Intra-annual variations of arsenic totals and species in tropical estuary surface sediments

Arsenic totals and species were found to vary during a one year period in the surface sediments of Godavari estuary (the third largest river in India). This study suggests that increasing salinity of overlying water column of sediments may alter the mobility of arsenic complexes in an estuarine system. The higher salt (NaCl) concentrations result in less arsenic adsorption to the sediment due to formation of weak arsenic complexes because of competition from Cl− ions or due to a reduction in interparticle attraction by the action of Na+. It is suggested that controlled freshwater discharge (from a dam) in an estuary influences the salinity of surface water and can have significant impact on the distribution and speciation of arsenic in the sediments and water column in such system.

► Increasing salinity of overlying water column reduces arsenic sorption at sediment.
► Controlled freshwater discharge (from a dam) can influence As speciation in sediments.
► DOC is a controlling factor in determining the speciation of arsenic in estuary.