Variation characteristics of stable hydrogen and oxygen isotopes in precipitation of Longtan trough valley and Maoba syncline in Youyang,Chongqing
This study aims to explore the characteristics and influencing factors of δ18O and δD in precipitation in two adjacent topographic areas of Longtan trough valley and Maoba syncline in Wuling mountain,southeastern Chongqing.Based on the sampling data about δ18O and δD in precipitation of Maoba syncline(altitude of 1,140 m)and Longtan trough valley(altitude of 330 m)in Youyang county of Chongqing in two hydrological years from June 2020 to May 2022,the meteoric water lines of the two studies areas were established,and the variation characteristics and influencing factors of hydrogen and oxygen stable isotopes in precipitation in these areas were also analyzed.The results show as follows.(1)The slopes and intercepts of meteoric water lines in Longtan trough valley and Maoba syncline exceeded those of the global meteoric water lines.The values of δ18O in precipitation in these two study areas show a significant effect of precipitation,while the influence of temperature effect is relatively weak.(2)The slope and intercept of the meteoric water line in Longtan trough valley were smaller than those in the Maoba syncline.The difference between the meteoric water lines in these two study areas was mainly controlled by the temperature and evaporation conditions during water vapor condensation.(3)The average values of δ18O and δD in precipitation in Longtan trough valley were more positive than those in Maoba syncline.The results of d-excess showed that there was a weak sub-cloud secondary evaporation of δ18O and δD in Longtan trough valley.The values of δ18O and δD in precipitation in Longtan trough valley and Maoba syncline exhibited significant seasonal changes,with negative values during the rainy season(May to October)and positive values during the dry season(November to the following April).(3)The values of δ18O in precipitation in Longtan trough valley and Maoba syncline showed a significant precipitation effect,while the influence of temperature effect is weak.During the same precipitation event,the values of δ18O in precipitation in Longtan trough valley were generally more positive than those in Maoba syncline,indicating that δ18O values in precipitation in Longtan trough valley and Maoba syncline were influenced by elevation effects.(4)The interannual variations of δ18O in precipitation in Longtan trough valley and Maoba syncline were mainly affected by the change of the proportion of water vapor transported from Indian Ocean.In the summer of 2020,the proportion of water vapor from the Indian Ocean to the study areas reached 76%,with negative δ18O in precipitation.However,the proportion decreased to 52%in the summer of 2021,with positive δ18O in precipitation.This study is of great significance for the understanding of the water cycle process in the karst trough valley areas of Southwest China and for future studies on the eco-hydrological process of Longtan trough valley and Maoba syncline.
precipitationhydrogen and oxygen stable isotopeslocal terrainLongtan trough valleyMaoba synclineWuling mountain
万方数据
维普
