Research on seasonal variations of the air’s main environmental factors in the Shihua Cave, Beijing

The CO2 concentration in cave air is an important factor not only controlling the deposition or corrosion of carbonate in caves but also affecting the stability of carbonate landscape and comfort of tourist in show cave. The CO2 concentration, temperature and relative humidity (RH) are monitored for near 4 hydrologic years in the Shihua Cave, Beijing. The results show that (1) cave temperature fluctuates around 15oC and is about 1oC higher in summer, which is related to tourism activities and the seasonal variation of temperature difference between inside and outside of the cave; (2) the CO2 concentration of cave air increases slowly with the air temperature until July, when it can increase quickly due to a large quantity of groundwater coming into the cave after the every strong rain. In August the highest CO2 concentration of cave air can reach 4334ppmv. After the rainy season, the CO2 concentration of cave air also attenuates slowly with the decreasing of the air temperature to reach minimum value (360～458ppmv) in February. In addition, it has two small CO2 concentration peaks in May and October with the increasing in tourists. The analyzed results indicate that high concentration CO2 in soil environment dissolved in drip water makes a greater contribution to CO2 concentration in cave air during rainy period. Respiration of tourists is another contributor during the busy traveling season. Therefore, both natural and anthropogenic factors can be considered when planning and management is carried out for show cave.