Effects of single and combined pollution of Cr3+ and Ni2+ on soil enzyme activities in paddy soil.

The effects of single and combined pollution of Cr3+ and Ni2+ on the activities of urease,acid phosphatase and catalase in paddy soil were investigated through the lab-scale experiment by artificially controlling temperature and humidity.The results showed that urease and acid phosphatase activities were stimulated under low added Ni2+ concentration in single Ni2+ treatments,while the activities of the three enzymes in the rest treatments were all inhibited.Ni2+ inhibited the enzyme activities in the order of urease acid phosphatase catalase,while the enzyme activities were inhibited by Cr3+ and Cr-Ni combined pollution in the following order of urease catalase≈acid phosphatase.The characteristics of Cr-Ni combined pollution for urease and acid phosphatase mainly exhibited synergistic effect;However,it largely pointed out synergistic effect for catalase in the early period of culture.