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Emerging Freshwater Contamination in Two Subtropical Austral River Systems of Zimbabwe
Summary
Researchers found high concentrations of microplastics alongside hormone-disrupting chemicals like BPA and phthalates in two rivers running through Harare, Zimbabwe, reflecting contamination from rapid urbanization and inadequate waste treatment. The co-occurrence of microplastics and endocrine disruptors in the same waterways amplifies health risks, since plastics can carry and concentrate these chemicals as they travel through the environment.
Rapid urbanisation, agriculture, and industrial discharges intensify contamination risks, threatening aquatic ecosystems and human health. Therefore, the current study aimed to investigate the occurrence of microplastics (MPs) and endocrine–disrupting chemicals (EDCs) in the Marimba and Mukuvisi rivers (Harare, Zimbabwe). The MPs for the two rivers had a mean of 413.8 ± 115 particles/L and 612.4 ± 485.7 particles/L, respectively. Five shapes (i.e., fibres, fragments, foam, film and beads) were found in this study; fibres and fragments were the most dominant types. Transparent (18.1–37.0%), black (17.4– 21.4%) and blue (9.9–22.2%) were the most observed MPs colour type. Alkylphenols (APs), phthalic acid esters (PAEs), and polybrominated diphenyl esters (PBDEs) in water and sediments were quantified using gas chromatography-mass spectrometry (GC–MS). The sum of PAEs, APs and PBDEs in the water were 20.7 ± 11.6 mg/L, 2.56 ± 2.24 mg/L, and 0.32 ± 0.28 mg/L for Marimba River, respectively, and 6.6 ± 3.7 mg/L, 3.73 ± 2.01 mg/L, and 0.75 ± 0.46 mg/L for the Mukuvisi River, respectively. For sediments, the APs, PAEs and PBDEs were 16.99 ± 19.28 mg/kg, 15.3 ± 9.4 mg/kg, and 0.46 ± 0.23 mg/kg for the Marimba River, respectively, and 21.25 ± 24.14 mg/kg, 15.01 ± 5.76 mg/kg, and 0.57 ± 0.70 mg/kg for the Mukuvisi River, respectively. Notably, from this study, high concentrations were observed for Bisphenol A (BPA) and dibutyl phthalate (DBP), which contributed 86–96% and 63–96% to the sum of APs and PAEs, respectively. The three classes of EDCs (i.e., APs, PAEs, PBDEs) observed in the study are highly toxic, carcinogenic, and mutagenic, and they can disrupt the endocrine system. Thus, without urgent mitigation measures, water quality degradation will threaten ecosystems and human health. The study highlights significant emerging freshwater contamination in Zimbabwe’s river systems, driven by agricultural runoff, industrial discharge, and urbanisation pressures (i.e., raw sewage spillages and discharges). Sustainable practices, stricter regulations, and community engagement are essential to safeguard these vital water resources for future generations.