Study On Migration And Enrichment Of Selenium In Soil Of Sanjiang County,Guangxi

In recent years,there has been a surge in the search for natural Se-rich land and the development of Se-rich agricultural products in China.This is aimed at accelerating the transformation of agricultural development mode,promoting modern agriculture,and contributing to rural revitalization.Guangxi,in particular,has been found to have a large area of selenium-rich soil with a relatively high degree of selenium richness.This presents a great potential for the development of natural selenium-rich agricultural products.In this paper,2812 surface soil samples,20 rock samples,10 parent material samples,10 surface soil samples at the same point,40 rice seed samples,19 tea samples,59 root soil samples at the same point and 180 vertical soil samples were systematically collected in Sanjiang County,Guangxi Province.The distribution characteristics and influencing factors of selenium content in soil were investigated and analyzed,and the migration and enrichment characteristics of selenium in the process of rock weathering and soil-formation,vertical soil profile and soil-crop system were also discussed.The ecological geochemical behavior of selenium element in the continuous system of"bedrock,parent material,soil and plant"was basically mastered,which provided certain scientific basis and technical support for the development and utilization of Se-rich land.The main achievements of this research are as follows:1)Se content in surface soil of the study area ranged from 0.11 to 14.41mg/kg,with an average value of0.63mg/kg,which was higher than the standard value of Se-rich soil（0.4mg/kg）,and significantly higher than the background value of Se content in soil of China.Se and Cd are highly associated with each other,and there are certain security risks for the exploitation of selenium-rich resources.Land use type,soil type and soil physical and chemical property indexes such as P,S,Mn,C_org,TFe₂O₃,Al₂O₃,p H and CIA are important factors affecting Se content distribution.Se content in surface soil was generally controlled by Se content in deep soil.2)The migration and enrichment characteristics of Se elements in the process of rock weathering into soil were discussed.The results showed that Se was strongly enriched in the process of rock weathering into soil,and the enrichment degree was the highest compared with other elements.The enrichment of Se may occur mainly in the"rock to parent material"stage,i.e.the early soil-forming stage,and less in the process of weathering parent material to form soil（late soil-forming stage）.3)From the vertical perspective,soil Se content increased first and then decreased from the deep to the surface laye.The enrichment of Se mainly occurred in the deep soil,and the infiltration or loss of Se near the surface occurred in different degrees.4)The Se absorption capacity of rice seeds and tea leaves was evaluated,and it was found that the Se absorption capacity of rice seeds and tea leaves reached a moderate absorption level.There was a positive correlation between Se content in rice seeds and Se content in root soil,but no significant correlation between Se content in tea and Se content in root soil.The Se bioenrichment coefficient of rice seeds and tea was negatively correlated with soil Cd,C_org,Se,Al₂O₃,TFe₂O₃,and positively correlated with p H and Si O₂.5)A prediction model of Se absorption in rice seeds was established by using multiple linear regression analysis.The accuracy of this model is 80%in the study area and 91.25%in other counties.It has certain applicability and can be used as one of the technical means to delineate selenium-rich agricultural products planting planning area.6)The migration and enrichment geochemical model of Se elements in the surface soil of the study area was established.