Mercury species in fish from a tropical river highly impacted by gold mining at the Colombian Pacific region

This study was carried out in the Atrato River basin, a tropical ecosystem in northwestern Colombia, highly impacted by gold mining. The aim of this study was to show how these activities have deteriorated the quality of fish species, and how their intensity has influenced the distribution of mercury (Hg) pollution in the Atrato River basin. Results showed that total mercury (THg, n = 842) ranged between 32 +/- 53 mu g kg(-1) (Cyphocharax magdalenae) and 678.5 +/- 345 mu g kg(-1) (Agneiosus pardalis); 38% of the samples exceeded the WHO limit for the protection of populations at risk, and 15% surpassed the WHO maximum limit of THg in fish for human consumption. A significant positive correlation (p < 0.001) was found between THg with total fish length and trophic level, indicating bioaccumulation and biomagnification of mercury in fish, respectively. Using the non-migratory and carnivorous fish species Hoptias malabaricus and Caquetaia kraussii, Hg contamination was found distributed from high mining activity zones (Rio Quito, Medio Atrato, and Murindo & Vigia del Fuerte - upstream zones) to low activity areas (Rio Sucio & Carmen del Darien, and Cienaga de Ungia & Tumarado - downstream zones). In the first-ever performed methyl-mercury (MeHg) measurements in 520 fish muscle samples analyzed from the Atrato River basin, a high MeHg/THg ratio (91% of the THg) in species such as A. pardalis and H. malabaricus were recorded. Results indicated that the environment and the fish species in the Atrato River basin had been greatly affected by gold mining activities practiced on the river and its tributaries. Therefore, environmental authorities must take protection measures for the inhabitants of the area as well as for the environment. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study revealed that gold mining activities in the Atrato River basin have deteriorated the quality of fish species, resulting in high levels of mercury pollution. The contamination was found to be distributed from high mining activity zones to low activity areas, affecting both the environment and the inhabitants in the region.