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    1998年以来兰州市地下水环境变化及驱动因素

    Changes and driving factors of groundwater environment in Lanzhou since 1998

    • 摘要: 以地下水污染调查数据、地下水监测数据和遥感数据为基础,分析了1998年以来(1998—2019年)兰州不同区域地下水环境变化趋势,探讨了土地利用变化、污染源排放、地下水开采等城市发展要素对地下水的影响。结果表明:1998年以来兰州市地下水环境变化的主要特征是水质恶化、水位上升。溶解性总固体、总硬度、硝酸根、氟等典型水化学指标在大部分地区呈稳定上升趋势,局部地下水中硝酸根比重增加,出现了硝酸型地下水。污染负荷增加是水质恶化的重要驱动因素,且恶化指标与城市主体功能存在直接关系,城关区是主要的居住、商业区,水质恶化的典型指标为硝酸盐;西固区是化工、冶炼等重工业集中区,地下水污染程度最重,反映工业污染的氟化物上升显著;七里河区、安宁区是商业、居住及轻工业的综合分布区,矿化度、总硬度、硝酸根等指标都有不同程度上升,但升幅不大。西固及三滩地区地下水位上升较为明显,其他城区相对稳定,城市不透水界面阻碍了降雨、灌溉等地表垂直入渗,使地下水位年内波动趋于平缓;水源地开采量减少、沿河工程建设以及地下管网渗漏等因素导致地下水补径排条件发生变化,不仅引起城区地下水位上升,还能够增强污染物淋滤和地下水蒸发浓缩,对水化学环境造成一定影响。

       

      Abstract: Based on groundwater pollution survey data, groundwater monitoring data and remote sensing data, the authors analyzed the groundwater environment change trend in different areas of Lanzhou City since the 1990s (1998-2013). The results show that, since 1998, the main groundwater environment change in Lanzhou has been characterized by deterioration of groundwater quality and rising of groundwater level. Typical hydrochemical indexes such as TDS, TH, nitrate and fluorine have different trends in different areas of Lanzhou, and most of them show a steady upward trend. Nitric acid groundwater has appeared in some areas. The increase of urban pollution load is an important driving factor for the rise of typical hydrochemical indicators, and there is a direct relationship between the characteristic indicators and the main functions of different urban areas. Chengguan District is the main residential and commercial area, with the typical index of water quality deterioration being nitrate. Xigu District is a concentrated area of heavy industries such as chemical industry and smelting, with the highest degree of groundwater pollution, and the increase of fluoride suggests that industrial pollution is significant. Qilihe District and Anning District are comprehensive distribution areas of commerce, residence and light industry, and TDS, TH, nitrate and other indicators have all risen in varying degrees, but the increase is not significant. The rise of groundwater level in Xigu and Santan area is more obvious, with that in other areas being relatively stable. Urban impervious interface hinders the vertical infiltration of rainfall, irrigation and other surface water, making the annual fluctuation of groundwater level gentle. Due to the reduction of groundwater exploitation, increasing construction along the Yellow river and the leakage of underground pipe network, the condition of groundwater recharge and discharge is changing. It not only causes the rise of groundwater level in the urban area, but also enhances the leaching of pollutants and the evaporation and concentration of groundwater, which has a certain impact on the hydrochemical environment.

       

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