Arsenic speciation and spatial and interspecies differences of metal concentrations in mollusks and crustaceans from a South China estuary.

Arsenic speciation and concentrations were determined in mollusks and crustaceans in the intertidal zone from twelve locations in Zhanjiang estuary, South China. Metal concentrations (Ag, As, Cd, Cu, Hg, Ni, Pb, and Zn) were also concurrently determined in these species. Arsenic speciation analysis showed that the less-toxic arsenobetaine (AsB) constituted 80.6-98.8 % of all As compounds, and dimethylarsinic acid (DMA) constituted 0.47-3.44 %. Monomethylarsonic acid (MMA) and As(V) were only detected in the whelk Drupa fiscella and the crab Heteropilumnus ciliatus, respectively. Arsenite [As(III)] was not detected in any of the sampled specimens, but there were also unidentified other As species. A strong spatial variation of metals in the oyster Saccostrea cucullata was found in the estuary, confirming that oysters can be used as a good biomonitor of metal contamination in the studied area. The concentrations of eight metals in the studied mollusks and crustaceans clearly revealed that these invertebrates accumulated different metals to different degrees. Furthermore, As, Cd, Cu, Hg, and Pb contents in mollusks and crustacean samples were below the Food and Agricultural Organization (FAO) safe concentrations, thus there was no obvious health risk from the intake of the metals through marine mollusks and crustaceans consumption.