| Selenium has been identified by the World Health Organization(WHO)as one of the essential nutrients for human beings.It has the effects of anti-tumor and cancer prevention,antioxidation,enhancing immune function,improving the basic metabolism of the body,and inhibiting the biotoxicity of arsenic,cadmium and lead.Early studies believe that there are 22 selenium-deficient provinces and regions on China’s land,accounting for about 70% of China’s total land area.In recent years,some scholars have found that the proportion of selenium-deficient areas in China’s soil has reached 51%,which is one of the countries with the most selenium deficiency in the world.Therefore,it has positive economic and social value to develop green selenium-enriched agriculture by finding,developing and utilizing green selenium-enriched soil resources.Taking Fogang County,Guangdong Province as the research object,this paper conducts statistical analysis of 162 surface(layer A)soil samples,37 deep(layer C)soil samples and 6 soil element profiles in the research area,and uses MAPGIS,SPSS,JADE,Excel and other analytical drawing software to conduct in-depth research.Analyze the geochemical characteristics of various soil elements in the research area,analyze the sources of various soil elements through PMF(Positive Matrix Factor)and PCA(Principal Component Analysis)receptor model methods,combine the geochemical characteristics and source analysis results of various soil elements,analyze the influenium content and their source problems in the research area,discuss the causes and influenrich soil factors,and provide a soil geochemical basis for the reasonable and effective development and utilization of green selenium-rich cultivated land soil resources and the development of high-quality characteristic agriculture in Fogang County.The main conclusions of the study are:(1)Through the geochemical investigation of soil elements in the research area,the geochemical characteristics analysis of the content of surface(layer A)and deep(layer C)in the research area,and the indicators of surface soil elements As,Cr,Cu,Hg,Mo,Ni,Cd,Pb,Se,Zn,B,Co,Mn,N,Nb,P,The arithmetic average content of Sb,Sr,Th,W and Zr is 11.52,26.16,11.90,0.108,1.55,10.14,0.130,49.72,0.548,67.86,49.29,7.73,339 respectively..31,941.38,23.57,425.65,0.829,35.12,39.08,5.38,303.09mg/kg,organic matter content arithmetic average of 9.7%,p H arithmetic average of5.22.The arithmetic average of deep(C layer)soil element indicators As,B,Cd,Co,Cr,Cu,Hg,Mn,Mo,N,Ni,P,Pb,Sb,Se,Sr,Th,W,Zn,Zr,Nb content is 10.56,35.22,0.05,8.75.24.21,8.30,0.05,472.41,2.26,234.70,9.24,233.52,46.76,0.83,0.44,35.65,47.18,5.59,65.62,242.31,16.41 mg /Kg,the average arithmetic value of organic matter content is 3.3%,and the average arithmetic value of p H is 5.17.The coefficient of variation of surface soil elements ranges from 19.93%(Nb)to113.49%(As),and the coefficient of variation of deep soil elements ranges from21.01%(Zr)to 114.64%(Sb).The enrichment coefficient of the element is between0.150 and 15.614.By comparing surface and deep soil elements,it is found that heavy metal elements and Se elements in surface soil have concentration characteristics.The spatial distribution characteristics are Cr,Ni,Co;As,B;Cd,Cu,Sb;Se and organic matter;and N and P are similar in spatial distribution.In terms of soil element profile distribution characteristics,the longitudinal change of heavy metal elements in the T01 and T04 profiles is small and there is no obvious change trend,and the soil element content in woodland is less affected by human factors.The longitudinal changes in the profiles of T02,T03,T05 and T06 are quite different,and the soil element content in paddy fields and orchards is greatly affected by human factors.There is a positive correlation between the characteristics of the Se element on the profile and organic matter,and a negative correlation with p H.(2)Through the source analysis of soil elements by PCA and PMF,it is found that the model analysis results of PCA and PMF are generally consistent,but there are some differences in the contribution rate of specific sources.PCA analysis results contribute29.617% of elements from geological background sources,including Cu,Mn,Cr,Ni,Co,V and Se;27.101% from transportation and industrial sources,Pb,Zn,Mo,B,Sb,As,Cd,W and Hg;and elements from agricultural sources.The contribution rate is13.820%,including N,P,Se,Mo,P,Hg.PCA’s cumulative contribution rate is 70.538%.PMF analysis results contribute 39.610% of elements from natural sources,Co,Cr,Cu,V,Ni,Mn,Se,B,elements from transportation and industrial sources are 36.103%,and elements are As,Sb,Cd,Hg,Mo,Pb,Sr,W,Z N;The element contribution rate of agricultural sources is 24.287%,and the elements are N and P.PMF’s cumulative contribution rate is 100%.(3)Through the analysis of clay minerals,it is found that the content of clay minerals and iron-aluminum oxides is also one of the factors affecting the content of selenium in soil.Through the analysis of XRD patterns of clay minerals,it is inferred that areas with more intense weathering may be more conducive to the content of selenium.enrichment.Based on the summary of previous research results,the element geochemical characteristics analysis of selenium and other elements and indicators in this paper,combined with the results of PCA and PMF source analysis,the main causes of selenium-enriched soil in the study area are the parent material and soil type,soil Physical and chemical properties,soil organic matter content,weathering,land use and topography. |
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