Effect Of Organic Fertilizer Application On Heavy Metal Release In Soil

Organic fertilizer application on the field is a kind of livestock and poultry manure management that conforms to the concept of sustainable development and environmental friendly.However,organic fertilizer contains amount of heavy metals,which are the main obstacles of organic fertilizer application on the field due to the ecological risks caused by the accumulation and leaching of these heavy metals in the soil.The study represented by different types of farmland soil in our country,according to the characteristics of heavy metals in the soil with organic fertilizer for comparative analysis.The mechanism of heavy metal release in organic fertilizer under soil acid and alkali conditions,redox processes,organic matter degradation and other geochemical conditions was systematically analyzed.It provides a scientific basis for the environmental security of organic fertilizer land use in China.The main conclusions are as follows:(1)This study seven typical farmland soils in China are Leaching soil(Suifenhe,Heilongjiang),Half-lying soil(Luancheng,Hebei),Primary soil(Shenmu,Shaanxi),Saline soil(Binzhou,Shandong),Arid soil(Alashan,Inner Mongolia autonomous region),Aquatic Soil(Qiqihar,Heilongjiang),and Iron and alumina soil(Qiyang,Hunan).The p H of TL is 5.04,and the organic matter content of CY is 0.69%.The risk of Cr,Ni and As pollution of agricultural land is low in LR.GH,BLR,CY and YJ have lower risk of As pollution in agricultural land.The content of other heavy metals is lower than the limited value of heavy metal risk of pollution by the state,and there is no risk of agricultural land pollution.(2)When organic fertilizer was added to soil with a mass ratio of 10%,the soil EC increased.The contents of dissolved organic carbon,humic substances and fulvic acid increased.The total amount of As,Cd,Cr,Cu,Fe,Ni,Pb and Zn increased,and the content of Zn increased the most,the percentage was 310%.Next is Cu,which increases 215%.(3)The order of acid-base buffering capacity of seven typical farmland soils is BLR< TL < LR < SC < YJ < GH< CY.After adding organic fertilizer,the soil acid-base buffering capacity of the LR,BLR,YJ,GH,TL was improved.The change of redox condition has no effect on soil acid-base buffering ability.(4)In the leaching process of heavy metals in soil-water mixed system,the maximum concentration of heavy metals leaching is less than 3% of the total amount of heavy metals in soil.When the p H is close to neutral,the leaching concentration of heavy metals is the lowest.In the main p H range of soil(5<p H<9),the addition of organic fertilizer(10% mass ratio)increased the leaching concentration of heavy metals Cu and Zn.Under alkaline conditions,adding organic fertilizers,the leaching concentrations of Cr,Cu,Ni,Pb and Zn increased with the increase of p H.(5)The change of redox condition had no obvious effect on soil EC,p H value and heavy metals content,but affected the process of organic matter degradation.The increase of dissolved organic carbon,humus substances and fulvic acid in soil under anaerobic environment was greater than that in aerobic environment after organic fertilizer was added into soil with a dry mass ratio of 10%.(6)The redox process of soil affects the release of heavy metals in water environment.Under alkaline conditions,the leaching concentrations of As,Cr,Cu,Ni,Pb and Zn of TL in anaerobic culture were lower than that in aerobic culture.Under the reduction conditions,Fe(III)is reduced to highly soluble Fe(II),which is further precipitated in large quantities under alkaline conditions.Other heavy metals in the water environment are carried away by adsorption,and the leaching concentration of heavy metals in water environment is reduced.