珠江泗河水流域降水事件中氢氧同位素特征分析

Characteristics Analysis of Hydrogen and Oxygen Isotopes of Rainfall Events in Sihe River Basin of the Pearl River

以珠江泗河水流域为研究对象,分析降水事件中降雨、河水和地下水氢氧同位素的变化特征和规律,研究降雨、河水和地下水的转化关系。研究结果表明:珠江泗河水流域雨季的降水线方程与全球大气降水线相比,斜率和截距偏小,反映其降水过程经历了一定的蒸发。场次降水事件中氘盈余平均值先减小后增加,反映了大气降水形成时水汽来源和运移过程中受环境变化影响导致的同位素分馏不平衡的差异。不同季节降水事件中降雨氢氧同位素组成差异显著,春末夏初降雨氢氧同位素组成较富集,随后同位素值逐渐贫化。单场降水事件中,降雨氢氧同位素值呈现先贫化后富集的现象。不同场次降水事件中,降雨的δD、δ18O含量变化范围较大,河水次之,地下水变化最小。不同水体δ18O~δD关系线斜率的大小为:地下水<河水<降雨,河水和地下水δ18O~δD关系线均偏离大气降水线,反映出泗合水流域河水和地下水经历了蒸发分馏过程。

In the paper,the change characteristics and rules of hydrogen and oxygen isotopes of rainfall,river water and groundwater during precipitation events in Sihe River Basin of the Pearl River are studied,and the transformation relationship of rainfall,river water and groundwater are also analyzed.The results show that the slope and intercept of the meteoric water line equation of Sihe River Basin of the Pearl River in rainy season are smaller than that of the global meteoric water line,which indicates that the precipitation process has experienced certain evaporation.The average value of deuterium surplus in precipitation events decreases first and then increases,which reflects the difference of isotope fractionation imbalance caused by environmental change in the process of precipitation.There are significant differences in the hydrogen and oxygen isotopic compositions of precipitation events in different seasons.At the end of spring and the beginning of summer,the hydrogen and oxygen isotopic compositions of precipitation events are relatively enriched,and then the isotopic values are gradually reduced.In a single precipitation event,the hydrogen and oxygen isotopic values of rainfall are first depleted and then enriched.In different precipitation events,the variation range ofδD andδ18O content of rainfall is larger,followed by river water,and the change range of groundwater is the smallest.The slope ofδ18O~δD relation lines of different water bodies is as follows:groundwater<river water<rainfall,and theδ18O~δD relation lines of river water and groundwater deviate from the meteoric water line,which reflects the effect of evaporation and fractionation of river water and groundwater in Sihe River Basin.