Determination and evaluation of the ecological risk of mercury in different granulometric fractions of sediments from a public supply river in Brazil

This work reports the quantification of total mercury in sediments collected in periods with and without rain from the Joanes River, Bahia, Brazil. Determinations were made using Direct Mercury Analysis (DMA), the ac-curacy of which was confirmed with two certified reference materials. The highest total mercury concentrations were found at the sampling point close to commercial areas and large residential condominiums. On the other hand, the lowest levels were found in the site close to a mangrove region. The geoaccumulation index was applied to the total mercury results, evidencing low contamination in the region studied. The contamination factor showed that of the seven stations investigated, four samples collected in the rainy season showed moderate contamination. The results of the ecological risk assessment were utterly consistent with the contamination factor data. This study showed that the smaller sediment particles concentrate more mercury, corroborating what has been predicted by the adsorption processes.

Automated summary

This study quantifies total mercury in sediments from the Joanes River in Bahia, Brazil, comparing periods with and without rain. Direct Mercury Analysis (DMA) was used, and its accuracy was confirmed with certified reference materials. The highest mercury concentrations were found near commercial areas and large residential condominiums, while the lowest levels were found near a mangrove region. The geoaccumulation index indicated low contamination in the studied area. The contamination factor showed moderate contamination in four out of seven sampling stations during the rainy season. The results of ecological risk assessment were consistent with the contamination factor data, confirming the concentration of mercury in smaller sediment particles due to adsorption processes.