Littérature scientifique sur le sujet « Kd coefficient »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les listes thématiques d’articles de revues, de livres, de thèses, de rapports de conférences et d’autres sources académiques sur le sujet « Kd coefficient ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Articles de revues sur le sujet "Kd coefficient"
1
Akter, Sonia, Lis Wollesen de Jonge, Per Møldrup, Mogens Humlekrog Greve, Trine Nørgaard, Peter Lystbæk Weber, Cecilie Hermansen, Abdul Mounem Mouazen et Maria Knadel. « Visible Near-Infrared Spectroscopy and Pedotransfer Function Well Predict Soil Sorption Coefficient of Glyphosate ». Remote Sensing 15, no 6 (22 mars 2023) : 1712. http://dx.doi.org/10.3390/rs15061712.
Texte intégralRésumé :
The soil sorption coefficient (Kd) of glyphosate mainly controls its transport and fate in the environment. Laboratory-based analysis of Kd is laborious and expensive. This study aimed to test the feasibility of visible near-infrared spectroscopy (vis–NIRS) as an alternative method for glyphosate Kd estimation at a country scale and compare its accuracy against pedotransfer function (PTF). A total of 439 soils with a wide range of Kd values (37–2409 L kg−1) were collected from Denmark (DK) and southwest Greenland (GR). Two modeling scenarios were considered to predict Kd: a combined model developed on DK and GR samples and individual models developed on either DK or GR samples. Partial least squares regression (PLSR) and artificial neural network (ANN) techniques were applied to develop vis–NIRS models. Results from the best technique were validated using a prediction set and compared with PTF for each scenario. The PTFs were built with soil texture, OC, pH, Feox, and Pox. The ratio of performance to interquartile distance (RPIQ) was 1.88, 1.70, and 1.50 for the combined (ANN), DK (ANN), and GR (PLSR) validation models, respectively. vis–NIRS obtained higher predictive ability for Kd than PTFs for the combined dataset, whereas PTF resulted in slightly better estimations of Kd on the DK and GR samples. However, the differences in prediction accuracy between vis–NIRS and PTF were statistically insignificant. Considering the multiple advantages of vis–NIRS, e.g., being rapid and non-destructive, it can provide a faster and easier alternative to PTF for estimating glyphosate Kd.
2
Kim, Do-Hyeon, et Jun-Yeop Lee. « Prediction of the Adsorption Behaviors of Radionuclides onto Bentonites Using a Machine Learning Method ». Minerals 12, no 10 (25 septembre 2022) : 1207. http://dx.doi.org/10.3390/min12101207.
Texte intégralRésumé :
This study builds a model to predict distribution coefficients (Kd) using the random forest (RF) method and a machine learning model based on the Japan Atomic Energy Agency Sorption Database (JAEA-SDB). A database of ten input variables, including the distribution coefficient, pH, initial radionuclide concentrations, solid–liquid ratio, ionic strength, oxidation number, cation exchange capacity, surface area, electronegativity, and ionic radius, was constructed and used for the RF model calculation. The calculation parameters employed in this work included two different hyperparameters, the number of decision trees and the maximum number of variables to divide each node, together with the random seeds inside the RF model. The coefficients of determination were derived with various combinations of hyperparameters and random seeds, and were employed to assess the RF model calculation result. Based on the results of the RF model, the distribution coefficients of 22 target nuclides (Am, Ac, Co, Cm, Cd, Cs, Cu, Na, Np, Ni, Nb, U, Sr, Sn, Pb, Pa, Pu, Po, I, Tc, Th, and Zr) were predicted successfully. Among the various input variables, pH was found to make the highest contribution to determining the distribution coefficient. The novelty of this study lies in the first application of the machine learning method for predicting the Kd value of bentonites, using JAEA-SDB. This study has established a model for reliably predicting the distribution coefficient for various radionuclides that is intended for use in evaluating the Kd value in arbitrary aqueous conditions.
3
Zolfaghari, Kiana, Claude R. Duguay et Homa Kheyrollah Pour. « Satellite-derived light extinction coefficient and its impact on thermal structure simulations in a 1-D lake model ». Hydrology and Earth System Sciences 21, no 1 (24 janvier 2017) : 377–91. http://dx.doi.org/10.5194/hess-21-377-2017.
Texte intégralRésumé :
Abstract. A global constant value of the extinction coefficient (Kd) is usually specified in lake models to parameterize water clarity. This study aimed to improve the performance of the 1-D freshwater lake (FLake) model using satellite-derived Kd for Lake Erie. The CoastColour algorithm was applied to MERIS satellite imagery to estimate Kd. The constant (0.2 m−1) and satellite-derived Kd values as well as radiation fluxes and meteorological station observations were then used to run FLake for a meteorological station on Lake Erie. Results improved compared to using the constant Kd value (0.2 m−1). No significant improvement was found in FLake-simulated lake surface water temperature (LSWT) when Kd variations in time were considered using a monthly average. Therefore, results suggest that a time-independent, lake-specific, and constant satellite-derived Kd value can reproduce LSWT with sufficient accuracy for the Lake Erie station. A sensitivity analysis was also performed to assess the impact of various Kd values on the simulation outputs. Results show that FLake is sensitive to variations in Kd to estimate the thermal structure of Lake Erie. Dark waters result in warmer spring and colder fall temperatures compared to clear waters. Dark waters always produce colder mean water column temperature (MWCT) and lake bottom water temperature (LBWT), shallower mixed layer depth (MLD), longer ice cover duration, and thicker ice. The sensitivity of FLake to Kd variations was more pronounced in the simulation of MWCT, LBWT, and MLD. The model was particularly sensitive to Kd values below 0.5 m−1. This is the first study to assess the value of integrating Kd from the satellite-based CoastColour algorithm into the FLake model. Satellite-derived Kd is found to be a useful input parameter for simulations with FLake and possibly other lake models, and it has potential for applicability to other lakes where Kd is not commonly measured.
4
Estrada-Arriaga, E. B., et N. P. Mijaylova. « A comparison of biodegradation kinetic models applied to estrogen removal with nitrifying activated sludge ». Water Science and Technology 62, no 9 (1 novembre 2010) : 2183–89. http://dx.doi.org/10.2166/wst.2010.441.
Texte intégralRésumé :
The biological degradation of estrone (E1), estradiol (E2) and ethinylestradiol (EE2) was studied in batch experiments at typical concentration levels using nitrifying activated sludge from a membrane bioreactor (MBR). Since first-order, pseudo first-order and Monod-type kinetics were observed. Pseudo first order kinetic was reformulated using only the soluble concentrations S and assuming adsorption coefficient KD of the estrogens. For the adsorption coefficients KD determination, activated sludge from MBR was spiked with the respective target compounds and stirred. Finally, the water was analyzed. The KD values of estrogens ranged from 0.323 to 0.474 L/g. Greater than 98% of E1, E2 and EE2 were found to be removed in batch reactors. The measured data were linearly regressed giving R2 values ranging from 0.748 to 0.990. According to these results, the biodegradation kinetics were adjusted to pseudo first-order assuming adsorption coefficient KD and Monod-type kinetic. The biodegradation rate constant k of the estrogens were: E1 and E2 > 78.52 L/gVSS d and 12.41 L/gVSS d for EE2. Monod-type kinetic indicates that these compounds are biodegradated by co-metabolism. E2 was oxidized into E1.
5
Castillo-Ramírez, Alejandra, Eduardo Santamaría-del-Ángel, Adriana González-Silvera, Robert Frouin, María-Teresa Sebastiá-Frasquet, Jing Tan, Jorge Lopez-Calderon, Laura Sánchez-Velasco et Luis Enríquez-Paredes. « A New Algorithm to Estimate Diffuse Attenuation Coefficient from Secchi Disk Depth ». Journal of Marine Science and Engineering 8, no 8 (25 juillet 2020) : 558. http://dx.doi.org/10.3390/jmse8080558.
Texte intégralRésumé :
The vertical diffuse attenuation coefficient Kd (PAR) is used for calculating the euphotic zone, the first optical depth that is important for primary productivity models. Currently, Kd (PAR) can be estimated using an irradiometer or a Secchi disk (SD). The main objective of this work is to define a model that can be applied to a wide range of optical marine conditions to estimate Kd (PAR) by SD. We used irradiance profiles and SD depth (ZSD) from 679 stations in various marine regions. Three parametric models were developed, and their statistical performance was evaluated in view of previous approaches reported and remote sensing data. The best results were obtained with an adaptive model representing three cases: clear-water, turbid-water, and a transition zone (R2 = 0.965, MAE = 0.083, RMSD = 0.239, BIAS = 0.01, and MPI = 0.854). Previous models considering a single optical depth figure at which the SD disappears did not capture the marine optical complexity. Our classification of 113 stations with spectral absorption data into Jerlov water types indicated that no unique correspondence existed between estimated Kd (PAR) and water type, making it ambiguous to associate compatible inherent optical properties and chlorophyll with ZSD. Although obtaining Kd (PAR) from ZSD is simple/low-cost, care should be taken in the methodology used to measure ZSD to ensure consistent results across different optical marine conditions.
