重金属Cd、Zn、Cu和Pb复合污染对土壤生物活性的影响

通过野外土样采集及室内培养试验(25℃),研究了云南东川铜矿区土壤酶和微生物特征,以及模拟重金属Cd、Zn、Cu、Pb复合污染对土壤微生物和酶活性的影响。结果表明,矿区土壤(距矿口0~800 m)重金属污染严重,Pb、Cd、Zn、Cu全量和有效含量是对照土壤(距矿口10 000 m)的3.7~141.0倍和2.2~773.2倍;距矿口越近,土壤有机质、有效氮、有效磷和速效钾含量及土壤pH亦越低,土壤酶活性和土壤微生物数量、微生物生物量碳和氮受到的抑制程度也显著增强。与对照土壤相比,距矿口0~800 m的土壤蔗糖酶、脲酶、酸性磷酸酶、过氧化氢酶和脱氢酶活性分别降低25.5%~47.3%、22.6%~74.2%、30.9%~83.1%、16.7%~69.1%和34.6%~92.3%;细菌、放线菌和真菌数量分别较对照下降30.5%~80.1%、8.1%~49.9%和3.3%~8.3%。土壤酶中的酸性磷酸酶和过氧化氢酶,土壤微生物中的细菌对重金属污染较为敏感。恒温(25℃)培养试验中,低量的Cd、Zn、Cu、Pb复合污染刺激了土壤酶活性和细菌、真菌、放线菌、微生物生物量碳和氮的数量,但高量的Cu、Zn、Pb、Cd复合污染使土壤酶活性、细菌、真菌、放线菌、微生物生物量碳和氮均显著下降。重金属Cd、Zn、Cu、Pb之间存在着一定的协同或拮抗作用,Cd、Zn、Cu和Pb之间在微生物生物量碳和氮上表现出明显的协同效应,Pb与Cd、Zn、Cu对细菌数量的复合效应机制为拮抗效应,Cd、Zn、Cu和Pb对真菌数量和放线菌数量的复合效应机制表现为协同效应和拮抗效应并存。

Effects of heavy metal compound contamination of Cd, Zn, Cu andPb on soil biological activity

Soil microbial indicators and enzyme activity in Dongchuan copper mining wasteland of Yunnan Province were comparatively studied in laboratory with collected field samples.Incubation experiment was also conducted to investigate the influence of combined heavy metal pollution of cadmium,copper,zinc and lead on soil microbial indicators and soil enzyme activity.The results indicated that soil organic matter,available nitrogen(N),phosphorus(P) and potassium(K),and pH significantly decreased with decreasing distance of soil sampling points from the mines.Enzyme activity,microbial quantity,microbial biomass carbon(C) and N also decreased with decreasing distance of soil sampling points from the mines.Compared to the control(10 000 m from the mines),sucrase,urease,acid phosphatase,catalase and dehydrogenase activities along with amounts of bacteria,actinomyces and fungi in collected soil samples at 0~800 m from mine decreased by 25.5%~47.3%,22.6%~74.2%,30.9%~83.1%,16.7%~69.1%,34.6%~92.3%,30.5%~80.1%,8.1%~49.9% and 3.3%~8.3%,respectively.Whereas microbial biomass C and N decreased by 23.7%~66.2% and 31.8%~74.7%,respectively,while microbial biomass carbon to nitrogen ratio increased with increasing decreasing distance from the mines.Soil Organic matter,available N,P and K significantly decreased probably due to significant reductions in soil enzymatic activity,microbial amount,microbial biomass C and N.Compared with other indicators,soil phosphatase and catalase activity along with soil bacteria population were more sensitive to the degree of heavy metal pollution.Under incubation experiment at 25 ℃,soil enzyme activity,microbial population,and microbial biomass C and N were enhanced by combined pollution of low Cd,Zn,Cu and Pb.This,however,obviously decreased under combined pollution of high Cd,Zn,Cu and Pb.There were synergistic and antagonistic effects among Cd,Zn,Cu and Pb.While synergistic effects between Pb and Cd,Zn or Cu were related to microbial biomass C and N,antagonistic effects between Pb and Cd,Zn or Cu were related to bacteria population.Synergistic effects coexisted with antagonistic effects between Pb and Cd,and Zn,and Cu in relation to fungi and actinomyces populations,respectively.