Sandy beaches contamination by arsenic, a result of nearshore sediment diagenesis and transport (Brazilian coastline)

We studied the distribution of As, Fe, Ca and Al in beach sands and near-shore surface sediments along the Brazilian coast from the equatorial zone to Rio de Janeiro state. High concentrations of As (up to 120 mg kg−1) exceeding the environmentally acceptable thresholds were found in the beach sands and near-shore surface sediment in several segments of the studied coast. That increased from north to south. The significant positive correlation (R2 = 0.58) between As and calcium carbonate in the beach sands corroborated the hypothesis that calcareous bioclasts participate in metalloid retention and its accumulation in beach sediments. Most likely, enrichment of As occurs in the oxic horizon of sediments caused by the diagenetic redistribution of various elements. Enrichment of As in beach sands occurs in the coast of Bahia and Espirito Santo states. That is facilitated by clastic material of calcareous algae.