Acta Geographica Sinica ›› 2018, Vol. 73 ›› Issue (9): 1687-1701.

• Earth Surface Process •

### Variation of CO2 and its response to the drip hydrogeochemistry in caves under the short-time high-strength tourism activities

ZHANG Jie1,2(),ZHOU Zhongfa1,2(),WANG Yanlin1,3,PAN Yanxi1,3,XUE Bingqing1,3,ZHANG Haotian1,2,TIAN Zhonghui1,2

1. 1. School of Karst Science/College of Geography and Environmental Sciences, Guizhou Normal University, Guiyang 550001, China
2. The State Key Laboratory Incubation Base for Karst Mountain Ecology Environment of Guizhou Province, Guiyang 550001, China
3. State Engineering Technology Center of Karst Rock Desertification Rehabilitation, Guiyang 550001, China
• Received:2018-01-02 Online:2018-09-25 Published:2018-09-19
• Supported by:
National Natural Science Foundation of China, No.41361081, No.41661088;Supported by Doctoral Research Project of Guizhou Normal University, No.GZNUD[2017]6;High-level Innovative Talents Training Program in Guizhou Province, No.2016-5674;Construction of Guizhou Branch Platform of National Remote Sensing Center, No.Z-2012-4003

Abstract:

The presence of CO2 in the caves affected by intense tourism activities has a significant impact on the drip hydrogeochemistry and sedimentation. In this investigation, a continuous monitoring on the indexes such as CO2, temperature, relative humidity, tourist number and drip hydrochemistry was conducted in Guizhou Suiyang Dafeng Cave from 30 September 2017 to 9 October 2017. Following the collection of data, different methods were applied systematically to analyze a number of elements comprehensively. The observed results show that, under the influence of factors such as tourist number and ventilation effect of cave, the partial pressure of CO2 in the cave (PCO2 (A)) presented obvious diurnal and interdiurnal variations in the time sequence, and showed a higher value in daytime whereas a lower value at nighttime, and also a higher value on days with many tourists and a lower value on days with few tourists. In space variation, due to different ventilation degrees and cavity volumes, the PCO2(A) of different monitoring points had obvious differences, from the deep cave to the entrance of cave as 3# (Magical Spring and Dewdrop) >1# (Time Tunnel)>2# (Legendary Luminous Pearl). Through the comparison of PCO2(A) and drip temperature, the former had more significant influence on the solubility of CO2 than the latter did. Moreover, the drip temperature and drip partial pressure of CO2 (PCO2(W)) of cave generally had the same trend of variation with that of PCO2(A), and also presented obvious diurnal and interdiurnal variations. The pH, SIc, and HCO3- generally had a trend of variation in the opposite way to that of PCO2 (A), EC and Ca2+ had no obvious diurnal variation but certain interdiurnal variation. With an increase in the strength of tourism activities, the variation amplitude of drip hydrochemistry gradually increased. Furthermore, the differences in the factors such as cavity structure, size and closeness caused differences in the diffusion speed of PCO2(A) and cave ventilation degree, and further influenced the hydrochemistry of the constituents of cave drip and sedimentation conditions of cave. Overall, this study will have a significant impact on the research on protection and management of cave environment as well as its karst cave carbon cycle.