6
Zhang, Yu, Zhantang Xu, Yuezhong Yang, Guifen Wang, Wen Zhou, Wenxi Cao, Yang Li et al. « Diurnal Variation of the Diffuse Attenuation Coefficient for Downwelling Irradiance at 490 nm in Coastal East China Sea ». Remote Sensing 13, no 9 (26 avril 2021) : 1676. http://dx.doi.org/10.3390/rs13091676.
Texte intégralRésumé :
The diurnal variation of the diffuse attenuation coefficient for downwelling irradiance at 490 nm (Kd(490)) has complex characteristics in the coastal regions. However, owing to the scarcity of in situ data, our knowledge on the diurnal variation is inadequate. In this study, an optical-buoy dataset was used to investigate the diurnal variation of Kd(490) in the coastal East China Sea, and to evaluate the Kd(490) L2 products of geostationary ocean color imager (GOCI), as well as the performance of six empirical algorithms for Kd(490) estimation in the Case-2 water. The results of validation show that there was high uncertainty in GOCI L2 Kd(490), with mean absolute percentage errors (MAPEs) of 69.57% and 68.86% and root mean square errors (RMSEs) of 0.70 and 0.71 m−1 compared to buoy-measured Kd12(490) and Kd13(490), respectively. Meanwhile, with the coefficient of determination (R2) of 0.71, as well as the lowest MAPE of 27.31% and RMSE of 0.29 m−1, the new dual ratio algorithm (NDRA) performed the best in estimating Kd(490) in the target area, among the six algorithms. Further, four main types of Kd(490) diurnal variation were found from buoy data, showing different variabilities compared to the area closer to the shore. One typical diurnal variation pattern showed that Kd(490) decreased at flood tide and increased at ebb tide, which was confirmed by GOCI images through the use of NDRA. Hydrometeorological factors influencing the diurnal variations of Kd(490) were also studied. In addition to verifying the predominant impact of tide, we found that the dominant effect of tide and wind on the water column is intensifying sediment resuspension, and the change of sediment transport produced by them are secondary to it.
7
Moiseev, S. I., A. I. Buyanovsky, A. N. Deminov, S. V. Klinushkin et S. A. Moiseeva. « Application of the morphometric maturity coefficient to determine terminal molt in the crab Chionoecetes angulatus from the Okhotsk Sea ». Trudy VNIRO 179 (26 octobre 2020) : 5–25. http://dx.doi.org/10.36038/2307-3497-2020-179-5-25.
Texte intégralRésumé :
Results of studies on the relationship between the claw morphometric parameters and the carapace width (CW) of the triangle crab (Chionoecetes angulatus) crab from the Sea of Okhotsk presented. For the operational screening and separation of males into morphometrically mature (ММ – large-clawed) and immature (MI – small-clawed) species, it is proposed to use the coefficient of morphometric maturity (K%). This coefficient can be defined as the ratio of claw height to carapace width (KH%) or as the ratio of claw diagonal to carapace width (KD%), expressed as a percentage. When assessing the coefficient of morphometric maturity (K%), the boundary value for KH% is 16, and for KD% it is 35, which allows reliable identification of large-clawed (MM) males at K% values above the boundary values, and small-clawed (MI) males at K% values below the boundary values. Four functional groups were distinguished in males of C. angulatus: 1) MI physiologically immature — CW ≤90 mm, KH% <13.5, and KD% ≤29; 2) MI physiologically mature — CW 90.1–120 mm, KH% 12–16 and KD% 25–35; 3) MI large-sized physiologically sexually mature — CW >120 mm, KH% 13–16 and KD% 29–35; 4) MM morphometrically and functionally mature — CW 74–167 mm, KH% >16 and KD% >35. The correlation of the onset of morphometric maturity with biochemical parameters of hemolymph and with the development of muscle tissue is discussed. For various functional groups of males C. angulatus, an abundance estimate was implemented taking into account the K% coefficient.
8
Onyeocha, Veronica O., O. D. Akpan, Ikejiofor A. Onuchukwu et Maduabuchi A. Chidiebere. « The Dimerization Effects of Some Solutes on the Partition Coefficient kD in Binary Immiscible Solvents ». International Letters of Chemistry, Physics and Astronomy 80 (décembre 2018) : 40–52. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.80.40.
Texte intégralRésumé :
The dimerization of a solute dissolved in binary immiscible solvents shows that the value of the partition coefficient, kD of the solutes are influenced by the dimerization constant, K of the solute in one of the solvents according to the description: (C_X^A)/(C_X^B ) = kD + 2kD2KCxB where CxA and CxB are the concentrations of the solute x in the solvents A and B respectively. Both kD and K are parameters that predict the extent of beneficiation for most minerals. Also, kD is a fundamental parameter that determines the extent of solute recovery during solvent extraction. In this study, it is found that the order K kD and K kD are the effects for acetic and succinic acids respectively in the binary solvents composed of carbon tetrachloride/water and diethylether/water systems respectively. These results suggest that the distributions of these solutes in the solvents are accompanied by the formation of succinic anhydride which is more favoured than the dimerization of the acetic acid. Also, the changes in the values of distribution enthalpies, HD are corroborated to explain these experimental observations.
9
Kraus, Cleber Nunes, Daniel Andrade Maciel, Marie Paule Bonnet et Evlyn Márcia Leão de Moraes Novo. « Phytoplankton Genera Structure Revealed from the Multispectral Vertical Diffuse Attenuation Coefficient ». Remote Sensing 13, no 20 (14 octobre 2021) : 4114. http://dx.doi.org/10.3390/rs13204114.
Texte intégralRésumé :
The composition of phytoplankton and the concentration of pigments in their cells make their absorption and specific absorption coefficients key parameters for bio-optical modeling. This study investigated whether the multispectral vertical diffuse attenuation coefficient of downward irradiance (Kd) gradients could be a good framework for accessing phytoplankton genera. In situ measurements of remote sensing reflectance (Rrs), obtained in an Amazon Floodplain Lake (Lago Grande do Curuai), were used to invert Kd, focusing on Sentinel-3/Ocean and Land Color Instrument (OLCI) sensor bands. After that, an analysis based on the organization of three-way tables (STATICO) was applied to evaluate the relationships between phytoplankton genera and Kd at different OLCI bands. Our results indicate that phytoplankton genera are organized according to their ability to use light intensity and different spectral ranges of visible light (400 to 700 nm). As the light availability changes seasonally, the structure of phytoplankton changes as well. Some genera, such as Microcystis, are adapted to low light intensity at 550–650 nm, therefore high values of Kd in this range would indicate the dominance of Microcysts. Other genera, such as Aulacoseira, are highly adapted to harvesting blue-green light with higher intensity and probably grow in lakes with lower concentrations of colored dissolved organic matter that highly absorbs blue light (405–498). These findings are an important step to describing phytoplankton communities using orbital data in tropical freshwater floodplains. Furthermore, this approach can be used with biodiversity indexes to access phytoplankton diversity in these environments.
10
Prasetyo, Budhi Agung, Vincentius Paulus Siregar, Syamsul Bahri Agus et Wikanti Asriningrum. « IN-SITU MEASUREMENT OF DIFFUSE ATTENUATION COEFFICIENT AND ITS RELATIONSHIP WITH WATER CONSTITUENT AND DEPTH ESTIMATION OF SHALLOW WATERS BY REMOTE SENSING TECHNIQUE ». International Journal of Remote Sensing and Earth Sciences (IJReSES) 14, no 1 (21 juin 2017) : 47. http://dx.doi.org/10.30536/j.ijreses.2017.v14.a2682.
