Abstract Underground reservoirs packed with coal gangue have been widely used to store and purify mine water in the coal mine areas of China; however, minimal information is available about the effects of pollutants released from the packed matrix on the quality of stored water. Column experiments were performed at 25 °C and Darcy fluxes of 0.39, 0.73, and 1.56 cm/h to investigate the effect of Darcy flux on the dynamic changes of dissolved organic matter (DOM) and nitrogen released from the packed coal gangue. Results showed that the values of dissolved organic carbon (DOC), UV254, organic nitrogen (ORG-N), nitrate, and total dissolved solids (TDS) in the effluent decreased rapidly within 3.7 pore volumes (PV) at the three Darcy fluxes and then decreased slowly and tended to become stable during the column experiments. However, the effluent concentrations of NH4+–N, which is the major nitrogen released from the packed matrix, and total nitrogen (TN) decreased and increased alternately, which can be relative to the lithology, mineral, and chemical composition of the studied matrix. The quantities of DOC, NH4+–N, ORG-N, and TN released from the studied matrix decreased with Darcy flux, suggesting a positive effect of hydraulic retention time (HRT) on the resolution of pollutants from the studied matrix. Moreover, the microbial environment got weakened with an increase in Darcy flux, as confirmed by the variation trends of the biological/autochthonous index (BIX) and the fluorescence index (FI). Thus, the evident accumulation of NO2− –N and the highest content of NO3−−N were observed due to incomplete nitrate reduction with a low efficiency at 1.56 cm/h. The findings will be helpful in estimating the variation of water quality during the storage of mine water in a coal mine underground reservoir in China.

中文翻译：

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达西通量对煤矿地下储层煤矸石中溶解有机物和氮释放的影响：柱实验

摘要 充填煤矸石的地下蓄水池已广泛用于我国煤矿区矿井水的储存和净化；然而，关于从填充基质释放的污染物对储存水质量的影响的信息很少。柱实验在 25 °C 和 0.39、0.73 和 1.56 cm/h 的达西通量下进行，以研究达西通量对填充煤矸石释放的溶解有机物 (DOM) 和氮的动态变化的影响。结果表明，在三种达西通量和 3.7 孔体积 (PV) 内，流出物中溶解有机碳 (DOC)、UV254、有机氮 (ORG-N)、硝酸盐和总溶解固体 (TDS) 的值迅速下降。然后在柱实验期间缓慢下降并趋于稳定。然而，NH4+–N（填充基质释放的主要氮）和总氮 (TN) 的出水浓度交替减少和增加，这可能与研究基质的岩性、矿物和化学成分有关。从研究基质中释放的 DOC、NH4+–N、ORG-N 和 TN 的数量随着达西通量的增加而减少，表明水力停留时间 (HRT) 对研究基质中污染物的分解有积极影响。此外，微生物环境随着达西通量的增加而减弱，生物/本土指数（BIX）和荧光指数（FI）的变化趋势证实了这一点。因此，由于硝酸盐还原不完全，在 1.56 cm/h 时效率较低，观察到明显的 NO2--N 积累和最高含量的 NO3--N。