Spatial and temporal variability and distribution of emerging contaminants in South African freshwater and wastewater

Abstract

Year-round variations of contaminants of emerging concern (CECs, also known as emerging contaminants) were examined in river water, dam water, and treated municipal wastewater in the South African setting. UPLC-MS/MS identified CECs belonging to different categories such as pesticides, licit and illicit recreational drugs, and particularly pharmaceuticals. Concentrations of up to 6 µg/L were identified but greatly varied spatially and temporally. Treated municipal wastewater was a harbinger for CECs (e.g., 6,055 ± 434 ng/L for efavirenz an HIV drug), while high CECs concentrations were also observed in river water (e.g., 3,228 ± 114 ng/L for acetaminophen). The high concentration for antiretroviral medication reflects the HIV/AIDS crisis in Sub-Saharan Africa and likely medicine misuse for illicit drug (whoonga/nyaope) manufacturing. Large intra-seasonal and intra-annual (seasonal) variations were observed (e.g., caffeine in dam water ranged from 73 ± 6 ng/L to 1,492 ± 30 ng/L), with overall high intra-seasonal and intra-annual variations (coefficient of variations up to 1.08 and 1.52, respectively) being observed. Individual risk quotients of up to 30 suggested high ecotoxicological risk potential. CECs pollution is apparent in South Africa, and likely across Sub-Saharan Africa and the Global South where similar problems persist, suggesting the need for effective wastewater treatment and policy intervention to curb CECs releases in freshwater.