1.Guangxi Karst Resources and Environment Research Center of Engineering Technology,Institute of Karst Geology,Chinese Academy of Geological Sciences;2.Hebei Key Laboratory of Water Quality Engineering and Comprehensive Utilization of Water Resources,Hebei University of Architecture
Supported by China Geological Survey (DD20230425, DD20221758) and National Key R&D Program (2017YFC0406104).
[Objective] In order to find out the sources and control factors of main ions and dissolved inorganic carbon（DIC）in karst wetland water. [Method] Groundwater and surface water samples were collected from Huixian karst wetland, and the characteristics of hydrochemistry and dissolved inorganic carbon isotope（δ13CDIC）were analyzed. [Results] The hydrochemical type of most groundwater and surface water of Huixian karst wetland is Ca-HCO3. Ca2+, Mg2+ and HCO3- are mainly from carbonate rock dissolution; NO3- mainly from agricultural fertilizer and nitrification of soil organic nitrogen; K+, Na+ and Cl- mainly from fertilizer, manure and sewage; SO42- mainly from acid rain and pyrite oxidation. DIC in wetland groundwater mainly comes from the dissolution of soil CO2 and carbonate minerals. According to the isotopic mass balance, the calculation results show that about 46% comes from soil CO2, and about 54% comes from the contribution of minerals themselves. Huixian Karst Wetland is not entirely the result of carbonate weathering under the participation of CO2. Sulfur-containing minerals, acid rain, and human activity derived H2SO4 also participate in the weathering of carbonate rocks as erosion media. In addition, the nitrification of agricultural input reduced nitrogen fertilizer cannot be ignored. Wetland surface water DIC mainly comes from groundwater. Wetland surface water δ13CDIC value is affected by photosynthesis of aquatic plants and CO2 degassing, and its composition is relatively positive compared with that of groundwater. [Conclusion] Water Chemistry and δ13CDIC can help understand the weathering and biogeochemical processes of karst wetlands, and it should also be combined with wetland hydrogeology and human activities to provide more accurate information.