Evaluation, Early Warning And Source Analysis Of Heavy Metal Pollution In Cultivated Land In A County Based On GIS And Geostatistics

Good soil quality of cultivated land is the basis for ensuring the safety of food production environment.Whether the cleanliness of the soil environment is directly determines the quality and safety of grain.Based on the theory of geostatistics,spatial autocorrelation theory and mathematical statistics,this paper uses GS + 9.0,SPSS22.0 and ARCGIS10.2 as the technical support and uses the Kriging method,the single factor evaluation method and the potential ecological risk assessment method to study the spatial variability,spatial heterogeneity and sources of five kinds of heavy metals such as Cd,Cr,Pb,As and Hg in the cultivated land of the county,to explore the status of pollution to make an assessment and early warning.The main conclusions are as follows:1.Heavy metals Cd,Pb,As and Hg were enriched in the soil of the study area,and the pollution of heavy metals was obvious,and As and Hg pollution occurred in the local area.The spatial correlation of heavy metal Cr content in the study area is very strong,and the structural factors dominate its spatial distribution.The spatial correlation of Cd,Pb,As and Hg contents is moderate,and their spatial distribution is formed by the synergistic effect of random factors and structural factors.The high risk of Cd pollution in the cultivated land is located in the town of Batuan Town,Gaolong Town and Pingshui Town,and the high pollution rate of Cr pollution is located in Lushui Town and Pingshui Town.The townships with high risk of Pb pollution are located in Batuan Town,Gaolong Town and Pingshui Town and Yantang Town,As high risk of pollution Township is located in Gaolong Town,Pingshui town and Yantang Town,Hg high risk of pollution Township is located in Pingshui Town,Zhitang Town,Gaolong Town,Yantang Town and Sicong Town.2.The results showed that the Cd pollution was the most serious(Cd> As> Hg> Cr> Pb)in the cultivated land of the study area by single factor and comprehensive pollution evaluation.Cd pollution is moderate pollution,while the Cr,Pb,As,Hg content of clean.Among the townships of the study area,the most polluted villages in the cultivated land Cd,As and Hg were Gaolong Town,and the most polluted villages of Cr and Pb were Lushui Town and Batuan Township.The results of the comprehensive pollution assessment of Nemerow showed that there was mild heavy metal pollution in the cultivated land of the study area.According to the potential ecological risk assessment,it was found that the risk of Cd pollution was the highest among the several heavy metals in the cultivated soil,and the risk level was moderate.The highest risk of pollution in the township is Gaolong Town.Cr,Pb,As and Hg pollution risk are slight.The comprehensive pollution risk of heavy metals in the cultivated land of the study area is moderate.Cd pollution risk coefficient has the highest contribution to RI(73.12%).Comprehensive pollution risk of the township is the highest town,followed with eight groups and Lu Town.Through the division of the early warning area,the area of the giant police area is 23.23km2,accounting for 5.17% of the total area of the cultivated land,mainly concentrated in the Gaolong Town,Batuan Town,Lushui Town,Pingshui Town and Sicong Town.3.Through the correlation analysis,principal component analysis,cluster analysis,global and local correlation analysis,we can see that the main sources of heavy metals Cd,As and Hg in the cultivated land are industrial discharge,the main source of Pb is coal,The source is a natural source,and the results of the three source analysis methods are mutually validated.