Release Mechanism And Potential Ecological Risk Assessment Of Pollutants In Coal Gangue Under Leaching

In recent years,the problem of mine pollution is serious,and the coal gangue deposited in open field will release a large amount of pollutants under the long term leaching to destroy the surrounding environment.Therefore,it is very important to analyze the release mechanism of pollutants under leaching.In this paper,the coal gangue in Hancheng mining area of Shaanxi Province is taken as the object of study.The pHysical conditions(coal gangue particle size,soil medium),chemical conditions(sulfur content of coal gangue,pH of leachate),biological conditions(coal gangue weathering degree)The effect of pollutant release in waste rock,and the migration equation of pollutants by means of data analysis and quadratic regression fitting.In this paper,combined with leaching experiments,Tessier continuous five-step extraction experiments,analysis of heavy metal morphological transformation characteristics,explained the mechanism of pollutant migration and transformation,evaluation of coal gangue emissions of potential ecological risk.1.Contaminants such as calcium,magnesium,sulfate,chlorine and carbonate in coal gangue are gradually decreased with the increase of leaching time,and finally stabilize.The sulfur content of coal gangue and leaching solution pH have a great effect on the release of cations.The higher the sulfur content is,the faster the ion release rate is.The release rate of cations such as calcium and magnesium is higher than that of alkaline in acidic state.The release rate in alkaline state is generally higher than acidity.2.The particle size of coal gangue,sulfur content,leachate pH,media environment,weathering degree are closely related with the release of heavy metals.The higher the degree of weathering,the greater the cumulative release of heavy metals,the greater the change in the state of occurrence;different states of coal gangue,weathering effect on the release of heavy metals to the The effect of the sulfur content on the chemical level and the pH of the leachate is greater than the effect of the medium and particle size at the physical level.3.The release of heavy metals Cd,Cu,Fe,Ni and Pb in coal gangue is accumulated.The occurrence of heavy metals is affected by the weathering degree,sulfur content and particle size of coal gangue.The higher the degree of weathering is,the higher the sulfur content is,and the heavy metal residue changes to other states.4.Through the fitting equation,it can be seen that most of the migration of pollutants showed a rapid decrease in the early stage,and the medium was stable in the middle period,and the later period was stable.The state of recovery.It is found that the particle size,sulfur content and leaching solution pH have little effect on the migration rate of heavy metals,but only have the influence of individual ions such as Cu and Cr.The higher the sulfur content is found by the fitting equation,the more the migration of the constant components fast.5.Through the potential ecological risk assessment of RAC,it was found that the heavy metals Cd and Cu with high potential pollution in the coal gangue after leaching had;The activity of heavy metals in coal gangue increases with the increase of sulfur content and the degree of weathering.The soil medium plays a buffer role in the release of heavy metals.6.Through the potential ecological risk assessment of Hakanson,it was found that the contents of Ag,Cd and Fe in the leaching increased over the background value,and the Cd value was several hundred times higher.The potential risk coefficient of heavy metals in coal gangue increases with the increase of sulfur content of gangue,and decreases with the increase of weathering time.In the presence of soil medium,the changes of the ecological factors of the heavy metals in the coal gangue are more complicated,which is likely to play a buffer role in the soil medium.