鼎湖山大气降水氢氧同位素特征及水汽来源

Characteristics of δD and δ^(18)O in Precipitation in Mt. Dinghu and Its Water Vapor Sources

[目的]鼎湖山自然保护区地处我国热带与亚热带交汇处,在全球气候变化研究中占居独特而重要的地位。全球气候变化背景下,降水格局变化将影响区域森林生态系统内部小气候。降水是森林生态系统水循环过程中重要的输入因子,研究鼎湖山大气降水氢氧稳定同位素特征和水汽来源,对探讨该地区森林生态系统水循环过程、森林群落演替动态及区域水资源合理利用和管理等具有重要理论和实践意义。[方法]运用氢氧稳定同位素技术,研究和分析鼎湖山2013年8月~2014年8月13个月108个大气降水的氢氧同位素组成及与环境因子的关系,并运用HYSPLIT模型后向轨迹法模拟大气降水气团传输途径和过程,判定该地区水汽来源。[结果]鼎湖山大气降水线方程为:δD=7.863δ^(18)O+9.664(R^2=0.975,n=108);δD和δ^(18)O值范围分别为-118.26‰^-15.52‰,-16.05‰~2.25‰,均值分别为-34.44‰,-5.58‰;大气降水过量氘(d)显示出冬高夏低的季节变化;鼎湖山降水量效应显著,温度效应不显著。[结论]鼎湖山大气降水氢氧稳定同位素特征存在明显的季节性变化;干季的气团主要来自局地蒸发、中国华北地区及寒冷干燥的亚欧大陆,湿季的气团主要来自温暖湿润的西太平洋、南海和印度洋。

[ Objective ]Mr. Dinghu National Nature Reserve, located in Guangdong Province, is a transitional zone of tropics and subtropics. It provides a unique and important opportunity for climate change studies. The change of precipitation pattern affects the microclimate within a regional forest ecosystem. The research on the characteristics of hydrogen （δD） and oxygen （δ18O） stable isotope in precipitation and the source of regional atmospheric precipi- tation are theoretically and practically important to understand the water cycling and community succession in the forest ecosystem of Mt. Dinghu, and wisely use and manage regional water resources. [ Method; The precipitation δD and δ18O data in the period from August 2013 to August 2014 were analyzed to examine the relationship between the characteristics of δD and δ18O and their environmental factors. Furthermore, the air mass transmission pathway was determined and the regional water vapor sources were identified based on HYSPLIT model. E Result ; The mete- oric water line equation is δD = 7. 863δ18O ＋ 9. 664 （R^2 = 0. 975, n = 108） ; the average δD value is -34.44‰, ranging from - 118.26‰ to - 15.52‰, and the average δ180 value is -5.58‰, ranging from - 16. 05‰ to 2.25‰. The atmospheric precipitation excess deuterium （d） follows a seasonal pattern with low value in winter and high value in summer. A ＂precipitation effect＂ exists significantly whereas the ＂temperature effect＂ is not obvious. [ Conclusion] There are obvious seasonal changes of δD and δ18O in atmospherie precipitation in Mt. Dinghu. In dry season, the air mass mainly comes from North China and Eurasia, as well as local evaporation, while in the wet season, the air mass mainly comes from the western Pacific Ocean, the South China Sea, and the Indian Oeean.