Mercury and selenium in arthropods and their bioaccumulation across food webs

Seven different types of arthropods, including nine species, were collected from Wan-shan mercury (Hg) mining region and Leishan control site for Hg and selenium (Se) analysis. Stable isotopes δ¹³C and δ¹⁵N were also measured. Results showed that average concentrations of Hg and Se in arthropods were 157±329 and 190±277 ng • g^-1in Leishan, respectively, which were much lower than the 5692±1472 ng • g^-1 for Hg and 2220±691 ng •g^-1 for Se in Wanshan. Mercury concentrations in carnivorous species were significantly higher than those of herbivorous animals from both Hg mining region and control site, demonstrating Hg' s ability to bioaccumu-late across food webs. However, Se did not show bioaccumulation in arthropods. A significant positive correlation (r = 0.983, P<0.001) between Se and Hg was observed in samples collected from the control site with a molar ratio of 2: 1, but such a relationship was not found in the Hg mining region. A positive correlation (r = 0.434, P<0.001) between δ¹⁵N with Hg showed that δ¹⁵N could better reflect the relationship among predators and prey than δ¹³C did.