The research oftypical karst surface water chemical characteristics of diurnal variation and carbon sequestrationin different seasons- A case study from a karst spring-fed pool of Xueyuwatershed in Fengdou, Chongqing

• 1、Chongqing Key Laboratoryof Karst Environment&School of Geographical Sciences, Southwest University, Chongqing 400715

Abstract：As the atmospheric CO2 concentration is rising continuously, it has very important influence on global climate change, and carbon cycle issue has received more and more attention from the scientific community. Recent research shows that, if starting from the angle of the Earth System Science, take the hydrosphere, lithosphere and biosphere into consideration together, dissolved inorganic carbon (DIC) derived from karst geological will be used by rivers or lakes′ aquatic plant photosynthesis, and it will finally form the organic matter and buried in the seabed. The research selected Xueyu cave underground river basin, which is located in Fengdu, Chongqing as the research object. We use MS-5 multi parameter water quality online recorder which producedby USAHACH company to monitor routine hydrochemistry characteristic index of groundwater and surface water for continuous monitoring for a period of one year (January to December of 2013), and then comparing both. We Selected representative months of four seasons in a year (January, April, July, November) to do four times diel monitoring for the length of 36 to 72 hours of field monitoring experiment to find out the difference between day and night, and the influence of aquatic plant photosynthesis on karst carbon cycle in different seasons.The results show that the chemistry indictors of karst ground water have obvious diurnal variation. Aquatic plant efficiency of using DIC in water are also different. According to calculation,we found that: the summer use efficiency is the highest, reached to 135.06kg/day, followed by spring, autumn and winter, they are 10.03kg/day, kg/day and 7.17kg/day 8.75 respectively. The loss of this part inorganic carbon will transform into organic carbon by the plant absorption, in the karst system it can form a long time scale nature carbon sequestration.

Keywords： Karst spring-fed pool water chemical characteristics diurnal variation net carbon sink effect