2012—2013年重庆雪玉洞洞穴系统碳循环特征
Carbon Cycle Characteristics in Karst Cave System of Xueyu Cave from 2012 to 2013

重庆雪玉洞洞内CO2浓度之高，在国内外皆罕见，但此洞穴系统碳循环特征及控制因素仍不清楚.利用土壤二氧化碳分压(PCO2-soil)、洞内大气二氧化碳分压(PCO2-cave)、地下河水二氧化碳分压(PCO2-eq)、方解石饱和指数(SIc)、地下河水溶解无机碳同位素(δ13CDIC)等指标来研究雪玉洞洞内CO2浓度变化、控制因素以及地下河对洞内碳循环的影响.结果表明：雪玉洞上覆PCO2-soil雨季高，旱季低；降雨量是控制上覆PCO2-soil的重要因子.雪玉洞PCO2-cave变化规律明显，暖季高，冷季低；温度变化导致洞内外气流频繁交换是PCO2-cave突变的重要原因，地下河水CO2脱气能够在短时间内让PCO2-cave上升到较高值.雨季由于土壤CO2效应，地下河水具有低SIc、高PCO2-eq特性，矿化度较高，并且部分月份地下河水具有溶蚀性；旱季由于土壤CO2效应及降雨较少，地下河水呈现高SIc、低PCO2-eq特性，矿化度较低，以沉积为主.
The high CO2 concentration in Xueyue cave, Chongqing, is rare at home and abroad. However, the circulation characteristics of carbon and its controlling factors in this cave system remain unknown. PCO2-soil, PCO2-cave, PCO2-eq, SIc, and δ13CDIC of subterranean stream were analyzed to investigate the laws of CO2 concentration variations in Xueyu cave and its contolling factors, as well as the impact on carbon cycle in this cave by subterranean stream. It is found that soil PCO2 mainly controlled by precipitation in subtropical areas was higher in rainy season than that of dry season. Cave air PCO2 exhibited seasonal variations, high cave air PCO2 typically occurred during warm periods, and low cave air PCO2 were typical of cold periods. It was ventilation driven by the temperature difference between cave and outside air that resulted in a sharp transition of cave air PCO2. Meanwhile, cave air PCO2 could rise to high level in a short period of time because of CO2 degassing from subterranean stream. Due to soil CO2 effect, groundwater became more mineralized water with low SIc and high water PCO2-eq, and dissolution in some months in rainy season. With the reduction of soil CO2 and precipitation, groundwater had low degree of mineralization with high SIc and low water PCO2-eq in dry season