| Popis: |
It was proved that karst processing during groundwater cycle is one of carbon sinks to the atmosphere CO2. To understand the carbon transfer path among the three phases of air, carbonate rocks and karst groundwater in epigenic karst system is very important for mechanic studies of karst carbon sink. There are 8 carbon stable isotope sample sites, including 5 groundwater sites and 3 gaseous CO2 sites in Banzhai river catchment. The total 41 samples, including 38 karst water samples and 3 CO2 samples are acquired in a whole hydrological year of 2010. 4 couples CO2 partial pressure including free air and soil air are tested in site. Based on analysis the carbon stable isotope and CO2 partial pressure data above, it is found that the mostly carbon in free air and karst water is from soil air. The carbon transfer path in epigenic karst system can be divided into 4 steps: 1 the photosynthesis of vegetation take CO2 from free air; 2 the respiration of plant roots and decomposition of humic substance release CO2 to soil layer; 3 the gaseous CO2 is transfer to liquid HCO3- negion by karst process during the water cycle; 4 the bicarbonate in groundwater move to river or ocean fellow the groundwater flow. The forest and soil takes a booster pump action increasing the CO2 partial pressure from free air to soil and it is very important in karst process. |
