Construction Of Soil Environmental Quality Standards Based On Varying Background Values

The methods for formulating soil environmental quality standards mainly include environmental geochemical methods and health risk assessment methods.Among them,the environmental geochemical method is closely related to the determination of the background value of the soil environment,and the soil environmental quality standard is formulated from the perspective of soil.In this paper,the Chizhou area is selected as the background area,and the Huayuangong granite is selected as the research object in the background area for deeply analyzed and improved the envirmental geochemical method.A total of 14 samples of soil and water sediments in the background area?including 3 samples for 7-stage screening?and 2 samples of contaminated water sediments were collected.At the same time,215 pieces of data about 1:200,000 regional watershed sediments in Chizhou area were collected.All of the 252 samples were used for the application and verification of the environmental geochemistry.In this study,the elemental statistical methods,elemental reference method and cumulative frequency curve method are used to calculate Geochemical background value of As,Cd,Cr,Cu,Hg,Ni,Pb and Zn in the samples from research area.In-depth study of these three methods,The results show that the background value estimated by the elemental statistical method,except As and Cd,the background upper limit of the other six elements has a large deviation from the domestic and international standard values.And the reference element statistical method study area only the content of Cd exceeded the standard,The estimation results of this method are more general and inaccurate.When using the element reference method to estimate the background value of the study area,the significance level is greater than 0.05 when fitting the linear regression equation.This method is not feasible in this study,highlighting the limitation the method.When the cumulative frequency curve method is used to estimate the background value of the study area,the results show that the samples in the study area are all over the standard.At the same time,it is found that the cumulative frequency curve method has human influence when judging the abnormal inflection point,and the result has great uncertainty.Therefore,the three environmental chemistry methods have certain unreasonable points in the process of determining the background of the elements,and the estimated background values are all fixed values,which brings great difficulties to the formulation of soil environmental standards.In order to overcome the limitations of the above methods,this paper uses the empirical equations proposed by the predecessors to quantitatively characterize the weathering behavior of trace elements to estimate the soil environmental background value of the study area.The background value estimated by this method is the value of the change,that is,the background value can be calculated for each sample.Using the pollution index P _experience=lgC _measured/(lgC _background+0.4)to determine the contamination of the sample,the results show that the D experience of 8 heavy metals in D15 and D16 samples are greater than 1,and the two samples are determined to be contaminated samples,which is related to the actual situation.Anastomosis.At the same time,it was determined that some samples in the study area were contaminated with Cd and Hg.The research finds that the method is not affected by the data in the process of determining the background value,and has relative objectivity.It overcomes the limitations of the three environmental geochemical methods and the background value is limited.It also solve the fundamental problem of“one size fits all”in the current standard setting process,and the introduction of changing background values also bring new ideas to the formulation of standards,and have important potential value and significance in the process of formulating soil environmental quality standards.