) and evaluate their effects with a global dynamic vegetation model (LPJ-GUESS). In the land-use models, carbon removal was achieved either via growth of bioenergy crops combined with carbon capture and storage, via avoided deforestation and afforestation, or via a combination of both. We compare these scenarios to a reference scenario without land-based mitigation and analyse the LPJ-GUESS simulations with the aim of assessing synergies and trade-offs across a range of ecosystem service indicators: carbon storage, surface albedo, evapotranspiration, water runoff, crop production, nitrogen loss, and emissions of biogenic volatile organic compounds. In our mitigation simulations cumulative carbon storage by year 2099 ranged between 55 and 89 GtC. Other ecosystem service indicators were influenced heterogeneously both positively and negatively, with large variability across regions and land-use scenarios. Avoided deforestation and afforestation led to an increase in evapotranspiration and enhanced emissions of biogenic volatile organic compounds, and to a decrease in albedo, runoff, and nitrogen loss. Crop production could also decrease in the afforestation scenarios as a result of reduced crop area, especially for MAgPIE land-use patterns, if assumed increases in crop yields cannot be realized. Bioenergy-based climate change mitigation was projected to affect less area globally than in the forest expansion scenarios, and resulted in less pronounced changes in most ecosystem service indicators than forest-based mitigation, but included a possible decrease in nitrogen loss, crop production, and biogenic volatile organic compounds emissions.