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Urban areas constitute a major hotspot of litter, including plastic litter, that stormwater can wash off towards waterways. However, few studies quantified and characterized litter densities in urban areas and fluxes transported by stormwater networks. Moreover, little information is available on litter transport dynamics in stormwater, and on the factors driving this transport. This study aims at characterizing and quantifying litter amounts transported by stormwater of two nested French urban catchments (total surface area of 105 ha). Litter densities relative to land uses and rain events were investigated in the same catchments as in a compagnon paper (Ledieu et al., 2024). The present study explores the impact of rain events on the transport of urban litter in stormwater. Litter collection and characterization combined with a capture/recapture experiment using tagged litter placed in stormwater inlets show total litter fluxes of 29 kg/year, in which 14 kg/year are plastics, exported at the stormwater outlet. These fluxes confirm that stormwater runoff is a considerable pathway from urban surfaces to waterways, especially regarding small plastic litter (< 2.5 cm). Item transport dynamic is however not linear and only 0.3% of the urban litter appear remobilized. Litter transport dynamics depends on several factors (urban litter densities, hydrometeorological parameters, item composition and morphologies, and stormwater management systems) that should be considered in global models.
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Microplastics (MPs, plastic items from 1 µm to 5 mm in size) are present in all environmental compartments. The evaluation of their concentration, fate, and spatial distribution is still a challenge for the scientific community. This concern is just debuting in developing countries, (i.e., Asia, South America, and Africa). This study deals with the MP contamination in the abiotic marine compartments of Northern Vietnam: seawater and intertidal sediments. Four sites located in the intertidal zone or near the coastline in Tonkin Bay, Vietnam were studied. A total of 16 samples (eight for each compartment) were collected in July 2020 (rainy season) and January 2021 (dry season). Anthropogenic particles (total observed fibers and fragments) were found at levels ranging from 3 to 303 particles/m3 in seawater and from 63 to 955 particles/kg dry weight in sediments. Most of these were fibers less than 300-µm long. Higher levels of seawater at the Nam Dinh site were found in the rainy season compared to the dry one. As the river flow was estimated six times higher during the rainy season than during the dry season, these results suggest the river discharge is a potential source of contamination for the coastal zone. The temporal variability was lower for the sediments than for the seawater, suggesting the long-term integration of the anthropogenic particles in this compartment. A small portion of sorted particles were analyzed by µFTIR (8.35%), and this sub-sample was only composed of fragments. Still, fragments were mostly composed of polypropylene (PP, 82%), polyethylene (PE, 9%), and polystyrene (PS, 9%). The fragment size was similar in the two studied compartments, but it was dependent on polymer types since PS fragments (140 ± 17 µm) were smaller than those made of PE (622 ± 123 µm) and PP (869 ± 905 µm). Future works should investigate the smallest fraction of MP (even nanoplastics) as well as find solutions in order to mitigate MP contamination in the marine environment.
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Baías , Monitoramento Ambiental , Sedimentos Geológicos , Microplásticos , Água do Mar , Poluentes Químicos da Água , Vietnã , Água do Mar/química , Sedimentos Geológicos/química , Poluentes Químicos da Água/análise , Microplásticos/análiseRESUMO
The contamination of freshwater with microplastics (MPs) has been established globally. While the analysis of MPs has predominantly involved spectroscopic methods for revealing particle numbers, the potential of employing spectroscopy for mass estimation has been underutilized. Consequently, there is a need to enhance our understanding of the mass loads of MPs and ensure the complementarity and comparability of various techniques for accurate quantification. This study presents the first comparative results on urban water samples using micro Fourier-transform infrared (µ-FTIR) imaging and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) to identify and quantify MPs in both particle numbers and mass concentration. Two sampling campaigns in summer and winter were conducted at 11 locations within the Amsterdam canal network. An advanced in-situ volume-reducing sampling pump was employed to collect MPs from the surface water within the size fraction of 10-300 µm. The analysis revealed MP concentrations within the range of 16-107 MP/m3, estimated to be 2.0-789 µg/m3 by µ-FTIR imaging and 8.5-754 µg/m3 by Py-GC-MS. The results of the two analysis techniques showed good comparability in terms of the general trends of MP abundances, with variations in polymer compositions due to the inherent inter-methodological differences. Elevated MP concentrations were observed in the city center compared to the suburban areas. In addition, seasonal differences in MP abundances were noted at the locations with high human activity.
