[Comparisons Between Seasonal and Diurnal Patterns of Cave Air CO2 and Control Factors in Jiguan Cave, Henan Province, China].

Cave air CO2 makes notable impacts on the deposition and dissolution of speleothem,affecting the stability of carbonate landscape and comfort of tourist in show caves.Cave air CO2 is a key factor of karstification occurrence.Studying the mechanism of cave air CO2 variation is important for understanding the pattern of karstification and cave protection.In order to understand the temporal and spatial variation characteristics and its possible controlling factors,inside and outside cave air CO2,hydrogeochemical index,temperature,relative humidity as well as precipitation and tourist amount were observed in the Jiguan Cave,which lies in the west Henan Province of south-north geographical boundary of China.Nearly five years monitoring of air CO2 of Jiguan Cave was carried out from December,2011 to May,2016.A diurnal monitoring was performed from 19 May,2016 to 20 May,2016.The results indicated that the cave air CO2 showed notable spatial and seasonal variations.① From the spatial variation,the sites closer to cave entrances,affected by strong cave ventilation,had lower pCO2.In addition,the special structure of Jiguan Cave and soil air pCO2 variation,vegetation respiration and soil microbial activity,which in turn were associated with changes in climate and environment also contributed to the variation of cave air pCO2.② On a seasonal scale,cave air CO2 was higher in summer and lower in winter.This variation of cave air CO2 was mainly influenced by tourism activity as well as karstification.③ Tourist amount was the mainly factor that influenced the variation of cave air CO2 on a daily scale.Because of tourism activity,cave air CO2 was increased,and also cave environment was disturbed.All of these intimidate the better conservation of cave environment.

[High-resolution Variations of Oxygen and Hydrogen Isotopes of Precipitation and Feedback from Cave Water: An Example of Jiguan Cave, Henan].

The stable isotopes of atmospheric precipitation that affect the isotopes of speleothem and cave water are controlled by a variety of factors, such as temperature, rainfall amount, altitude, vapor source and others. Knowledge in the factors causing rainfall stable isotopes change is one of the keys to understanding the cave water stable isotopes change of monsoon-sensitive area in the north-south China intersection. The samples collected from 4 ground water sites in Jiguan Cave and the instantaneous heavy rain during Aug.4th-6th, 2015 were analyzed, and combined with the precipitation oxygen and hydrogen isotopes data for samples from almost 6 years (2009-2015) collected in Jiguan Cave of Luanchuan County in Henan Province, leading to the following findings:① The precipitation was divided into 2 stages with different vapor sources (high-altitude water vapor from the South China Sea and inland areas from near the ground to evaporate moisture) that could be recorded in the δ18O of single rainfall by HYSPLIT model. ② The evaporation of stage 2 masked the temperature effect to some extent, which also decreased the slope and intercept of LMWL and d-excess of precipitation. ③ The δ18O values feature of cave drip water in Jiguan Cave during this rainfall was mainly a response to the summer monsoon precipitation from sea source vapor. The cave drip water of Jiguan Cave responded to the heavy rain very quickly, and the time was ~3 h. The δ18O of drip became heavier when dripping rate increased and then decreased slowly. The same pattern could be found in underground river with slight delay, and the pool near the cave entrance reflected the difference of precipitation δ18O in two stages.

[Response and Control Factors of Groundwater to Extreme Weather, Jiguan Cave, Henan Province, China].

Geochemical dynamics of cave water were monitored to unveil its variation and controlling factors from October 2009 to December 2013 in Jiguan Cave,west of Henan province,southeastern coast of the loess plateau. The results showed that: (1) the hydrochemical types of the cave water are HCO(3-)-Ca(2+)-Mg2+ and HCO(3-)-Mg(2+)-Ca2+. HCO(3-) are over 80% of the anions, Ca2+ and Mg2+ are the dominate cations, and ground river keeping in erosion and pool water drips in deposition all the year. (2) Dripping water and pool water in Ji guan cave can respond perfectly to the change of external climate environment, which geochemistry indexes possess the extraordinary seasonal effects. (3) The concentration changes of the Ca2+, Mg2+ , SO4(2-) responded sensitively to annual precipitation change. Ca2+, Mg2+, SO4(2-) rise in waterlogging year and fall in drought year. Because HCO(3-) controlled by CO2 concentration. HCO(3-) concentration showed a unconspicuous response to the change of external climate environment. (4) The concentration changes of Ca2+, Mg2+, SO4(2-) have no obvious seasonal variation and showed a unconspicuous response to the change of external climate environment.