Study On The Sampling Grid Of Soil Investigation In Heavy Metal Contaminated Sites

Heavy metal pollution has become one of the main types of soil environmental pollution.Heavy metals in the environment are not easy to be removed in the process of material circulation and energy exchange,and are easy to be enriched and transferred in organisms.They endanger human life and health through the food chain.At the same time,in the soil plant system,the pollution process has the characteristics of concealment,latency,irreversibility,long-term,indirect harm,companion,difficult treatment and long period.Therefore,it is urgent to obtain the pollution distribution information of heavy metals in soil environment.The most common,direct and important way to obtain the information of soil environmental status and pollution spatial distribution is through soil investigation.In soil investigation,the key link directly related to the investigation quality,investigation duration and cost is sample collection and laboratory testing,in which point layout is the premise of sample collection and sample testing.On the premise of ensuring the survey quality,the research on the representativeness of sampling point layout and sampling quantity has become one of the current research focuses.Taking a pharmaceutical factory as the research area,this thesis studies the reasonable sampling grid,and studies the influence of heavy metal pollutants and the area of the investigation site on the reasonable sampling grid.On the basis of previous data collection and sampling data,the six heavy metal elements of soil pollutants arsenic,nickel,lead,cadmium,copper and mercury are taken as the research objects,the sampling grid of 40 m×40 m,60 m×60 m,80 m×80 m,120 m×120 m,160 m×160 m,200 m×200 m is taken as the sampling grid,and the spatial variability analysis,sample representative test method and cross test method are taken as the discrimination basis.According to the function of the research site,the428066m2 site area is divided into three situations:314175m~2,196169 m~2 and 113948m~2.The influence of the above four site areas on the reasonable sampling grid of each heavy metal is studied,and the research results are verified in other sites.The main conclusions are as follows:The reasonable sampling grid of arsenic and mercury is greatly affected by the area of the research site,the impact of copper is small,and nickel,lead and cadmium have almost no impact.The study site covers an area of 420000 m~2,310000 m~2,200000 m~2 and 110000 m~2.The reasonable preliminary sampling grids for arsenic are 160 m×160 m,120 m×120 m,80m×80 m and 60 m×60 m respectively.The reasonable sampling grids for the second sampling survey are 60 m×60 m,60 m×60 m,40 m×40 m and 40 m×40 m respectively;The reasonable preliminary sampling grids of mercury are 120 m×120 m,120 m×120 m,120 m×120 m and 80 m×80 m respectively,and the reasonable sampling grids of the second sampling are 60 m×60 m,40 m×40 m,40 m×40 m and 40 m×40 m respectively;Except that the sampling area of copper is 420000 m~2(the reasonable sampling grid for the preliminary survey and the second survey are 160 m×160 m and 80 m×80 m),the reasonable sampling grids of the other three research sites are 120 m×120 m and 60 m×60 m;The reasonable sampling grids for nickel,lead and cadmium are 120 m×120 m and 60 m×60 m.Under the condition of ensuring certain accuracy,the reasonable sampling grids for the preliminary sampling survey and the second sampling survey are 120 m×120 m and 60 m×60 m respectively,and the number of sampling points for the preliminary survey shall not be less than 10.The research results are applied to a chemical plant in Shenyang.Based on the pollution uncertain area predicted by the 120 m×120 m sampling results of the preliminary investigation grid,the 60 m×60 m sampling grid is densely distributed in the uncertain area.The sampling results obtained can accurately and effectively reflect the pollution situation of the site.