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Monitoramento Ambiental , Cromatografia Gasosa-Espectrometria de Massas , Microplásticos , Poluentes Químicos da Água , Poluentes Químicos da Água/análise , Monitoramento Ambiental/métodos , Cromatografia Gasosa-Espectrometria de Massas/métodos , Microplásticos/análise , Países Baixos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Cidades , Água Doce/químicaRESUMO
Here, microplastic atmospheric deposition data collected at an urban site during the French national lockdown of spring 2020 is compared to deposition data from the same site in a period of normal activity. Bulk atmospheric deposition was collected on the vegetated roof of a suburban campus from the Greater Paris and analysed for microplastics using a micro-FTIR imaging methodology. Significantly lower deposition rates were measured overall during the lockdown period (median 5.4 MP m-2.d-1) than in a period of normal activity in spring 2021 (median of 29.2 MP m-2.d-1). This difference is however not observed for the smallest microplastic size class. The dominant polymers identified were PP, followed by PE and PS. Precipitation alone could not explain the differences between the two campaigns, and it is suggested that the temporary drop in human activity during lockdown is the primary cause of the reduced deposition rates. This study provides novel insight on the immediate impact of human activities on atmospheric microplastics, thus enhancing the global understanding on this topic.
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COVID-19 , Microplásticos , Humanos , Plásticos , Monitoramento Ambiental , Controle de Doenças TransmissíveisRESUMO
During wet weather events, combined sewer overflows (CSOs) transfer large amount of particulate matter and associated pollutants into surrounding water bodies, thereby deteriorating the recipients' ecological health. Resuspension of sewer sediments during these events contributes significantly to pollution level of these discharges. However, how much this in-sewer process contributes to CSOs' quality regarding microplastic (MP) pollution is little known. Therefore, an investigation on sewer deposits inside the Parisian combined sewer network was carried out. The study found high MP concentrations stored in this matrix, ranging from 5 × 103 to 178 × 103 particle/kg dry weight. Polymer composition is similar to what found in raw wastewater, containing a high proportion of polyethylene and polypropylene. Thus, the results indicated the persistence of MPs in sewer network during transport during dry weather periods to treatment facilities. Once resuspension of sewer deposits happens, MPs can be released into water flow and get discharged along with CSOs. This highlights another potential pathway of MPs into freshwater environment.
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Microplásticos , Esgotos , Plásticos , Paris , Água , ChuvaRESUMO
This study aims to examine tire and road wear particle (TRWP) emissions under realistic conditions in order to provide some valuable insights into understanding their sources and fate in the environment. TRWP emissions were evaluated with a fully instrumented vehicle driving on five representative road types: urban, ring road, suburban, highway, and rural. Multiple vehicle dynamic variables were recorded to assess the factors influencing these emissions. For the first time, emitted particles were collected on filters and analyzed by means of pyrolysis coupled with gas chromatography-mass spectrometry to determine the polymeric content of tires, in specifically quantifying styrene-butadiene rubber (SBR) and butadiene rubber (BR) pyrolytic markers. The measurements obtained from the five road types revealed similar size distributions for SBR + BR emissions, with maxima found in the (ultra)fine fraction (< 0.39 µm). Upon applying an SBR + BR-to-TRWP conversion factor, (ultra)fine fraction TRWP emissions proved to be the highest for suburban (64 ± 5 µg/km), followed by highway, urban, ring road and rural routes. The output represents up to 480 tons of TRWP per year emitted in the EU27, thus suggesting a widely impregnated atmospheric compartment capable of threatening human health. Furthermore, an analysis of variables revealed that acceleration, tire constraints, and constant sustained driving factors had specific impacts on TRWP emissions.
