雾水的D和18O同位素研究进展

凝结水的D、¹⁸O同位素研究目前主要集中在雾水方面，露水和土壤吸附水的相关研究仍属空白。由于形成时的温度较高，大多数雾水的D、¹⁸O同位素较当地雨水富集，但不同类型雾的同位素特征存在差异。平流式海洋雾为单级的蒸发—冷凝封闭循环系统的首次凝结，D、¹⁸O同位素较当地雨水显著富集；热带云雾林中的地形雾与降雨同时发生，且水分源于同一云团，δD、δ¹⁸O值差异较小；内陆辐射雾因部分水汽源于当地水分的再循环，过量氘和δD、δ¹⁸O值高于降雨。目前有少量研究用D、¹⁸O同位素指示雾水对植被、地下水和地表径流的补给作用，但以定性分析为主，基于端元混合模型的定量评价极少。露水和土壤吸附水的稳定同位素研究是干旱区凝结水研究的重要方向；D、¹⁸O同位素与其它同位素或化学指标的结合有助于促进凝结水生态水文效应的研究进展；短间隔、高密度的长期观测和用于稳定同位素分析的凝结水采样器的设计是需要进一步开展的工作。

Advances in the D and 18O Isotopes of Fog Water

The previous studies on stable isotopes of condensation water are all about fog, without any study about dew or water vapor adsorbed by soil. In most of the studies, more isotopes have been found in fog than in rainfall, due to differences in the temperature of condensation of the water vapor, as well as the history of the air mass producing the precipitation. Fog isotope values have a large range depending on the temperatures and vapor sources in the study areas. Advective oceanic fog is quite isotopically enriched compared to rain in the same area because it is an early stage condensate representing a single stage evaporation (over the open ocean) condensation (at the coast) cycle. In tropical cloud forest where orographic fog and rain are from the same cloud and occur simultaneously, fog has been found to be more isotopically enriched than rain, but differences between fog and rain are relatively small. Inland radiation fog, with water vapor partially originating from terrestrially recycled water, has the larger deuterium excess value and δD and δ¹⁸O values than precipitation originating from water vapor evaporated from the oceans. Stable isotope techniques have been used in a few cases to evaluate possible contribution of fog water to stream flow, plant transpiration, or groundwater recharge. But few studies assessed quantitatively the contribution employing end member mixing model. Directions for future research may include the stable isotope studies of dew and water vapor absorbed by soil in arid regions, the combination of D and ¹⁸O with other isotopes or chemical indexes to evaluate eco hydrological roles of fog, the long term and intensive sampling strategies in stable isotope studies of condensation water, and the design of fog collectors for stable isotope samples. 