Acta Geographica Sinica ›› 2020, Vol. 75 ›› Issue (5): 1008-1021.doi: 10.11821/dlxb202005009

• Climate Change and Surface Process • Previous Articles     Next Articles

The vertical conversion characteristics and influence of the partial pressure of CO2 in the water-soil-atmosphere of critical karst zone

WANG Yanlin1,3, ZHOU Zhongfa1,3(), XUE Bingqing1,3, LI Po3,4, TIAN Zhonghui1,3, ZHANG Jie1,3, TANG Yuntao1,2   

  1. 1.School of Karst Science/School of Geography & Environmental Science, 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.The State Key Laboratory Incubation Base for Karst Mountain Ecology Environment of Guizhou Province, Guiyang 550001, China
    4.Guizhou Engineering and Technology Research Center for Development & Utilization of Cave Resources, Guiyang 550001, China
  • Received:2018-12-04 Revised:2020-03-03 Online:2020-05-25 Published:2020-07-25
  • Contact: ZHOU Zhongfa E-mail:fa6897@163.com
  • Supported by:
    National Natural Science Foundation of China(41361081);National Natural Science Foundation of China(41661088);Doctoral Research Project of Guizhou Normal University(GZNUD[2017]6号);High-level Innovative Talents Training Program in Guizhou Province(2016-5674);Construction of Guizhou Branch Platform of National Remote Sensing Center(2012-4003)

Abstract:

The critical karst zone is the central area with the combined action of the carbon cycle in the lithosphere, atmosphere, hydrosphere, and biosphere, and the interaction among different layers forms distinctive reaction systems, where CO2 plays a vital role. Through monitoring the concentration of CO2 in the overlying soil of Shuanghe cave, cave water, and atmosphere, the vertical conversion characteristics of CO2 were systematically analyzed based on the carbonic acid equilibrium theory by adopting statistical analysis. The results show that the vertical conversion process of CO2 is influenced by the changes in temperature inside and outside the cave, pH value of the dripping water and the process of degassing precipitation, and the source of CO2 and ion saturation conditions, which are significantly different between the rainy and dry seasons. During the rainy season, the infiltration rate of atmospheric precipitation is high in the soil, forming a relatively stable enclosed environmental soil. The surface karst belt has weak activity in complementing CO2 in the infiltration water, and the partial pressure of CO2 (PCO2) in the infiltration water varies in the range of 0.035~0.126 vol%, and the partial pressure of CO2 in the water-atmosphere (△lg PCO2) inside the cave is above 0. The cave water is featured by the corrosion property, and CO2 in the lower part of the surface karst belt is the primary source of CO2 in the cave water, whereas during the dry season, due to a small amount of precipitation, the infiltration water has sufficient time to receive CO2 supplement from the soil and surface karst belt, forming an open system. The infiltration water changes in the range of 0.038~0.129 vol%, which is more conducive to the occurrence of the prior calcite precipitation (PCP). At this time, PCO2 in the atmosphere inside the cave is smaller than that in cave water (△lg PCO2 < 0), prompting the recurrence of degassing precipitation inside the cave. Also, both the soil and surface karst belt are the major sources of CO2 in the cave water.

Key words: karst critical zone, vertical conversion, water-soil-atmosphere PCO2, source of CO2, Shuanghe cave system