Curtis, CJ;
Rose, NL;
Yang, H;
Turner, S;
Langerman, K;
Fitchett, J;
Milner, A;
... Shilland, J; + view all
(2024)
Contamination of depressional wetlands in the Mpumalanga Lake District of South Africa near a global emission hotspot.
Science of the Total Environment
, 938
, Article 173493. 10.1016/j.scitotenv.2024.173493.
(In press).
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Abstract
The Mpumalanga Lake District (MLD) of South Africa hosts a regionally unique cluster of water bodies of great importance for wetland biodiversity. It is also located close to a global hotspot for coal-fired power station emissions but the local impacts from these sources of pollution are poorly understood. Sediment cores from three contrasting wetlands were ²¹⁰Pb dated and analysed for a range of contaminants linked to fossil fuel combustion, including trace elements, Hg, sulphur and spheroidal carbonaceous fly-ash particles (SCPs). At the two sites with pre-industrial (1900) baseline sediments, Pb, Zn and especially Cr concentrations and fluxes showed significant increases in the impact period (post-1975). Mercury showed the greatest proportional increase in flux (>4-fold) of all trace metals. Mercury and sulphur concentrations and fluxes showed highly significant correlations with emissions over the corresponding periods, while SCPs in sediments also closely tracked emissions. In a global context, levels of sediment contamination are relatively minor compared with other heavily industrialised regions, with only Cr exceeding the sediment Probable Effects Concentration for biological impact post-1975. Despite the relatively large increases in Hg, concentrations do not reach the Threshold Effects Concentration. The unexpectedly low levels of contamination may be due to i) low levels of many trace contaminants in South African coals compared to global averages, ii) prevailing recirculation patterns which transport pollution away from the study area during the wet season, minimising wet deposition, and iii) pollutant remobilisation through desiccation of wetlands or volatilization. The effects of hydrology and sediment accumulation rates lead to differential transport and preservation of organic-associated and more volatile contaminants (e.g. Hg, S) relative to non-volatile trace elements in wetlands of the MLD. The greatest fluxes of Hg and S are recorded in the site with the highest catchment: lake area ratio, lowest salinity and greatest sediment organic matter content.
| Type: | Article |
|---|---|
| Title: | Contamination of depressional wetlands in the Mpumalanga Lake District of South Africa near a global emission hotspot |
| Location: | Netherlands |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.scitotenv.2024.173493 |
| Publisher version: | https://doi.org/10.1016/j.scitotenv.2024.173493 |
| Language: | English |
| Additional information: | © The Author(s), 2024. This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/. |
| Keywords: | ¹⁵N, Atmospheric deposition, Chromium, Mercury, SCPs, Sulphur |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL SLASH UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > Dept of Geography UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > SHS Faculty Office UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > SHS Faculty Office > UCL Institute for Advanced Studies |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10193571 |
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