Study On The Law Of Spatial Heterogeneity Of Soil Heavy Metals In A Mollisol Watershed Of In Black Soil Area

Land is the material basis for human survival,and the safety of cultivated land is an important prerequisite and guarantee for food production.Since the introduction and implementation of the ‘Soil Pollution Prevention and Control Action Plan’ in 2016,the country has paid more and more attention to soil heavy metal pollution,especially the problem of heavy metal pollution in cultivated soil.Heavy metal pollution in cultivated land can accumulate in the human body through the effect of the food chain,which has a serious impact on human health.Therefore,systematic exploration of heavy metal pollution in cultivated land,understanding the basic status of soil heavy metal pollution in the study area and its spatial formation mechanism,and identifying the specific source of heavy metal pollution has an important guiding role in land security and management and control zoning.The black soil area of northeast my country has become an important food production area in my country with its fertile soil.At the same time,the industry and urbanization process in this area have also developed relatively early.The frequent human activities of production and life have a non-negligible impact on soil pollution safety.In order to explore the soil heavy metal pollution in the black soil area and realize the risk prevention and control of heavy metal pollution,the small watershed is used as the research scale,through the design of indoor sampling plan,field sampling and indoor test analysis,the soil surface of the small watershed in the research area(0-20cm)The content of six heavy metals Cu,Zn,Hg,As,Ni and Cr in 181 samples.Based on classical statistics and geostatistics,comprehensive "3S" base,using semi-variance function model,Moran index,Kriging interpolation,principal component analysis and positive definite matrix factor analysis model and other model methods to study and analyze the black soil area The spatial variability,spatial distribution simulation,and pollution source analysis of heavy metals Cu,Zn,Hg,As,Ni and Cr in the soil of the small watershed,and comprehensive zoning of the pollution situation in the study area,the results show that:(1)Through the determination and calculation of the six heavy metal elements in the soil in the small watershed of the study area,based on the soil background value of Heilongjiang Province,the heavy metals Cu,Zn,Hg,Ni,and Cr in the soil in this area all exceed the standard phenomenon.The rate of exceeding the standard is 16.2%,28.7%,93.4%,48.5% and 19.1% respectively.The over-standard rate is Hg>Ni>Zn>Cr>Cu.The highest percentage of Hg element exceeding the standard reaches 93.4%,indicating the existence of soil in this area.Heavy metal pollution is more serious.All heavy metal elements are at a moderate degree of variation,indicating that their distribution is affected by external factors.(2)According to the simulation results of the semi-variation variance function model,the nugget coefficients of the heavy metal elements in the watershed are all greater than 75%,and the variation is random.The optimal semi-variation of the heavy metal elements Cu,Zn,Hg,As,Ni and Cr The function models are respectively an exponential model,a Gaussian model,an exponential model,a spherical model,an exponential model and an exponential model.The analysis of the global spatial autocorrelation and local spatial autocorrelation of the soil heavy metal content shows that the soil heavy metals Cu,Zn,Hg,As,Ni,and Cr in the study area all have spatial autocorrelation.The blue coefficient fluctuates greatly with the increase of the spatial separation distance.(3)The spatial interpolation result of heavy metal content clearly reflects the distribution of heavy metal content in the study area.The distribution of As and Cr high value areas is similar,mainly in the northwest,middle and northeast of the study area.Cu The high value areas of Ni and Zn are mainly distributed in the northwest part of the study area.Hg has contiguous high value areas in a large area in the northwest and a small area in the southeast of the study area.The high value areas of Ni are mainly concentrated in the northwest and appear as a band.Distribution,the general trend of the distribution of heavy metals in the basin is that the pollution in the northwest is higher than that in other regions,which is consistent with the land use in the basin.The northwest of the basin is mainly farmland,the east is woodland,and the towns and villages in the west are denser than in the east.(4)Through correlation analysis,principal component analysis and PMF model analysis,it can be basically determined that soil heavy metal pollution in the study area mainly comes from 4 aspects,and their contribution to pollution is natural sources and atmospheric deposition pollution sources>industrial and agricultural pollution sources>life.Pollution source>Traffic pollution source.The accumulation of Hg is mainly related to coal burning activities;the accumulation of Cu,Zn and Ni is mainly caused by industrial and agricultural activities;As and Cr are mainly related to natural elements such as soil parent materials;the development of transportation also affects the accumulation of Ni,Cr and Zn.It can be concluded that the accumulation of heavy metals in the soil in this area is mainly caused by the rapid development of heavy industry and agriculture and the demand for heating in winter.The determination coefficient of the PMF model is r2>0.8.The measured value of the model and the predicted value have a good fit.The selected factors can fully explain the information contained in the original data.The source analysis results obtained are more reasonable and are roughly equivalent to the principal component analysis results.Consistent,the analysis results obtained are basically consistent,which can provide a more scientific reference basis for the risk management and control of soil heavy metal pollution in this area.(5)Taking the toxicity response coefficient of each heavy metal element as the weight and the background value of the soil element in Heilongjiang Province as the reference standard,superimposing the spatial distribution of the heavy metal elements in the study area and interpolating the simulation results to obtain the comprehensive pollution situation in the soil in the study area,and clustering through the fuzzy c mean value.The results show that the number of best management districts for soil pollution in the study area is two.The two districts are located in the northwest and east of the study area.The soil pollution in the study area is generally higher in the west and lower in the east.