Study On The Characteristics And Causes Of Heavy Metal Pollution In Typical Industrial Areas

With more and more attention paid to human health,except water and air quality,soil safety has become one of the key issues to be solved,especially the environmental quality of agricultural land.Soil pollution of agricultural land is the result of interaction of multi factors,multi-scale and multi process.Therefore,it is a difficult and key point to analyze soil pollution status and identify pollution sources,which can also build a foundation for pollution control and soil supervision.In this study,372 samples were collected from agricultural land in a typical industrial cluster area.Eight common soil heavy metal elements Cd,Hg,As,Pb,Cr,Cu,Ni,Zn and pH values were measured respectively.Based on the environmental background value of Hunan Province,five mainstream pollution evaluation methods were used to evaluate the heavy metal pollution in the study area,and the study was determined with GIS Based on the spatial distribution characteristics of heavy metals in the study area,the qualitative analysis chart of two variable LISA(clustering significance)and the positive definite matrix factorization method were used to quantify the components of pollution sources and the contribution rate of heavy metals to the soil.Finally,the pollution status distribution and pollution sources in the study area were given.The analysis shows that:(1)The pollution of Cd,As and Pb in the study area is more prominent.The average content of Cd is 10.35,3.47 and 5.35 times higher than the background value of soil environment in Hunan Province.The content of Cd is higher than the background value of soil environment in Hunan Province.The samples with Pb and As exceeding the background value account for 97.85% and 80.91% respectively.The coefficients of variation of Cd,Pb and As are all greater than 162%,which indicates that Cd,As and Pb vary greatly and have poor continuity,and are obviously affected by external factors.(2)The conclusions of the five methods are basically the same.In the evaluation of single factor pollution index,the top three ranking of the proportion of moderate pollution and heavy pollution are Cd(96.78%)> Pb(58.87%)> As(42.47%);Nemero comprehensive evaluation shows that 82.53% of the sample points belong to heavy pollution,and the whole study area belongs to heavy pollution;the potential ecological hazard index shows that only Cd in the study area has strong ecological risk;the land accumulation index and soil environmental quality The results showed that Cd,Pb and As were the main pollutants.(3)Bivariate LISA map is a good tool to reveal the interaction between heavy metals and polluting enterprises.We can provide better decision support for soil risk management and control based on the analysis of spatial interaction;while the predicted values of heavy metals simulated by the positive definite matrix decomposition model are well linear with the measured values,and the pollution sources in the study area are respectively natural sources through the model The contribution rate of agricultural,industrial and traffic mixed sources,industrial emission sources,lead-zinc mine pollution sources and air subsidence to the study area is 39.19%,11.05%,12.29%,34.15% and 3.34% respectively;the combination of qualitative and quantitative analysis methods can more effectively analyze the pollution sources.