Study On Selenium And Cadmium Influencing Factors And Soil Safety In The Soil-Crop System In The Western County Of Ankang

The content of selenium in most soils and crops in the western county of Ankang,Shaanxi,has reached the level of selenium-enrichment,which is suitable for the development of selenium-enriched industries.In this study,by studying the distribution characteristics and influencing factors of element content in soil and crops in the county area of western Ankang,Shaanxi Province,the relevant prediction models of agricultural products were established,and the land use security zoning was developed to obtain the following main understandings:1.The selenium,cadmium and fluorine in the soil were higher than the national surface soil background value and Shaanxi surface soil background value,while the iodine was slightly lower than the national surface soil background value and Shaanxi surface soil background value.Geochemical evaluation results show that the soil in the study area is very rich in selenium resources,and there is a high risk of pollution from fluorine and cadmium.2.There is a high correlation between selenium and heavy metal elements such as cadmium,which is mainly controlled by the geological background of the black rock series.Different soil types and land use types have effects on soil selenium and cadmium;the average content of selenium and cadmium in yellow-brown podzolic soil is significantly higher than other soil types,and the content of selenium in tea garden soil is higher than other soils use type.3.By comparison with national food safety standards,the main crops of corn,potatoes,rapeseed and rice in the study area have selenium enrichment rates exceeding 60%,are good selenium-rich agricultural products;there is no excess of arsenic,chromium,copper,nickel,mercury,and zinc in the main crops in the study area;however,cadmium exceeds the standard in corn,potato,and rape samples,and cadmium in potato samples The exceeding standard rate of the elements reached 86.7%,indicating that there was a common cadmium pollution phenomenon in the potato samples in the study area.In addition,the absorption of selenium and cadmium by different types of crops is also significantly different.Corn is a better selenium-rich crop,while potatoes are relatively cadmium-rich.4.Based on the statistical analysis of the element content of the main crops in the study area,combined with the element content of the root soil,a model of selenium and cadmium is established,and the model is used to partition the land security,and the priority protection area,safe use area,structural adjustment area and strict control area.It is recommended that priority be given to protected areas to promote the cultivation of selenium-rich agricultural products,structural adjustment areas to grow non-cadmium-rich crops,and strictly controlled areas to stop growing agricultural products.This study provides first-hand data and theoretical basis for local land use safety.