雾水和降水的氢氧稳定同位素差异及其影响因素

Hydrogen and oxygen stable isotope difference between fog water andprecipitation and influencing factors

为深入分析不同陆地系统中雾水和降水的氢氧稳定同位素差异及其主要影响因素,在全球尺度下搜集了雾水和降水的氢氧稳定同位素数据,统计分析了不同地区雾水和降水的氢氧稳定同位素特征及二者差异的显著性。结合雾水的lc-excess值,分类讨论并揭示了同位素差异的主要形成原因及其与雾发生类型的关系。结果表明:整体上,雾水比降水更富集重同位素,δ2H和δ18O的差值分别在10‰~60‰和1.2‰~5.5‰之间。根据雾水lc-excess的特征,各地区雾水和降水氢氧稳定同位素差异可分为3类:lc-excess值近似为0,雾水分布在LMWL的95%置信区间内;lc-excess值大于0,雾水分布在LMWL上方;lc-excess值小于0,雾水分布在LMWL下方;这3类差异的主导因素分别为水汽来源、凝结温度、环境湿度。因地形雾、辐射雾、平流雾对应的水汽条件和冷凝过程不同,因此三者与降水的同位素差异也不同:地形雾与降水的同位素无显著差异;辐射雾与降水的同位素组成差异较大,雾水中重同位素明显富集;平流雾与降水的同位素组成重叠区域较小,雾水中的重同位素明显更加富集。

To further understand the hydrogen and oxygen stable isotope composition differences between fog water and precipitation in different terrestrial systems and major influencing factors,the global-scaleδ2 H andδ18 O research data for fog water and precipitation were collected and the significance of their differences was statistically analyzed.Combing the calculation of fog water’s lc-excess values,the isotopic difference rules between fog water and precipitation were classified,and corresponding causes and relations to fog types were further discussed and revealed.Results suggest that generally the fog water is significantly more enriched in heavier isotopes than the precipitation,withδ2 H andδ18 O differences of 10‰to 60‰and 1.2‰to 5.5‰,respectively.The differences between fog and precipitation isotopic composition can be classified into three categories based on lc-excess values of fog water:the lc-excess value is approximately 0 and the fog water is within the 95%confidence interval of LMWL;the lc-excess value is greater than 0 and the fog water is distributed above the LMWL;the lc-excess value is less than 0 and the fog water is distributed below the LMWL.The water vapor source,condensation temperature and environmental temperature are three major factors that influence the isotopic difference between fog water and precipitation,with different categories correspondingly dominated by different factors.Orographic fog,radiation fog,and advection fog have different water vapor conditions and condensation processes,leading to different patterns of isotopic differ ences in fog and precipitation.There is no significant difference in the isotopic composition between terrain fog and precipitation,while there is a significant difference in the isotopic composition between radiation fog and precipitation,with significant enrichment of heavy isotopes in fog water.The overlap area of isotopic composition between advection fog and precipitation is small,and heavy isotopes in fog water are obviously more enriched.