Distribution Characteristics and Bioavailability of Cadmium in Soil Profile from Karst High Geological Background and Mining Activities Superimposed Pollution Area of Northwest Guangxi,China
The combination of karst high geological background and mining activities in northwest Guangxi leads to increase soil pollution risk,which poses a potential threat to food and ecological security.Study on the spatial distribution characteristics and bioavailability of cadmium(Cd)in soil profiles in this region can effectively assess the pollution status and ecological risk of Cd in soil.Soil samples were collected from rice field profiles(0-100 cm)at three different positions within Dachang mining area,located in the typical karst region of Nandan county,Hechi city,Guangxi.The distribution characteristics and bioavailability of Cd in soil profiles were analyzed,and the ecological risk and pollution status of Cd in three soil profiles were evaluated by using the enrichment index method and risk assessment index.The results show that the vertical distributions of Cd contents are different among the three soil profiles,and the soil Cd is significantly enriched in the surface(0-20 cm),with 86.7％of samples showing soil enrichment factor values over 2,indicating that there is obvious accumulation of heavy metal Cd from human sources in the soil surface.According to Soil Environmental Quality:Risk Control Standard for Soil Contamination of Agricultural Land(GB 15618-2018),the Cd contents of some samples in the two soil profiles far from the mining area exceed the screening value of soil pollution risk of agricultural land,and in the soil profile adjacent to the mining area,the Cd contents of 90％soil samples surpass the pollution risk control value for agricultural land.The Cd content of soil profiles in the study area is mainly controlled by the superimposed effects of multiple factors such as geological background,agricultural cultivation and mining activities.The difference in the content of soil profiles mainly depends on the distance to the mining area(the closer the distance to the mining area,the higher the Cd content),while the same profile is primarily influenced by pH value and organic matter content.The Cd predominantly exists in the Fe-Mn binding state,ion exchange state,and residue state within the soil matrix.The bioavailability of Cd is primarily influenced by total Cd content,pH value,organic matter content and fixation of Fe-Mn oxides in soil,showing a relatively high availability in soil profile and soil surface far from the mining area.
heavy metalCdsoil profileenrichment characteristicspeciation distributionbioavailabilitykarst areaGuangxi
万方数据
维普
