中文摘要：

洞穴空气CO2浓度是影响洞穴次生化学沉积物沉积和溶蚀的重要因素之一。基于对本溪水洞洞穴空气CO2浓度、温度和湿度连续两个昼夜的系统观测结果,结合洞外大气CO2浓度、温度和湿度数据,初步分析了本溪水洞洞穴空气CO2浓度空间分布特征和昼夜变化规律：（1）洞穴空气CO2浓度自洞口开始快速增高至一定深度后趋于稳定,这个快速升高的距离与不同季节洞穴交换能力有关,秋季大约是370 m。洞穴CO2浓度稳定区的空间差异可能主要与洞穴结构和裂隙发育情况有关,在洞体变小的倚天长剑景点附近出现峰值,而在洞体变大的石瀑布景点和游客无法进入的源头区出现低谷。（2）观测期间,洞穴空气CO2浓度总体上呈递降趋势,基本上与游客数量有关。（3）在洞穴空气CO2浓度急剧上升的近洞口段,洞穴空气CO2浓度每个昼夜出现两个峰值,分别对应正午12时和午夜前后。本溪水洞洞穴空气CO2浓度的这种变化特点,受游客与工作人员的呼吸排放和洞穴与大气间的气体交换作用的双重影响。

英文摘要：

CO2 concentration in cave air is one of major factors controlling the precipitation and erosion of carbonate in caves,especially in show caves.In order to understand the spatial and diurnal variation and the possible controlling factors,CO2 and temperature as well as relative humidity in cave air are observed by portable CO2 meter linked with auto data logger and auto temperature as well as RH data logger respectively in the Benxi Water Cave,Liaoning,China.The results show that the spatial distribution of CO2 concentration in the cave＇s air can be divided into two situations.Firstly,CO2 increases abruptly from 500 ppm at the cave entrance to 4 500 ppm at 370 m deep of the cave;secondly,the CO2 concentration keeps stable with small regimes between 4 500 and 4 800 ppm.Compared with data observed in other seasons,the distance in the first situation differs from one season to another.This may be controlled by seasonal change in temperature led by the exchange of airs between the outside atmosphere and the inner cave air,and also may be modulated by the human activity.The mean values of CO2 in cave air,in the second situation,decreases slowly during observing period,which corresponding to the deceasing trend of visitor number and indicating that visitor number makes important effect on diurnal variation of CO2 concentration in cave air.The slight variation of CO2 concentration in the second situation maybe relates to the change of volume of cave chamber or the distribution of fractures and fissures.The auto data logger set at 250 m away from entrance records two CO2 concentration peaks every day with one peak at noon and another at mid night more or less.By comparing with the variation of air temperature both inside and outside the cave,this double peak pattern possibly contributes both to respiration of people and exchange of air in cave with atmospheric air.