Texte intégralRésumé :
Diffuse attenuation coefficient, Kd(λ), has an empirical relationship with water depth, thus potentially to be used to estimate the depth of the water based on the light penetration in the water column. The aim of this research is to assess the relationship of diffuse attenuation coefficient with the water constituent and its relationship to estimate the depth of shallow waters of Air Island, Panggang Island and Karang Lebar lagoons and to compare the result of depth estimation from Kd model and derived from Landsat 8 imagery. The measurement of Kd(λ) was carried out using hyperspectral spectroradiometer TriOS-RAMSES with range 320 – 950 nm. The relationship between measurement Kd(λ) on study site with the water constituent was the occurrence of absorption by chlorophyll-a concentration at the blue and green spectral wavelength. Depth estimation using band ratio from Kd(λ) occurred at 442,96 nm and 654,59 nm, which had better relationship with the depth from in-situ measurement compared to the estimation based on Landsat 8 band ratio. Depth estimated based on Kd(λ) ratio and in-situ measurement are not significantly different statistically. Depth estimated based on Kd(λ) ratio and in-situ measurement are not significantly different statistically. However, depth estimation based on Kd(λ) ratio was inconsistent due to the bottom albedo reflection because the Kd(λ) measurement was carried out in shallow waters. Estimation of water depth based on Kd(λ) ratio had better results compared to the Landsat 8 band ratio.
Thèses sur le sujet "Kd coefficient"
1
Nordanstorm, Nika. « Evaluation of distribution coefficients (KOC and Kd) for per- and polyfluoroalkyl substances ». Thesis, Linnéuniversitetet, Institutionen för biologi och miljö (BOM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-101693.
Texte intégralRésumé :
The dominating factors affecting sorption of per- and polyfluoroalkyl substances (PFAS) remain subject of research and debate. Traditionally, distribution coefficients (e.g., Kd and KOC) are used to calculate the fractionation of the contaminant between soil and water, to estimate leaching and subsequently the risks it imposes reaching water reservoirs. Research has aimed to establish the sorption mechanisms for PFAS but, due to the complexity of interactions between the substance specific physiochemical properties and geochemical sorbent characteristics, it has shown to be a complicated task. For PFOS, one of the most commonly encountered PFAS, the Swedish Geotechnical Institute (SGI) recommends using the 10th percentile of a small data set for the organic carbon-water distribution coefficient KOC (500 L/kg) and multiply this with the organic content of the in-situ soil to obtain the soil-water distribution coefficient (Kd). The result of this study shows that this method is insufficient to obtain a good approximation of the mobility of PFOS at a contaminated site. With a review of recent research on PFAS sorption and a case study performed at Stockholm Arlanda Airport, this study concludes that as of today, and due to PFAS potent mobility, well measured field coefficients for each soil type present in the soil profile and an elaborate geohydrological model is necessary to estimate PFAS environmental transport, fate and associated risks. It also concludes that parameters such as anionic exchange capacity and soil protein content may be highly relevant to estimate PFAS sorption.
2
Soares, Marcio Roberto. « Coeficiente de distribuição (Kd) de metais pesados em solos do estado de São Paulo ». Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-31052005-170719/.
Texte intégralRésumé :
A disposição de resíduos sólidos e a aplicação de pesticidas e fertilizantes podem levar ao aumento da concentração de metais pesados em solos e águas subterrâneas. A legislação sobre metais pesados quase sempre se refere aos seus teores totais, mas a avaliação do potencial de risco e da toxicidade requer a avaliação da proporção de metal que é móvel e, possivelmente, biodisponível. Alguns parâmetros numéricos têm sido utilizados para tomadas de decisões e para direcionar estratégias de prevenção ou de remediação de áreas contaminadas. O coeficiente de distribuição sólido-solução (Kd), definido como a relação entre as concentrações adsorvida e em solução, permite a comparação do comportamento de elementos em diferentes sistemas. Agências de proteção ambiental utilizam valores genéricos de Kd encontrados em referências bibliográficas que, por terem sido gerados a partir de condições distintas das da região tropical, podem levar a incorretas estimativas de risco. É evidente a necessidade da obtenção de valores de Kd que validem estas estimativas de contaminação ou que norteiem estratégias de intervenção em áreas já contaminadas. Os objetivos deste trabalho foram avaliar a retenção de metais pesados em 30 solos representativos do Estado de São Paulo, a partir da quantificação dos valores do coeficiente de distribuição (Kd) e da relação com atributos dos solos, tais como pH, CTC e teores de argila, matéria orgânica e de diversas formas de óxidos de Fe, Al e de Mn. Os coeficientes de distribuição foram obtidos de isotermas lineares de adsorção, construídas após a adição de 0,1; 0,5; 1,0; 2,5 e 5,0 mg L-1 de Cd, Co, Cr, Cu, Ni, Pb e Zn, em experimentos tipo batch. As menores variações nos valores de Kd foram registradas para o Pb (uma ordem de magnitude 121 a 7.020 L kg-1) e para o Ni (duas ordens de magnitude - 6 a 998 L kg-1), enquanto variações de quatro ordens de magnitude foram observadas para Cd (7-14.339 L kg-1), Co (2-34.473 L kg-1) e para Cr (1-21.267 L kg-1). Coeficientes de distribuição de zinco estiveram entre 5 a 123.849 L kg-1, variando cinco ordens de magnitude. Os valores foram similares àqueles que vêm sendo utilizados pela CETESB, exceto os de Cr e Ni. Obteve-se a seguinte ordem de afinidade: Pb>>>Cu>>Cd>Zn≅Ni≅Cr>Co. Mais de 55% da variação dos coeficientes de distribuição de cátions metálicos dos grupos IIB (Cd e Zn) e VIIIB (Co e Ni) foram explicados pelo pH. Na análise conjunta, CTC e pH explicaram cerca de 80% da variação dos valores de Kd de Cd, Co e de Ni e evidenciaram que mecanismos de adsorção não-específica estão envolvidos na retenção destes elementos. No caso dos coeficientes de distribuição de Cu e de Pb, o pH e os teores de argila responderam por cerca de 63% da sua variação. Os valores de Kd de Cr apresentaram correlação inversa com o pH, principalmente na análise conjunta com os teores de argila, e 61% da sua variação foi explicada por estas variáveis.Disposal of solid residues and application of pesticides and fertilizers can lead to an increase in the concentration of heavy metals in soils and groundwater. The legislation on heavy metals nearly always refers to the total contents of these elements; however, an evaluation of their hazard potential and toxicity requires an assessment of the metal fraction that is mobile and possibly bioavailable. A few numerical parameters have been used as a foundation to make decisions and to focus on prevention or remediation strategies in contaminated areas. The solid-solution distribution coefficient (Kd), defined as the relation between metal concentrations that are adsorbed and those present in the solution, allows a comparison between the behavior of elements in different systems. Environmental protection agencies use generic Kd values found in bibliographic references; these values are often obtained under distinct conditions from those found in the tropical region, and may lead to an erroneous hazard estimates. Thus, it becomes clearly necessary to obtain Kd values that will validate these contamination estimates or provide guidance for intervention strategies in already contaminated areas. The objectives of this work were to evaluate heavy metal retention in 30 representative soils of the State of São Paulo, based on a quantification of distribution coefficient values (Kd) and their relation with soil attributes, such as pH, CEC and clay contents, organic matter, and various forms of Fe, Al, and Mn oxides. The distribution coefficients were obtained from linear adsorption isotherms, constructed after the addition of 0.1; 0.5; 1.0; 2.5; and 5.0 mg L-1 Cd, Co, Cr, Cu, Ni, Pb, and Zn, in batch-type experiments. The smallest variations in Kd value were recorded for Pb (one order of magnitude 121 to 7,020 L kg-1) and Ni (two orders of magnitude - 6 to 998 L kg-1), while variations indicating four orders of magnitude were observed for Cd (7-14,339 L kg-1), Co (2 - 34,473 L kg-1), and Cr (1 - 21,267 L kg-1). Zinc distribution coefficients were between 5 and 123,849 L kg-1, with a variation of five orders of magnitude. The values herein obtained were similar to those that have been used by CETESB, except for Cr and Ni. The following order of affinity was obtained: Pb>>>Cu>>Cd>Zn≅Ni≅Cr>Co. More than 55% of the variation in distribution coefficients for metallic cations of the groups IIB (Cd and Zn) and VIIIB (Co and Ni) were explained by pH. In the joint analysis, CEC and pH explained about 80% of the variation in Kd values for Cd, Co, and Ni, and showed that nonspecific adsorption mechanisms are involved in the retention of these elements. Regarding the distribution coefficients for Cu and Pb, pH and clay content accounted for about 63% of the variation. Kd values for Cr showed an inverse correlation with pH, especially in the joint analysis with clay contents, and 61% of the variation were explained by these variables.
3
Pinel, Franck. « Chimie de 63Ni et de 137Cs dans le système sol-plante ». Montpellier, ENSA, 2002. http://www.theses.fr/2002ENSA0007.
