Risk Assessment of Mercury in Soil, Water, and Sediments Collected in a Region Impacted by Gold Mining

This work reports the determination of mercury and the assessment of health risks in water, river sediments, and soil samples collected in the city of Jacobina, Brazil, located in a region impacted by gold mining. The mercury determinations were performed using the direct method analyzer (DMA) method, which was carefully validated according to the IUPAC recommendations. Total mercury contents ranged from 0.10 to 1.77 μg L^-1 in water samples, from 0.005 to 0.278 μg g^-1 in soil samples, and from 0.014 to 0.317 μg g^-1 in river sediment samples. The contamination factor (CF) and the ecological risk index were applied to the data obtained from soil and sediment analyses. Only one of the twenty-one soil samples had CF > 1 (1.11), denoting moderate contamination for this sampled site. All 20 other samples had CF < 1 (0.02 to 0.69), showing low mercury contamination in the soils collected throughout Jacobina. The results of the ecological risk index perfectly corroborated the results found by the CF, denoting that only one sample had a moderate potential ecological risk. Among the 13 sediment samples, two had CF > 1 and Er in the range of 40 to 80, denoting moderate contamination and moderate ecological risk in these two sampled locations. All 11 other samples had CF < 1 and Er less than 40, demonstrating that the sediments analyzed have low contamination and low potential for ecological risk due to mercury. All mercury levels found in water samples are below the maximum limit (2 μg L^-1) established by the CONAMA, the Brazilian Government, for class 3 freshwater. The assessment of daily mercury exposure was also performed using the routes of exposure through dermal contact (ADIder), inhalation (ADIinh), ingestion (ADIing) in the soil samples, and dermal contact and ingestion in the water samples employing the health risk indices established by the USEPA. The results obtained did not indicate noncarcinogenic risks for adults and children.