Cr^3＋对土壤脲酶活性特征的影响

采用模拟方法对Cr^3＋的土壤脲酶效应进行了研究,结果表明,土壤pH对Cr^3＋的生态毒性有重要影响;酸性土壤脲酶受到显著抑制,活性及动力学特征参数与Cr^3＋浓度间达显著或极显著负相关,而且模型U=β0（/β1×C＋1）揭示其间机理为完全抑制,动力学则进一步细化为非竞争性抑制;获得土壤轻微和中度污染时的生态剂量ED10和ED50分别为50.59和865.7 mg.kg^-1;酸性土壤中脲酶活性、Vmax、k可作为土壤Cr^3＋污染的监测指标之一,而碱性土壤则反应不敏感,其随铬浓度增加,脲酶活性及动力学参数呈先增加后降低的规律性变化,总体变幅较小;两类土壤的差别可能主要是由于土壤环境引起了不同价态铬转变的缘故。

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 different species chromium. By indoor simulations, soil urease activity and kinetic characteristics were studied in soils polluted by Cr^3＋, the results showed as follows. Soil pH had the most important influence on Cr^3＋ ecological toxicity, soil urease was inhibited by Cr^3＋ 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 Cr^3＋ concentrations. The reaction mechanism was fully inhibition by the regression equation U=β0/（β1×C＋1 ）between soil urease activity （U）and Cr^3＋ 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 Cr^3＋ respective in acid soils. Soil urease activities, Vmax, Vmax/Km and k could be monitor indexes of polluted by Cr^3＋ in acid soils. In alkaline soils, soil urease is not sensitive to C^3＋. urease characteristics 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 alkaline soils ）.