Located in an arid and semi-arid region, the northern Ordos Basin is one of the key coal mining areas of China. The Zhiluo (J₂z) sandstone aquifers, which overlay the Yan’an (J₂y) coal seam layer, are a major source of drinking water. However, the hydrochemical evolution and possible impacts of coal mining on pollution of J₂z groundwater over recent decades, and the water inrush hazard it presents, are not well understood. In this study, we investigate the groundwater’s origins and the factors controlling its quality and hydrochemical characteristics in these areas. In the northern and southern areas, J₂z groundwater hydrochemistry shows distinct hydrochemical features, being Ca-HCO₃ type with lower total dissolved solids (TDS) in the north, and Na + K-SO₄ type with higher TDS in the south. Different water–rock interactions and coal mining activities may be the causes of such differences. We suggest that greater attention should be paid to preventing water inrush events during mining, as J₂z groundwater has a good hydraulic connection with shallow groundwater in the northern area. Water treatment is also needed, as J₂z groundwater in the southern area exceeds the safe limits for drinking and irrigation. In conclusion, the main factors determining local groundwater hydrochemistry and quality are mining activity, ground temperature, groundwater flow velocity, and groundwater circulation.

鄂尔多斯盆地北部地处干旱、半干旱地区，是我国重要的煤矿区之一。覆盖延安（J ₂ y）煤层的直洛（J ₂ z）砂岩含水层是饮用水的主要来源。然而，近几十年来，煤炭开采对 J ₂ z 地下水污染的水化学演变和可能的影响，以及它所带来的突水危害，尚不清楚。在这项研究中，我们调查了这些地区地下水的来源和控制其水质和水化学特征的因素。在北部和南部地区，J ₂ z 地下水水化学表现出明显的水化学特征，为Ca-HCO ₃北方总溶解固体 (TDS) 较低的类型，南方 TDS 较高的Na + K-SO ₄类型。不同的水-岩相互作用和煤炭开采活动可能是造成这种差异的原因。我们建议在采矿过程中应更加注意防止突水事件，因为J ₂ z 地下水与北部地区的浅层地下水具有良好的水力联系。还需要进行水处理，因为南部地区的J ₂ z 地下水超过了饮用和灌溉的安全限值。总之，决定当地地下水水化学和水质的主要因素是采矿活动、地温、地下水流速和地下水循环。