Total and hexavalent chromium Cr(VI) were measured in sediment in a coastal lagoon to assess the relationship between sediment geochemistry and chromium speciation, which in turn controls the mobility, bioavailability, and toxicity of chromium. Surface (first top 5 cm) sediment samples were also tested for pH, redox potential, acid-volatile sul没des (AVS), and organic matter content. In whole sediments, total chromium and Cr(VI) concentrations ranged from 16 to 81 mg/kg and from 0.5 to 1.9 mg/kg, respectively. Concentrations of AVS (ranging between 1.8 and 9.2 umol/g) and other geochemistry measurements indicated anoxic, reducing conditions in the majority of sediment samples. The results of this study are consistent with sediment studies conducted elsewhere indicating low chromium bioavailability in sediment under reducing conditions
