环境同位素在北京平谷盆地山前侧向补给研究中的应用

Application of environmental isotopes in the study of lateral recharge in front of Pinggu Basin Beijing

利用地下水水化学和同位素测试分析成果,结合区域地质、水文地质条件研究了平谷北山山区侧向补给情况和中桥水源地地区第四系松散孔隙水和下伏岩溶水关系。结果表明:研究区第四系松散孔隙水和基岩岩溶地下水均来源于大气降水,地下水化学类型均为HCO_(3)^(-)—Ca^(2+)·Mg^(2+)型;平谷北山山前基岩岩溶水侧向补给平原区第四系松散孔隙水和下伏岩溶地下水;通过D值估算得到中桥水源地第四系浅层地下水的山区岩溶水侧向补给和垂向降水入渗补给比例为57∶43;中桥水源地基岩岩溶水接受山区岩溶水侧向补给和第四系孔隙水垂向越流补给比例为87∶13。研究成果为平谷地区地下水资源量评价和地下水动力场数值模型的建设提供了关键参数,为区域地下水的合理开采和有序回补涵养提供了科学依据。

Obejctive: As an important water source of Beijing, Pinggu basin provides an important support for the Beijing municipal water supply, in order to better understand the lateral recharge of Pinggu mountain area and the recharge and drainage relationship between Quaternary groundwater and underlying bedrock karst water in Zhongqiao water source area, establish and improve regional groundwater flow model, calculation and evaluation of regional groundwater resources, and put forward groundwater reasonable utilization and protection measures. Methods: Based on the basic theories of water cycle and hydrogeology, the regional hydrogeological conditions are analyzed. and the recharge sources, recharge relations, recharge elevations and recharge ratios of different recharge sources of regional groundwater are analyzed by hydrochemistry and isotope hydrology Results: The quaternary water and bedrock karst groundwater in the study area all come from atmospheric precipitation, and the chemical type of groundwater is HCO_(3)^(-)—Ca^(2+)·Mg^(2+). The quaternary loose pore water and the underlying karst groundwater are supplied by The bedrock karst water in front of the North Mountain. According to the estimation of ~2H,18O and T values, the ratio of lateral recharge of karst water to vertical precipitation infiltration recharge of Quaternary shallow groundwater in Zhongqiao water source area is 57 ∶ 43. The ratio of bedrock karst water to lateral recharge of mountain karst water and vertical overflow recharge of Quaternary pore water is 87 ∶ 13. Conclusions: Mountain karst groundwater not only supplies the underlying bedrock karst water in the plain area, but also supplies the quaternary loose pore water in the plain area. There is a close relationship between bedrock karst water and Quaternary loose pore water in the water source area of Zhongqiao.