Spatio-temporal distribution of trace metals in tropical mangrove sediment cores, northeastern Brazil

Mangrove sediments are effective archives of trace metals (TM) accumulation and provide insights into natural and anthropogenic influences on coastal environments. This study evaluated the spatial and temporal distribution, sources, and potential ecological risks of TM in sediment cores collected from seven mangrove estuaries along the coast of Bahia, northeastern Brazil, covering approximately 25–91 years of sediment deposition. Concentrations of As, Cd, Cr, Cu, Ni, Pb, and Zn varied among estuaries, with spatial variability greater than temporal variability within individual cores. Protected areas exhibited the lowest concentrations (e.g., Cu ≤ 4.4 mg kg −1 ; Zn ≤ 24.9 mg kg −1 ), whereas higher concentrations were observed in estuaries influenced by urbanization, agriculture, and industrial activities. Notably, Cu concentrations were elevated in the São Paulo River estuary (27.6–45.7 mg kg −1 ), while southern estuaries showed higher As (up to 24.5 mg kg −1 ) and Zn (up to 58.9 mg kg −1 ) levels. Multivariate analyses indicated that metal distributions reflect a combination of natural geochemical background and localized anthropogenic contributions. These results can represent a regional baseline for mangrove sediments in Bahia.