Study On The Interaction Between Dissolved Organic Matter And Heavy Metals Under Water-rock Interaction In Coal Mine

Heavy metal pollution is a key characteristic of coal mine water pollution.Dissolved organic matter（DOM）in water will affect the transfer and transformation of heavy metals.Taking Xinjulong coal mine as the research object,the composition characteristics of DOM and heavy metals in mine water were analyzed by field sampling.The indoor water-rock interaction simulation test was carried out to analyze hydrochemical indexes,heavy metal elements,dissolved organic matter and the relationship between DOM-heavy metals during the water-rock interaction of mine water in Xinjulong mine.Therefore,the study on the formation characteristics and interaction of heavy metals and DOM during the formation of mine water is helpful to solve the problems of high salinity and heavy metal pollution of mine water.The results were as follows:（1）The coal samples in Xinjulong coal mine mainly contain quartz and clay,and the main chemical components are SiO₂ and CO₂.The pH value of mine water is between 7.75～8.53 which is alkaline,and the concentration of TDS is between 2570～4870 mg/l,which belongs to high salinity mine water.The chemical type of mine water is SO₄-Na type.The concentration of DOC of mine water is not more than 4 mg/L.The maximum value of SUVA₂₅₄ in coal roadway indicates that DOM has higher aromaticity and contains more kinds of humus,while the maximum value of S_275-295and S_R in goaf indicates that DOM has lower molecular weight,reflecting the degradation of organic matter by microbial activity.The components of DOM are fulvic acid-like,tryptophan-like and chorine-like substances.The fluorescence parameters of FI,BIX and HIX indicate that Dom in mine water mainly comes from microbial degradation.（2）The smaller the particle size,the bigger the specific surface area,the more complete the reaction,and the higher the concentration of ions and heavy metals.The specific surface area of rock is about 6 m²/g larger than that of coal,and the water-rock interaction is more intense.With the increase of coal particle size,SUVA₂₅₄ increases,and the aromaticity and humic degree of the components increase,while that of rock is opposite.The decrease of particle size could increase S_275-295 and S_R,indicating the formation of small molecular weight DOM and the enhancement of microbial activity.The fluorescence component of DOM consists of tryptophan-like acid and tryptophan-like acid.The content of tryptophan-like acid increases and the content of tryptophan-like acid decreases with time.Clay,which has a higher content in the rock,will compete with DOM for binding with heavy metals.The protein-like components of DOM were preferentially bound to the tryptophan-like components,and the smaller the particle size,the stronger the lysis and reverse cation exchange,and the increase of Ca²⁺and Mg²⁺could compete with the heavy metals for the binding sites.The enhancement of microbial activity in water caused the formation of small molecule DOM,which increased the fluorescence intensity of DOM.（3）The evaporation concentration and reverse cation exchange reaction are more intense in the open environment.The concentration of DOC in the closed environment was 85%higher than that in the open environment.The concentration of SUVA₂₅₄ in the closed environment was 0.75 L·mg^-1·m^-1higher than that in the open environment,indicating that the degree of aroma and humus of DOM was higher.While the concentration of S_275-295 and S_R in the closed environment was higher than that in the open environment,indicating that microbial activity was stronger,which is easier to generate small molecular weight DOM.The main fluorescence components of DOM are fulvic acid-like,tryptophan-like and chorine-like compounds,which increase gradually in the open environment and increase in the closed environment.The release of HCO₃^-may be promoted by replacing Mn adsorbed on the surface of minerals in the closed environment.Mn has strong binding ability with fulvic acid-like substances in the open environment and tryptophan-like acids in the closed environment.The binding ability of DOM to Mn in the open environment was 64%higher than that in the closed environment,indicating that the binding ability of DOM to heavy metals was higher in the case of stronger water-rock interaction.There are 45 figures,7 tables and 114 references in this thesis.