海原盆地地下水咸化特征和控制因素

地下水是海原盆地唯一的供水水源，近年来部分地区地下水溶解性总固体(TDS)增高，引起了有关部门和水文地质工作者的高度关注。通过分析69组地下水样品的水化学和氢氧稳定同位素数据，对地下水补给来源和咸化的水文地球化学过程进行了研究。结果表明:地下水TDS值198.2~6 436.4 mg/L，沿着地下水流向，咸化程度增加，水化学类型从基岩区的HCO3—Ca·Mg型演化至滞留—排泄区的SO4·Cl—Na·Mg型。地下水补给来源主要为大气降雨和基岩裂隙水侧向径流，补给源—对地下水咸化贡献较小。溶滤作用具空间差异，基岩区和补给区以碳酸盐、硅酸盐风化为主，径流区和滞留—排泄区则为蒸发岩风化，硫酸盐是地下水中阳离子的主要来源。补给水、溶滤和蒸发对第四系地下水TDS的贡献比率分别为4.8%~81.2%、11.9% ~85.9%、1.7%~29.5%，溶滤作用是控制海原盆地地下水咸化的首要因素。当地有关部门应加大对基岩泉水的综合利用，同时注意控制海原县和西安镇等地区地下水开采量，防止地下水进一步咸化。另外，在微咸水分布区可引进地下水去除硫酸盐技术，提高微咸水利用程度。

Groundwater salinization characteristics and controlling factors in the Haiyuan Basin

Groundwater is the dominant resource of water supply for meeting domestic needs in the Haiyuan Basin. In recent years, the increasing salinity has been found in groundwater around some areas, to which high attention has been pain by the relevant departments and hydrogeologists. Determining the distribution of groundwater total solved solids and understanding the salinization mechanism are important for water supplies and sustainable development. Isotopic and geochemical analyses are conducted for 69 water samples from springs and boreholes to identify groundwater recharge sources and potential processes that control the increasing salinity. The results show that the total dissolved solid (TDS) in the groundwater range from 198.2 to 6436.4 mg/l and increase along the groundwater flow path. The hydrochemical types evolve from HCO3—Ca·Mg type in the bedrock area to SO4·Cl—Na·Mg type in the discharge area. The sources of natural groundwater recharge include precipitation and lateral groundwater flows from the mountain areas in the southwest of the basin, both of which have minor contributions to the groundwater salinity. Carbonate and silicate weathering plays a dominant role in the bedrock recharge area, and evaporate weathering, in the flow-through and discharge area. The contribution ratios of the initial water, dissolution and evaporation to TDS of the groundwater vary from 4.8% to 81.2%, 11.9% to 85.9% and 1.7% to 29.5%, respectively. The dissolution process is the first order controlling factors on the groundwater salinization in the Haiyuan Basin. It is suggested that the springs in the bedrock area should be developed and the groundwater exploration should be adjusted in Haiyuan County and Xi′an village to prevent salinization. Furthermore, the technology that can remove sulfate from groundwater should be introduced in the areas where brackish water exists.