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The dispersed pollution caused by microplastics (MPs) represents a current and global concern. While the fragmentation of plastic debris into smaller particles occurs in rivers, little MP research is done on freshwater species and is published compared to the marine environment. The Loire River is the longest river in France and is subject to moderate to high anthropic pressure while it represents major societal and economic issues. However, there are not many studies that have been put forward with regards to the effect of environmental MPs (EMPs) on aquatic organisms and no policies have been enacted to monitor the plastic pollution. In this study, freshwater bivalves, Corbicula fluminea, were exposed for 21 days to environmentally relevant concentrations of a mixture of <200 µm MPs generated from plastic litter collected directly along the banks of the Loire River. This mixture was composed of 40% polyethylene (PE), 40% polypropylene (PP), 10% polyethylene terephthalate (PET) and 10% polyvinylchloride (PVC) (mass percentage). Ecotoxicological effects were assessed from the individual to the molecular levels on several endpoints: condition index, filtration efficiency, enzyme activities, lipid peroxidation, energy reserves and gene expression. The ingestion of EMPs caused damages at the biochemical level. Indeed, we reported an increase in catalase activity in gills and digestive mass, a decrease in TBARs in gills, a decrease in acetylcholinesterase activity in the digestive mass, a decrease of glycogen and lipid contents in the whole organisms and a significant induction of the expression of gst, cat, mp, acp genes. The current results suggest therefore that long-term exposure to realistic doses of EMPs causes toxicity towards freshwater benthic biota. The analysis of biomarker activities and the analysis of gene expression are complementary to prevent the effects of a plastic contamination at higher biological levels in aquatic organisms.
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Corbicula , Poluentes Químicos da Água , Animais , Microplásticos/toxicidade , Plásticos/toxicidade , Rios , Acetilcolinesterase , Poluentes Químicos da Água/toxicidade , Poluentes Químicos da Água/análiseRESUMO
The aim of this study was to explore the adverse effects of a microplastic (MP) mixture obtained from litter accumulated in the Seine River (France) compared to those of their major co-plasticizer, dibutylphthalate (DBP), on the sentinel species Hediste diversicolor. A suite of biomarkers has been investigated to study the impacts of MPs (100 mg kg-1 sediment), DBP (38 µg kg-1 sediment) on worms compared to non-exposed individuals after 4 and 21 days. The antioxidant response, immunity, neurotoxicity and energy and respiratory metabolism were investigated using biomarkers. After 21 days, worms exposed to MPs showed an increasing aerobic metabolism, an enhancement of both antioxidant and neuroimmune responses. Energy-related biomarkers demonstrated that the energy reallocated to the defence system may come from proteins. A similar impact was depicted after DBP exposure, except for neurotoxicity. Our results provide a better understanding of the ecotoxicological effects of environmental MPs and their associated-contaminants on H. diversicolor.
