Natural archives of long-range transported contamination at the remote lake Letšeng-la Letsie, Maloti Mountains, Lesotho

Neil L. Rose, Alice M. Milner, Jennifer M. Fitchett, Kristy E. Langerman, Handong Yang, Simon D. Turner, Anne Lise Jourdan, James Shilland, César C. Martins, Amanda Câmara de Souza, Christopher J. Curtis

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

Naturally accumulating archives, such as lake sediments and wetland peats, in remote areas may be used to identify the scale and rates of atmospherically deposited pollutant inputs to natural ecosystems. Co-located lake sediment and wetland cores were collected from Letšeng-la Letsie, a remote lake in the Maloti Mountains of southern Lesotho. The cores were radiometrically dated and analysed for a suite of contaminants including trace metals and metalloids (Hg, Pb, Cu, Ni, Zn, As), fly-ash particles, stable nitrogen isotopes, polycyclic aromatic hydrocarbons (PAHs) and persistent organic pollutants such as polychlorinated biphenyls (PCBs), polybrominated flame retardants (PBDEs) and hexachlorobenzene (HCB). While most trace metals showed no recent enrichment, mercury, fly-ash particles, high molecular weight PAHs and total PCBs showed low but increasing levels of contamination since c.1970, likely the result of long-range transport from coal combustion and other industrial sources in the Highveld region of South Africa. However, back-trajectory analysis revealed that atmospheric transport from this region to southern Lesotho is infrequent and the scale of contamination is low. To our knowledge, these data represent the first palaeolimnological records and the first trace contaminant data for Lesotho, and one of the first multi-pollutant historical records for southern Africa. They therefore provide a baseline for future regional assessments in the context of continued coal combustion in South Africa through to the mid-21st century.

Original languageEnglish
Article number139642
JournalScience of the Total Environment
Volume737
DOIs
Publication statusPublished - 1 Oct 2020

Keywords

  • Contamination
  • Fly-ash
  • Lake sediments
  • Lesotho
  • Long-range transport
  • Persistent organic pollutants
  • Trace metals
  • Wetlands

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

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