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Kang Z.Q.,Hubei University | Kang Z.Q.,Key Laboratory of Karst Dynamics | Kang Z.Q.,International Research Center on Karst | Yu F.F.,Hubei University | And 9 more authors.
Water-Rock Interaction - Proceedings of the 13th International Conference on Water-Rock Interaction, WRI-13 | Year: 2010

The hydrogeological condition of an interfluve area, located in the town of Mengxu, Guangxi, China, is discriminated by using the trace element strontium. The Ca/Sr ratio can be used as an indicator of the karst groundwater runoff conditions. In this case, 3 strong flow zones could be distinguished by the Ca/Sr ratio value of 400. For verification purposes, 9 boreholes and 2 geophysical exploration sections were carried out. The boreholes and geophysical data support the hydrogeochemical results. © 2010 Taylor & Francis Group, London. Source

Kang Z.Q.,Guangxi General Institute of Geological Exploration | Kang Z.Q.,Chinese Academy of Geological Sciences | Kang Z.Q.,International Research Center on Karst | He S.Y.,Chinese Academy of Geological Sciences | He S.Y.,International Research Center on Karst
Advanced Materials Research | Year: 2013

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. © (2013) Trans Tech Publications, Switzerland. Source

Kang Z.-Q.,Guangxi Geological Survey | Kang Z.-Q.,Institute of Karst Geology | Kang Z.-Q.,International Research Center on Karst | Liang L.-G.,Guangxi Geological Survey | And 4 more authors.
Acta Geoscientica Sinica | Year: 2014

Based on years' automatic monitoring of dynamic hydrological state of an epikarst spring in Nongla, Guangxi, the authors found that, under the good vegetation coverage, the discharge mode is different in different seasons. It is mainly the runoff discharge by spring in the wet season and consumption of ecological water requirement in the dry season. In 2012, the precipitation from April to August accounted for 66.24% of the whole year. At the same time, the discharge of spring accounted for 90.89% and the karst carbon sink accounted for 90.46% of the whole year. It is evident that the karst carbon sink occurs mainly in the wet season because of the higher runoff coefficient. In the study area, carbon sink is controlled by rainwater dilution, CO2 effect and water-rock interaction (WRI). At the beginning of precipitation, the concentration of HCO3 - is continuously reduced, controlled by rain dilution. However, it is also obviously affected by CO2 effect and WRI. HCO3 - concentration fluctuation with time. At the later stage of spring discharge, WRI is dominant again and HCO3 - concentration tends to be somewhat stable. From the monitoring data obtained in the past decade, the concentrations of Ca2+, Mg2+ and HCO3 - in the karst dynamic system were significantly increased with the recovery of the secondary forest vegetation. With the concentration of HCO3 - as an example, the average value was 356.55 mg/L during the period of 2003-2005, whereas it was 432.97 m/L in 2012, the difference being 76.42 mg/L, and the value was increased by 21.4% during the ten years. Source

Kang Z.,Karst Dynamics Laboratory | Kang Z.,International Research Center on Karst | He S.,Karst Dynamics Laboratory | He S.,International Research Center on Karst | Luo Y.,Guangxi Geology Survey
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2015

Limestone and dolomite are common carbonate rocks. Because of their different karstification mechanism, the different landscape would be formed. In Southwest of China, dolomite locates on the different classes of karst basis level of erosion, while the pure limestone locates at upper the mountain. So, the epikarst zone has a duality structure because of the special strata combination. Based on the mornitoring to discharge and hydrochemistry of Landiantang epikarst spring, Nongla, Guangxi, it is found that the hydrochemical type of most water samples is HCO3-Ca·Mg. The variation trend of the Ca2+ and Mg2+ is not very clear in seasonal timescale. But it is more sensitive to short-term precipitation dilution and CO2 effect of forest vegetation. “Equivaleng dissolution line”(EDL) is defined by the relationship between concentration of Ca2+ and Mg2+. In this paper, EDL can be used to distinguish the causes of the differences of spring hydrochemistry under different precipitation conditions. In addition, based on the analysis on nearly ten years data of the hydrochemistry and discharge data of Landiantang epikarst spring, it is shown that spring discharge and major ions concentration in karst water are all increased under the situation of vegetation restoration. All of above is further evidence of the vegetation effect in karst process. ©, 2015, Jilin University Press. All right reserved. Source

Cao J.,Chinese Academy of Geological Sciences | Cao J.,International Research Center on Karst | Yuan D.,Chinese Academy of Geological Sciences | Yuan D.,International Research Center on Karst | And 8 more authors.
Acta Geologica Sinica | Year: 2012

Carbonate rock outcrops cover 9%-16% of the continental area and are the principal source of the dissolved inorganic carbon (DIC) transferred by rivers to the oceans, a consequence their dissolution. Current estimations suggest that the flux falls between 0.1-0.6 PgC/a. Taking the intermediate value (0.3 PgC/a), it is equal to 18% of current estimates of the terrestrial vegetation net carbon sink and 38% of the soil carbon sink. In China, the carbon flux from carbonate rock dissolution is estimated to be 0.016 PgC/a, which accounts for 21%, 87.5%-150% and 2.3 times of the forest, shrub and grassland net carbon sinks respectively, as well as 23%-40% of the soil carbon sink flux. Carbonate dissolution is sensitive to environmental and climatic changes, the rate being closely correlated with precipitation, temperature, also with soil and vegetation cover. HCO 3 - in the water is affected by hydrophyte photosynthesis, resulting in part of the HCO 3 - being converted into DOC and POC, which may enhance the potential of carbon sequestration by carbonate rock dissolution. The possible turnover time of this carbon is roughly equal to that of the sea water cycle (2000a). The uptake of atmospheric/soil CO 2 by carbonate rock dissolution thus plays an important role in the global carbon cycle, being one of the most important sinks. A major research need is to better evaluate the net effect of this sink in comparison to an oceanic source from carbonate mineral precipitation. Source

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