中文摘要：

重金属污染影响微生物活性，土壤中微生物活性的变化反映着土壤质量。通过实验模拟，研究不同浓度的外源重金属Cd对土壤微生物活性的影响，选择山林土和田园土为研究对象，测定土壤呼吸强度、脲酶活性、过氧化氢酶活性来表征土壤中微生物活性。结果表明，田园土中土壤呼吸强度、过氧化氢酶活性及脲酶活性均高于山林土。Cd对微生物活性具有明显的抑制作用，表现为随着Cd浓度的升高，土壤呼吸强度、过氧化氢酶活性及脲酶活性均总体呈现下降趋势；当Cd质量浓度为1．0mg／kg时，土壤脲酶活性增强，说明低浓度Cd对一些微生物活性有促进作用；当Cd质量浓度为10．0mg／kg时，土壤呼吸强度和过氧化氢酶活性增强，说明土壤呼吸强度和过氧化氢酶活性对逆境有强烈的反应机制。土壤中的有效态Cd随培养时间的延长会减少，使其对微生物活性的抑制作用减弱。

英文摘要：

Heavy metal contamination has strong effect on the soil microbial activities and microbial activities reflect the status of soil quality under Cd pollution. The influence of exogenous Cd on biological activities in soils was studied using traditional incubation under laboratory conditions. Soils in forest land and rural land were selected as the research objects in the experiment. By measuring some principal indexes of the microbial activities in soil such as the respiration,urease activity and catalase activity, the experiment observed and analyzed soil microbial activities which affected by Cd pollution. The result indicated that the microorganisms in forest soil contaminated by Cd was more sensitive than rural soil under same condition. Further more, the respiration and enzyme activity in rural soil were higher than that in forest soil. It was no doubt that Cd had inhibitory effect on microorganism and the results showed that the respiration and enzyme activity in soil decreased with high Cd concentration. It was found that the variation of soil urease activity was enhanced under the condition of the concentration of cadmium at 1.0 mg/kg,which suggested that low concentration of cadmium bad a stimulating effect on some microbial activities. Respectively, the respiration and the activity of catalase was enhanced under the concentration of cadmium at 10.0 mg/kg. It suggested that respi- ration and the activity of catalase had strong reaction under severe environment. With increasing of incubation time, the available Cd would reduce and weaken the inhibitory effect of Cd on microorganism.