Effects Of Heavy Metal Pollution On Soil Microbial Activity In Desert Steppe

Desert steppe is a transitional type from steppe to desert.With the development of industry,pollutants such as heavy metals are released into the soil during production,combustion and transportation,posing a serious threat to the fragile ecological environment of desert steppe.In order to explore the response of soil microbial activity in desert steppe to heavy metal pollution,this study took the soil of Gaoshawo Industrial Zone and surrounding desert steppe soil in Ningxia as the main research object.To reveal the environmental chemical behavior of heavy metals in desert steppe soil,and provide scientific basis and reference for early warning and control of heavy metal pollution in desert steppe soil under the influence of industrial activities.The main conclusions are as follows:(1)According to the Kriging interpolation method and the Nemerow comprehensive pollution index method,the soil heavy metal pollution in the study area was analyzed.The results showed that there were different pollution levels among the sample points,and the heavy metal pollution in the north of the expressway was more serious.,and concentrated near industrial parks and highways.This shows that industrial activities such as industrial production and transportation have a serious impact on the soil environment in the study area.According to the Nemerow classification standard,the 96 plots in the study area were divided into five areas:non-pollution area Ⅰ,mildly polluted area Ⅱ,moderately polluted area Ⅲ,heavily polluted area Ⅳ,and severely polluted area Ⅴ.The average values of Cd,Pb,Zn and Mn in the soil exceeded the background value of heavy metals in the soil in Ningxia,among which the content of Pb was the most serious,followed by Cd,Zn and Mn.In the PCA analysis,the contribution coefficients of Cu,Pb,Zn and Cd elements were large and all on the right side,indicating that heavy metal pollution was the main factor affecting the change of soil environmental quality in the desert steppe in this region.Heavy metal pollution has a certain impact on the basic chemical properties of soil.The pH,organic matter,total nitrogen and total potassium showed a positive correlation with the content of each metal element.Alkali-hydrolyzed nitrogen,total phosphorus,available phosphorus and available potassium were negatively correlated with the content of each metal element.(2)The number of bacteria in the soil of the study area was the largest,followed by the number of actinomycetes,and the least number of fungi.With the intensification of heavy metal pollution,the total number of microorganisms showed a downward trend.The numbers of bacteria,fungi and actinomycetes were significantly negatively correlated with Cu,Pb,Zn and Mn(P<0.05).The soil microbial biomass carbon and nitrogen contents were higher under mild and moderate pollution,indicating that mild and moderate pollution were beneficial to the growth of microorganisms and increased the soil microbial biomass carbon and nitrogen levels.With the increase of soil heavy metal pollution degree,this promoting effect turns into an inhibitory effect.(3)There were differences in soil enzyme activity in each polluted area.The activities of urease and alkaline phosphatase reached the highest value in moderate pollution,indicating that moderate heavy metal pollution has a certain promoting effect on urease and alkaline phosphatase.The activities of catalase and sucrase gradually decreased with the intensification of heavy metal pollution,and they were significantly negatively correlated with Cu,Pb,Zn and Mn(P<0.01).Alkaline phosphatase activity was significantly positively correlated with soil organic matter,available phosphorus,available potassium,microbial biomass carbon,the number of bacteria,and the number of actinomycetes(P<0.01).The activities of catalase and sucrase were significantly positively correlated with alkali-hydrolyzed nitrogen,microbial biomass nitrogen,and the number of three types of microorganisms(P<0.01)To sum up,the desert steppe soil in the study area is greatly affected by the heavy metal Pb.Through the analysis of soil microbial activity in the study area,it can be seen that industrial activities have a significant effect on the enzyme activity,microbial quantity,microbial biomass carbon and nitrogen in the desert steppe soil.Impact.