Literatura académica sobre el tema "Microplastics quantification"

Microplastics (i.e., plastics particles < 5mm) are widespread emerging contaminants that have been detected in various aquatic environments worldwide including freshwater and marine ecosystems. Contamination of the environment with microplastics has become an environmental issue due to the potential of plastics to remain for thousands of years and to accumulate in the aquatic environment. The abundance of microplastics in the aquatic environment is assumed to increase due to continuous fragmentation of macro and microplastic debris, which can lead to a decrease in the average size ranges of microplastics over time (Cole et al., 2011). Moreover, concerns have been raised regarding the potential of microplastics to physically (e.g., blockage of digestive tract) and chemically (e.g., leaching of sorbed chemicals and toxic additives) harm aquatic organisms. Microplastics can enter the aquatic environment from both aquatic-based and landbased sources. Recently, wastewater treatment plants (WWTP) have been identified as one of the important land-based sources of microplastics. While microplastics have been reported in WWTP effluent in Asia, Europe, USA and Russia, little is known about the presence of microplastics in Australian WWTP effluent. More importantly, the lack of standardized techniques to sample and characterize microplastics in environmental samples, especially in complex samples such as wastewater, has led to inaccurate estimations of microplastic concentrations. In response to the current knowledge gaps, a novel validated high-volume sampling device was developed for in situ fractionation of microplastics from wastewater effluent as part of this project. The developed method was applied to three Australian WWTPs utilizing primary, secondary and tertiary treatments to provide a snapshot of the fate and removal of microplastics during various wastewater treatment processes. To achieve an accurate estimation of microplastics, the sampling technique was combined with an efficient sample processing method. Microplastic polymer type, shape and potential origin were further determined using microscopy analysis and Fourier Transform Infrared (FTIR) spectroscopy. The efficiency of the sampling device was found to be between 92 to 99% for 500 and 25 μm mesh screens. The results showed that the concentrations of microplastics were 1.5, 0.6 and 0.2 microplastics per liter of effluent in primary, secondary and tertiary effluent, respectively. It was also found that the majority of detected microplastics in the studied WWTPs were polyethylene terephthalate (PET) fibers, which is assumed to originate from synthetic clothing. Polyethylene (PE) beads and fragments, which may be associated with cosmetic products, were the second most frequently detected type of microplastic. Despite a thorough sample processing method, FTIR spectroscopy revealed that between 22 to 90% of the suspected microplastic particles were in fact non-plastic particles. This study suggests that WWTPs can act as a significant source of microplastics to the aquatic environment given the large volume of wastewater discharged to the aquatic environment. To date, the effects of microplastics on aquatic organisms have mostly been examined using high and often unrealistic concentrations of microplastics (e.g., milligram per liter range). Moreover, while the presence of different types of microplastics together in aquatic ecosystems has been widely reported, the potential effects of microplastics when they occur as mixtures are largely unknown. To cover these knowledge gaps, the potential adverse effects of wastewater-based microplastics (such as fibers and beads) at lower concentrations on the freshwater organism Ceriodaphnia dubia were evaluated. The acute (48 h) and chronic (192 h) effects of PET fibers and PE bead microplastics on C. dubia were assessed alone and as a binary mixture. The results showed a dose-dependent trend on survival, with C. dubia more sensitive to PET fibers than PE microplastics. The 48 h EC50 value of fibers was 1.5 mg/L compared to 2.2 mg/L for PE beads. The binary mixture of microplastic beads and fibers demonstrated