贵州赫章土法炼锌导致的土壤重金属污染特征及微生物生态效应

Soil heavy metal accumulation induced by local smelting and its microbial environmental effects in Hezhang County, Guizhou Province

贵州省赫章县妈姑镇新关寨附近的土法炼锌不仅导致植被的破坏,而且使附近土壤中重金属有不同程度的积累,Zn达到162.23～877.88mg/kg,Pb为37.24～305.56mg/kg,Cd为0.50～16.43mg/kg,大大超过了当地的土壤背景值;而且重金属含量(特别是Pb和Zn含量)与土壤中的Fe2O3和Al2O3有极显著的正相关关系,显示土壤中铁氧化物和粘土矿物对重金属的固定作用。化学形态研究表明,Pb和Zn在土壤中主要表现为铁锰氧化物结合态与残渣态,而Cd的情况与Pb和Zn完全相反,其形态以可交换态为主。本区土壤微生物生物量(用含碳量表示)较低,仅为57.00～388.00μg/g,而且与土壤重金属间有显著的负相关关系,特别是与Zn的相关系数高达-0.7801,反映出重金属对微生物的毒害作用。Biolog测试结果表明,土壤微生物群落结构间没有明显的差别;土壤微生物DNA经PCR(聚合酶链式反应)和DGGE(变性梯度胶电泳)反应后的基因片段非常一致,反映出不同程度的重金属污染并没有导致土壤微生物群落结构的改变和基因损伤,另一方面也表明,土壤本身有强烈的固定重金属能力,抵御了重金属对土壤生物的进一步毒害。

Local smelting near the Xinguan village, Magu town, Hezhang County, Guizhou Province not only causes the damage of vegetation, but also induces various accumulation of heavy metals in the vicinal soils. Heavy metal Zn in soils varies from 162.23 to 877.88 mg/kg, Pb from 37.24 to 305.56 mg/kg, while Cd in the range of 0.50 to 16.43 mg/kg, which are obviously over the local soil heavy metal background values. And extremely positive relationship can be observed between the heavy metal contents (especially Pb and Zn) and the soil Fe2O3, Al2O3 levels, which implies the strong immobilization of soil iron oxides and clay minerals to heavy metal inputs. Sequential extraction results give the deep impression of occupied chemical forms of Pb and Zn being Fe Mn oxide bound and residue forms, while Cd dominating as the exchangeable form. Spot soils gain lower levels of microbial biomass only ranging from 57.00 to 388.00 μ g/g, and negative correlation can be observed for heavy metal content and soil microbial biomass level, especially for Zn, the correlation coefficient can reach - 0.7801, reflecting the poison of heavy metal to soil microorganisms. There was no remarkable shift of microbial community structures deduced from Biolog tests. Soil microbial DNA fragments purified from different polluted levels of heavy metals match very well after PCR (polymerase chain reaction) amplification and DGGE (denaturing gradient gel electrophoresis) reaction, which indicates heavy metal accumulation at different levels have not caused pollution induced diversity in soil microbial community structure, neither the DNA damage, on the other hand, strongly binding capacity of soils on heavy metals can resist the impairment of soil organisms from these pollutants in some degree.<P>