贵州麻黄洞空气CO_(2)与上覆土壤空气CO_(2)相关性研究

Study on the response relationship between soil and cave CO_(2) concentrations in Mahuang Cave,Guizhou province

CO_(2)作为岩溶作用的驱动力,在岩溶作用中起着关键作用。岩溶区特有的地上地下二元结构表明,洞穴系统作为地下空间的窗口,对其CO_(2)及δ^(13)C_(CO_(2))研究是十分必要的。本研究对贵州绥阳麻黄洞上覆土壤空气CO_(2)、洞穴内部和外部大气参数以及CO_(2)浓度和δ^(13)C_(CO_(2))进行了为期12个月的监测,监测结果表明:①麻黄洞洞穴空气和上覆土壤空气CO_(2)与δ^(13)C_(CO_(2))均呈现出明显的时空变化规律,表现出雨季CO_(2)浓度高、δ^(13)C_(CO_(2))偏轻,旱季CO_(2)浓度低、δ^(13)C_(CO_(2))偏重的特征。②土壤CO_(2)是内源性CO_(2)以及大气CO_(2)经平流渗透综合作用的结果,在温度、湿度双向调控下土壤微生物作用存在差异进而导致CO_(2)浓度和δ^(13)C_(CO_(2))存在时空差异,洞穴CO_(2)浓度和δ^(13)C_(CO_(2))主要受上覆土壤CO_(2)及其通风效应的影响。③麻黄洞CO_(2)主要来源于上覆土壤CO_(2)以及外部大气,在通风干预下洞穴内部产生稀释效应或者集聚效应。探究土-气CO_(2)和δ^(13)C_(CO_(2))变化特征,探明洞穴CO_(2)来源,不仅有利于了解洞穴系统碳循环机制,而且对全球碳循环中“遗漏碳汇”研究具有积极意义。

CO_(2) plays a vital role as a driving force of karstification.The unique structure of the ground and underground in the karst region underscores the necessity to study the CO_(2) andδ^(13)C_(CO_(2)) of the cave system,which is the window of the underground system.In our study,we monitored the concentration of CO_(2) andδ^(13)C_(CO_(2)) in Mahuang cave and other parameters related to soil,air,cave,and atmosphere for 12 months.The results show that:(1)CO_(2) andδ^(13)C_(CO_(2)) of soil and cave demonstrated evident spatio-temporal variation,with high CO_(2) concentration and lighterδ^(13)C_(CO_(2)) in the rainy season and low CO_(2) concentration and heavierδ^(13)C_(CO_(2)) in the dry season.(2)Soil CO_(2) mixes with endogenous and atmospheric CO_(2) through advective infiltration under different temperatures and humidity,controlling soil bioactivity and leading to the spatio-temporal difference in soil CO_(2) andδ^(13)C_(CO_(2)).Cave CO_(2) andδ^(13)C_(CO_(2)) are mainly affected by the soil CO_(2) and ventilation effect.(3)The CO_(2) of Mahuang Cave mainly comes from the soil and atmospheric CO_(2).With the intervention of the ventilation effect,the cave generates a dilution or an agglomeration effect.Exploring the variation characteristics of soil-cave CO_(2) andδ^(13)C_(CO_(2)) and the source of cave CO_(2) will be beneficial to the study of the carbon cycle mechanism of the cave system as well as be of positive significance to the study of the“missing carbon sink”in the global carbon cycle.