Texte intégral
4
Taghavi, Lobat. « Dynamique de transfert des pesticides en périodes de crue sur les bassins versants agricoles gascons ». Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0098/document.
Texte intégralRésumé :
Ce travail de thèse porte sur l’étude des mécanismes et des bilans de transfert des pesticides vers les cours d’eau sur deux bassins versants agricoles emboités, de tailles différentes en Gascogne (Sud Ouest de la France) : la Save à Larra (1110 km2).et le Montoussé (3,28 km2) à Auradé. Dans cette région, les pratiques d’une agriculture intensive conduisent à des risques importants pour les ressources en eau, notamment pendant les périodes de crue. C’est pour cela que nous avons porté une attention particulière dans cette étude à ces événements au cours desquels une grande quantité de contaminants sont transportés par les cours d’eau. Quatorze molécules de pesticides (herbicides et fongicides) largement utilisées sur ces bassins versants ont été étudiées grâce à un échantillonnage intensif, notamment en périodes de crue, durant deux années hydrologiques (2007/2008 et 2008/2009). La majorité des molécules étudiées présentent des concentrations qui dépassent les limites autorisées par l’Union Européenne pour l’eau potable (0.1 μg.L-1 pour chaque molécule et 0.5 μg.L-1 pour l’ensemble des molécules), notamment en périodes de crue. L’analyse des hystérésis mises en évidence sur les relations entre les concentrations (pesticides, MES, COD, POC) et les débits du cours d’eau permet de mieux comprendre les mécanismes de transfert des pesticides et de leurs paramètres de contrôle. Ces hystérésis montrent pour un même débit des concentrations différentes en montée et en descente de crue ; elles peuvent être dextres (sens des aiguilles d’une montre) ou senestres (sens inverse) suivant l’origine des molécules et l’écoulement responsable de leur transfert des sols vers les eaux. C’est pourquoi nous avons procédé dans cette étude à une séparation des différentes composantes (ruissellement superficiel, écoulement hypodermique, écoulement de nappe) de l’écoulement fluvial pour mieux comprendre la dynamique de transferts des pesticides et de leurs paramètres de contrôle. On peut ainsi mettre en évidence des relations positives entre MES, COD, COP ou certaines molécules de pesticides et les débits des écoulements de surface (ruissellement superficiel ou écoulement hypodermique suivant les caractéristiques physico-chimiques des molécules). Les calculs de flux des différents pesticides exportés par les cours d’eau montrent que 60 à 90% (suivant les molécules) des transports annuels se font durant les épisodes de crue. Les flux spécifiques (masse exportée par unité de surface) calculés sont plus importants sur le bassin versant de la Save que sur celui du Montoussé et les relations flux spécifiques-débits mettent en évidence des concentrations plus élévées sur la Save où l’utilisation des pesticides est globalement plus importante que sur le Montoussé où les pratiques sont raisonnées. L’analyse des pesticides dans l’eau filtrée et non filtrée nous a permis d’estimer la distribution de chaque molécule entre les phases particulaires et dissoutes (Kd). De plus, les valeurs de flux calculés pour chaque crue nous ont permis d’estimer un Kd moyen pour chaque molécule. Ces valeurs de Kd présentent une très bonne relation avec les valeurs de Kow (coefficient de partage octanol-eau) extraites de la littérature. De même, les pourcentages calculés de chaque pesticide exporté sous forme particulaire sont aussi très bien corrélés au Kow de chaque moléculeThe mechanisms of pesticides transport to stream flow were studied in two agricultural nested catchments of different size in Gascogne region (South West of France): the Save river basin at Larra (1110 km2) and the Montoussé experimental watershed at Auradé (3.28 km2). The intensive agricultural practices used in this region lead to an important risk for water resources by pesticides, especially during storm events. This is why we have paid special attention on storm events when a large quantity of contaminant was transported during hydrological periods. Fourteen molecules of pesticides (herbicides and fungicides) were investigated during the study period. Both of these groups are widely used for agricultural purposed in these catchments. The results achieved over the two years monitoring (2007-2009) enable us to emphasize the principal processes, implied in pesticide transfer on these agricultural catchments. The majority of compounds are detected during storm runoff events. And, the average concentrations of some pesticides are exceeded at the authorization limit of the European Union for pesticide concentrations in drinking water (0.1 µg.L-1 for individual pesticides and 0.5 µg.L-1 for total pesticides). To better understand the mechanisms of pesticide transport hysteresis, patterns on the concentration-discharge relationship (result of different concentration of pesticides in rising and falling limb of storm) were studied. However, clockwise or anticlockwise hysteresis patterns could be observed for some molecules of pesticide and their controlling factors such as dissolved organic carbon (DOC), particulate organic carbon (POC) and total suspended matters (TSM) according to their transfer dynamic in the catchment. We proceeded with hydrograph separation of the main stormflow components (surface runoff, subsurface flow and groundwater) so that the main pesticide routing could be traced for its soil-river transfers. We also came to the conclusion that there is a positive relationship between riverine TSM, DOC and pesticide, concentrations and the discharges of surface or subsurface runoffs according to pesticide properties. Pesticide flux calculation shows between 60 to 90% of the molecule transport takes place during storm periods. Specific flux calculation also demonstrated the higher flux value in Save catchment than in Aurade with higher pesticide concentration for a given specific discharge. The latter result may be due to the more consumption of pesticide in Save catchment. The analyses of pesticides both in filtered and unfiltered water enabled us to estimate the distribution of pesticides into particulate and dissolved phases. Moreover, the pesticide flux values allow calculating average partition coefficients kd between dissolved and particulate fractions which present good relationship with Kow values (octanol-water) extracted from literature. The percentage of each pesticide transported as particulate forms is also well correlated to Kow
5
Johansson, Emilia. « Factors controlling the sorption of Cs, Ni and U in soil : A statistical analysis with experimental sorption data of caesium, nickel and uranium in soils from the Laxemar area ». Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-281938.
Texte intégralRésumé :
In the fall of 2006, soils from three small valleys in the Laxemar/Oskarshamn area were sampled. A total of eight composite samples were characterized for a number of soil parameters that are important for geochemical sorption and were later also used in batch sorption experiments. Solid/liquid partition coefficients (Kd values) were then determined for seven radionuclides in each of the eight samples. To contribute to the interpretation of the sorption results together with the soil characterizations, this study aims to describe the sorption behavior of the radionuclides caesium, nickel and uranium and also discern which parameters that could provide a basis for estimating the strength of sorption of radionuclides in general. The methodology included quantitative methodologies such as compilation of chemical equilibrium diagrams by the software Hydra/Medusa and correlation analyses using the statistical software SPSS statistics. Based on the speciation diagrams of each radionuclide and identified important linear and non-linear relationships of the Kd values with a number of soil parameters, the following soil- and soil solution properties were found to have controlled the sorption of Cs, Ni and U, respectively, in the Laxemar soils. Cs: the specific surface area of the soil coupled to the clay content. Ni: the cation exchange capacity, alkaline solution pH, soil organic matter and dissolved organic matter. U: the cation exchange capacity, soil organic matter, dissolved organic matter, dissolved carbonate and alkaline solution pH. The soil that showed the strongest sorption varied between the nuclides, which can be related to the individual sorption behavior of caesium, nickel and uranium, as well as the different physicochemical properties of the soils. The parameters that should be prioritized in characterizations of soil samples are identified to be: solution pH, the cation exchange capacity, the specific surface area of the soil, soil organic matter and soil texture (clay content).För att kunna fatta beslut relaterade till hypotetisk framtida kontaminering från slutförvar av radioaktivt avfall är det direkt avgörande att förstå mobiliteten av radioaktiva element i miljön. Sorption är en av de viktigaste kemiska mekanismerna som kan minska spridningen av radionuklider i vatten/jord/bergssystem, där nukliderna fördelar sig mellan vätskefasen och ytor på fasta partiklar i dessa system. Fördelningskoefficienter (Kd värden) används generellt som ett kvantitativt mått på sorptionen, där ett högt Kd värde innebär att en större andel av ämnet i fråga är bundet till den fasta fasen. Under hösten 2006 togs jordprover från tre dalgångar i Laxemar/Oskarshamn. Totalt åtta jordprover karakteriserades för ett antal jordparametrar som är viktiga för geokemisk sorption och användes senare i batchförsök tillsammans med ett naturligt grundvatten. Fördelningskoefficienter (Kd värden) bestämdes för sju radionuklider (Cs, Eu, I, Ni, Np, Sr and U) för vart och ett av de åtta jordproverna. För att bidra till tolkningen av sorptionsresultaten tillsammans med jordprovernas egenskaper syftar denna studie till att beskriva sorptionsbeteendet hos radionukliderna caesium, nickel och uran samt urskilja vilka parametrar som kan fungera som grund för att uppskatta sorptionsstyrkan av radionuklider i allmänhet. För att uppnå detta syfte så har studien följande mål. Identifiera de jord- och marklösningsegenskaper som kontrollerar sorptionen av Cs, Ni respektive U i de åtta Laxemar proverna. Bestämma vilket Laxemar-jordprov som starkast sorberar de tre radionukliderna. Identifiera de jordparametrar som bör prioriteras vid jordkarakteriseringar, baserat på deras sorptionsinflytande, för att kunna uppskatta Kd värden endast med begränsad information om ett jordsystem. Metoden innefattade kvantitativa metoder såsom sammanställning av kemiska jämviktsdiagram med programvaran Hydra/Medusa och korrelationsanalyser med hjälp av statistikprogramvaran SPSS statistics. De kemiska jämviktsdiagrammen bidrog till att beskriva specieringen av respektive nuklid som en funktion av pH och korrelationsanalyserna bidrog till att identifiera linjära samband mellan par av variabler, tex mellan Kd och jordparametrar. Baserat på specieringsdiagrammen för varje radionuklid och identifierade viktiga linjära och icke-linjära förhållanden mellan Kd-värdena och ett antal jordparametrar har följande egenskaper hos jordarna och marklösningen visat sig huvudsakligen kontrollera sorptionen av Cs, Ni respektive U i de åtta Laxemar jordarna: För caesium gäller jordens specifika ytarea kopplad till lerinnehållet, medan för nickel är det katjonbytarkapaciteten, organiskt material, alkaliska pH-värden samt löst organiskt material. Sorptionen av uran befanns kontrolleras av katjonbytarkapaciteten, organiskt material, löst organiskt material, alkaliska pH-värden samt lösta karbonater. Den jord som visade starkast sorption varierar mellan de tre nukliderna, vilket kan relateras till nuklidernas individuella sorptionsbeteende i jord samt jordarnas olika fysikaliska och kemiska egenskaper. Parametrarna som bör prioriteras vid karaktärisering av jordprov identifierades vara: pH, katjonbytarkapaciteten, jordens specifika ytarea, mängden organiskt material samt jordtexturen (lerinnehåll).
