Stormwater Detention Reservoirs: An Opportunity for Monitoring and a Potential Site to Prevent the Spread of Urban Microplastics

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Abstract

Stormwater runoff carries pollutants from urban areas to rivers and has the potential to be a main contributing source of microplastics (MPs) to the ecosystem. Stormwater detention reservoirs (SDRs) differ from ponds and lakes in that SDRs retain most particulate matter and they are emptied after storm events. This paper investigates the occurrence of MPs in the SDR of the Alto-Tietê catchment area, Itaim stream in Poá city, São Paulo, Brazil. The MPs found were classified in different categories: shapes (fragment, line/fibre, film/sheet and pellet); size (<0.5 mm, between 0.5 mm and 1 mm and >1 mm); and polymer composition. Results have shown that most of the MPs found in the samples are fragments (57%), followed by pellets (27%), fibres/lines (9%), and then films/sheets (6%). Small particles (<0.5 mm) represented 89% of the total MPs, and this category mainly included fragments (62%) and pellets (30%). MPs were found in a vast variety of shapes and colours, which shows a likely variety of sources. Besides the occurrence of MPs in the stormwater samples, the potential of SDRs as a first sanitary barrier to retain MPs before they reach the ecosystem has been speculated.

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Microplastics in the marine environment: a review of the methods used for identification and quantification.

Valeria Hidalgo-Ruz, Lars Gutow, Richard Thompson … (2012)

This review of 68 studies compares the methodologies used for the identification and quantification of microplastics from the marine environment. Three main sampling strategies were identified: selective, volume-reduced, and bulk sampling. Most sediment samples came from sandy beaches at the high tide line, and most seawater samples were taken at the sea surface using neuston nets. Four steps were distinguished during sample processing: density separation, filtration, sieving, and visual sorting of microplastics. Visual sorting was one of the most commonly used methods for the identification of microplastics (using type, shape, degradation stage, and color as criteria). Chemical and physical characteristics (e.g., specific density) were also used. The most reliable method to identify the chemical composition of microplastics is by infrared spectroscopy. Most studies reported that plastic fragments were polyethylene and polypropylene polymers. Units commonly used for abundance estimates are "items per m(2)" for sediment and sea surface studies and "items per m(3)" for water column studies. Mesh size of sieves and filters used during sampling or sample processing influence abundance estimates. Most studies reported two main size ranges of microplastics: (i) 500 μm-5 mm, which are retained by a 500 μm sieve/net, and (ii) 1-500 μm, or fractions thereof that are retained on filters. We recommend that future programs of monitoring continue to distinguish these size fractions, but we suggest standardized sampling procedures which allow the spatiotemporal comparison of microplastic abundance across marine environments.

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Microplastics in freshwaters and drinking water: Critical review and assessment of data quality

Albert A Koelmans, Nur Hazimah Mohamed Nor, Enya Hermsen … (2019)

Microplastics have recently been detected in drinking water as well as in drinking water sources. This presence has triggered discussions on possible implications for human health. However, there have been questions regarding the quality of these occurrence studies since there are no standard sampling, extraction and identification methods for microplastics. Accordingly, we assessed the quality of fifty studies researching microplastics in drinking water and in its major freshwater sources. This includes an assessment of microplastic occurrence data from river and lake water, groundwater, tap water and bottled drinking water. Studies of occurrence in wastewater were also reviewed. We review and propose best practices to sample, extract and detect microplastics and provide a quantitative quality assessment of studies reporting microplastic concentrations. Further, we summarize the findings related to microplastic concentrations, polymer types and particle shapes. Microplastics are frequently present in freshwaters and drinking water, and number concentrations spanned ten orders of magnitude (1 × 10−2 to 108 #/m3) across individual samples and water types. However, only four out of 50 studies received positive scores for all proposed quality criteria, implying there is a significant need to improve quality assurance of microplastic sampling and analysis in water samples. The order in globally detected polymers in these studies is PE ≈ PP > PS > PVC > PET, which probably reflects the global plastic demand and a higher tendency for PVC and PET to settle as a result of their higher densities. Fragments, fibres, film, foam and pellets were the most frequently reported shapes. We conclude that more high quality data is needed on the occurrence of microplastics in drinking water, to better understand potential exposure and to inform human health risk assessments.