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Poliquetos , Poluentes Químicos da Água , Humanos , Animais , Microplásticos , Espécies Sentinelas/metabolismo , Antioxidantes , Plastificantes/toxicidade , Plastificantes/metabolismo , Plásticos/toxicidade , Rios , Dibutilftalato/toxicidade , Dibutilftalato/metabolismo , Biomarcadores/metabolismo , Poliquetos/fisiologia , Poluentes Químicos da Água/metabolismoRESUMO
Although sediments are considered to be a major sink for microplastics (MP), there is still a relative lack of knowledge on the factors that influence the occurrence and abundance of MP in riverine sediments. The present study investigated the occurrence and distribution of MP in riverine sediments collected at twelve sites representative of different populated and urbanized rivers (To Lich, Nhue and Day Rivers) located in the Red River Delta (RRD, Vietnam, during dry and rainy seasons. MP concentrations ranged from 1600 items kg-1 dw to 94,300 items kg-1dw. Fiber shape dominated and MP were made of polypropylene (PP) and polyethylene (PE) predominantly. An absence of seasonal effect was observed for both fragments and fibers for each rivers. Decreasing MP concentrations trend was evidenced from the To Lich River, to the Nhue River and to the Day River, coupled with a decreasing fiber length and an increasing fragment area in the surface sediment from upstream to downstream. Content of organic matter was correlated to MP concentrations suggesting that, high levels of organic matter could be MP hotspots in urban rivers. Also, high population density as well as in highly residential areas are related to higher MP concentrations in sediments. Finally, a MP high ecological risk (RI: 866 to 4711) was calculated in the RDD.
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The contamination of microplastics (MP) in freshwater environments represent a major way for the MP transport in the environment. The assessment of MP pollution in freshwater compartments is then important to visualize the pressure and the impacts on medium, and to set up necessary measures. In this context, this study focused on the influence of anthropogenic activities of a medium French city (Angers) on MP levels in samples collected from the Loire River, the longest river in France. Abiotic and biotic matrices were collected upstream and downstream Angers. A first analysis was performed based on microscopy to determine the size, colour and shape of suspected MP and a complementary analysis by µ-FTIR (micro-Fourier Transform InfraRed) was conducted to determine the composition of plastic particles. Three organisms belonging to different trophic levels were studied: when the MP level was expressed per individual, the lowest abundance of MP was found in Tubifex sp. Followed by Corbicula fluminea, while the highest was measured in Anguilla anguilla. To establish the relationship with their habitat, the presence of MP in sediment and water was also analysed. Therefore, this works constitutes a complete overview of the MP levels in freshwater abiotic and biotic matrices. Overall, the presence of MP in analysed samples did not follow a particular pattern, neither in the sites nor matrices: the characteristics depending on a multifactorial outcome (feeding mode, organism size ). However, correlation of MP pattern between clams and sediment was quite evident, while the one between worms and their habitat was not. This demonstrates the relevance of investigating plastic contamination both in biotic and abiotic matrices. Finally, a standardisation of sampling and analytical analysis protocols would be helpful to make comparisons between studies more robust.
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Corbicula , Poluentes Químicos da Água , Animais , Microplásticos , Plásticos/análise , Poluentes Químicos da Água/análise , Monitoramento Ambiental/métodos , Água Doce/análise , FrançaRESUMO
Bis(2-ethylhexyl) phthalate (DEHP) is a plasticizer that has been massively used since the second part of the twentieth century by the plastic industry to provide softness properties to PVC. This chemical is considered as toxic to reproduction and endocrine disrupting, and a wide range of uses are now forbidden by the EU. Despite these regulations, DEHP is still found to be a widespread contaminant in watersheds in the EU. In this study, we calculate retrospective and prospective scenarios of past and future emissions of DEHP in the environment (water, soil, air) in the EU 28, taking into account the entire lifecycle of the substance, from its production and its inclusion in polymer (mainly PVC) and non-polymer products (adhesive and sealant, ceramic and printing ink) to the recycling and end of life of these products. We develop a stock and flow model based on dynamically estimating the stocks of DEHP present in products on the market. Our results show that the introduction of recent regulations to limit the use of DEHP (that bring a 70% reduction of DEHP contained in products placed on the market in 2020 and 75% in 2040) will not reduce significantly future emissions. This persistence of emissions is explained by the high stocks built in the economy and the long-term presence of soft PVC waste in landfills. Our results suggest that DEHP will remain a cause of environmental contamination many decades after uses have declined and even ceased, and it appears to be too late for market regulation at the market stage to offset the effect of past stock buildup and landfilling. It is likely that several chemicals that are not considered as persistent and therefore not the focus of international regulations could exhibit the same characteristics. Regulations should avoid possible use patterns that make hazardous chemicals persistent in products, because they have the potential to create long-term and almost irreversible environmental pollution and impacts.
