| The large distribution area of karst,high cadmium geological background,poor soil and active agriculture characterized the northern Luodian county in Guizhou.In order to explore whether there is excessive cadmium in the soil and crops in the study area and whether there is potential health risk to local resident,small-scale sampling?with villages and towns as units?was carried out,combined with the Geostatistics and ArcGIS technology,to analyze the content characteristics,spatial distribution,pollution degree and influencing factors of Cadmium in soil and crops,and the health risk evaluation was conducted.The research results are as follows:?1?According to the spatial distribution of soil level:the soil in the karst area of the study area is generally neutral,the geometric mean of cadmium content in cultivated soil and natural soil is 1.33 mg·kg-1,and 1.57 mg·kg-1,respectively.The soil in non-karst is generally acidic,and the geometric mean of cadmium content in cultivated soil and natural soil is 0.27 mg·kg-1and 0.22 mg·kg-1,as well as the variation coefficients were greater than 1,belongs to the strong variation.Overall,the cadmium content in the karst area is greater than the non-karst area with a significant difference?P<0.05?,indicating the enrichment of cadmium appear in the karst area,and the karst area cadmium content for the cultivated soil is lower than the natural soil.The Vertical distribution rule is can be concluded that the cadmium content in the surface soil?0-10cm?in most of the cultivated soil profile has an obvious accumulation phenomenon,and its content is generally higher than that in the middle and deep soil.The whole trend is that cadmium content decreases with depth.?2?Semi-variogram analysis showed that soil Cd content had strong spatial autocorrelation,with structural spatial variation as the main control factor and natural factors as the main control factor.The spherical model is selected as the optimal theoretical model of Cd.According to the spatial distribution map,Cd content in some non-karst areas?Moyang town,Jiaoyan town?is lower than the soil pollution standard risk screening value,and Cd shows no pollution and low potential ecological risk.In karst areas,the content of Cd is generally higher than 0.3mg·kg-1,and Cd presents mild to severe pollution and moderate to strong potential ecological risk,especially in western muyao town,luosha township and chestnut wood township,where the content of Cd is higher than the standard risk control value of soil pollution.?3?The average values of Cd content in corn and rice in karst area are 0.033mg·kg-1 and 0.109 mg·kg-1,The average values of Cd content in corn and rice in non-karst area are 0.01 mg·kg-1 and 0.08 mg·kg-1,both lower than the limits of pollutants in national food safety standards.In different lithology partition,rice Cd content are higher than maize,both of them have a significant difference?P<0.05?,the rice and maize average single factor index is below 1.?4?Among the villages and towns in the study area,the content of Cd in crops in Bianyang town and Limu town are generally higher than that in other towns and villages.A total of 15 samples in the research area exceeded the standard,and the over-standard rate of crops is 9.68%.The Cd enrichment ability of rice is higher than that of corn,the enrichment coefficient of corn is 0.98%,belonging to weak enrichment,and the rice enrichment coefficient is 3.74%,belonging to moderate enrichment.According to the spatial distribution map of crops,areas with high Cd content in corn are located in the south of Bianyang town,while areas with high Cd content in rice are located in the southeast of Limu township and the west of Dongdang township.By comparing the spatial distribution of Cd content in maize and rice in the study area with that in soil,it is found that there is no obvious consistency between the spatial distribution of Cd content in both corn and rice,and the correlation analysis results also showed that there is no obvious correlation between crops and soil.This indicated that there is no significant relationship between the content of soil Cd in the study area and the accumulation of Cd in edible parts of crops.?5?The health risk assessment showed that the non-carcinogenic risk and carcinogenic risk of adults and children in the karst region were higher than that in the non-karst region due to different exposure routes of Cd in soil and crops.In karst areas,Cd content is not a non-carcinogenic risk for adults,but there is a potential non-carcinogenic risk for local children,and the carcinogenic risk is acceptable range for adults and children.In the non-karst areas,Cd content has no non-carcinogenic risk for adults and children,and the carcinogenic risk is also within the acceptable range.The carcinogenic risk and non-carcinogenic risk of children are higher than that of adults;The risk values of adult and child crops were the highest,especially rice. |
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