Effects Of Mineralization Of Organic Fertilizer On The Forms And Migration Of Heavy Metals In Soil And Model Prediction

Livestock manure is an important source of fertilizer in agricultural production and plays an important role in improving soil properties and improving the quality and yield of agricultural products.However,with the development of the aquaculture industry,in order to prevent diseases and improve the utilization rate of feed,additives containing heavy metals such as Cu and Zn are added to the feed to carry a large amount of heavy metal elements in the feces,and heavy metals are brought into the soil and crops by fertilization.At the same time,livestock manure contains a lot of organic matter,and its mineralization will affect the physical and chemical properties of the soil and affect the fraction and migration of heavy metals.In order to clarify the influence of livestock manure application on the form and migration ability of heavy metals in soil,and provide a basis for rational fertilization in agricultural production,this study uses typical alkaline vegetable soil in Wuqing and typical acid paddy soil in Hunan as the research object and conduct the aging experiment and column experiment,and the following results were obtained:(1)The results of aging experiments showed that the change of heavy metals in pore water changed significantly in the first 30 days.According to the analysis of the heavy metal concentration and physical and chemical properties in pore water,the dominant factors affecting the concentration of Cu in pore water were DOM and Eh,Zn was pH.Cd and Pb are pH and organic matter,while As is mainly affected by the Eh which affected by mineralization of organic matter.(2)Sequential extraction of heavy metals in soil showed that the application of pig manure brought a lot of active Cu and Zn to the soil,and it would transform into inactive components with time.The flooding treatment could not reduce the availability of Cu and Zn.The dominant factors affecting the form of Cu are pH and the Eh change caused by mineralization of organic matter.The dominant factor affecting the form of Zn is pH.Application of pig manure in clean soil enhancing the bioavailability of Cd while reducing the bioavailability of Cd in contaminated soil.Flooding treatment can reduce the Cd availability and pH,Eh and a large amount of P input by pig manure are also affecting its from.The application of pig manure significantly reduced the bioavailability of Pb and promoted its conversion to inactive components due to the large amount of P in pig manure,and flooding do not affect the from of Pb.The application of pig manure and flooding treatment reduce Eh while greatly enhancing the environmental risk of As,and in the case of extremely low Eh,the As of the inactive component is released and converted into active form.(3)The results of column experiments show that DOM promotes the migration of As,Cd,Cu,Pb,Zn and P.In the absence of DOM,Cu retained more than 90% in the column,but only about 60% in the presence of DOM.The introduction of DOM can release As,Cd and Pb from the soil,greatly enhancing the risk of migration.(4)DOM and POM have different effects on heavy metal migration.For Cd and Pb,the interaction of a large number of P elements adsorbed by POM with Cd and Pb inhibits migration.Mineralization of POM reduces soil Eh value and enhances the migration of As.The application of pig manure input a large amount of Zn,but the Zn migration ability of the treated group was weaker than that of the control group when the simulating solution was introduced,and the dominant factor affecting the migration ability of Zn in the absence of DOM was pH.The higher the pH,the weaker the migration ability of Zn.