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Dietilexilftalato , Dietilexilftalato/toxicidade , Polímeros , Estudos Prospectivos , Estudos Retrospectivos , Plastificantes , Poluição Ambiental , Europa (Continente)RESUMO
Land-based sources of riverine macrolitter are now recognized as a major concern, but few field data on litter amount, composition and sources are available. This is especially the case for macrolitter hotspots like high frequented roadways that could generate large amount of macrolitter potentially reaching rivers. This dataset provides macrolitter amount and composition over one year from a retention pond collecting stormwater and carried macrolitter from a 800 m portion of a highly frequented roadway (around 90,000 vehicles per day). The typology of macrolitter was defined using the TSG-ML/OSPAR classifications. A total of 36,439 items in which 84% of plastics were individually counted, classified and weighted by category for a total mass of 88.5 kg (60% of plastics). Raw data are available in Mendeley Data (DOI:10.17632/t6ryv6crjd.4). Top 10 items represent 92% by count of the total with plastic fragments (31%), cigarette butts (18%), EPS fragments (17%) or foam packaging (11%) as most common items. Top 10 items represent 72% by mass of the total with plastic fragments (24%) and Cardboard (13%) as most common items, followed by foam packaging (6%), wood fragments (6%), industrial plastic sheets (5%), rubber fragments (4%) and EPS fragments (4%). More than 94% of plastic items are below 1.9 g/item. This dataset is related to the research paper Amount, composition and sources of macrolitter from a highly frequented roadway.
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Studies on the influence of hydrodynamic conditions on anthropogenic microfiber (MF) and microplastic (MP) distributions in freshwater environments are sparse. In this study, we evaluated the influence of urbanisation gradient on the spatial variability of MFs and MPs. Temporal variability was also assessed by comparing the concentrations and fluxes of MFs and MPs under low flow conditions with those during the January-February 2018 flood event. For each period, Seine river water was collected upstream and downstream of Greater Paris and filtered through an 80 µm net at three different sampling sites. MFs were counted using a stereomicroscope, while MPs were analysed using micro-Fourier transform infrared spectroscopy coupled with siMPle analysis software. The highest concentrations of MFs and MPs were reported at the furthest downstream sites during both periods. However, high water flowrates and urbanisation gradient did not significantly impact MF and MP concentrations, sizes, or polymer distributions. The median MF and MP concentrations were 2.6 and 15.5 items/L and their interquartile ranges were 1.6 and 4.9 items/L (n = 10), respectively, illustrating relatively stable concentrations in spite of the urbanisation gradient and variations in the flowrate. In contrast to the concentration, size, and polymer distribution characteristics, MP mass fluxes were strongly affected by river flow. MF and MP fluxes show increases in the number and mass of particles from upstream to downstream. The downstream site presents high MP mass fluxes, which range between 924 and 1675 tonnes/year. These results may indicate significant MP inputs from the Paris Megacity through wastewater treatment plant effluents and untreated stormwater. The January-February 2018 flood event, which represented 14.5% of the year (in terms of time), contributed 40% of the yearly MP mass fluxes. Thus, flood events contribute strongly to MP fluxes.
