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Hydrogen and Oxygen Isotope Geochemistry of Karst Groundwater in Chongqing
详细信息   
摘要


     Karst groundwater constitutes the important water resources and life support systems in the karst areas, and its geochemical research is an indispensable method for karst aquifer protection. There are approximately 380 subterranean karst streams SS which are the important part of the groundwater resources in Chongqing City. The isotope geochemistry of 51 subterranean karst streams in Chongqing shows that all the SS waters originate from modern precipitation because their 3180 and δD values are distributed along the line of GMWL or LMWL, which shows that the evaporation of groundwater does not occur or is not strong. Under the control of movement of rain cloud cluster from south to north atmospheric circulation effect and the regional relief, the regional distribution of δ180 and OD for SS in Chongiqng in rain season is in order of northeastern Chongqing western Chongqing, central area of Chongqing southeastern Chongqing the symbol "〈" means more minus"). In dry season, the regional distribution of δ18O and δD for SS is not clear due to the slower movement velocity in karst aquifer. Because of the slower movement velocity and longer staying time in karst aquifer in dry season, the d-excess value of SS in dry season is obvious smaller than that in wet season. Considering the relationship, between the altitude and the mean value of δ180 for SS within 100 m altitude, the authors established the second order polynomial ofkarst groundwater between δ18O and altitude. According to the equations, the δ18O-elevation gradient of karst groundwater in Chongqing is -0.34 %o/100 m in dry season and -0.31%o/100 m in wet season. These results are very useful to the study of the groundwater cycle in karst aquifers. The achievements obtained by the authors are applicable to the reasonable protection and exploitation of subterranean karst streams.

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