| Soil is the foundation of human survival,is the material basis of food safety production and the guarantee of human basic life.In the agricultural production process,due to the large-scale application of agricultural production activities such as pesticides,fertilizers and sewage irrigation,cause the heavy metals and other pollutants enter the farmland soil and accumulate in it,thus,soil environmental problems such as the decrease of soil environmental capacity are caused Soil environmental capacity assessment can not only reflect the self purification ability of regional soil environment,but also analyze the enrichment of pollutants in the soil environment,and improve the quality standard of soil safety environment and remediation of polluted soil.In recent years,with the increase of agricultural intensification and oasis urbanization,the farmland soil environment in Yanqi Basin was polluted by heavy metals to different degrees.In this paper,the environmental capacity of heavy metals in farmland soil in Yanqi basin was studied,providing important reference and scientific basis for the prevention and control of heavy metal pollution in farmland soil,the maintenance of farmland soil quality and the rational and effective management of agricultural production in the study area.The main achievements of this paper are as follows:(1)The average contents of As,Cd,Cr,Cu,Ni,Pb,and Zn in farmland soils in Yanqi Basin did not exceed the limits of risk screening values for soil contamination of agricultural land of the national standard(GB15618—2018).The average content of each element in the soil of Baghrash exceeded the soil background value of xinjiang.The average content of As in farmland soil of Hejing,Hushut and Yanqi did not exceed the soil background values of Xinjiang,while the average content of other elements exceeded.(2)According to the analysis results of the static environmental capacity of heavy metals in farmland soil,the total static capacity of As,Cd,Cr,Cu,Ni,Pb,and Zn in farmland soil was 31.05,1.08,451.58,164.93,367.65,338.85,and 520.2 kg·hm-2.The order of the existing environmental capacity of heavy metals in farmland soil was the same as that of the total static environmental capacity of heavy metals in farmland soil,The existing environmental capacity of arsenic in farmland soil of each county was greater than the total static environmental capacity,and the existing environmental capacity of the other six elements was all less than the total static environmental capacity.The existing environmental capacity of each element in the farmland soil of each county in the study area was reduced to different degrees.(3)According to the analysis results of the dynamic environmental capacity of heavy metals in farmland soil,the allowable annual inputs of the dynamic environmental capacity of each heavy metal in the same years was ranked as: Zn,Cr,Ni,Pb,Cu,As,and Cd.The allowable annual input of heavy metals in farmland soil which consumed the dynamic environmental capacity of each element in different control years decreased with the increase of control years and finally stabilizes around a certain value,its allowable annual input of heavy metals was ranked as: 10 a,20 a,50 a,80 a,100 a.In different control years,the annual dynamic environmental capacity is larger than the annual existing environmental capacity,the reduction of annual existing environmental capacity and it’s speed was faster than the annual dynamic environmental capacity in different control years,and the total dynamic environmental capacity of each heavy metal in farmland soil was always higher than the total static environmental capacity.(4)According to the analysis result of heavy metal environmental capacity index in farmland soil of Yanqi basin,the single environmental capacity index of each element was high,and most of the areas were in the middle or high capacity areas.The environmental capacities of Cr,Cu,and Ni were all at middle or high capacity levels,and the spatial distribution pattern of environmental capacity index was relatively uniform,the soil pollution level was slightly polluted or no pollution,and the environmental capacity was controlled by geochemical causes.The environmental capacities of As,Pb,Cd,and Zn were widely distributed in low-level capacity areas,which were distributed at parts of Baghrash,Yanqi County and the junction of four counties in the northern part of the study area,the pollution level was serious,and the environmental capacity was controlled by human factors.The comprehensive capacity index of farmland soil in all counties was greater than 0.7,and was ranked as: Yanqi,Hejing,Baghrash,and Hushut,The comprehensive capacity of all elements belong to the medium capacity level.The level of farmland soil pollution in the study area was slightly polluted.(5)According to the analysis of the correlation between farmland soil environmental capacity index of heavy metals and soil properties,the relationship between heavy metal environmental capacity index and soil properties was not strong,but the correlation between Cd,Cr,Ni,and Pb and soil pH was significant.Soil CEC and As,Ni and Pb showed significant correlation.There was a significant correlation between soil OM and environmental capacity indexes of elements Cu and Ni.Soil pH,CEC,and OM can affect the spatial distribution of the environmental capacity index,which should be paid more attention to in future studies. |
