基于地质大数据技术对云南土壤重金属地质高背景区的划定

Delineation of areas with high geological background values of heavy metals in soils in Yunnan Province,China based on geological big data technology

为系统研究云南省土壤重金属地质高背景区的分布范围及超标元素,以全省1∶20万水系沉积物重金属元素含量数据和区域地质图为基础,采用GIS空间分析功能,并利用昆明、玉溪、昭通等地区的土壤重金属数据进行验证,确定云南省土壤重金属含量值超农用地筛选值的地质单元61个,占全省国土面积的21.09%,其中位于地质高背景区的耕地面积约284.41万公顷,占全省国土面积的7.22%;影响土壤重金属超标的岩性主要为碳酸盐岩、基性—超基性火山岩、中基性侵入岩、含煤碎屑岩和含基性组分碎屑岩;地质高背景区超标重金属元素主要为Cu、Cr、Ni、Cd,而As主要于碳酸盐岩地层中存在超标风险,Pb、Zn仅于个别地层中存在超标风险,Hg基本无超标风险。

This study aims to systematically investigate the distribution and over-limit elements of areas with high geological background values of heavy metals in soils in Yunnan Province.GIS spatial analysis was conducted based on the heavy metal content data from a province-wide 1∶200,000 stream sediment survey and the regional geological map.The analysis results were validated using the data of heavy metals in soils in Kunming,Yuxi,Zhaotong,and other regions.A total of 61 geological units were identified,with heavy met-al content in soils exceeding the screening values of agricultural land,accounting for 21.09%of the total land area of Yunnan.The cultivated land in high geological background areas covers an area of approximately 2.8441 million hectares,accounting for 7.22%of the total land area of Yunnan.The lithologies that cause over-limit heavy metals in soils primarily comprise carbonate rocks,mafic-ul-tramafic volcanic rocks,intermediate mafic intrusive rocks,coal-bearing clastic rocks,and clastic rocks with mafic components.The o-ver-limit heavy metal elements in high geological background areas are dominated by Cu,Cr,Ni,and Cd.In contrast,As manifests an over-limit risk mainly in carbonate rock formations,Pb and Zn only exhibit an over-limit risk in individual strata,and Hg almost shows no over-limit risk.