6
Nobile, Cécile. « Phytodisponibilité du phosphore dans les sols agricoles de La Réunion fertilisés sur le long-terme avec des résidus organiques : la dose d’apport est-elle le seul déterminant à prendre en compte ? » Thesis, La Réunion, 2017. http://www.theses.fr/2017LARE0059/document.
Texte intégralRésumé :
Le recyclage des résidus organiques (RO) en agriculture pourrait permettre de limiter l’utilisation des ressources minérales de phosphore (P), à condition de déterminer leur efficacité pour fournir du P aux cultures. L’objectif de ce travail était donc d’étudier les mécanismes déterminant l’effet des RO apportés au sol sur la biodisponibilité du P pour la plante (phytodisponibilité). Ce travail a été basé sur cinq essais de terrain à La Réunion, fertilisés sur une décennie avec des fertilisants organiques ou minéraux, et sur des expérimentations d’incubations en conditions contrôlées et de cultures de plantes en pot. Le P inorganique (Pi) et organique (Po) disponible du sol a été déterminé par des extractions (eau, Olsen), la technique des diffusive gradients in thin films (DGT) et la dilution isotopique associée à des membranes échangeuses d’ions. La capacité de sorption en Pi des sols a été évaluée avec des courbes de sorption. Le P phytodisponible a été déterminé en mesurant le P prélevé par la plante. Dans les différents types de sol (andosol, andique cambisol, nitisol et arenosol), l’apport de RO a augmenté le Pi disponible relativement au Po, suggérant que la minéralisation du Po issu des RO n’est pas un facteur limitant la disponibilité du Pi. Les RO ont augmenté le Pi disponible principalement par l’augmentation du pH du sol et par conséquent la diminution de sa capacité de sorption de Pi. Le P phytodisponible a augmenté avec le Pi disponible du sol, mais a diminué avec l’augmentation du pH du sol. Au-delà de la dose de P, l’effet de l’apport de RO à long-terme sur la phytodisponibilité du P semble principalement contrôlé par l’évolution induite du pH du solApplication of organic residues (OR) on agricultural soils could reduce the use of mineral phosphorus (P) fertilizers, but this implies to determine the efficiency of OR to meet crop requirements. We thus aimed to study mechanisms determining the effects of OR on P bioavailability to plants (phytoavailability). Our work was based on five field trials with decadal organic or mineral fertilization located in Réunion island, and on incubations and plant growth experiments under controlled conditions. Available inorganic P (Pi) and organic P (Po) was determined using extractions (water, Olsen), the diffusive gradients in thin films technique (DGT) and the isotopic dilution associated to anion exchange membranes (EAEM). Phytoavailable P was determined as the plant P uptake. Soil Pi sorption capacity was determined using sorption curves. For all soil types studied (andosol, andic cambisol, nitisol, and arenosol), RO increased mainly available Pi and had few effects on available Po, which suggests that mineralization of Po applied with RO does not limit Pi availability. Application of RO increased available Pi mainly by increasing soil pH and consequently by decreasing soil Pi sorption capacity. Phytoavailable P increased with soil available Pi, but decreased with increasing soil pH. Our work suggests that except the dose of P applied, effect of RO on P phytoavailability depends mainly on soil pH changes induced
7
Joubert, Antoine. « Etude de l'effet de facteurs environnementaux sur les processus biogéochimiques de mobilisation du Pb, Zn, Cd, As et Hg dans les sols - Modélisation empirique de la mobilité et phytodisponibilité des ETM ». Phd thesis, Université Henri Poincaré - Nancy I, 2008. http://tel.archives-ouvertes.fr/tel-00289902.
Texte intégralRésumé :
La pollution des sols par les Eléments Traces Métalliques est un problème majeur car, contrairement aux autres milieux, le sol possède une plus faible capacité à s'épurer. Les différents modèles empiriques exprimant la solubilité et le coefficient de distribution Kd de ces polluants inorganiques dans les sols ne tiennent pas compte de l'influence des facteurs environnementaux. Le travail de thèse a consisté à étudier l'effet de facteurs environnementaux, dits « sensibles au changement global », sur la mobilité de Cd, Pb, Zn, As et Hg dans les sols, à l'aide d'un plan factoriel fractionnaire 2^(4-1). Onze échantillons de sol représentatifs de 3 sites d'études industriels et agricoles des bassins de la Meuse et de l'Ebre ont été étudiés dans le cadre du projet européen AQUATERRA. Le comportement de As n'est pas significativement corrélé à la nature intrinsèque des échantillons de sol mais à l'augmentation de la température et à une condition anoxique. Ces facteurs stimulent les activités microbiennes de solubilisation de As tels que réduction dissolutive microbienne des oxyhydroxydes de Fe et la réduction de As(V). La forte implication de l'activité microbienne permet de modéliser la mobilité de As en fonction des facteurs environnementaux, pour l'ensemble des 11 échantillons de sol. A l'inverse, le comportement de Cd, Pb et particulièrement Zn, est très significativement corrélé à la nature des échantillons de sol et notamment le pH du sol. Enfin, la phytodisponibilité de Cd, Pb, Zn et As a été estimée, à l'aide d'un système à compartiment, et modélisée de manière empirique, afin de permettre une meilleure compréhension des phénomènes de transfert sol-plante.
8
Doherty, David. « Determination of tributyltin environmental contamination and Kd partition coefficients in sediments using a HPLC analytical method ». Thesis, University of Strathclyde, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.502361.
Texte intégralRésumé :
Tributyltin (TBT) was used as an anti-fouling paint and applied to the hulls of ships in order to prevent buildup of organisms. Major shipping routes are now contaminated with TBT due to the chemical's persistence In the environment. The use of TBT as an anti-fouling paint was banned in the 1980's due to scientific findings that the chemical causes toxic effects in aquatic life. TBT is widely known as a gender-bending chemical due to its endocrine disrupting properties. There are concerns that TBT may also present health problems for humans, and is classed as a Persistent Organic Pollutant (POP). The disposal of sediments contaminated with TBT presents a problem, as disposal to sea will cause unacceptable pollution of the environment. An Integrated pollution control strategy is needed for disposing of dredged sediments in a manner which is cost-effective and sustainable.