less than additive effects. EC50 values for the chronic bioassay were 429 μg/L for fibers and 958 μg/L for PE microplastics. A positive trend of decreasing growth (body size of adults) and reproduction rate (number of neonates) with increasing microplastic concentration was observed for both PE and fiber microplastics during the chronic bioassays. Using scanning electron microscopy (SEM) we observed deformities, such as carapace and antenna deformation, in C. dubia exposed to fibers at a high concentration, but not at the lower (environmentally relevant) concentrations. Given the likelihood that microplastics will eventually sink to the bottom sediment in the aquatic ecosystem the effects of microplastics were investigated on a freshwater sediment-dwelling organism (Chironomus tepperi) at environmentally relevant concentrations of PE microplastics (500 particles/kgsediment). Possible size-dependent effects of microplastics were also examined using four different size ranges of PE beads including 1-4, 10-27, 43-54 and 100-126 μm. The results revealed that exposure to an environmentally relevant concentration of microplastics had a detrimental impact on the survival, growth (i.e., body length and head capsule) and emergence of C. tepperi. The observed effects were strongly dependent on microplastic size with C. tepperi more sensitive to microplastics in the size range of 10-27 μm. No negative effects were observed on growth and survival of C. tepperi exposed to the larger microplastics (100-126 μm), though a significant decrease in the number of emerging adults was observed in the organisms exposed to the same size range of microplastics. Further, SEM showed a significant reduction in the size of the head capsule and antenna in C. tepperi exposed to microplastics in the size range of 10-27 μm. These results showed that environmentally relevant concentrations of microplastics in sediment can result in adverse effects on the development and emergence of C. tepperi, with effects strongly dependent on particle size. Finally, we evaluated the effects of PE microplastics on the acute toxicity of a pyrethroid insecticide (bifenthrin) to midge larvae (C. tepperi) in water. To test the single and combined effects of bifenthrin and PE microplastics, C. tepperi larvae were exposed to six concentrations of bifenthrin ranging from 0.1 to 3.2 μg/L in the presence and absence of microplastics. To examine the possible effects of bifenthrin and microplastics in synthetic and real water, the bioassays were performed in both moderately hard water (MHW) and river water. We performed an uptake study using three different size ranges of microplastics (10-27, 43-54, 100-126 μm) during 8-day microplastics-spiked water exposure. The results showed that microplastics in the size range of 10-27 μm were mostly ingested by C. tepperi larvae. Using this finding, 10-27 μm microplastics were selected for the bioassays. The results of the bioassays using MHW demonstrated a significant decrease in the toxicity of bifenthrin in the presence of microplastics. This is likely attributable to the tendency of bifenthrin to bind to the microplastics, which reduces the bioavailability of bifenthrin to midge larvae. However, in the bioassays conducted in river water with a total organic carbon (TOC) concentration of 9.6 mg/L, no significant difference was observed between the toxicity of bifenthrin to C. tepperi in the presence and absence of microplastics. This is likely due to the interaction between organic carbon and bifenthrin, which reduces the bioavailability of bifenthrin to C. tepperi larvae. This thesis highlights that microplastic fibers and beads are released to the aquatic environment from WWTPs, and that this can negatively affect survival, reproduction and the life cycle of aquatic organisms (both pelagic and benthic) through entanglement (fibers) and ingestion (beads). The effect of microplastics on chemical contaminants is complex, and microplastics may act both as carriers but also as “chelators” of chemicals in the water, thereby reducing their bioavailability.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Environment and Sc<br>Science, Environment, Engineering and Technology<br>Full Text

