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Seasonal variations of deuterium and oxygen‐18 isotopes and their response to moisture source for precipitation events in the subtropical monsoon region
Author(s) -
Wu Huawu,
Zhang Xinping,
Xiaoyan Li,
Li Guang,
Huang Yimin
Publication year - 2014
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.10132
Subject(s) - meteoric water , precipitation , δ18o , environmental science , hysplit , monsoon , moisture , atmospheric sciences , groundwater recharge , air mass (solar energy) , isotopes of oxygen , climatology , stable isotope ratio , hydrology (agriculture) , groundwater , geology , meteorology , aerosol , geography , aquifer , physics , geotechnical engineering , boundary layer , quantum mechanics , thermodynamics , geochemistry
Deuterium and oxygen‐18 are common environmental tracers in water used to investigate hydrological processes such as evaporation and groundwater recharge, and to trace moisture source. In this study, we collected event precipitation from 01 January 2010 to 28 February 2011 at a site in Changsha, Yangtze River Basin to estimate the influence of moisture source and atmospheric conditions on stable isotope compositions. The local meteoric water line, established as δD = (8.45 ± 0.13) δ 18 O + (17.7 ± 0.9) ( r 2 = 0.97, n = 189), had a higher slope and intercept than global meteoric water line. Temperature–δ 18 O exhibited complex correlations, with positive correlations during Nov.–Apr. superior to during Jun.–Sep., which was attributed to distinctive moisture sources, but vague the overall period; amount effect examined throughout the year. Linear regressions between δ 18 O and δD value in different precipitation event size classes revealed progressively decreasing slope and intercept values with decreasing precipitation amount and increasing vapour pressure deficit, indicating that small rainfall events (0–5 mm) were subject to secondary evaporation effects during rainwater descent. In contrast, snowfall and heavy precipitation events exhibited high slope and intercepts for the regression equation between δ 18 O and δD. High concentrations of heavy isotopes were associated with precipitation events sourced from remote westerly air masses, degenerated tropical marine air masses from the Bay of Bengal (BoB), and inland moisture in the pre‐monsoon period, as determined from backward trajectories assessed in the HYSPLIT model. Meanwhile, low concentrations of heavy isotopes were found to correspond with remote maritime moisture from BoB, the South China Sea, and the west Pacific at three different air pressures in summer monsoon and post‐monsoon using HYSPLIT and records of typhoon paths. These findings suggest that stable isotope compositions in precipitation events are closely associated with the meteorological conditions and respond sensitively to moisture source in subtropical monsoon climates. Copyright © 2013 John Wiley & Sons, Ltd.