Study On Migration Characteristics Of Cr，Ni，Cd In The Acid Black Soil

In the soil environment，heavy metal element is a part of its composition.the content ofheavy metal element overweight once，that can make pollution enter into environment ofsoil.And it can impact the health of animals，plants and human directly or indirectly，theinflunce is very obvious.So the mobility and transfer of heavy metals in the soil is used forproviding the theory basis for safety assessment in the soil environment.This paper studiesthe adsorption desorption behavior of Cr，Ni，Cd and discusses the three elements ofleaching rule.Oscillation method is used to study adsorption desorption behaviors of Cr，Ni，Cd.Adsorption desorption experiment is to study the effect of adsorption desorption byadding the same nitrogen content of urea and ammonium sulfate， changing the exogenouspH value of heavy metal solution and changing the organic matter content of Cr，Ni，Cd ofblack soil.Leaching experiment is to study the influence of vertical migration by changingthe type of leaching solution，the leaching solution pH，leaching method，organic mattercontent of Cr，Ni，Cd of black soil，thus we can clear the leaching rule of Cr，Ni，Cd insoil.The results show that， in the adsorption kinetics study of Cr，Ni，Cd，when thereaction time is480min，three elements are in a state of adsorption equilibrium.And theadsorption process is divided into rapid absorption，slow adsorption，adsorption equilibriumstages.At45℃， adsorption quantity of adsorption of Cr， Ni， Cd are greater than at25℃.By the Freundlich equation fitting，then calculating the thermodynamic parameters，theresult shows that the apparent adsorption process of Cr，Ni，Cd are ispontaneous，endothermic and entropy increase process. Raising the temperature can promote theadsorption of Cr，Ni，Cd，and weaken migration activity.When applied into the samenitrogen content of different forms of fertilizer (urea，ammonium sulfate)，the threeelements of adsorption were greater than the control group，and the adsorption quantity ofurea is greater than the adsorption quantity of ammonium sulfate.The results showed thatapplying nitrogen fertilizer inhibited the activity of Cr，Ni，Cd migration.Under acidcondition，with the increase of pH，adsorption of Cr，Ni，Cd of the tested soil quantity willalso increase.In acidic conditions，the increase of pH inhibited the soil adsorption.Afterremoval of the tested soil organic matter，adsorption capacity decreased significantly.Cr，Ni，Cd adsorption ability were weaked. In the process of desorption， raising the temperature of Cr，Ni，Cd promoteddesorption.When applying into the same nitrogen content of different forms of fertilizer(urea，ammonium sulfate， urea and ammonium sulphate were promoting the desorption ofCr，Ni，Cd. Compared the urea and ammonium sulfate，urea desorption function wasstronger.Acidic conditions，increaseing as the solution pH，desorption quantity of Cr，Ni，Cd decreased. Under acid condition， by increaseing pH， it abated the migration ability ofCr，Ni，Cd. pH is an important factor of Cr，Ni，Cd desorption.After the removal of organicmatter，desorption quantity of Cr，Ni，Cd in the soil is obvious more than desorptionquantity without removing organic matter.Amount of Cr，Ni，Cd leaching is less than using deionized water leaching by Usingleaching solution. When pH=8.9，migration characteristics of Cr，Ni，Cd is relatively weakin the alkaline soil，In the alkaline soil or alkaline precipitation conditions，the risk of heavymetal pollution is relatively small. When pH=4.2acidic，migration capabilities of Cr，Ni，Cd in the soil enhanced precipitation in acidic soil.Contamination risk of heavy metal willbe relatively large. Intermittent leaching of Cr，Ni，Cd leaching amount of each successiveleaching of74.5%，47.8%，50%. In continuous leaching process adsorption capacity ofCr，Ni，Cd enhanced. The total amount of leaching out of Cr，Ni，Cd is more， it’s morethan the total amount of intermittent leaching. And it conducive Cr，Ni，Cd ’s adsorption.High organic matter promote the adsorption of Cr，Ni，Cd effectively，and inhibits leachingout of high organic matter in the soils of Cr，Ni，Cd.Cr，Ni，Cd are not easy to migration，higher organic matter content，the worse their migration characteristics.