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Microplásticos , Poluentes Químicos da Água , Monitoramento Ambiental , Inundações , Plásticos , Poluentes Químicos da Água/análiseRESUMO
Microplastics (MPs) and microfibers (MFs) in stormwater have been poorly investigated. Data on their intra and inter rain events variability over time are still sparse. For the first time, the variability of microlitter concentrations in stormwater has been studied. MF and MP concentrations were investigated in stormwater runoff at the outlet of the suburban catchment at Sucy-en-Brie (a suburb of Paris, France), during four rain events. Median MF and MP concentrations were 1.9 and 29 items/L, with an interquartile range of 2.3 and 36 items/L, respectively (N = 18). A different pattern was observed between MFs and MPs. While no relationship or trends were observed for MFs, the highest MP concentrations were observed before the flow rate peak of the rain events. This could indicate a difference in the behaviour between MFs and MPs. We estimated the median MP mass concentration to be 56 µg/L with an interquartile range of 194 µg/L, whereas the mass concentration of macroplastics was estimated to be 31 µg/L with an interquartile range of 22 µg/L at the same sampling site, in a previous study. For this sampling site, MPs and macroplastics have the same order of magnitude. This study may have strong implications on microplastic assessment in urban waters.
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Microplásticos , Poluentes Químicos da Água , Monitoramento Ambiental , Plásticos , Chuva , Movimentos da Água , Poluentes Químicos da Água/análiseRESUMO
Microplastics contaminating drinking water is a growing issue that has been the focus of a few recent studies, where a major bottleneck is the time-consuming analysis. In this work, a micro-optofluidic platform is proposed for fast quantification of microplastic particles, the identification of their chemical nature and size, especially in the 1-100 µm size range. Micro-reservoirs ahead of micro-filters are designed to accumulate all trapped solid particles in an ultra-compact area, which enables fast imaging and optical spectroscopy to determine the plastic nature and type. Furthermore, passive size sorting is implemented for splitting the particles according to their size range in different reservoirs. Besides, flow cytometry is used as a reference method for retrieving the size distribution of samples, where chemical nature information is lost. The proof of concept of the micro-optofluidic platform is validated using model samples where standard plastic particles of different size and chemical nature are mixed.
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Stormwater possibly represents a significant input for plastic debris in the environment; however, the quantification and composition of plastic debris and other macrolitter in stormwater are not available in literature and the amounts discharged into freshwater have been poorly investigated. To obtain a better understanding, the occurrence, abundance, and composition of the macrolitter in screened materials from stormwater were investigated at a small residential suburban catchment (Sucy-en-Brie, France) in Greater Paris. The macrolitter, particularly the plastic debris, was sorted, weighed, and classified based on the OSPAR methodology. On average, plastics accounted for at least 62% in number and for 53% of the mass of all the anthropogenic waste found in the screened materials. The most common items were plastic bags or films, crisp or sweet packets, cigarette butts, plastic fragments of unknown origin, garbage bags or garbage bag strings, foil wrappers, tampon applicators, plastic cups, and medical items such as bandages. Plastic debris concentrations in runoff water ranged between 7 and 134 mg/m3 (i.e. 0.4-1.7 kg.yr-1.ha-1 or 4.8-18.8 g.yr-1.cap-1). When extrapolated to the Greater Paris area, the estimated amount of plastic debris discarded into the environment through untreated stormwater of separate sewer systems ranges from 8 to 33 tons.yr-1.
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Plásticos , Poluentes Químicos da Água , Monitoramento Ambiental , França , Paris , Resíduos/análise , Poluentes Químicos da Água/análiseRESUMO
Monitoring the removal of organic micropollutants (OMPs) in advanced wastewater treatment facilities requires expensive and time-consuming analytical methods that cannot be installed online. Spectroscopic techniques such as fluorescence excitation/emission spectroscopy were demonstrated to offer the potential for monitoring OMPs removal in conventional wastewater treatment plants or ozonation pilots but their application to activated carbon (AC) adsorption processes was only investigated at lab scale and not in real treatment facilities. In this study, indexes from fluorescence emission/excitation matrices (EEMs) were used to find correlations with the removal of 28 OMPs from a large-scale AC pilot in fluidized bed employed for wastewater advanced treatment, as well as from batch experiments. Differences in OMPs removal could be observed depending on the operational conditions (i.e. pilot or batch experiments, contact time, type of AC) and the physico-chemical properties of the molecules. 7 PARAFAC components were derived from the fluorescence EEMs of 60 samples obtained before and after adsorption. Positive correlations were obtained between the removal of fluorescence indexes and most OMPs, and correlation coefficients were much higher than the ones obtained with UV254, confirming the interesting potential of fluorescence spectroscopy to accurately monitor adsorption performances at the industrial scale. The highest correlation coefficients were obtained for OMPs having the best removals while the ones that were refractory to adsorption, as well as to interactions with DOM, exhibited weak correlations. These results suggest that interactions between OMPs and fluorescing DOM and their subsequent co-adsorption onto AC were at the origin of the correlations found. Lower correlations were also found for the most biodegradable OMPs, which indicated that the occurrence of biological effects could make the monitoring of these compounds more challenging.
