The distribution characteristics and bioaccumulation of arsenic in food webs around a realgar mine, China

Arsenic (As) is a ubiquitous but carcinogenic metalloid element. Shimen realgar mine has the largest As mine in Asia with a mining history of 1500 years, therefore it could induce substantial increase of arsenic concentration in the environment and living organisms, and ultimately into human bodies. The total As in surface soil, sediments and water were in the range of 35-5000 mg/kg, 43-4543 mg/kg and 5-3293 μg/l, respectively. The As concentrations were decreasing with the distance from the central mining sites, indicating the As mining activities had produced eminent impact on As contamination in Shimen. Throughout the study sites, the rank order of As in biota was tadpole>earthworms>crab>frog>loach>other fishes. The total As concentrations in soil, litter and earthworms showed a significant positive relationship. The δ 13 C and δ 15 N value in the same species of organisms varied greatly with sites, which suggest the impact of diet difference 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 15 N 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, however, the reservoir showed slight arsenic concentrations and obvious biomagnification 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 food chain. It found that the organic As species increased with trophic level in the contaminated streams, while the reservoir showed contrast pattern.