ABSTRACT
Arsenic (As) bioaccmulation and trophic transfer were studied in various species of aquatic organisms from the streams and a reservior (Zaoshi Lake) around Shimen realgar mine, which had been closed since 2001. The As concentrations in top soils, sediments and water were decreasing with the distance from the central mining sites, indicating the As mining activities had still produced eminent impact on As contamination around the mine. Throughout the sampling sites, the As in biota was ranked in an order of tadpole > crab > frog > loach > other fishes. The δ 13C and δ 15N values in the same species of organisms varied greatly with sites, suggesting the impact of diet variation on the trophic levels of the same species in the food chain. The trophic levels for various species of organisms were determined as from 1.25 to 3.76 based on δ 15N values. In streams, As levels were much higher in lower trophic organisms, but were quite stable at higher trophic levels, indicating no bio-magnification of As in the food chain, while in the reservoir organisms had much lower arsenic concentrations but obvious biomagnification trend through the food webs. Moreover, the As speciation, including iAs(III), iAs(V), MMA, DMA, AsB and other species were analyzed to explore the biotransformation of As and the sources and bio-transfer of organic As in the food chain. It was found that the organic As species increased with trophic levels in streams, while in reservoir they showed opposite patterns.
