中文摘要：

摘要：土壤酶和微生物量碳是反映土壤健康的重要微生物性质指标。土壤重金属污染能够对土壤微生物性质产生影响，然而土壤酶和微生物量碳对土壤重金属污染的响应受到土壤本身理化性质的影响。通过北京市建成区233个样点的数据监测和实验室模拟，研究了土壤脲酶活性和微生物量碳对土壤低浓度重金属污染的响应以及受土壤理化性质的影响。研究结果表明：在野外主要重金属污染的浓度范围内（Cd0．003—0．98μg·g-1，Cu13．4～207．9μg·g-1，Zn29．4—322μg·g-1，Pb4．02～174μg·g-1），土壤脲酶活性、微生物量碳（MBC）和有机碳（SOC）的含量与土壤中Cd、Cu、Zn和Pb的浓度正相关，而微生物量碳占有机碳的比率（MBC／SOC）与重金属浓度负相关；脲酶活性、MBC／SOC与重金属浓度建立的相关关系只能解释总变异的5％～10％。实验室模拟试验表明，土壤酶活性受土壤重金属含量和土壤性质联合效应的影响；土壤有机质含量和pH是影响酶活性的主要土壤理化性质。引入土壤有机碳含量和pH两个参数，重新建立脲酶活性、MBC／SOC与土壤中重金属浓度的关系，建立的相关关系的决定系数变大，能够解释总变异的14％～17％。

英文摘要：

Soil enzymes and microbial biomass carbon are important microbial indexes of soil health. Soil heavy metal pollution would affect the activities of soil enzymes and microbial biomass carbon content. The impacts however change with soil properties. In this research, field monitoring and laboratory simulation were carried out to study the impact of soil heavy metals contaminations on urease activity and the ratio of （microbial bio-mass carbon） / （soil organic carbon） （MBC / SOC）. In field monitoring experiments, 233 points of Beijing urban soils inside the 5th ring road were sampled. Soil inside the 5th ring road of Beijing was polluted by low con- centration of heavy metal （Cd 0.003 ~ 0.98 Ixg＂ g-1, Cu 13.4 - 207.9 Ixg＂ g-1, Zn 29.4 ~ 322 Ixg＂ g-~, Pb 4.02 ~ 174 ~g.g-1）. Relationship between urease activity and MBC / SOC and concentrations of Cd, Cu, Zn and Pb of those soils were analyzed. Under the range of soil heavy metal concentrations in Beijing, Cd, Cu, Zn and Pb would have a promotion on the urease activity and reduce the MBC / SOC value. There was a significant posi- tive correlation between urease activity, MBC, SOC and heavy metal concentrations, while there was a negative correlation between MBC / SOC and heavy metal concentrations. Soil heavy metal pollution could only explain 5% ~ 10% of the total variance between urease activity or MBC / SOC and heavy metal concentrations. Labora- tory simulation experiment revealed that soil enzymes activities were affected by the interaction of heavy metals and soil properties. Correlation analysis showed that soil organic matter content and pH were the major soil fac- tors impacting urease activity. A greater R2was got, when introducing soil organic matter content and pH. Soil heavy metal concentrations and the two soil properties could explain 14% - 17% of the total variance.