重金属积累对土壤酶活性的影响

研究了华北平原某铅冶炼厂附近农田33个土壤样品中重金属积累对土壤酶活性的影响。结果表明,样品中Pb和Cd全量的平均值分别为144和5.59mg·kg-1,DTPA态Pb和Cd含量平均值分别为54.1和0.964mg·kg-1,均超过了未污染农田潮土的正常范围,而Cu、Ni和Zn的有效性和全量与未污染土壤接近;土壤过氧化氢酶活性与DTPA态Pb和Cd含量、全Pb含量均呈显著的负线性关系(P<0.01);与磷酸酶和脲酶相比,土壤脱氢酶活性更易受到土壤中Pb和Cd积累的影响;随DTPA-Ni含量增加,土壤蛋白酶和碱性磷酸酶活性增加(P<0.1);土壤脲酶活性与重金属全量或有效态重金属含量无显著相关性(P>0.1)。以上结果说明,利用土壤过氧化氢酶和脱氢酶活性能够表征基本性质较为一致的土壤中重金属污染程度;与重金属全量相比,有效态重金属对土壤酶活性影响更大。

Effects of Accumulation of Heavy Metals in Soils on Enzyme Activities

Thirty-three soil samples were collected from farmland near a lead smelter in North China Plain, which were analyzed for the effect of accumulation of heavy metals in soils on the enzyme activities. The results indicated that average contents of the total Cd and Pb were 5.59 and 144 mg·kg^-1, respectively. Average contents of DTPA-extractable Cd and Pb were 0.964 and 54.1 mg·kg^-1, respectively. These values were higher than these in unpolluted Chao soil, while the total and DTPA-extractable contents of Cu, Ni and Zn were similar to the values of unpolluted Chao soil. Significant negative linear correlations were found between catalase activity and DTPA-extractable Pb, Cd and the total Pb (P<0.01). Compared with the activities of urease and phosphatase, the accumulation of heavy metals had a more serious effect on the activity of dehydrogenase. The activities of protease and phosphatase increased with increasing levels of DTPA-extractable Ni (P<0.1). No significant correlation was found between the urease activity and the total or DTPA-extractable contents of Cu, Zn, Ni, Pb and Cd (P>0.1). The results suggest that the activities of catalase and dehydrogenase in soil could be used to distinguish the degree of heavy metal pollution in soils with similar properties. DTPA-extractable heavy metals have a more profound effect than the total concentrations of heavy metals in soil on enzyme activities.