Study On The Migration And Transformation Rule Of Dissolved Organic Matter In The Underground Water Of Mine Area

This paper mainly studies the rule of migration and transformation of dissolved organic matter(DOM) in underground aquifers. To achieve our research purpose, we carried out the dynamic column experiments of dissolved organic matter at different conditions in indoor. In the experiment, the water of Wujiang river(which is the recharge source of Pingdingshan Coal groundwater) is used as water sample, and quartz sand and marl rock are used as rock sample. And comparative study on characteristics of migration and transformation of DOM in different rock sample is done. The results show that(1) the hydrodynamic dispersion in the simulated sandy column model could be enhanced at the faster seepage velocity and higher temperature. In the transport process of dissolved organic matter, the adsorption effect between quartz sand and dissolved organic matter and biological effect are very weak, so the main effect is convection–dispersion. With the increase of seepage velocity, the longitudinal dispersive coefficient of dissolved organic matter increases, and the ability of migration and diffusion enhances. When the temperature rises, longitudinal dispersive coefficients and dispersity of dissolved organic matter increase, while Pleclet number decreases, and the ratio of convection and diffusion effect is reduced.(2) In the transport process of dissolved organic matter in marl rock, change trend of DOM’s mass concentration(characterized by CODcr) are relatively similar at different temperatures, namely, there are four stages that are rising slowly, rising rapidly, stable fluctuation, decreasing slowly and tending to be stable. In the first three stages of the migration process, transformation way of DOM is mainly adsorption; however, in the fourth stage, transformation way of DOM is biodegradation. And within a certain temperature range, as the temperature increases, the adsorption effect between quartz sand and DOM decreases, but biodegradation is enhanced. At different seepage velocity, change trend of DOM’s mass concentration experiences the previous four stages, and in the first to third stages, transformation way of DOM focuses on adsorption, but in the fourth stage, transformation way of DOM focuses on biodegradation. And the adsorption effect between quartz sand and DOM and biodegradation decreases at the faster seepage velocity.(3)There are some similarities on characteristics of migration and transformation of DOM, but there are significant differences too. Similarities are that change trend of DOM’s mass concentration all experiences three similar stages which are rising slowly, rising rapidly and stable fluctuation. The difference is that in quartz sand, during the transport process of dissolved organic matter, main effect is convection–dispersion, while the adsorption effect between quartz sand and dissolved organic matter and biological effect are very weak. However, in marl rock, during the transport process of dissolved organic matter, besides existing convection–dispersion, the adsorption effect between quartz sand and dissolved organic matter and biological effect are quit significant. And within a certain temperature range, with temperature increasing, the adsorption effect between quartz sand and DOM decreases, while biodegradation is enhanced. And the adsorption effect between quartz sand and DOM and biodegradation decreases at the faster seepage velocity.