Inorganic As speciation and bioavailability in estuarine sediments of Todos os Santos Bay, BA, Brazil

► Total concentration of As at several stations along Todos os Santos Bay, was above TEL value. ► At Subaé and Paraguaçu systems, As (V) was the dominant species, which is less toxic and less mobile than As (III). ► Arsenic concentrations at Jaguaripe estuary were higher than in other estuaries and As (III) was the dominant species. ► Relationship between As, Fe, Mn and sand indicated that As enrichment at Jaguaripe River is natural. ► As concentrations in sediments and biota suggest that As is bioavailable and it is accumulating in marine organisms, which may impose human risks. ► Slurry sampling showed to be a easy, accurate procedure to be used for As determination in estuarine samples.