Distribution and Bioavailability of Heavy Metals in Soil Aggregates from the Fenhe River Basin, China

Accumulation, bioavailability and potential ecological risk of seven heavy metals - chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd) and lead (Pb) - have been analyzed in agricultural soil aggregates with particle size of > 1 mm, 0.25-1 mm, 0.05-0.25 mm, and < 0.05 mm from the Fenhe River Basin (FRB). Accumulation factor (AF) analysis demonstrated that heavy metals tend to be enriched in < 0.05 mm soil aggregate. The bioavailability to plants of Cu, Zn, and Cd was higher than that of other metals and increased with the decrease in soil aggregate particle sizes. Risk assessment code (RAC) of Ni, Cu, Zn and Cd were 13.84%-21.08%, 7.13%-13.74%, 32.08%-51.82% and 29.38%-43.82%, indicating that Cu, Zn, Cd and Ni had a low to very high risk to other ecosystems, and the smaller the particle size (0.05-0.25 mm and < 0.05 mm), the greater ecological risk.