Microplastics are particles that are < 5 mm in size and come from a wide range of sources. The global distribution in terrestrial and aquatic environments indicates they are likely to cause harm to living organisms. They are used in a variety of personal care products and kitchen scourers. To advance further studies, different approaches have been developed in recent years. In this research, a comparison of methods and analytical techniques were applied to characterise microplastics in two toothpastes and two facial scrubs. The analysis of microplastics was determined using light microscopy, laser diffraction, Fourier-transform infrared spectroscopy. This research reports for the first time, the application of Imaging flow cytometry to characterise microplastics, and was explored to characterise smaller sized particles in each product. The methods developed where validated by characterising particles abraded from kitchen scourers. Two market leading and three chain store brands of kitchen scourers were utilised for the characterisation of microplastics. The application of the different techniques indicated differences in the size, number and morphological characteristics of the particles analysed. The different approaches developed for particle extraction, and the analytical techniques had an apparent influence on the results produced. Currently, there are no universally accepted laboratory protocol and analytical techniques to characterise microplastics. However, this research can serve as a reference point to promote more studies on laboratory methods and analytical techniques to characterise microplastics, with the hope of understanding better these complex particles.

Plastic, including microplastic, is a common product in the society today and is starting to be more common in oceans where it can stay for a long time. Microplastic is defined usually in the size range five millimeter and smaller and together with the important Chao Phraya river in Bangkok, Thailand, the main subject of this paper is described. More clearly, the aim of this paper is to provide a first-hand quantification of microplastics flowing into the Chao Phraya River. Samples were taken at upstream, middle and downstream locations in the river with a pump-system and were then analyzed in a lab. The result showed an increasing load of microplastic entering the river from Bangkok, for example the result for size range five to one millimeter showed a six times increase of microplastic between the upstream and downstream point.<br>Plast, däribland mikroplaster, är en vanlig förekommande produkt i samhället idag och börjar bli allt vanligare i hav där det också kan stanna ett långt tag efter att det hamnat där. Mikroplaster definieras oftast med storleks intervallet fem millimeter och mindre och tillsammans med den viktiga floden Chao Phraya i Bangkok, Thailand, är huvudämnet för denna studie beskriven. Mer tydligt, målet för denna studie är att förse en första kvantifiering av mikroplaster som flödar in till Chao Phraya floden. Prover togs på platser som var uppströms, i mitten och nedströms på floden och sedan analyserades dessa prover i ett laboratorium. Resultatet som framkom visade på ökande belastning av mikroplaster i floden från Bangkok, exempelvis visade resultatet för storleks intervallet fem till en millimeter på en sex gånger ökning av mikroplaster mellan uppströms platsen och nedströms platsen. Ökningen som troligen kommer från innerstaden kan bero på olika faktorer såsom väder, stadens avfallshantering och användningen av engångsprodukter som är av plastmaterial. Således påvisar detta vikten av, bland annat, en fungerande avfallshantering.

In recent years, the problem of "microplastics" has become increasingly worrying, as the amount of plastics that will be produced in the future will increase significantly. Microplastics are defined as emerging pollutants, due to the risks they may cause to the environment and especially to human health. The analytical issue behind their quantification in environmental matrices is quite complex. The thermoanalytical Py-GC/MS technique can provide qualitative and quantitative information about the microplastics more accurate than already applied optical techniques. The first aim of this thesis project was to determine the potentialities and limitations of such method for the quali-quantitative determination of polymers such as PET, PA6, PA66, PS, PP, PE and PVC. Particular attention was put on the interaction between polymers’ pyrolysis products. While this aspect has not been widely addressed in literature yet, it could result a limitation to the application of such technique for quantification purposes. Along this work pyrolytic interactions between PET with PA6, PA66 and PVC that lead to the formation of new compounds, were determined. These interferences were thought to be responsible in part for compromising the reproducibility of quantitative analyses.For this reason, polymers derivatisation tests were carried out with TMAH, an already widely used reagent for the analysis of microplastics. BSTFA and HMDS, other more innovative derivatisers in this field of research, were tested. TMAH proved to be very effective in eliminating interferences from a qualitative point of view. It also produced more satisfactory results for quantitative determination. However, the silylating reagents showed limitations in eliminating interactions. This precluded their use for possible quantification tests. The results of this study provides the basis for the development of a robust thermoanalytical technique for microplastic quantification in environmental samples.

Plastic waste is recognised as a global threat to ecosystems. Microplastics may enter the food chain directly or indirectly in contaminated water or prey, respectively. Totally, 47 fishes from the inside and outside of aquaculture cages were analysed from Leros, a Greek island situated on the Aegean Sea. In addition, 11 samples of seawater were collected around aquaculture cages. The microplastics quantified were identified through a stereomicroscope and confirmed by a hot needle test. The results showed that in seawater and fish samples, fibres were the predominant type of microplastics, the main size was between 0.5 to 2 mm. Blue was the principal colour in fish and black was the principal colour in seawater samples. Furthermore, aquaculture and wild fishes are exposed to direct intake of microplastics from the seawater. This project demonstrates that the contamination and bioaccumulation of microplastics represent a real danger along the food chain.<br>Os resíduos de plástico são reconhecidos como uma ameaça global para os ecossistemas. Os microplásticos podem entrar na cadeia alimentar direta ou indiretamente em água ou presa contaminada, respetivamente. No total, 47 peixes de dentro e fora das jaulas flutuantes de aquacultura foram analisados. Provenientes de Leros, uma ilha grega situada no Mar Egeu. Além disso, 11 amostras de água do mar foram recolhidas próximo das jaulas da aquacultura. Os microplásticos quantificados foram identificados através de um estereomicroscópio e confirmados pelo teste da agulha quente. Os resultados mostram que na água e nos peixes as fibras foram o tipo de microplásticos predominante, o tamanho principal foi de 0,5 a 2 mm. O azul foi a cor principal em peixes e o preto a cor principal nas amostras da água do mar. Adicionalmente, os peixes de aquacultura e selvagens estão expostos à ingestão directa de microplásticos da água do mar. Este projeto demonstra que a contaminação e bioacumulação de MPs representam um perigo real ao longo da cadeia alimentar.