Spatial distribution of chemical elements in the surface sediments of a tropical estuary in north-eastern Brazil

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The high socioeconomic importance of estuarine environments is contributing to their continuous and increasing settlement by human populations and a growing negative impact on those sensitive habitats. Considering the natural importance of estuarine regions, this study aimed to quantify and spatialize the distribution of the chemical elements iron (Fe), aluminium (Al), manganese (Mn), vanadium (V), barium (Ba), zinc (Zn), copper (Cu), lithium (Li), cobalt (Co), chromium (Cr), nickel (Ni), lead (Pb) and arsenic (As) and produce a potential risk assessment from the surface sediments along the extent of the Serinhaém Estuary, Bahia, Brazil, in order to evaluate the environmental quality of the estuary. The mean concentrations of the chemical elements followed the order: Fe > Al > Mn > Ba > Zn > V > Cr > As > Pb > Co > Li > Cu > Ni. Through analysis using the geo-accumulation index, the concentrations of the chemical elements were determined to reflect the local lithology and not the influence of human activities for all the elements, with the exception of Ba, the enrichment of which came from Camamu Bay. The chemical elements in the sediments do not pose a risk to the local biota or the human population. The distribution maps revealed a tendency for the accumulation of higher concentrations of elements in some sectors of the channel. This study can be used in the future as a complete profile of the background concentrations of the studied elements in the sediments, aiding in the continuity of monitoring actions.