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Poluentes Químicos da Água , Purificação da Água , Adsorção , Carvão Vegetal , Espectrometria de Fluorescência , Águas Residuárias , Poluentes Químicos da Água/análiseRESUMO
As microplastic studies grow, environmental concerns of all kinds of fibers are currently investigated. However, there is a gap in data regarding the impacts of digestion protocols on fibers integrity. This work focuses on the impact of five commonly used digestion protocols on the seven most produced fibers in traditional textile: three synthetics (polyamide 6.6 (PA 6.6), polyethylene terephthalate (PET) and polyacrylonitrile (acrylic)), one artificial (viscose), two vegetal natural (cotton and flax) and one animal natural (wool). The protocols to be tested were selected based on the literature: 10% KOH at 40 °C for 24 h; 10% KOH at 60 °C for 24 h; diluted NaClO at room temperature (~20 °C) for 15 h; 30% H2O2 at 40 °C for 48 h; Fenton's reagent with 30% H2O2 for 2 h at room temperature (~20 °C). The fibers were characterized before and after digestion. The effects of those protocols on fibers integrity have been assessed using several of their performance parameters. High degradations were observed for PET with 10% KOH 60 °C whereas almost no impact was observed at 40 °C. H2O2 digestion affects mechanical properties of different fibers, particularly PA 6.6. Both protocols should be avoided for synthetic fibers analyses. NaClO digestion mainly affected flax and viscose. Diluted NaClO at room temperature for 15 h, 10% KOH at 40 °C for 24 h and Fenton's reagent are more appropriate to maintain fibers integrity.
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Many studies have been conducted to quantify microplastic contamination, but only a few of them have actually the sampling methodology and associated uncertainties. This study seeks to examine the influence of sampling strategy on the confidence interval of river microplastic estimates. 16 samples are collected in the Gave de Pau River (southwestern France) during a three-hour window with a 330-µm mesh size net. Three different exposure times (3, 5 and 7 min) allow for a respective filtration rate by the net of 35.6 m3 (3 samples), 59.4 m3 (10 samples), and 83.2 m3 (3 samples) of water. Organic matter contained in samples is removed by hydrogen peroxide oxidation. The plastic particles are then counted and classified under a binocular microscope. The microplastic concentrations vary between 2.64 and 4.24 microplastics/m3, with a median value of 3.26 microplastics/m3. Statistical analysis does not show differences in microplastic concentrations for the three exposure times. This result seems to demonstrate that a filtration of approx. 35 m3 of water is sufficient under similar conditions (similar flow condition and degree of microplastic contamination) and can help reduce sampling and sample processing time. Other analyses, based on 10 filtrations of 59.4 m3, show that the higher the number of samples, the lower the confidence interval. For triplicates, the mean confidence interval reaches 15% of the median value. Thus, collecting triplicates would seem to offer a reasonable optimum, in combining an acceptable error percentage and time efficiency. These results might depend on the microplastic load of the river, therefore making it necessary to conduct similar analyses on other rivers. This study reports for the first time uncertainties related to microplastic sampling in rivers. Such findings will serve to set up long term monitoring, highlight spatial differences between sites and improve the accuracy of annual microplastic fluxes in rivers.