土壤是受人类活动强烈影响的一类特殊物质，对重金属污染具有一定的缓冲能力，它即是被污染的对象也是作物的污染源。在不同地区之间，不同类型的重金属含量存在着显著差异，不同的土壤类型，表现的重金属污染程度也不一样。因此本文选用了塿土作为主要的研究对象，同时以西安塿土为代表。 本文通过外源添加重金属Pb、Cd、Cr盆栽小白菜实验，模拟不同浓度土壤重金属污染对土壤磷酸酶活性的影响，得出如下结论: 1.在不同浓度的Pb的影响下，塿土磷酸酶活性主要受到抑制作用，并随着浓度的增加，抑制作用增加；未添加Pb的土壤磷酸酶活性最高达到51μg/kg，当浓度在250-350 mg/kg时达到最低，磷酸酶活性为44.2μg/kg；塿土磷酸酶活性可作为土壤重金属Pb污染时的酶学指标; 2.当Cd浓度小于0.2mg/kg时，磷酸酶活性受抑制；在Cd浓度为0.2-0.7mg/kg时，磷酸酶活性变化波动基本在48μg/kg左右；浓度为0.4mg/kg时，磷酸酶被激活达到52 μg/kg；随时间的延长，酶活性有降低趋势，降至39.7-44.5 μg/kg；塿土磷酸酶活性可作为土壤重金属Cd污染时的酶学指标; 3.Cr浓度为80-110mg/kg时，酶活性相对较高达到54μg/kg；与Pb、Cd相比，Cr影响下的磷酸酶活性变化最为平缓，没有明显抑制或激活作用，塿土磷酸酶活性不能作为土壤重金属Cr污染时的酶学指标; 4.在Pb、Cd的污染下，污染等级1、2、3的磷酸酶活性临界值分别为53.7、46.2、38.7μg/kg；52.24、47.12、34.98μg/kg； 5.在重金属Pb、Cd、Cr单一污染下，对塿土磷酸酶活性的抑制效应顺序为Pb>Cd> Cr，随着时间的延长，酶活性越趋于稳定;小白菜生长受受抑制的顺序为Cr>Pb>Cd；塿土磷酸酶活性对小白菜生长影响不大。

Soil is a special kind of soil strongly influenced by human activities, heavy metals pollution also has a certain buffer capacity, it is an object that is contaminated crops are also sources of pollution.In different areas, different types of heavy metals there are significant differences between different soil types, the performance of heavy metal pollution are not the same.Therefore, this paper selected manural loessial soil as the main object of study, to Xi'an, manural loessial soil represented. This article by adding heavy metals Pb, Cd, Cr, to simulate different concentrations of heavy metal pollution, study Chinese cabbage and soil phosphatase sensitivity of heavy metals, conclusions were as follows: 1.The effects of different concentrations of Pb, manural loessial soil mainly by inhibition of phosphatase activity. With the increase of the concentration the inhibition increased. Without Pb the soil phosphatase activities reached 51μg/kg, when the concentration between 250-350 mg/ kg，it become the lowest 44.2 μg/kg.Phosphatase activity can be used as heavy metal Pb contamination of the enzyme target. 2.When the Cd concentration is smaller than 0.2 mg/kg, the soil phosphatase activity reduces unceasingly, During the period of concentration is 0.2-0.7 mg/kg, the phosphatase activity change fluctuation is greatly basic in 48 μg/kg about; When the density is 0.4 mg/kg, the phosphatase is activated achieves 52 μg/kg; But along with the raise time's extension, the enzyme activity has reduces the tendency, drops to 39.7-44.5 μg/kg. Phosphatase activity can be used as heavy metal Cd contamination of the enzyme target. 3.The Cr concentration between 80 to 110mg/kg, the activity is relatively high to 54 μg/kg; and compared to Pb and Cd, phosphatase activity under the influence of Cr change in the most gentle, no significant inhibition or activation. Phosphatase activity can not be used as heavy metal Cr contamination of the enzyme target. 4. Under the Pb, Cd pollution, the phosphatase activity were 53.7,46.2,38.7 μg / kg; 52.24,47.12,34.98 μg / kg on the pollution level of 1,2,3; 5. Under a single pollution，the order of Pb、Cd and Cr inhibitory effects soil phosphatase activity is Pb >Cd>Cr. With time, the more activity tends to stabilize; the order of cabbage growth was inhibited is Cr>Pb>Cd; soil phosphatase activity has little effect on the growth.