Spatial Variability And Sources Of Heavy Metals And Selenium In Potential Se-enriched Areas In Lujiang County,Anhui Province

Soil is the natural environment for human survival and the main resource for agricultural production.Influenced by natural and human factors,soil components have significant spatial variability.Among them,due to the particularity of pollution and hazard of soil heavy metals,the spatial variability of the soil is widely concerned by researchers.The surrounding area of Fanshan-Nihe in Lujiang county,Anhui Province is a potential Se enrichment area.It is of great significance to identify the spatial variation characteristics of soil heavy metals and other elements in the region,and to explore the influencing factors and sources of spatial variation for the development of the landscape ecological leisure area in south Lujiang County and the utilization of selenium-rich soil.In this study,3630 top soil samples were collected from potential selenium-enriched areas around the Fanshan-Nihe area in Lujiang County,Anhui Province.Soil pH,soil nutrients and typical heavy metal elements were determined.Spatial variability analysis of soil heavy metals and Se elements was carried out by means of GIS,geostatistics,correlation analysis and principal component analysis.The effects of different factors on the spatial distribution of heavy metals were investigated and the sources of each element were analyzed.The main results of this study are as follows:?1?The median values of As,Se,Cd,Cu,Pb and Zn are 9.2 mg/kg,0.43 mg/kg,0.163 mg/kg,48.3 mg/kg,36.1 mg/kg and 75.5 mg/kg,respectively.The contents of S,K₂O and TFe₂O₃ in soil were mainly at the rich level,N was mainly at the medium level,and OM and P were mainly at the medium and poor levels.?2?The spatial distribution patterns of soil As,Pb and Se are similar,with the high value area concentrated in the middle of the study area and the low value area in the northwest.The high value areas of Cd,Cu,Pb and Zn all show a trend along the northeast-southwest direction,and their high value centers coincide.The spatial distribution of Cr and Ni are very similar,with high content in the north and low content in the south.The high value area of Cu is located in the south,while the low value area is located in the north,showing an opposite trend to the spatial distribution of Cr and Ni.The high-value region of Hg is distributed in the middle,and the high-value centers overlap with Pb and Se,which is less similar to the spatial distribution of other heavy metals.and the similarity with the spatial distribution of other heavy metals is small.?3?Scale has different effects on the spatial variability of different elements.At the larger scale?1:250000?,the ratios of nugget to sill of soil Hg,Pb,Se and Zn elements were far less than 0.25,showing strong spatial autocorrelation,and their spatial variation characteristics were strongly influenced by structural factors.Ni,Cr,Zn,Cd and Cu have moderate spatial autocorrelation,and the spatial variability is affected by both structural factors and random factors.The spatial autocorrelation of elements at smaller scales?1:50,000 and 1:10,000?were not much different,and both showed moderate spatial autocorrelation characteristics,but the ratio of nugget to sill of each element was greater than 1:250,000,which can further identify the increasing influence of random factors.?4?Structural factors such as soil type and topographic conditions affect soil element content.The contents of elements are relatively high in skeletal soil and low in paddy soil and yellow cinnamon soil.The higher the slope and the altitude are,the higher the content of As,Cu,Pb,Se and Zn are.The distribution of Cd and Hg are not affected by the altitude.Cr and Ni contents decrease with the increase of slope and altitude.?5?Soil nutrients and conditions affect soil element content.Soil OM,N,S are positively correlated with Hg,Pb,Se contents.Soil P,K₂O and TFe₂O₃ are negatively correlated with Cr and Ni contents,and positively correlated with Zn,Cd,Cu,Hg,Pb,Se and Zn contents.Soil pH is significantly positively correlated with Cd,Cr,Cu,Ni,and Zn,and significantly negatively correlated with As,Hg,Pb,and Se.?6?Based on the results of semi-variance analysis,correlation analysis and principal component analysis,the soil element contents are affected by mining activities,soil parent material,agricultural activities,etc.Among them,As,Cu,Pb and Zn are mainly derived from vein development and mining activities.Cd is derived from mining activities and agricultural activities.Cr and Ni are derived from the parent material.Se is derived from selenium-enriched rocks.Hg is affected by selenium-enriched rocks and random factors.