Study On The Geochemistry Evaluation Method Of Land Quality In The Typical Area Of Enshi

As a kind of non-renewable natural resource,soil is the material basis for the sustainable and development of human.In recent years,economic development highlights soil environmental issues such as heavy metals pollution and fertility decline.As a result,human health and agricultural and economic development have been adversely affected.Spatial interpolation methods play an important role in understanding the spatial distribution of soil heavy metals elements and nutrients elements.In this paper,four spatial interpolation methods including inverse distance weighted(IDW),radial basis function(RBF),local polynomial interpolation(LPI)and ordinary kriging(OK)were used to study soil heavy metals elements and nutrient elements in typical areas in Hubei province.The interpolation precision and interpolation effect of the four interpolation methods were compared and analyzed under the precondition of optimal parameters.The spatial distribution maps of pollution probability of soil heavy metals elements in typical areas were plotted by using the indicator kriging(IK).In order to control the soil contamination issues in the study area,the geochemical classification of soil environmental elements and nutrient elements were further graded according to the specification for geochemical evaluation of the land quality.The results showed that the prediction accuracy of the four spatial interpolation methods for the same element was not significantly different in the case of using the optimal parameters,but the spatial distribution had a certain difference.The smoothing effect of LPI was mostly obvious,and the effects of the other three methods were similar.Overall,the parameters of IDW were easier to choose,and the interpolation effect was better.On the basis of optimal parameters,the cross validation and the result of spatial distribution were analyzed and the optimal spatial interpolation method was determined.Taking the background values of soil elements in deep soil as the guidelines for pollution,the eight heavy metal elements in the soil of the study area all presented the risk of pollution.The central and northern part of the study area were vastly distributed with light to moderate contamination of Cr,Cu,Hg and Ni.Most parts of the study area have light to moderate pollution of Cd,indicating high risk of soil Cd pollution,and the central region has reached the degree of moderate-intensity pollution.Due to the influence of pollution caused by soil cadmium,the comprehensive quality of soil environment in the study area was poor,and the proportion of grade 5(heavy polluted)of land area was 36.06%.With the result of the lack of nitrogen,the comprehensive quality of soil nutrients was mainly the third grade(medium level),of which the proportion was 49.48%.The comprehensive evaluation of soil quality showed that the total account of soil area of third grades(medium),fourth grades(poor)and fifth grades(inferior)was 99.02%.The current situation is not optimistic.