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Microplastics in freshwater water environments
Expanded Title:The world is continually faced with increased complexities of water pollution and its effects. Current legacy water pollution issues are addressed through a number of global conventions and agreements, such as the Stockholm Convention which deals with persistent organic pollutants (POPs), the Minamata Convention dealing with Mercury, etc. However, there are emerging and new pollutant issues, currently not covered where there is a clear concern, but the science has not caught up yet to convince and assist in policy and practical interventions. Plastic and microplastic pollution, along with related nanoparticles (Hernandez et al., 2017), is one such ‘emerging’ concern. Plastic pollution in the marine environment is well documented, however, there are few studies on the extent of pollution in freshwater and treated water sources. This project addresses microplastics in South African freshwaters, noting that almost all existing knowledge is derived from the large volume of literature from marine studies. Given the low dilution potential of South African freshwaters, coupled with waste management deficiencies (notably the obvious large amounts of plastics in our environment), microplastic pollution is an unknown component of possible impact and injury to our freshwaters and freshwater-dependent biological processes. This scoping study is an attempt to characterise the presence, levels, and potential implications of microplastics in freshwaters, as well as provide recommendations on areas of concern, as well as research gaps and future priorities for South Africa. METHOD As part of the literature survey, a scan on existing definitions of microplastics and particles was conducted. The literature survey done included grey literature such as reports, on microplastics and microparticles in the aquatic environment. Findings made from literature were categorised into common themes such as sources, pathways, threats, possible accumulation of extraneous pollutants, long range transport, breakdown, uptake by organisms, and any other issues. In addition, an annotated compendium of relevant sampling and analytical methods was made, with specific attention as to the situation and conditions in South Africa, accepted methods and recommendations made by the National Oceanic and Atmospheric Administration. Sampling and analysis for microplastics was done in a variety of freshwaters, including drinking and ground water in selected locations in North West, Gauteng and the Free State, mainly in commercially important river systems such as the Vaal River, Mooi River and Wasgoedspruit River. Municipal water samples were collected from the greater metropolitan municipalities such as City of Johannesburg and Tshwane. A synthesis was made from each of the work packages above and translated to the situation in South African freshwaters and water cycles, including potential threats to human health and biota. From this potential hot-spots or areas of concern, and potential mitigating actions, as well as research gaps and future priorities were identified. RESULTS Microplastics in surface water sources Based on the sites used for this project, freshwater sources were found to contain microplastics between 56 and 0.33 particles per litre. Two sites had very high concentrations of plastic particles; 56 and 39 particles per litre, respectively. The geographic distributions are also insightful as very high fragment concentrations at was observed at 2 Sites. The heavily used Crocodile River that drains most parts of Johannesburg recorded the highest the total particle, fragment and fibre counts. At the Vaal Dam and towards the north, larger particles were observed and make up greater proportions. Fragments and fibres are also prominent to the west near Potchefstroom, while northern and eastern parts have noticeably lower concentrations. As has already been shown, small particles dominate at all sites. The fibre size classes were more homogenously distributed. Fragments had a very clear pattern when compared against size classes, with the smallest size class (20-300 µm) having four times more particles than the other fragment particle size classes combined. This pattern could be due to a significant release of small manufactured fragments in excess of larger particles, the resultant effect of the breakdown from larger to smaller fragments, or a combination of both. For fibres, there was no size-class pattern discernible although the Kruskal-Wallis analyses did indicate some size-class differences
Date Published:26/07/2018
Document Type:Research Report
Document Subjects:Water Resource Management/IWRM - Water Governance, Ecosystem - Resource Economics
Document Keywords:Water Quality
Document Format:Report
Document File Type:pdf
Research Report Type:Standard
WRC Report No:2610/1/18
ISBN No:978-0-6392-0005-7
Authors:Bouman H; Minaar K; Bezuidenhout C; Verster C
Project No:K5/2610
Originator:WRC
Organizations:North West University
Document Size:5 210 KB
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