Study On CO₂ Coupling Relationship Between Water And Gas And Its Influence On Environment Of Cave In Shuanghe Cave,Guizhou Province

The karst cave is one of the important geomorphologic forms under the karstification.It is an important resource that integrates tourism and scientific research.The landscape of carbonate speleothem in the cave is very attractive to tourists.Compared with the external environment,the cave environment is a semi-closed and relatively stable microenvironment.Cave air CO₂ concentration is one of the most important indexes in cave environment.It has a direct effect on the dissolution and balance of chemical deposits of carbonate rock in caves,the paleoclimate reconstruction of cave stalagmites and the tourist comfort of cave tourists.Therefore,it is necessary to carry out systematic monitoring and research on the water-gas environment of the cave.This is of great significance to the protection of cave karst cave environment and cave sediment landscape.At the same time,it is of great significance for the study of carbon conversion and carbon cycle of karst dynamic system.This study takes Dafeng Cave as the research point.Based on the analysis of relevant literature and field investigation,the air environment index and water environment index of the cave are systematically monitored.From the time scale and spatial variation of CO₂ in cave air,the mechanism of water and gas transformation and the influence of water and gas coupling on the hydrogeochemistry of cave and the environment of cave sediments are analyzed.Draw the following conclusions:?1?It is influenced by the number of tourists and the time of staying in the cave,the ventilation inside and outside the cave and the geometry of the cave.On the seasonal scale,PCO_2?A?is obviously high in summer and autumn in cave,but low in winter and spring.The spatial variation of PCO_2?A?in the diurnal scale is obviously higher than that in the night.The spatial variation of PCO_2?A?rises in the summer from the orifice to the hole,and in winter,the change is stable for a long time and slightly increased in the deep part of the cave.?2?The trend of seasonal variation of PCO_2?w?seems to be consistent with that of PCO_2?A?,which shows obvious seasonal variation,that is,the rainy season is high and the dry season is low.The seasonal variation of PCO_2?S?is not obvious.From the CO₂ concentration,PCO_2?S?is obviously higher than PCO_2?W?,indicating that PCO_2?S?is a stable source of PCO_2?W?.The spatial change of PCO_2?W?.The drop point PCO_2?W?of Dafeng Cave is#13,#12,#14 and#09,respectively,from high value to low value.It is determined mainly by the size of cavity cavity and the degree of closure.The drop point PCO_2?S?of Dafeng Cave is#13,#12,#09 and#14,respectively,from high value to low value.Similar to PCO_2?W?,but far higher than PCO_2?W?indicates that PCO_2?S?is a direct source of PCO_2?W?.?3?The linear fitting of PCO_2?A?and PCO_2?W?shows that the changes of PCO_2?W?and PCO_2?A?have obvious consistency.The transformation between the two is mainly dependent on the CO₂ concentration gradient between the two.The fitting relationship between PCO_2?A?and PCO_2?S?is not obvious,which indicates that the variation of PCO_2?A?is slightly changed by PCO_2?S?,but in terms of quantity,the variation of PCO_2?A?is not obvious.PCO_2?S?is much higher than that of PCO_2?A?,which indicates that PCO_2?S?is an important and stable source of PCO_2?W?and PCO_2?A?.On the Temporal and spatial Series of the Pressure Difference of the Water-gas CO₂ in the Dafeng Cave.The effect of CO₂ on air environment in cave is mainly manifested in the process of degassing and inhalation,and the influence of artificial CO₂ on the air environment of cave and the air exchange rate inside and outside the cave.These show that there is a significant difference in the effect of water air CO₂ coupling on the air environment in different seasons.?4?It is found that the overall change trend of PCO_2?A?in 9#monitoring sites is significantly inverse correlated with pH and SIc in cave dripping,which is obviously consistent with PCO_2?W?,HCO₃^-and water temperature.Electrical conductivity and Ca²⁺have certain response,but the rule is not obvious.This shows that the increase of the human CO₂ concentration in the cave has an obvious effect on the water chemistry of the cave dripping water.This shows that when the intensity of human activities in the cave is within a reasonable range,the change of the cave environment is still relatively stable and tends to be balanced,which is similar to the natural environment.But when the intensity of human activity is too high,the influence on cave environment is very obvious.The relationship between water-gas CO₂ and SIc shows that SIc is negatively correlated with PCO_2?W?in cave drip water,but weakly correlated with?PCO₂.It can be concluded that air CO₂ has obvious interference with PCO_2?W?in cave drip water.It also shows that PCO_2?A?is one of the important factors affecting the transformation of water and gas in caves.