New insights into diffusive kinetic fractionation during liquid condensation under supersaturated environment: an alternative approach for isotope tagging of ground-level water vapour.
IF 1.1 4区 环境科学与生态学Q4 CHEMISTRY, INORGANIC & NUCLEAR
Akash Ganguly, Virendra Padhya, Harsh Oza, Gerhard Strauch, Rajendrakumar D Deshpande
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引用次数: 0
Abstract
Stable water isotopes in ground-level vapour are key to estimating water exchange between geospheres. Their sampling, however, is limited to laser-absorption spectrometers and satellite observations, having inherent shortcomings. This study investigates diffusive kinetic fractionation during liquid condensation under supersaturated environment, providing a cost-effective, reliable way of sampling ground-level vapour isotopes (18O, 2H). Experiments were undertaken at three locations in India with 'liquid' samples collected from condensation of ambient air at 0°C. Simultaneously, pristine 'vapour' was sampled via cryogenic-trapping using liquid nitrogen-alcohol slush at -78°C. The 'liquid' condensed under supersaturation was progressively more depleted in 18O, and less enriched in 2H than expected under equilibrium fractionation, with an increasing degree of supersaturation expressed as saturation index (Si). This study revealed: (1) Si, molecular density, Rh, T together control the extent of isotopic kinetic fractionation. (2) The presence of diffusive concentration gradient inhibits the flow of heavier isotopes during liquid condensation. (3) The stochastic nature of the process cannot be explained using a physics-based model alone. The artificial neural network model is hence deployed to sample δ18O (δ2H) within -0.24 ± 1.79‰ (0.53 ± 11.23 ‰) of true value. (4) The approach can be extended to ground-validate isotope-enabled general circulation models and satellite observations.
期刊介绍:
Isotopes in Environmental and Health Studies provides a unique platform for stable isotope studies in geological and life sciences, with emphasis on ecology. The international journal publishes original research papers, review articles, short communications, and book reviews relating to the following topics:
-variations in natural isotope abundance (isotope ecology, isotope biochemistry, isotope hydrology, isotope geology)
-stable isotope tracer techniques to follow the fate of certain substances in soil, water, plants, animals and in the human body
-isotope effects and tracer theory linked with mathematical modelling
-isotope measurement methods and equipment with respect to environmental and health research
-diagnostic stable isotope application in medicine and in health studies
-environmental sources of ionizing radiation and its effects on all living matter