Mercury Concentrations in Water, Sediments, Soil, and Fish Around Ancestral Afro-Descendant Territories Impacted by Gold Mining in the Cauca Department, Colombia

Although mercury (Hg) is ubiquitously present in natural ecosystems, human activities have promoted its accumulation and toxicity in the environment. The aim of this study was to assess the concentrations of total Hg (T-Hg) in different environmental matrices from two territories of Afro-descendant communities: Aires of Garrapatero (CCAG) and Cauca River Basin, Micro Basin of the Teta and Mazamorrero Rivers (CCMTM). Total Hg (T-Hg) was quantified using a direct Hg analyzer. The average T-Hg values from water and sediments collected in CCAG (0.86 ± 0.09 µg/L and 0.18 ± 0.02 µg/g) were statistically similar to those from CCMTM (0.65 ± 0.08 µg/L and 1.72 ± 0.64 µg/g). However, high Hg levels were detected in sediments from the Teta River (4.67 ± 1.32 µg/g). Surface soil displayed a pattern similar to that registered in sediments (0.09 ± 0.01 µg/g vs. 0.42 ± 0.14 µg/g). The contamination factor and geo-accumulation index of Hg in soil showed a relatively high degree of pollution with Hg at sites near the Teta River. In most fish species examined (53%), T-Hg concentrations were above the WHO limit (0.5 μg/g), with the highest levels (> 1.0 µg/g) found in Pseudopimelodus bufonius (2.53 µg/g), Saccodon dariensis (1.75 μg/g), and Gilbertolus sp. (1.04 µg/g). The most economically important fish species, Prochilodus magdalenae , registered 0.56 ± 0.06 µg/g. Risk assessment based on Hg exposure from diet suggested that the current Hg levels found in local fish represent considerable health risks for children, pregnant women, and adults. In short, the Teta River is a hotspot for Hg pollution in the territory and requires urgent remediation programs to reduce environmental exposure to this toxic metal. Moreover, fish consumption from species collected in local water bodies represents a health risk to the community. Both educational and monitoring programs are required to reduce adverse effects from Hg exposure.