Livres sur le sujet "Kd coefficient"
1
United States. Environmental Protection Agency. Office of Radiation and Indoor Air, United States. Dept. of Energy. Office of Environmental Restoration et United States. Environmental Protection Agency. Office of Air and Radiation, dir. Understanding variation in partition coefficient, Kd, values : A cooperative effort. [Washington, D.C.?] : U.S. Environmental Protection Agency, Office of Air and Radiation, 1999.
Trouver le texte intégral
2
"Tennen Baria Kd" Senmon Kenkyūkai (1999 Kyōto Daigaku Genshiro Jikkenjo). "Tennen Baria Kd" Senmon Kenkyūkai hōkokusho : Kaisaibi 1999-nen 11-gatsu 24--25-nichi. Ōsaka-fu Sennan-gun Kumatori-chō : Kyōto Daigaku Genshiro Jikkejo, 2000.
Trouver le texte intégral
3
United States. Environmental Protection Agency. Office of Air Quality Planning and Standards, dir. Understanding Variation In Partition Coefficient, KD, Values... Volume II : Review Of Geochemistry And Available KD Values For Cadmium Chromium..., U.S. Environmental Protection Agency... Aug. 1998. [S.l : s.n., 1999.
Trouver le texte intégral
4
Using Thermodynamic Sorption Models for Guiding Radioelement Distribution Coefficient (Kd) Investigations. OECD, 2001. http://dx.doi.org/10.1787/9789264192935-en.
Texte intégral
5
Nea. Using Thermodynamic Sorption Models for Guiding Radioelement Distribution Coefficient (Kd) Investigations : A Status Report (Radioactive Waste Management). Organization for Economic, 2001.
Trouver le texte intégralChapitres de livres sur le sujet "Kd coefficient"
1
Sharma, S. « Graphitic Carbon Nitride based Photocatalytic Systems for High Performance Hydrogen Production : A Review ». Dans Materials Research Foundations, 161–92. Materials Research Forum LLC, 2021. http://dx.doi.org/10.21741/9781644901359-5.
Texte intégralRésumé :
Pectin cerium(IV) iodate (PcCeI) and cerium(IV) iodate (CeI) cation ion exchange materials were synthesized via sol–gel methods. The materials were characterized by using Fourier transform infrared spectroscopy, X-ray diffractometer, thermogravimetric analysis, and scanning electron microscopy. The ion exchange capacity (IEC), thermal stability, distribution coefficient (Kd), and pH titrations were investigated to recognize the cation exchange behavior of the materials. The IEC of pectin-cerium(IV) iodate (PcCeI and cerium(IV) iodate CeI were reported as 1.80 meq/g and 0.92 meq/g, respectively. The higher distribution coefficient values of 250.01 and 219.14 mg/L confirmed the selectivity of pectin-cerium(IV) iodate hybrid ion exchanger for As3+ and Zn2+. The antibacterial activity of synthesized ion exchangers was explored for E. coli bacteria and observed relatively higher for PcCeI as compared to CeI.
2
Carder, Kendall L., et David K. Costello. « Optical Effects of Large Particles ». Dans Ocean Optics. Oxford University Press, 1994. http://dx.doi.org/10.1093/oso/9780195068436.003.0017.
Texte intégralRésumé :
Two important problems facing the ocean optics research community in the coming decade concern optical model closure and inversion (see Chapter 3). We obtain model closure if we can describe the measured light environment by combining elementary measurements of the optical properties of the medium with radiative transfer theory. If we can accurately deduce the concentration of various constituents from a combination of measures of the submarine light field and inverse model calculations, we term this process model inversion. The most elementary measurements of the optical properties of the sea are those that are independent of the geometry of the light field, the inherent optical properties (Preisendorfer, 1961). Optical properties that are dependent on the geometry of the light field are termed apparent optical properties (AOP). Models of the submarine light field typically relate apparent optical properties to inherent optical properties (see Chapter 2). Examples include the relationship between the AOP irradiance reflectance R and a combination of inherent optical properties (backscattering coefficient bb and absorption coefficient a), and the relationship between the AOP downwelling diffuse attenuation coefficient kd and a combination of the absorption coefficient, backscattering coefficient, and downwelling average cosine μd (e.g., Gordon et al., 1975; Morel and Prieur, 1977; Smith and Baker, 1981; Morel, 1988; Kirk, 1984a). Under some circumstances these relationships work well enough that the absorption coefficient can be derived indirectly. This is important since measurement of the absorption coefficient by direct means has been difficult. Derived values for the absorption coefficient by model inversion methods are not easily verified by independent measurements, however, because of the difficulty of measuring the absorption coefficient. Model closure and model inversion both become more tenuous when the following phenomena are present: 1. Transpectral or inelastic scattering such as fluorescence (e.g., Gordon, 1979; Carder and Steward, 1985; Mitchell and Kiefer, 1988a; Spitzer and Dirks, 1985; Hawes and Carder, 1990) or water Raman scattering (Marshall and Smith, 1990; Stavn, 1990; Stavn and Weidemann, 1988a,b; Peacock et al, 1990; Chapter 12 this volume). 2. Particles that are large relative to the measurement volume for inherent optical property meters such as beam transmissometers, light-scattering photometers, fluorometers, and absorption meters.
3
Sposito, Garrison. « Mineral Weathering ». Dans The Chemistry of Soils. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780190630881.003.0009.
Texte intégralRésumé :
Mineral weathering begins with mineral dissolution, typically as induced by protons or by ligands that form strong complexes with metals (Section 1.4). Proton-induced dissolution begins with H+ adsorption, exemplified in Eq. 3.2 for a metal oxyhydroxide mineral. In the absence of ligands that could replace the positively charged water molecule resulting from this rapid reaction, proton adsorption is followed by slow detachment of the metal, which then equilibrates as a soluble species in the soil solution, as illustrated in Fig. 5.1 (pathway 1) for gibbsite [Al(OH)3; see Fig. 2.7] at a pH value low enough that the detached Al3+ does not hydrolyze. Ligand-induced dissolution is also illustrated in Fig. 5.1 (pathway 2). The ligand is a fluoride anion, which forms a strong complex with Al3+ (see problem 3 in Chapter 4). Adsorption in this case occurs by ligand exchange, which is illustrated for carboxylate in Eq. 3.3. A similar reaction occurs for F-:...Slow detachment of the AlF2+ complex then follows. Whenever a mineral dissolution reaction induced by either of these two-step mechanisms is far from equilibrium, it is not influenced by the very low concentration of the constituent released from the dissolving mineral and its rate can be described by zero-order kinetics (Table 4.2). Accordingly, if [A] is the concentration of a constituent released, then the rate law can be expressed as...where kd is a rate coefficient independent of [A] , but a function of temperature, pressure, pH, the chemical properties of the mineral, and, if appropriate, the concentration of the ligand inducing dissolution via the second mechanism in Fig. 5.1. The mineral dissolution rate on the left side of Eq. 5.2 can be mass-normalized to express it in moles per mole of mineral per second by dividing the molar concentration [A] with the solids concentration of the mineral expressed in units of moles per liter. This mass-normalized rate does not depend on the amount of mineral dissolving. For proton-induced dissolution, the rate is then a function of temperature, pressure, pH, and the chemical nature of the mineral.
4
« Appendix B 1. Determination of Kinetic Coefficients KS, μmax, Yobs and Kd from Laboratory Data. » Dans Studies in Environmental Science, 395–98. Elsevier, 1993. http://dx.doi.org/10.1016/s0166-1116(08)70534-x.
Texte intégral
5
Bethke, Craig M. « Surface Complexation ». Dans Geochemical Reaction Modeling. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195094756.003.0012.
