厦门沿岸地区大气降水中氢、氧稳定同位素组成及其影响因素

The hydrogen and oxygen isotope composition of precipitation in the Xiamen coastal area

利用2004年4月至2006年4月采集于厦门沿岸地区的44个雨水样品,对降水中的氢、氧同位素组成及其影响因素进行了分析和研究,结果表明:(1)厦门沿岸地区大气降水中δ18O值为-10.30‰～-0.13‰,平均值为-3.67‰;δD值为-74.7‰～7.3‰,平均值为-20.5‰,均处于全球及国内降水中δ18O和δD值的变化范围内。(2)厦门沿岸地区大气降水中的δ18O和δD值受纬度效应影响。(3)厦门沿岸地区大气降水中δ18O和δD值的季节差异较大,季风气候及其导致的降雨量效应是影响该地区δ降水值季节变化的主要因素。(4)降水中的氘过剩值(d值)为1.21‰～17.10‰,平均值为8.87‰,小于世界大部分区域雨水中的d值,说明厦门沿岸地区的降水源区蒸发速率比较缓慢,降水云团主要来自海洋汽团。(5)厦门沿岸地区大气降水线为:δD=7.67δ18O+7.68(p<0.0001,R2=0.9876),与全球及国内的降水线接近,说明雨滴在降落过程中存在一定的再蒸发过程,该特征在夏季较显著。

The hydrogen and oxygen isotope compositions of rainwater collected from 44 rain events in the Xiamen coastal area during April 2004 to April 2006 were studied. The rainfall δ18O range from -10.30‰ to -0.13‰, with a mean value of -3.67‰, and the δD values have a wide range, varying from -74.7‰ to 7.3‰, with an average of -20.5‰. These data are comparable to those already reported for other areas. The factors which controlled the composition of hydrogen and oxygen isotope in precipitation were discussed and the latitude effect was an important factor. The seasonal variations of δ18O, δD were great, and the monsoon climate and rainfall effect played an important role in the seasonal variations. The d values for precipitation fell in the range from 1.21‰ to 17.10‰ with an average of 8.87‰ which were lower than that of the globe average value, suggested that the evaporation rate was slow at the moisture source area and the vapour sources of precipitation mainly originated from ocean air masses. The meteoric water line （δD=7.67δ18O＋7.68） obtained for the region reflected that the re-evaporation from falling droplets was existed, especially in the summer.