渭南大气降水中氢氧同位素特征与水汽来源关系

Characteristics of δD and δ^(18)O in precipitation and the moisture origin in Weinan

利用渭南大气降水δD和δ^(18)O实测值及相关的气象观测资料,分析了降水δD和δ^(18)O的特征及其变化与水汽来源的关系。结果表明:大气降水的同位素值变化幅度大,且呈现春季高、其他季节较低的季节变化;大气降水线的斜率低于全球大气降水线,截距接近且略高于全球大气降水线;大气降水的δ^(18)O与温度效应相关关系非常弱,温度效应不存在,存在降水量效应,但春冬季不显著,夏秋季较显著;大气气团来源的后向轨迹显示,冬半年降水水汽主要受控于西风环流,同时存在少有的局地蒸发作用,夏半年水汽来源于东南和西南海洋蒸发水汽,明确了氢氧稳定同位素存在季节变化的原因。

Based on the measured δD and δ18O in precipitation and related meteorological observation data, we investigated the characteristics of precipitation isotopes and the moisture origin in Weinan. The analysis results showed that variations of the isotopic values in atmospheric precipitation were obvious, presenting high in spring and low in other seasons. The intercept of local meteoric water line was lower than the global meteoric water line, but the slope was slightly higher than the global meteoric water line, which indicated the complex moisture ori- gins. The relationship of temperature and δ18O in precipitation was very weak, in other words, temperature effect did not exist in Weinan. There was precipitation effect in precipitation isotopes variation, especially in summer and fall. The backward trajectories of atmospheric water source suggested that the seasonal difference of moisture origins was significant. In winter, the moisture source was mainly controlled by west wind circulation, with local evaporation sometimes. The combined impact of southeast and southwest marine moisture evaporation produced precil3itation in summer. Thereout, the reason for seasonal variation of δ18O was clear.