Texte intégralRésumé :
An important consideration in constructing certain types of geochemical models, especially those applied to environmental problems, is to account for the sorption of ions from solution onto mineral surfaces. Metal oxides and aluminosilicate minerals, as well as other phases, can sorb electrolytes strongly because of their high reactivities and large surface areas (e.g., Davis and Kent, 1990). When a fluid comes in contact with minerals such as iron or aluminum oxides and zeolites, sorption may significantly diminish the mobility of dissolved components in solution, especially those present in minor amounts. Sorption, for example, may retard the spread of radionuclides near a radioactive waste repository or the migration of contaminants away from a polluting landfill. In acid mine drainages, ferric oxide sorbs heavy metals from surface water, helping limit their downstream movement (see Chapter 23). A geochemical model useful in investigating such cases must provide an accurate assessment of the effects of surface reactions. Many of the sorption theories now in use are too simplistic to be incorporated into a geochemical model intended for general use. To be useful in modeling electrolyte sorption, a theory must account for the electrical charge on the mineral surface and provide for mass balance on the sorbing sites. In addition, an internally consistent and sufficiently broad database of sorption reactions must accompany the theory. The Freundlich and Langmuir theories, which use distribution coefficients Kd to set the ratios of sorbed to dissolved ions, are applied widely in groundwater studies (Domenico and Schwartz, 1990) and used with considerable success to describe sorption of uncharged organic molecules (Adamson, 1976). The models, however, do not account for the electrical state of the surface, which varies sharply with pH, ionic strength, and solution composition. Freundlich theory prescribes no concept of mass balance, so that a surface might be predicted to sorb from solution without limit. Both theories require that distribution coefficients be determined experimentally for individual fluid and rock compositions, and hence both theories lack generality. Ion exchange theory (Stumm and Morgan, 1981; Sposito, 1989) suffers from similar limitations. Surface complexation models, on the other hand, account explicitly for the electrical state of the sorbing surface (e.g., Adamson, 1976; Stumm, 1992).
Actes de conférences sur le sujet "Kd coefficient"
1
Jamet, Cedric, Hubert Loisel et David Dessailly. « Estimation of the diffuse attenuation coefficient Kd(lambda) with a neural network inversion ». Dans IGARSS 2011 - 2011 IEEE International Geoscience and Remote Sensing Symposium. IEEE, 2011. http://dx.doi.org/10.1109/igarss.2011.6048911.
Texte intégral
2
Novikov, V. N., S. A. Belkov, S. A. Buiko, I. N. Voronich, D. G. Efimov, A. I. Zaretsky, G. G. Kochemasov et al. « Gain measurements of transverse stimulated Raman scattering in KDP, KD*P ». Dans The European Conference on Lasers and Electro-Optics. Washington, D.C. : Optica Publishing Group, 1998. http://dx.doi.org/10.1364/cleo_europe.1998.cwf42.
Texte intégralRésumé :
The gain measurement method of radiation at Stimulated Raman Scattering (SRS) excitation in medium placed into transverse pump cavity /1/ has been developed and tested. On the third harmonic of iodine laser ISKRA-4 (λ=438 nm) values of gain coefficient (g) for transverse SRS (TSRS) radiation have been measured in benzene and in the frequency converter crystals (KDP, KD*P) grown following the traditional and rapid-growth technology, cut out by Type-II (9=60°). At the g measurement in crystals pumping wave was ordinary, the pumping and scattered wave vectors and the crystal optical axis were coplanar.
3
Schmeltz, M., J. M. Froidefond, F. Jourdain et N. Martiny. « IOP from reflectance measurements to obtain the Kd coefficient : application to the Gabon and Congo coastal waters ». Dans SPIE Optical Engineering + Applications, sous la direction de Robert J. Frouin. SPIE, 2009. http://dx.doi.org/10.1117/12.828851.
Texte intégral
4
Jamet, Cédric, Hubert Loisel et David Dessailly. « Empirical nonlinear determination of the diffuse attenuation coefficient Kd(490) in coastal waters from ocean color images ». Dans SPIE Asia-Pacific Remote Sensing, sous la direction de Robert J. Frouin, Hong Rhyong Yoo, Joong-Sun Won et Aiping Feng. SPIE, 2010. http://dx.doi.org/10.1117/12.869730.
Texte intégral
5
Wu, Tao, Amayri Samer, Jakob Drebert, Luc R. Van Loon et Tobias Reich. « Determination of Diffusion Parameters by a Computer Code (FDP) Based on Mathematica 6.0 ». Dans 18th International Conference on Nuclear Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/icone18-29334.
Texte intégralRésumé :
A computer code named Fitting for Diffusion Parameters (FDP) based on Mathematica 6.0 has been developed for modeling through- and out-diffusion experiments. FDP was used to determine the diffusion coefficients (De) and the rock capacity factors (α) for tritiated water (HTO) and 22Na+ and the distribution coefficient (Kd) of 22Na+ in Opalinus Clay (OPA). The values for De and α were obtained by fitting the results of experimental data of both transient and steady-state phases to the analytical solution of accumulated activity. The quality of the parameters De and α was tested by using them as input parameters in the equation of flux. Moreover, the diffusion parameters of HTO and 22Na+ were determined also by out-diffusion experiments. Under ambient condition at pH 7.6, the De value of (1.5 ± 0.1) × 10−11 m2/s for HTO is lower than that of (1.9 ± 1.1) × 10−11 m2/s for 22Na+, which could be explained by the electrostatic attraction between the negative surface charge of OPA and the sodium cations. For the non-sorbing species HTO, α was 0.15 ± 0.01. For the weakly sorbing species 22Na+, α was 0.50 ± 0.02 and Kd equaled (1.5 ± 0.3) × 10−4 m3/kg. The obtained diffusion parameters for HTO and 22Na+ in OPA are in good agreement with previous results by Van Loon et al. [1, 2]. FDP developed in this study has been used successfully to determine the parameters De and α for the diffusion of 237Np(V) in OPA [3].
6
Sepehri, Ali, Stuart Harbert et Dave Holberry. « A Study on the Influence of Sea Water Convective Heat Transfer Coefficient in Design Verification of Subsea HPHT Equipment ». Dans ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65594.
Texte intégralRésumé :
As HPHT activity continues to grow and well conditions become more severe, more advanced analysis methods are required. Thermal/heat transfer and structural Finite Element Analyses (FEA) play a fundamental role in the design of subsea equipment for HPHT application. The objective of this study is to evaluate the effect of seawater convective heat transfer coefficient on design verification of a subsea drilling connector in the HPHT environment (bore pressure more than 15,000 psi, and/or bore temperature more than 300°F). The design verification work contains the elastic-plastic assessments including protection against plastic collapse (global), local failure, hydrotest and ratcheting criteria. The fatigue study is also performed per ASME Boiler & Pressure Vessel Code, Section VIII, Div. 3, Article KD-4 in compliance with API 17TR8. The effect of seawater convective heat transfer coefficient on the global, ratcheting and fatigue criteria is studied/presented. Results show that the higher value of heat transfer coefficient (convection) results in more thermal gradients through assembly causing higher stress and plastic strain deformation in the connector components and lower fatigue life.
7
Mimura, Hitoshi, Minoru Matsukura, Tomoya Kitagawa, Fumio Kurosaki, Akira Kirishima, Daisuke Akiyama et Nobuaki Sato. « Evaluation of Adsorption Properties of U(VI) for Various Inorganic Adsorbents ». Dans 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-81338.
Texte intégralRésumé :
Large amounts of highly contaminated water over 800,000 m3 accumulated in the reactor, turbine building and the trench in the facility were generated from the nuclear accident of Fukushima NPS (BWR) caused by the Great East Japan Earthquake. At present, the cold shutdown is completed stably by the circulating injection cooling system (SARRY, KURION) for the decontamination of radioactive nuclides such as 134Cs and 137Cs using zeolites and crystalline silicotitanate (CST). Further, the Advanced Liquid Processing System (ALPS) is under operation for the decontamination of 62 nuclides such as 90Sr, 129I and 60Co, etc. However, the adsorption behaviors of actinoids through the decontamination systems are complicated, and especially their adsorption properties for zeolites and CST, major inorganic adsorbents, are not yet clarified. In near future, the decontamination of actinoids leached from the crushed fuel debris will be an important subject. In this study, the practical adsorption properties of U(VI) for various inorganic adsorbents were evaluated under different solution conditions. The adsorption properties (distribution behaviors and adsorption kinetics) were evaluated by batch adsorption method; 19 kinds of inorganic adsorbents including zeolites and CST (crystalline silicotitanate) were contacted with U(VI)) solutions. The conditions of 5 kinds of U(VI) solutions were as follows; Solution 1: [U(VI)] = 50 ppm, initial pH = 0.5 ∼ 5.5 Solution 2: [U(VI)] = 50 ppm, [NaCl] = 0.1 M, initial pH = 4.0 Solution 3: [U(VI)] = 50 ppm, [CaCl2] = 0.1 M, initial pH = 4.0 Solution 4: [U(VI)] = 4.84 mM, [NaCl] = 0.1 M, initial pH = 3.18 Solution 5: [U(VI)] = 4.86 mM, 2,994 ppm boric acid/30% seawater, initial pH = 4.25 The uptake (%) and distribution coefficient (Kd. cm3/g) were estimated by counting the radioactivity using NaI(Tl) scintillation counter and liquid scintillation counter. In the simple Solution 1, the Kd values for zeolites increased linearly with equilibrium pH up to pH 7. The Kd value for tin hydroxide had a maximum profile around pH 7 and a relatively large Kd value above 104 cm3/g was obtained. In the presence of NaCl and CaCl2 (Solution 2 and 3), relatively large Kd values above 102 cm3/g were obtained, other than mordenite and clinoptilolite, and the effect of [Ca2+] on U(VI) uptake was larger than that of [Na+]. In Solution 4 containing high concentration of U(VI), the uptake(%) was considerably lowered, while that for zeolite A, X and Y was estimated over 20%. Similar tendency was observed in Solution 5, and, in the case of granulated potassium titanate, yellow precipitate was observed on the surface due to the increase of equilibrium pH up to 5.25. The adsorption behavior of U(VI) on inorganic adsorbents is mainly governed by three steps; ion exchange, surface precipitation of hydrolysis species and sedimentation depending on equilibrium pH, and hence it should be noted the change of U(VI) chemical species. These basic adsorption data are useful for the selection of inorganic adsorbents in the Fukushima NPS decontamination process.
