Distribution Characteristics Of Heavy Metals And Microbial Communities In Different Types Of Polluted Soil

The development of economy and the aggravation of human production and life lead to the breaking of the natural geochemical cycle of heavy metal elements.They enter the soil ecological cycle,and eventually pose a threat to human health,making soil heavy metal pollution become one of the most harmful environmental problems.Heavy metals mainly come from human activities,including industrial pollution,agricultural pollution and domestic pollution.The distribution of heavy metals in soils polluted by different pollution sources has their own characteristics.It is of great practical significance to clarify the spatial distribution characteristics of heavy metals in different types of contaminated soils for the remediation of soil heavy metal pollution,and to provide the basis for taking more specific treatment methods.(In this study,the soil polluted by industrial wastewater,livestock manure and sewage,and domestic waste was selected as the research object to explore the physical and chemical properties and the distribution characteristics of heavy metals in three kinds of polluted soil,and the microbial community in soil plays an important role in the above interaction.It has great practical significance for the remediation of heavy metals pollution in soil,and could provide basis for effective treatment methods.The main conclusions are as follows:(1)The surface soil of 0-30 cm of industrial wastewater is weakly acidic,and the deep soil is weakly alkaline;the soil polluted by livestock manure and domestic waste is weakly alkaline.Nitrogen in soil mainly exists in the form of organic nitrogen.The order of organic carbon content was livestock manure and sewage > domestic waste > industrial wastewater.Among them,there was no significant difference of organic carbon in the vertical direction of the soil polluted by livestock manure and sewage,and the content of organic carbon in the remaining two kinds of polluted soil gradually decreased in the vertical direction.The main DOM components in soils from different sources were leucine-like,tryptophan-like.(2)The contents of Zn and Cu in soil polluted by domestic waste(0-30cm)and livestock manure and sewage(0-100 cm)exceeded the standard.In the soil polluted by industrial wastewater,Zn(0-50 cm),Cu(0-30 cm),As(0-50 cm)and Cd(0-100 cm)all exceed the standard values.The speciation distribution of heavy metals in soils from different sources is different.The occurrence forms of As and Cd were mainly residue with high stability in the soil polluted by domestic waste and livestock manure and sewage,while there were active forms in the 0-30 cm topsoil polluted by industrial wastewater.The occurrence forms of Zn and Pb in the three contaminated soils are mainly residuals and active forms.The active forms of Cu in the soil polluted by domestic waste and industrial wastewater were mainly distributed in 0-30 cm topsoil,while in the soil polluted by livestock manure and sewage,they were evenly distributed in 0-100 cm soil layer.In this study,the TN,Organic carbon,fulvic acid-like and humic acid-like substances in DOM were positively correlated with the active forms of heavy metals.(3)There are specific genera in different polluted soils,which are resistant to heavy metals.There are norank＿f＿Anaerolineaceae,MND1,norank＿f＿norank＿o＿SBR1031,Sphingomonas in the soil polluted by industrial wastewater;Desulfurivibrio,Sulfurimonas,norank＿f＿norank＿o＿OPB41,unclassified＿f＿Gallionellaceae,Desulfitobacterium,Thiobacillus were found in the soil polluted by livestock manure and sewage;Thiobacillus,Pseudoarthrobacter,norank＿f＿norank＿o＿SBR1031 in the soil polluted by domestic waste。 These functional microorganisms detoxify heavy metals in the process of self-metabolism and have certain resistance to heavy metals.