Effect of Trivalent Chromium on Soil Urease Activity Characterisitics

Chromium was one of four major polluted heavy metals in environment;there were big difference in ecological toxicity among dif-ferent species chromium.By indoor simulations,soil urease activity and kinetic characteristics were studied in soils polluted by Cr3+,the re-sults showed as follows.Soil pH had the most important influence on Cr3+ ecological toxicity,soil urease was inhibited by Cr3+ in acid soil samples,there were remarkable or significantly negative correlation between soil urease characteristics(such as activity,Vmax,Vmax/Km and k values)and Cr3+ concentrations.The reaction mechanism was fully inhibition by the regression equation U=β0(/β1×C+1)between soil urease activity(U)and Cr3+ concentrations(C),furtherly it was no-competitive inhibition by urease kinetic parameters analyse.The ecological dose ED10 and ED50 were 50.59 and 865.7 mg.kg-1 when soil was slight and medium polluted by Cr3+ respective in acid soils.Soil urease activities,Vmax,Vmax/Km and k could be monitor indexes of polluted by Cr3+ in acid soils.In alkaline soils,soil urease is not sensitive to Cr3+.urease char-acteristics parameters were less change during Cr3+ concentrations tested,that activated at the lower concentrations and inhibited at the higher concentrations.It was because Cr species and state may be changed in the difference environmental conditions(such as acid soils and alka-line soils).