云南省宣威市农耕区土壤重金属元素分布影响因素及生态风险评价

为探究云南省碳酸盐岩风化区重金属污染特征及分布影响因素，选取云南省宣威市农垦区为研究对象，利用1∶5万土地质量地球化学调查成果，通过分析表层土壤重金属元素累积特征及分布规律，并结合土壤理化性质及地形因素等数据，研究驱动农垦区土壤重金属元素富集的影响因素，并利用富集指数法(EF)和潜在生态风险评价(RI)进行污染评价。结果发现，表层土壤中As、Cd、Cr、Cu、Hg、Ni、Pb、Zn的含量分别是云南省A层土壤背景值的1.61、5.46、2.14、2.22、1.40、1.34、1.15、1.45倍，出现不同程度的富集。EF分析结果显示，Cd是研究区内重污染元素，As、Cr、Cu污染程度次之，其余元素污染水平较低。受研究区Cd高含量的影响，农耕区内RI总体处于中等生态风险和强生态风险之间。通过对比不同成土母质采样区重金属元素累积特征发现，成土母质是驱动区内重金属元素富集的主要因素，在灰岩母质区土壤中8种重金重均出现显著富集现象；在母岩为碎屑岩的土壤中As、Cd、Hg元素次生富集明显；在砂页岩区上覆土壤中重金属出现贫化现象。重金属与地形因素协同分析结果表明，Cd、Cr、Cu、Ni、Zn在高海拔...

Influencing factors and ecological risk assessment of soil heavy metals in agricultural areas of Xuanwei City, Yunnan Province

This work aims to explore the characteristics and influencing factors of heavy metals pollution in soil of carbonate weathering areas of Yunnan Province. Based on the 1:50000 land quality geochemical survey datasets of typical agricultural areas in Xuanwei City, in combination with the soil physical and chemical properties and topographic datasets, this work discussed the accumulation characteristics and the distribution of heavy metals. In addition, the enrichment index (EF) and the potential ecological risk assessment (RI) of heavy metals were studied. The results show that the average contents of eight heavy metals in the surface soil of the agricultural areas in Xuanwei exceeded the background values of Yunnan Province and were 1.61 (As), 5.46 (Cd), 2.14 (Cr), 2.22 (Cu), 1.40 (Hg), 1.34 (Ni), 1.15 (Pb) and 1.45 (Zn) times of those background values, indicative of different enrichment degrees of soil heavy metals. The EF shows that Cd was heavy pollution element, followed by As, Cr, and Cu, while other elements showed low potential ecological risk. The ecological risk index (RI) ranged between a moderate ecological risk and strong ecological risk, which was mainly caused by the high content of Cd. By comparing the accumulation characteristics of eight heavy metals in different soil parent materials, it is inferred that the enrichment of heavy metals was mainly controlled by parent rocks. There was significant enrichment of eight heavy metals in the parent rocks of limestone areas. And it was obvious that the secondary enrichment of As, Cd and Hg in the soil whose parent rocks were clastic rocks, while the eight heavy metals were depleted in the soil with sandstone and shale as parent rocks. The correlation analysis between eight heavy metals and topographic factors suggests that Cd, Cr, Cu, Ni, Zn were depleted in high altitude areas and significantly accumulated in low altitude areas. By contrast, As and Pb were accumulated as the elevation increases. Partial correlation analysis of heavy metals, fertility elements and soil physical and chemical properties suggests that TK was the main influencing factors of As and Pb enrichment. Moreover, SOM and TN were the main driving factors of Cd, while TP was the main controlling factors of Cu and Zn. And Cr, Hg, Ni were controlled by other factors rather than pH, TN, TP, TK, SOM.