Speciation and Bioavailability of Metals in Sediments from a Stream Impacted by Abandoned Mines in Maoshi Town, Southwest of China.

The speciation of metals in surface sediments, as well as metal concentrations in muscle and liver of sharpbelly Hemiculter leucisculus from a stream near the Mo-Ni polymetallic mines in Maoshi town were investigated. The results indicated that metal concentrations were generally highest in the most upstream sampling location that is closest to the former mine operation. The total concentrations of Mn in sediments were higher than other metals. The Cr was mainly associated with residual fraction, while the order of bioavailability of metals (sum of the concentrations of exchangeable, reducible, and oxidizable fractions) was as follows: Cd (89.95%) > Mn (82.32%) > Ni (45.58%) > Mo (29.39%) > Hg (29.23%) > As (22.60%) > Pb (17.38%) > Cr (6.21%). The Cd concentration in muscle of H. leucisculus exceeded the permissible limit which indicated that the fish from this area are not safe for human consumption. The potential ecological risks of Cd cannot be ignored in this study area.