Study On The Content And Pollution Of Heavy Metals In The Soil Near Fufeng And Qishan Counties In Shaanxi Province

Heavy metal pollution in soil is harmful to ecological environment and human health,so it is of great scientific and practical significance to study it.In order to find out the characteristics and distribution of soil heavy metals in the vicinity of Fufeng and Qishan County in Shaanxi Province,and to provide scientific basis for the prevention and control of soil heavy metals pollution,this paper deals with the wheat field,apple forest land,vegetable field near Fufeng County.This paper deals with wheat field,apple forest land,vegetable field near Fufeng County and three Holocene loess paleosol profiles near Fufeng and Qishan county were sampled.The pH value,conductivity value,particle size composition and magnetic susceptibility of 196 soil samples were measured by pH meter,conductivity meter,magnetic susceptibility meter and laser particle size meter.The contents of major elements and heavy metals in 196 soil samples were analyzed by X-Ray fluorescence spectrometer.Based on the experimental data,the level,distribution,source and correlation with physical and chemical properties of heavy metals in soil of this region were studied.At the same time,the single factor index method,Nemero comprehensive pollution index method and potential ecological risk index method were used to evaluate the pollution degree of soil heavy metals in the study area.Through research,we have obtained the following conclusions:(1)The total average values of the contents of major elements in the topsoil surface of three different utilization types of Fufeng are Si>A1>Ca>Fe>K>Mg>Na.In the three loess-paleosol profiles of Fufeng and Qishan,the four oxides of Al,Si,K,and Fe all had the highest content in the S0 horizon,and the Ca content was highest in the L1 horizon.(2)The heavy metal content in the surface soil of three different types of Fufeng shows that the content of six heavy metal elements As,Cr,Cu,Ni,Pb,and Zn in the three types of samples does not exceed the secondary standard limit of the heavy metal quality environment in China.China's agricultural soil standards.Among them,the contents of three heavy metals Cu,Pb,and Zn in Fufeng vegetable fields exceed the standard natural background values.The content of As and Pb in the soil of' Fufeng apple forest and the content of Ni,Pb,As in the wheat field were the natural background values of soil environmental quality standards in China.(3)In the 3m-thick loess-paleosol section,the contents of heavy metals inHolocene Loess L0,Holocene paleosol S0 and Ma Lan loess L1 show regular change.The heavy metal content is generally Holocene paleosol(S0)>Holocene Loess(L0)>Ma Lan loess(L1).(4)In addition to the slight pollution of heavy metals on the surface of the soil in the study area,the middle and lower parts of the three loess profiles with a thickness of about 2.5 m were also enriched and slightly polluted by the number of gold from nature.(5)The evaluation results of the single factor index of the surface soil of the wind-supporting surface with reference to the soil background value of Shaanxi Province showed a higher pollution index of Mn,Co,Cu,As,and Pb,followed by Ni,Cr,and Zn,among which Cu and The single factor pollution index of Zn in vegetable fields was the highest,which was greater than the single factor pollution index in apple forest land and wheat field.The size of the Nemerow comprehensive pollution index was vegetable land>apple forest land>wheat land,but all belonged to mild pollution.The evaluation result of potential ecological risk index was vegetable plot>apple forest land>wheatland,all within the range of low pollution grade.(6)There are two kinds of heavy metal elements in topsoil of three different types of Fufeng use:the first one is As,Cr,Mn,and Ni,which are mainly from the natural sources of the soil itself.The second type is Cu,Zn,Co,and Pb,which mainly come from artificial sources such as chemical fertilizer application and automobile traffic pollution emissions.Three heavy metal elements about 2.5m thick in the loess-paleosol profile are mainly from natural sources.(7)The CIA and Na/K ratios of three thick 2.5m thick loess-palaeosols,together with clay and magnetic susceptibility,indicate that during the period of S0 development in paleosols,the climate was warmer and more humid,and the chemical weathering formed stronger soils,resulting in more clay particles.The relatively warm and humid climate has led to a greater concentration of heavy metals in the palaeosol.During the development period of loess L1,the weather was cooler and colder,and the chemical weathering and soil formation was weaker.The formation of clay was less,and the dry and cold climate caused the low content of heavy metals in the loess layer.