蒸发皿中水面蒸发氢氧同位素分馏的实验研究

Experimental study on the fractionation mechanism of hydrogen and oxygen stable isotopes in evaporation from water surface of evaporation pans

气象要素与蒸发密切相关,通过室内外不同气象条件下的器皿水蒸发实验,获得了水面蒸发氢氧稳定同位素分馏因子与气象要素的关系。实验结果表明,随着蒸发的进行,剩余水体中逐渐富集重同位素;自由水体蒸发同位素分馏在垂线上有分层现象,表层水体同位素值比垂线平均的同位素值略富集;不同温度条件下的室内蒸发实验中,温度越高,液-气间分馏系数越小,相应于同一剩余水体体积比,剩余水体稳定同位素值则越低。室外器皿水自由蒸发实验中得出的蒸发线方程斜率较大地偏离了当地降水线,表明实验期间水体蒸发分馏作用较明显。该研究为进一步揭示水体蒸发分馏规律提供了可靠的实验依据。

There is a close relationship between meteorological factors and evaporation. In this paper, the relationship between evaporation fractionation factor of stable isotopes and meteorological factors is analyzed through the water evaporation experiments under different meteorological conditions. The results indicate that the residual water is gradually enriched in heavy isotopes along with the evaporation. In the outdoor evaporation experiment, isotopic stratification phenomenon takes place in different water layers of the evaporation pans where the isotopic ratios of surface water are more concentrated than that of deeper water due to the discrepancy of the sunlight radiation, heat convection and wind speed. It is also shown that the fractionation factor of stable isotopes is inversely proportional to the evaporation temperature. Moreover, the evaporation line of outdoor experiment obviously deviates from the local meteoric water line, which demonstrates that the evaporation action of the surface water is strong in course of the experiment. Therefore, the research provides credible experimental data for revealing the evaporation fractionation mechanism further.