Journal article

Quantifying changes in litter loads in urban stormwater run-off from Cape Town, South Africa, over the last two decades


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Publication Details

Author list: Weideman E, Perold V, Arnold G, Ryan PG

Publisher: Elsevier

Publication year: 2020

Journal: Science of the Total Environment

Volume number: 724

Start page: 1

End page: 9

Total number of pages: 9

ISSN: 0048-9697

URL: http://dx.doi.org/10.1016/j.scitotenv.2020.138310


Abstract

To implement effective mitigation measures to stop the flow of litter from land-based sources into the sea, it is
important to identify key pollution sources and to monitor litter trends over time. We sampled plastic and
other anthropogenic debris in urban stormwater run-off in Cape Town, South Africa, from three catchment
areas representing different land-use types: residential, industrial and a mixed commercial/residential area. Samplingwas
conducted in 2018–19 by placing nets over stormwater outlets during rain events. Organic matter constituted
79% of material by dry mass (industrial: 51 ± 22%, commercial/residential: 86 ± 4%, residential: 88 ±
13%). The nets caught 5–576 anthropogenic litter items·ha−1·day−1 (2–377 g·ha−1·day−1) with significantly
higher densities in the industrial and commercial/residential areas than the residential area. Among anthropogenic
litter items, 40–78% were made of plastic (52–64% by mass).Most plastic items were single-use packaging,
but industrial pellets washed out of the industrial outlet during every rain event. Compared to a similar study
conducted in 1996, the number of litter items decreased by ~20% in the industrial and residential areas but tripled
in the commercial/residential area. The proportion of plastics in the litter streamwas broadly similar to 1996.We
extrapolate that some 60–570 t of plastic are released fromCape Town stormwater outlets annually,which is orders
of magnitude less than predicted by global models. It is nevertheless clear that stormwater outlets are a significant
source of litter into the sea. Intercepting this waste before it reaches the sea would greatly reduce litter
loads in coastal waters around Cape Town.


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Last updated on 2021-19-03 at 09:50