鹰潭地区大气降水中氢氧稳定同位素特征研究

Stable isotopes of hydrogen and oxygen in the precipitation of Yingtan

降水中氢氧稳定同位素组成与降水地区各种气象因素变化密切相关。同时,降水中氢氧稳定同位素关系是水同位素应用的主要基础,对深入研究降水中水汽来源,地下水补给等水循环过程具有重要意义。根据江西鹰潭地区2012年4月至2013年3月大气降水中氢氧稳定同位素组成和气象资料,研究了该地区大气降水中氢氧稳定同位素关系及降水量,温度等气象因素对氢氧稳定同位素组成的影响。研究表明,该地区大气降水线方程为δD=8.61δ18O+18.34(n=72,R2=0.98),与全球大气降水线方程(δD=8δ18O+10)相比,鹰潭地区大气降水线的斜率和截距均偏大,这与凝结物在未饱和大气中降落时重同位素的蒸发富集作用有关,同时反映了该地区湿润多雨,降水过程中受二次蒸发影响较小的气候特点。该地区降水中δD(-113.3‰~7.5‰)、δ18O(-14.9‰^-0.9‰)和氘盈余(3.8‰~23.2‰)变化幅度很大并呈现出明显的季节性变化,夏半年(4-9月)δD、δ18O与氘盈余均显著低于冬半年(10-3月)(P<0.01),反映出不同季节降水的水汽来源及蒸发条件的差异。对该地区降水同位素与降水量和温度相关性的分析表明,降水中δ18O与降水量和温度存在显著负相关关系,方程式分别为:y=-0.056x–4.7(R2=0.39,P<0.01)和y=-0.203x–2.99(R2=0.23,P<0.01),说明该地区降水中氢氧稳定同位素存在显著的降水量效应和反温度效应。

The δD and δ18O composition in precipitation are closely related to local meteorological factors. Meanwhile, being the primary basis of the isotope hydrology, stable isotopes of hydrogen and oxygen composition can be applied in the study of water cycle, such as evaluating sources of water vapor, groundwater recharge, etc. In this study, stable isotopes of oxygen and hydrogen compositions of the precipitation in Yingtan area from April, 2012 to March, 2013 were investigated. According to the isotopes of precipitation, local meteoric water regression lines could be described as： δD=8.61δ18O＋18.34 （n=72,R2=0.98）. Its slope and intercept were higher than those of global meteoric water line （δD=8δ18O＋10） due to the evaporation and enrichment of heavy isotopes condensation in the unsaturated atmosphere. Large ranges of δD （-113.3‰~7.5‰）, δ18O （-14.9‰^-0.9‰） and dexcess values （3.8‰~23.2‰） were found in precipitation in this region, and the values of δD, δ18O and dexcess in the summer half year （April-September） were significantly lower than those in the winter half year （March-October） （P〈0.01）, indicating different evaporative conditions and atmospheric water vapor sources between the two seasons. The relationship between δ18O and precipitation amount, temperature could be described as y=-0.056x-4.7 （R2=0.39, P〈0.01） and y=-0.203x-2.99 （R2=0.23, P〈0.01）, indicating the precipitation amount effect and anti-temperature effect of isotopes in precipitation respectively.