Geochemical Characteristics And Risk Assessment Of Soil In Xiangtan Area

Xiangtan City of Hunan Province,is an important grain-producing area in southern China.Heavy metal pollution in cultivated soil is very serious.This paper takes the Xiangtan area of Hunan as the research object.This paper systematically collected surface soil,crops and root soil as samples,analyzed and tested various elements and indicators affecting land quality,and studied the regional geochemical composition and distribution characteristics of the elements.Besides,this paper divided the soil harmful elements and the geochemical grade of nutrient elements and the geochemical grade of soil quality,and proposed the scientific use of land resources accordingly.The spatial distribution of nutrient elements in the study area is:the trend of higher in the East and north and lower in the West and south,B,Mo,Mn are the most typical.The high value areas are mainly concentrated in the northeast of the study area.The high value areas of N and K₂O are distributed along the river,especially K₂O.It can be inferred that the distribution of nutrient elements in the study area is related to the rivers in the middle of the study area.The high-value areas are distributed along the river,mainly in the northeastern part,while the northeastern part of the study area is also the main cultivated land distribution area.There is serious heavy metal pollution in the study area,and Cd is the most serious.87.33% of the sampling points have Cd exceeding the standard phenomenon,and 24 sites have Cd content exceeding the control value.There is still a certain degree of pollution.According to the geochemical grading of land quality,there are some problems in land quality in the study area.The first-class high-quality land is only 0.07 km²,accounting for only 0.09% of the area of the study area;the second-class good land is also very small,only 0.27 km²;the study area is mainly the third-class medium land,with an area of 40.75 km^2,accounting for 50.94%of the study area;the fourth-class and fifth-class inferior areas account for 25.26 km² and 13.65 km²,respectively,accounting for 31.57% and 17.06% of the study area.Generally speaking,the comprehensive quality of soil geochemistry in the study area is of medium level,and there are certain pollution conditions.The scattered distribution of high-quality land and good land should be paid attention to.According to the investigation results of cadmium content in soil in the study area,low and high cadmium exposure areas were selected in Xiangtan,Hunan Province,respectively.Population epidemiological survey and dietary survey were carried out in the study area.The contents of cadmium and other elements and the biomarkers of renal injury in urine were determined to understand the relationship between cadmium exposure level and renal health effects in the local population.The results of human health risk assessment showed that in high cadmium exposure areas,early renal impairment had occurred in local residents due to cadmium nephrotoxicity,while in low cadmium exposure areas,cadmium had no significant effect on the health of the local.