A Comparative Study On The Risk Assessment Methods Of Heavy Metal Pollution In Reclaimed Soil

Soil heavy metal is one of the important indicator of soil quality. However, the content of heavy metals in soil possess the characteristics of spacial variability, it is not universally applicable for the forecasting methods to use in different dimensions, besides, different research areas also tend to have specific properties. Due to the high-intensive exploitation in large area of the coal base in Loess Plateau for a long time, the soil, vegetation and water resources of the mining area were seriously damaged, and the ecological environment was continuously deteriorative. Together with the pace of urbanization continues to accelerate, many villages will soon be or have been obsolete, the complex reclamation work of village is imminent. In order to improve the prediction accuracy, provide basis for the risk assessment of heavy metal pollution and provide reference for the reclamation of pressing coal villages, it is important to assess the soil heavy metal content and compare different evaluation methods.This paper takes Xigao village, Zezhou county, Shanxi province as the study area, it mainly includes:(1) The introduction and review of comprehensive prediction of the regional soil heavy metal content at home and abroad, explore the emphases of different research contents and methods, clarify the starting point;(2) By analyzing the descriptive statistics of the soil data in studied area, pre determine the internal parameters of spatial interpolation method;(3) Using inverse distance weighted interpolation, Kriging interpolation method, radial basis function interpolation method and a global polynomial interpolation method, based on four methods of optimal model parameters, mercury, arsenic, lead, cadmium, chromium and copper of 56 sampling points in the study area were spatially interpolated, and the accuracy of the interpolation results were verified using cross validation method and partition with degree method;(4) To determine the optimal distribution model and the internal parameters of heavy metal in different soils from the aspect of prediction precision., and to make the design sketch of the spatial distribution of heavy metals, determine the method for pollution assessment.Through the research of the above content, we can get the following conclusion:(1) The average content of the six soil heavy metal elements(mercury, arsenic, lead, cadmium, chromium and copper) is low, in addition to lead is a two standard, the rest are a standard.(2) The best fitting model formercury and arsenic is Gaussian model, and spherical model for lead, cadmium and copper, exponential model for chromium.(3) The optimal heavy metals pollution risk assessment interpolation method for mercury, lead, cadmium and chromium was radial basis function interpolation method, and inverse distance weighted interpolation method and lognormal Kriging interpolation method were the optimal interpolation method for arsenic and copper, respectively.(4) The regional soil heavy metal content of the homestead build before 1950 was the lowest, the heavy metal content was centered in the homestead build between 1950 to 1990, and the highest after 1990.(5) Soil heavy metal pollution is affected by the soil properties, industrial production, transportation, household waste, agricultural production, spraying of fertilizer and pesticide, sewage irrigation and other aspects.