8
Wang, X. D., P. Basseras, R. J. D. Miller et H. Vanherzeele. « KTP : a new electro-optic device for high-power, high-repetition-rate applications ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.mnn7.
Texte intégralRésumé :
In addition to having attractive nonlinear-optic characteristics, KTP has promising electro-optic and dielectric properties that make it useful for various electro-optical applications, such as modulators and Q switches.1 We report an experimental study of a 4 × 8 × 4 mm hydrothermally grown KTP Pockels cell that uses the effective electro-optic coefficient rcl = r33 − (ni.n3)3r13 = 28 pm/v. Compensation of the static birefringence of KTP, when it is used as an amplitude modulator has been realized. Our investigations revealed that, unlike other electro-optic materials, KTP Pockels cells do not suffer from piezoelectrically induced parasitics (acoustic ringing). Because of this, we have been able to demonstrate stable high-repetition rate pulse slicing. The dynamic half-wave voltage is close to the static one (2.9 kV) and it is significantly lower than that of the commonly used LiNbO3 Pockels cell. An additional advantage of KTP over other Pockels-cell materials, such as KD*P and LiNbO3, is its high damage threshold. Therefore, KTP is an ideal material for intracavity electro-optic applications, in particular for high-peak power regenerative amplifiers operating at high-repetition rate.2 We have successfully studied this mode of operation, and our results will be discussed.
9
Kim, Young-Taek, et Jong-In Lee. « Experiments on Stability of Concrete Armor Units at Convex Corner Trunk ». Dans ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61429.
Texte intégralRésumé :
The breakwater is one of the most important structures in coastal areas and the rubble mound breakwaters have been most widely designed and constructed. When designing the rubble mound structures, the determination of the stable weight of concrete armor units is the most significant and critical problems. The stable weight of concrete armor units could be calculated by Hudson or van der Meer formula. The breakwater is assumed to be straight and the waves are propagating normally to the structures when using this formula. The weight of concrete armor units at the round breakwater head should be protected by 1.3∼1.6 times of that at the trunk part because the coastal engineers think it to be vulnerable. Recently the damage of concrete armor units at the convex corner of breakwater trunk was reported several times in Korea. However, there were no any design standards for this area. In this study, three-dimensional hydraulic model tests were performed to investigate the stable weight of concrete armor unit at convex corner area. The tetrapod was used to the target concrete armor unit in the study. The stable weight is suggested by stability coefficient, Kd by using Hudson formula. From this study, the stable armor weight at the convex corner is similar with that at the round breakwater head and this means that about 1.4 times of weight for trunk area was needed at convex corner area.
10
Gewirtz, A., C. L. shepiro, R. Bovd et R. W. Colman. « REGULATION OF FACTOR V (FV) EXPRESSION IN HUMAN MEGAKARYOCYTES ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643280.
Texte intégralRésumé :
We have suggested that synthesis of FY by human megakaryocytes (MEGS), is a maturation relrted event. This is based on our finding that when MEGS are cloned from progenitor cells in vitro in FY depleted medium, FY is immunochemically detectable only in morphologically recognizable (mature) cells (Blood 67:1639, '86). The stimuli which induce FY synthesis in MEGS are unknown, but if they are related or linked to factors which regulate terminal maturation processes cellular FY levels might increase as the maturation routine proceeds. To test this hypothesis, mature human MEGS were isolated from normal bone marrow by counterflow centrifugel elutrietion, deposited onto gloss slides by cytocentri-fugation, and then fixed in methanol:acetone. Individual cells were then staged, geometric meon cell diometer (size) determined with on opticol fylor, end FY end DNA levels measured. FV expression in a large area of the MEG (38 urn in diameter) was semi-quantitated by microspectrophotometry (MSPEC) using a sensitive Texas Red labeled streptavidin-biotin detection system and a monoclonal antibody probe (B10) directed against the non-binding FY activation peptide (150,000 kd). Cells were then reacted with Chromomycin A3 to allow for simultaneous DNA quantitation by MSPEC in the same cell. Correlation coefficients (r) and coefficient of determination [r2] were computer generated to discern potential relationships between FY expression, and MEG maturation stage, size or ploidy level in a total of 532 MEGS. Characteristics of the population, and r/r2 vs. MEG FV content ere shown below:r/r2 values did not significantly change when total MEG FY content was measured in 100 additional MEGS. Therefore, MEG FY levels varied independently with cell size and ploidy, and did not appear to correlate with degree of mature MEG maturation as determined by standard critera. In two of four preliminary experiments, low dose (8nM ql2h × 4 doses) tetradecanoyl phorbol acetate augmented both the number of MEGS expressing FV, and the level of FY expressed per individual cell. We conclude from these data that once FV synthesis is initiated, FY synthesis and events relating to final cell size and ploidy development are regulated independently. Our data also suggest that MEG FV synthesis may be regulated in part by the phosphoinositide-protein kinase C system.
Rapports d'organisations sur le sujet "Kd coefficient"
1
Serkiz, S. M. Recommended Partition Coefficient (Kd) Values for Nuclide Partitioning in the Presence of Cellulose Degradation Products. Office of Scientific and Technical Information (OSTI), février 2001. http://dx.doi.org/10.2172/775082.
Texte intégral
2
Sullivan, T. Recommended values for the distribution coefficient (Kd) to be used in dose assessments for decommissioning the Zion Nuclear Power Plant. Office of Scientific and Technical Information (OSTI), juin 2014. http://dx.doi.org/10.2172/1143601.
Texte intégral
3
Sullivan, T. Recommended values for the distribution coefficient (Kd) to be used in dose assessments for decommissioning the Zion Nuclear Power Plant. Office of Scientific and Technical Information (OSTI), septembre 2014. http://dx.doi.org/10.2172/1178623.
Texte intégral
4
Wibowo, Johannes, et Jamie López-Soto. Field Jet Erosion Tests on Benbrook Dam, Texas. Engineer Research and Development Center (U.S.), décembre 2021. http://dx.doi.org/10.21079/11681/42545.
Texte intégralRésumé :
This report summarizes the results of eight field Jet Erosion Tests (JETs) performed on Benbrook Dam, TX. The results from these tests will be used by the U.S. Army Corps of Engineers, Fort Worth District, in assessments of the erosion resistance of the Benbrook Dam with regards to possible overtopping by extreme flooding. The JETs were performed at four different locations, i.e., two locations at the lowest crest elevation and two locations at the mid-slope face of the downstream embankment. Variations in estimated critical hydraulic shear stress and erosion rate values may have been caused by differences in soil composition, i.e., when the material changed from silt/sand to clay. The resulting values of the Erodibility Coefficient, Kd, and Critical Stress, τc, are very useful information in assessing the stability of Benbrook Dam during an overtopping event. Because of the observed natural variability of the materials, combining the erosion parameters presented in this report with the drilling logs and local geology will be imperative for assessing erosion-related failure modes of Benbrook Dam.
5
Kaplan, D. I. Distribution Coefficients (Kd Values) for Waste Resins Generated from the K and L Disassembly Basin Facilities. Office of Scientific and Technical Information (OSTI), décembre 2002. http://dx.doi.org/10.2172/805607.
Texte intégral
6
Kaplan, D. Recommended Distribution Coefficients, Kd Values, for Special Analysis Risk Calculations Related to Waste Disposal and Tank Closure on the Savannah River Site. Office of Scientific and Technical Information (OSTI), août 2005. http://dx.doi.org/10.2172/890185.
Texte intégral