蒋家沟流域雨季降水中氢氧同位素特征分析

通过分析蒋家沟流域2001—2009年内降雨资料,发现降雨频率服从幂指数分布,分析蒋家沟流域2010年雨季降水的氢氧同位素组成,得出当地大气降水线,其截距与我国大气降水线相比较小,这与研究区地处内陆干热河谷、蒸发作用强烈有关;降水中氘盈余7月中旬之前较大,均为正值,7月中旬到8月中旬由于空气湿度相对较高,氘盈余减小,8月中旬之后,随着空气湿度重新减小,d值增大;根据次降雨采集的降水样品分析,δ18 O显示出明显的降水量效应,即降水量较大的降水场次内δ18 O较小,在同一场降雨内,δ18 O也随着降雨时间的持续和降水量的增加而呈减小趋势;受山区降雨的随机性影响,蒋家沟流域内稳定同位素的高程效应较为反常,海拔越高的地方,δ18 O越大。

Characteristics of Hydrogen and Oxygen Isotopes in Rainy Season Precipitation in Jiangjiagou Watershed

The rainfall events occurred from 2001 to 2009 in Jiangjiaou watershed was analyzed.The rainfall frequency and cumulative frequency of rainfall before triggering of a debris flow can be fitted by power exponent distribution and logarithmic distribution,respectively.This result shows that the triggering of debris by rainfall is a random phenomenon,and subjects a random distribution.The isotopic compositions of precipitation over the Jiangjiagou watershed in the summer of 2010 are studied.Local meteoric water line is fitted as δD=7.1086δ18O-14.22.Its intercept is lower than that of Chinese meteoric water line which is related to the geographical and meteorological characteristics in this area.With the change of air humidity,the values of deuterium excess are positive before mid-July,and are much lower during mid-July and mid-August,then increase again after the mid-August.The δ18O value in an individual rainfall is lower as the rainfall increases.By the effort of the randomness of the mountain area precipitation,the stable isotopic concentration is higher as the attitude rises.