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分析参与水循环过程的不同水体中D和18O组成的变化特征,是应用氢氧稳定同位素示踪技术研究水循环机理的必要前提。对北京地区的大气降水、地表水(河、库)、地下水(包括泉水)中的D和18O组成作了对比分析。结果表明,北京平原区大气降水中的D和18O组成存在显著的季节变化,是不同季节大气降水水汽来源的不同所致,即主要受控于季风气候,而区域气象条件只是次要影响因素;北京地区地表干流中δD和δ18O的均值介于大气降水和地下水的相应值之间,表明在维持有一定河川径流量方面,地下水的向河排泄在枯水期发挥着重要作用;各干流中D和18O组成存在明显的空间变化,且沿着各径流方向总体有增大的趋势;地下水中的D和18O组成也存在明显的空间变化,其中在浅层地下水中的特征反映出含水层所处的气候比较干燥的蒸发盆地的特点,而在垂向上自上而下由大到小的变化趋势则反映了全新世以来气温总体上逐渐变暖的气候变化特征;泉水与普通地下水在D和18O组成上的一致性,表明它们之间存在比较密切的水力联系。根据这些研究结果还进一步分析了研究区的区域水循环机理和不同水体之间的相互作用和转化机制。
It is necessary precondition to study the mechanism of water cycle by using stable oxygen isotope tracer to analyze the variation of D and 18O composition in different water bodies involved in water cycle. The composition of D and 18O in the precipitation, surface water (river and reservoir), groundwater (including spring) in Beijing area were analyzed. The results show that there is a significant seasonal variation of D and 18O composition in the precipitation in the Beijing Plain, which is caused by the different sources of atmospheric precipitation and precipitation in the different seasons, that is, mainly controlled by the monsoon climate and the regional meteorological conditions are only the secondary influencing factors. Beijing The average values of δD and δ18O in the surface land surface are between the corresponding values of precipitation and groundwater, indicating that the excretion of groundwater to the river plays an important role in the dry season in maintaining a certain amount of river runoff. D and 18O in each main stream There is a clear spatial variation, and there is an overall trend of increasing along each runoff direction. There is also a significant spatial variation in the composition of D and 18O in groundwater, where the characteristics in shallow groundwater reflect the climate in which aquifers are located Dry and evaporative basins. However, the downward trend from top to bottom in vertical direction reflects the climatic change characteristics of the generally warmer temperatures since the Holocene. The spring water and ordinary groundwater are mainly composed of D and 18O Consistency indicates that there is a close hydraulic connection between them. Based on these results, the mechanism of regional water cycle and the interaction and transformation mechanism between different water bodies are further analyzed.