黄土丘陵区不同水体中氢氧同位素特征及相互关系

Characteristics of Hydrogen and Oxygen Isotopes in Different Water Bodies in the Typical Loess Hilly Region

为了研究典型黄土丘陵区不同水体氢氧同位素特征及水体间补给转化关系,合理利用干旱半干旱区水资源,通过野外采集2019年6月至11月延安市安塞墩山周围降水、河水、地下水和土壤水样品,运用同位素示踪技术,结合混合模型探索研究区不同水体氢氧同位素特征及水循环转化关系。结果表明:河水、地下水较土壤水富集氢氧同位素;各水体D和^(18)O含量的非稳定性表现为降水>土壤水>河水>地下水;降水、土壤水、河水氢氧同位素随时间变化较大,8月和11月较其他月份贫化,地下水同位素含量较稳定;受强烈的非平衡蒸发作用影响,土壤水、河水和地下水蒸发线的斜率与截距均小于大气降水线,其中土壤水最小。降水和地下水补给河水的比例分别为32.54%、67.46%。土壤水和河水补给地下水的比例分别为72.35%、27.65%。研究区地下水的主要补给水源为土壤水,河水的主要补给源为降水。

In order to investigate the characteristics of hydrogen and oxygen isotopes in different water bodies and the recharge and conversion relationship between water bodies in typical loess hilly regions,and to use water resources rationally in arid regions,precipitation,river water,groundwater,and soil water samples around Ansai Dun Mountain,Yan’an city,were collected from June to November in 2019.Stable isotope technology and mixed model were used to explore the hydrogen and oxygen isotope characteristics of different water bodies in the study area and water cycle conversion relationship.The results showed that river water and groundwater in the study area are enriched with hydrogen and oxygen isotopes compared with soil water.The instability of D and^(18)O content in each water body decreased in orders of precipitation>soil water>river water>ground water.The hydrogen and oxygen isotopes of precipitation,soil water and river water changed greatly with time,and were more depleted in August and November than in other months,the isotopic content of groundwater is stable.Due to the intense nonequilibrium evaporation,the slope and intercept of evaporation line of soil water,river water and groundwater are all smaller than that of atmospheric precipitation line,among which soil water is the smallest.The contribution of precipitation and groundwater that recharge rivers are 32.54%and 67.46%,respectively.The proportion of groundwater recharged by soil water and river water was 72.35%and 27.65%,respectively.The main recharge source of groundwater in the study area is soil water,and the main recharge source of river water is precipitation.