Variation of stable hydrogen and oxygen isotopes in precipitation and groundwater in northeast Hunan
Background,aim,and scope There are abundant water resources in the middle and lower reaches of the Yangtze River,where the water resources and ecology problems are becoming more and more prominent.Thus,the research with thorough understanding of the hydrological cycle process is of great significance for regulating the effective utilization of water resources and mitigating the ecological environment problems in northeast Hunan.Here,isotopic monitoring and analysis of atmospheric precipitation and well water with different depths in Jinjing Town,Changsha County,northeast Hunan Province,are carried out to preliminarily explore the hydrological cycle,and to improve the management of water resources and ecological environment in this area.Materials and methods During October 2021 to February 2023,precipitation and well water with different depths(～4.7 m and～61 m)in Jinjing area were collected monthly.And the stable hydrogen and oxygen isotopes(δD,δ18O)in precipitation and well water are tested and analyzed.Monthly precipitation dexcess,are calculated fromδ18O and 8D.The meteorological data of Jinjing are downloaded from Changsha Meteorological Resource Sharing Public Platform.The integrated moisture transport flux(from surface to 300 hPa)are from National Climate Centre,China Meteorological Administration Hybrid Single Particle Lagrangian Integrated Trajectory Model is from National Oceanic and Atmospheric Administration,U.S.Department of Commerce.Results The behavior ofδ18O,δD and dexcess in precipitation present significant seasonal variation,with lower value in summer and higher value in winter.The δ18O and δD in well water is little fluctuation,but with lower value in winter and higher value in summer.Discussion The changes of δ18O and δD in precipitation are mainly controlled by the source of moisture or associated air mass and the degree of rain removal during its transmission path,in addition to the effect of rainfall amount.Although the original source of groundwater is precipitation,groundwater exhibits little and opposite seasonal variation compared with precipitation.This may be resulted from groundwater recharge by precipitation need the media of surface water,which is a long-term process and could generate a lag response of groundwater to precipitation.Besides,the δ18O and 8D in shallow well water show a larger fluctuation than that of deep phreatic water in summer,implied the shallow groundwater is more susceptible to external environment.Conclusions The δ18O and 8D in precipitation present significant seasonal variation,which may be resulted from the change of source of moisture or associated air mass and the degree of rain removal in the upstream regions,in addition to the influence of rainfall amount.There is a strong connection between precipitation and groundwater,although the variation of δ18O and δD in well water with small range is contrast with that of precipitation.And the shallow groundwater is more susceptible to external environment.Recommendations and perspectives Long-term stable isotopic monitoring of water bodies and improved sampling designments are still needed to better understand hydrological cycle processes.The results of this study show the relationship between groundwater and precipitation,which may be helpful for water resources management in this area.
northeast Hunanatmospheric precipitationgroundwaterstable hydrogen and oxygen isotopes
万方数据
维普
