Characteristics of spatial temporal variation of air environment in tourism cave and its cause analysis: A case study of the Dafeng cave in Suiyang county, Guizhou Province

This study is to explore the fact and causes of the spatial and temporal variation of air environment in the Dafeng cave. 10 monitoring points were set up along the horizontal tunnel of Dafeng cave; and CO2 concentration,temperature and relative humidity of each monitoring point had been continuously monitored for a period of 11 months (from October 2015 to August 2016). Through the analysis of these data gained from the cave, its air environment variation can be summarized as follows,(1)The air environment elements (i.e. CO2, temperature, relative humidity) of the tunnel show an obvious seasonal variation. In general, their values are low in winter and high in summer; (2)Due to weak air exchange with the external in the seasons of spring, summer and autumn, the CO2 concentration and humidity gradually increase to the deep in the cave, while the temperature gradually decreases, and all of which stabilize at a certain depth of the cave tunnel owing to very limited cave air exchange with the outside. In winter time, the temperature curve does not indicate the abrupt change, but the CO2 content and humidity fluctuate much in vertical direction from the roof to the bottom; (3)Vertically (from the bottom to the cave roof), the values of CO2 concentration and humidity are different and they are higher at the bottom than those of the cave roof. To the further deep cave these three environmental elements get stabilized.