北京市泉水的水化学、同位素特征及其指示作用

    Hydrochemical and isotopic characteristics of springs in Beijing and their implications

    • 摘要: 对北京市泉水的水温、溶解氧、电导率、氧化还原电位、pH值、总溶解固体等进行了现场检测,对泉水中的K+、Na+、Ca2+、Mg2+、Cl-、SO42-、HCO32-、NO3-离子,D、18O组成和Sr、87Sr/86Sr比值等进行了实验室检测,对泉水按成因进行了分类,并与30年前的泉水普查资料作了对比。调查表明,曾以泉多著称的北京市,1980s初存在的几乎全部二类泉和60%的一类泉如今已消失,仅存的13眼泉的出水量也明显减小,这与降水量的减少和大规模开采地下水有关。水质分析表明,现在绝大部分泉水水质良好,物理和水化学指标与30年前相比变化甚微,明显没有受人类活动的污染;泉水仅在浅部循环,在地下滞留时间较短,更新能力强;泉水接受大气降水补给,与浅层地下水联系密切,构成了统一的地下水系统;泉水中的Sr为碳酸盐岩风化来源。

       

      Abstract: Field tests on temperature, dissolved oxygen, electric conductivity, redox potential, values of pH and total dissolved solid of spring waters were carried out in Beijing, and chemical and isotopic components in waters such as K+, Na+, Ca2+, Mg2+, Cl-, SO42-, HCO32-, NO3-, D, 18O, Sr2+ and 87Sr/86Sr were also tested in labs. Springs in Beijing were classified into four types based on their formation mechanisms, and a comparative analysis between data obtained during this investigation and those obtained during the past 30 years were also made. The results indicate that most of the second kind springs and 60% of the first kind springs existent in early 1980s have disappeared, runoffs from the survived thirteen springs have decreased sharply, which is mainly attributed to the decreasing precipitation and the exploitation of groundwater. Quality analysis of spring waters obtained shows that qualities of most spring waters are good, and physical and chemical indexes of these waters have changed slightly compared with those 30 years ago, which implies that qualities of these spring waters have not been obviously impacted by human activities. These spring waters only participate in shallow groundwater circulation, and detention of these waters is comparatively short, suggesting strong renewability. These springs are recharged by infiltration precipitation, and have close dynamic interconnections with other shallow groundwater. Sr ions in spring waters are derived from weathering of carbonate rocks.

       

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