地质高背景区农田土壤镉的污染叠加过程与作用机制

贵州喀斯特土壤镉(Cadmium)地球化学背景值为0.31×10-6，是丰度值的2.5-3.5倍，黔西北土法炼锌重金属排放与地质源叠加，导致土壤Cd污染严重、农产品超标，是区域突出的环境问题。选择炼锌厂污染叠加小流域，以未污染小流域为对照，研究母质-土壤-水体-大气-作物体系中Cd的分布、形态和迁移转化；利用多元统计PCA和GIS空间分析，结合源排放清单法和Cd同位素（δ114/110）比值法等，解析农田土壤Cd的自然源和人为源，估算Cd输入输出通量和质量平衡，厘清土壤Cd污染叠加的过程和路径；选择马铃薯（块茎类）和白菜（叶菜类）进行盆栽试验，研究作物Cd富集的差异，探明作物Cd的大气沉降、土壤吸收来源、途径和累积贡献；应用土壤微生物和动物的生物量、活性和群落组成来表征土壤污染的生物效应，探索土壤动物取食活性原位生物检测土壤重金属污染的方法，补充和完善污染土壤的生态风险评价方法和评估体系。

Cadmium is known to be both extremely toxic and ubiquitous in natural environments. It occurs in almost all soils, surface waters and plants, and it is readily mobilized by human activities such as mining. Ingestion of even trace quantities of Cd can influence not only the physiology and health of individual organisms, but also the demographics and the distribution of species. Guizhou province in southwest China is covered by large area of carbonate rocks where the average Cd concentrations in soil and sediment is 0.31×10-6 in surface, it's as 2.5-3.5 times as that in other parts of the country. Cd contaminated soils in northwest Guizhou province are one of the consequences of the industrial development, mining exploitation, agriculture, all around the geological source, Cd was also observed to concentrate in local food crops, this issues is a serious environmental problem in the region, so the biogeochemical processes of Cd and the associated environmental effects will require additional in-depth study. Choosing 2 small watershed as study areas, one with a zinc-smelting plant, and another one without any pollution source as control, both areas is located in Weining county, northwest Guizhou province with high geological background of heavy metals. This study focuses on the pollution processes and the action mechenism of Cd in parent rock, soils, water, atmosphere, and crops in the small watershed environmental system. Multivariate statistical method - PCA, spatial analysis method based on GIS, the source emission inventory and Cd isotope（δ114/110 ), etc., all be used to identify the Cd might come from natural or anthropocentric source, that could help to reveal input and output flux of Cd and the mass balance, know more about the process of Cd pollution overlay in soils; Potato (tuber crops) and cabbage (leafy vegetables) were selected for pot experiment to study the differences of Cd accumulation in crops, to explore contributions of atmospheric deposition, soil absorption and fertilizer application affect on Cd accumulation, also to study physiological and biochemical properties responses of crops to Cd stress, the biological effect and mechanism of soil Cd pollution were characterized by the biomass, activity and community composition of soil microorganisms and soil fauna, to explore the method of in situ biological detection of heavy metal pollution in soil by feeding activity of soil fauna, the study is useful for the identification and risk assessment about heavy metal pollution in soils in this special region.