庐山地区大气降水中稳定同位素变化特征

氢氧稳定同位素技术被广泛用来研究水循环过程中的水汽来源、水量平衡及不同水体间的补给关系。以2016年4月至2017年4月在庐山地区三个不同研究点（庐山西北面莲花镇,山顶牯岭镇和东南面海会镇）采集的102个次降水样品同位素资料为基础,应用线性回归分析和对比分析等方法,对庐山地区大气降水中氢氧稳定同位素和氘盈余的时空分布特征及大气水汽来源进行了研究。结果发现：庐山地区夏半年降水中的稳定同位素值δ¹⁸O平均值（-6.1‰）小于冬半年（-4.8‰）;氢氧同位素特征和氘盈余呈现明显的季节差异;平均氘盈余值（10.6‰）大于全球大部分地区的评估值（10.0‰）;当地大气降水线（LMWL）δD=7.45δ¹⁸O+8.36与全球大气降水线（GMWL）δD=8δ¹⁸O+10相比,其斜率和截距均偏小。结合HYSPLIT后向轨迹模型分析同位素特征发现,庐山地区大气水汽夏半年主要来源于低纬度南海和印度洋,冬半年来自于干燥的华北和西北内陆;局地水汽影响和地理位置差异导致了降雨同位素特征的空间差异性。本研究可为今后展开庐山地区水循环过程的研究提供科学依据。

Variation characteristics of stable isotope in precipitation in Mount Lu area

Stable isotope technique is widely used to study the source of water vapor during water cycle, the supply relationship and water balance among different waters. From April 2016 to April 2017, the thesis selects three different sites in the Mount Lu area (Lianhua Town lies to the west of Mount Lu, Guling Town at the top of hill, and Haihui Town to the east of Mount Lu). Based on the isotopic data of 102 precipitation samples collected from the three places, we used linear regression analysis and comparative analysis to explore the temporal and spatial characteristics of hydrogen and oxygen stable isotopes and deuterium excess in precipitation in the Mount Lu area and their influencing factors. The results show that: In the study area, the stable isotope value of δ¹⁸O in summer precipitation was lighter than that in winter. The seasonal difference of water vapor source is obvious. The deuterium excess also showed a significant seasonal difference, and the deuterium excess value was higher than that in most parts of the world, being 10.0‰. Compared with the global meteoritic water line (GMWL) δD=8δ¹⁸O+10, the slope and intercept of the local meteoritic water line (LMWL) δD=7.45δ¹⁸O +8.36 are smaller in the Mount Lu area than in the global meteoritic water line (GMWL) δD= 8δ¹⁸O+10. Based on the HYSPLIT model, the atmospheric water vapor in this region is mainly derived from the South China Sea and the Indian Ocean at low latitudes in summer, and the dry inland in North and Northwest China in winter. The influence of local water vapor and geographical location differences lead to the spatial differences of rainfall isotopic characteristics. This study provides a scientific basis for the future study of water cycle in Mount Lu area.