铅锌尾矿砂污染下的岩溶土壤微生物群落碳源代谢特征

Carbon Metabolism Characteristics of the Karst Soil Microbial Community for Pb-Zn Mine Tailings

以广西阳朔思的村铅锌矿尾砂污染的水稻田、玉米地、柑橘园以及对照(旱地)土壤为研究对象,采用碳素利用法和18S rRNA变性梯度凝胶电泳技术探究岩溶区重金属污染下土壤微生物群落碳源代谢特征以及土壤真菌与土壤有机碳的交互关系.结果表明,广西阳朔思的村铅锌矿尾砂污染区土壤重金属总体含量(Pb、Zn、Cu、Cd)依次为:水稻田>玉米地>柑橘园>对照;同时地累积综合指数显示该区重金属污染以Pb、Cd为主,其中Cd带来的环境风险最高.受Pb、Zn、Cu、Cd等重金属复合污染物影响,土壤微生物生物量碳、微生物熵和碳源代谢速率表现出随总体重金属质量分数增加而降低的变化规律,但土壤总有机碳质量分数却表现为:水稻田>对照>柑橘园或玉米地.DGGE结果进一步显示对照组土壤存在担子菌门多孔菌目Pycnoporus sp.ZW02.30,柑橘园和玉米地土壤存在镰刀菌属Fusarium solani和Fusarium oxysporum以及柑橘园土壤存在青霉属Penicillium decumbens.然而,上述参与淀粉、纤维素、半纤维素、木质素等糖类降解过程的真菌没有在水稻田土壤检出.加之,水稻田土壤微生物功能多样性指数和微生物熵最低而土壤有机碳质量分数最高,说明铅锌尾矿砂通过影响不同样地土壤微生物糖类代谢过程,进而调节土壤碳在微生物特别是真菌作用下的矿化速率.

BIOLOG and 18 S rRNA PCR-DGGE methods were used to estimate the characteristics of carbon source metabolism of the soil microbial community as well as the relationship between soil fungi and soil organic carbon in different karst land use types（ corn field,citrus field,and paddy field） contaminated by Pb-Zn tailings at Sidi Village,Yangshuo,Guangxi Zhuang Autonomous Region,SW China. It was found that the concentrations of Pb,Zn,Cu,and Cd were highest in the paddy field,followed by the corn field,citrus field,and control group（ dry field）. In addition,the geo-accumulation index indicated that the heavy metal pollution at this area was caused by Pb and Cd and that Cd was the key environmental risk factor. With the Pb-Zn tailings,there was low microbial biomass carbon,biological entropy,and microbial carbon source metabolism in the soil samples. The highest soil organic carbon and heavy metal concentrations were found in the paddy field,followed by the corn field and citrus field. According to the DDGE results,it was found that Pycnoporus sp. ZW02. 30 was found in control group soils,Fusarium solani and Fusarium oxysporum were found in the corn field and citrus field,and Penicillium decumbens was found in citrus field. These were involved in the degradation of sugars,such as starch,cellulose,hemicellulose,and lignin. However,the fungi were not found in the paddy field. Based on the low functional diversity of the soil microbial community and biological entropy as well as the high soil organic carbon concentration in the paddy field,it was concluded that soil microbial carbohydrate metabolism and the mineralization rate of the soil organic carbon was controlled by soil microorganisms,especially fungi,in different land use soils in the karst area contaminated by Pb-Zn tailings.