基于稳定氢氧同位素的黄河流域内蒙古段水体转化关系

Water Transformation Relationship in Inner Mongolia Section of the Yellow River Basin Based on Stable Hydrogen and Oxygen Isotopes

通过采集黄河流域内蒙古段2021年7月(丰水期)、10月(平水期)和2022年4月(枯水期)的大气降水、地表水和地下水,运用稳定同位素技术,对流域“三水”的氢氧稳定同位素进行时空变化分析,利用MixSIAR混合模型揭示水体转化关系.结果表明,黄河流域内蒙古段丰、平、枯水期地下水同位素均值差异较小,地下水更新较慢,滞留时间长,季节变化不明显,地表水δD值丰水期较平水期和枯水期高;从δ18O与δD关系得出,3个时期地表水线的斜率和截距均小于当地降水线的斜率和截距,地表水在接受降水补给后受到蒸发分馏作用的影响;黄河北岸从上游至下游,地表水δD值整体表现出先升高再降低的变化趋势,黄河南岸从上游到下游,地表水δD值表现出逐渐降低的变化趋势;丰水期地表水中地下水的补给贡献率为2.9%,降水为97.1%,平水期地表水中地下水为5.0%,大气降水为95.0%,枯水期地表水中地下水为56.6%,降水为43.4%,丰水期降水和地表水对地下水的补给贡献率分别为47.6%和52.4%,平水期分别为30.7%和69.3%,枯水期分别为37.8%和62.2%,大气降水是地表水的主要补给来源,表现出丰水期补给比例大于平水期和枯水期,地表水是地下水的主要补给来源,表现出枯水期>平水期>丰水期的规律.

By collecting the atmospheric precipitation,surface water,and groundwater in the Inner Mongolia section of the Yellow River Basin in July 2021(wet season),October(normal season),and April 2022(dry season),stable isotope technology was used to analyze the temporal and spatial changes in hydrogen and oxygen stable isotopes in the"three rivers"of the basin,and the MixSIAR mixing model was used to reveal the water body transformation relationship.The results showed that the mean difference in the groundwater isotope was small in the abundance period,flat period,and dry period in the Mongolia section of the Yellow River Basin.The groundwater regeneration was slow,the retention time was long,the seasonal variation was not obvious,and theδD value of surface water was higher in the abundance period than in the normal period and dry period.According to theδ18O andδD diagrams,the slope and intercept of surface water lines in the three periods were smaller than those of local precipitation lines,and surface water was affected by evaporative fractionation after receiving precipitation recharge.TheδD values of surface water on the north bank of the Yellow River showed a trend of first increasing and then decreasing from upstream to downstream,while theδD values of surface water on the south bank of the Yellow River showed a trend of gradually decreasing from upstream to downstream.The recharge contribution of groundwater in surface water in the high-water period accounted for 2.9%,precipitation accounted for 97.1%,surface water accounted for 5.0%,atmospheric precipitation accounted for 95.0%,surface water accounted for 56.6%,and precipitation accounted for 43.4%,and the recharge contributions of precipitation and surface water to groundwater in the high water period were 47.6%and 52.4%,respectively.Those in the normal period were 30.7%and 69.3%,and those in the dry period were 37.8%and 62.2%,respectively.Atmospheric precipitation was the main replenishment source of surface water,showing that the replenishment ratio in the wet season was larger than that in the normal season and dry season,which was closely related to the total precipitation and its distribution in each period.Surface water was the main replenishment source of groundwater,showing that dry season>normal season>wet season.