| Selenium is one of the trace elements necessary to maintain the normal functioning of human body.Its biological function plays an important role in human and animal health,but it cannot be synthesized in the body and can only be obtained from the outside world.In the rock-soil-biological cycle of Se,soil is the direct source of Selenium in the ecosystem.Finding out the distribution of soil Se and its ecological effects play an important role in the subsequent development and utilization of Selenium resources.Through the test and analysis of the surface soil,vertical soil profile and crop samples in the study area,this article mainly obtains the following knowledge:1.The average content of Se in topsoil was 0.47μg/g.The Se enrichment rate of surface soil was over 50%.The spatial distribution of Se in soil is obviously controlled by geological bodies,and the area with high Se content is highly consistent with that of carbonate rocks,which is mainly controlled by Devonian and Carboniferous strata;The low Se content area is highly consistent with the Quaternary sediments and the distribution area of clastic rocks on both sides of the Quaternary sediments,which is mainly affected by the Quaternary and Paleogene strata.2.The content of Se in soils of different parent materials showed the trend of Carbonate>Igneous>Clastic>Quaternary,and the trend of Carboniferous>Devonian>Permian>Triassic>Cretaceous>Quaternary>Paleogene in different strata.In different land use types of soil,the Se content in grassland and woodland soil is relatively high,while the Se content in paddy soil is relatively low;The content of Se in red soil,yellow red soil,red soil and brown lime soil was higher than that in paddy soil and purple soil.3.In the vertical profile of different soil forming materials,the influence factors of Se content change are different.In the Carbonate profile,the vertical characteristics of Se are related to the parent rock and secondary enrichment,and are affected by the external input,mainly related to the Corg and p H in the soil;In the Quaternary soil formation profile,the vertical characteristics of Selenium are related to secondary enrichment and external input,mainly related to Corg in soil.In the Clastic soil forming section,the vertical characteristics of Selenium are mainly affected by weathering and leaching,and mainly related to Si O2 and Al2O3 in the soil.4.The heavy metal elements such as Cr,Hg and Pb in crop seeds in the study area are not over standard,only As in rice and Cd in sugarcane are sporadically over standard samples,and the se rich rate of crop samples is higher,among which the Se rich rate of rice,corn and other food crops is more than 60%.Se rich rice is mainly distributed in Quaternary sediment distribution area,while Se rich corn is mainly distributed in clastic rock distribution area.Se uptake by rice seeds was related to Corg,Si O2,TFe2O3,Mn and S in soil;The Se uptake by maize seeds was mainly affected by soil p H,Si O2,TFe2O3,Mn and S.5.The prediction model of Se content in rice seeds was established,and the prediction accuracy was 76.8%.Based on the Se content of soil and the Se content of crops predicted,the Se content of land in the study area was classified and zoned,and the proportions of deficient,marginal,moderate,high and extremely high grade areas were 0.24%,1.77%,38.28%,59.34%and 0.37%respectively. |
