重庆市芙蓉洞空气环境变化特征与影响因素分析

Characteristics of Environmental Change and Studying on the Influencing Factors in Furong Cave, Chongqing

为探索岩溶洞穴环境变化特征以及洞穴pCO_2与洞穴内外环境的关系,选取重庆市芙蓉洞2012～2016年洞穴内、外环境监测数据进行分析。结果显示:(1)位于洞穴深部的"辉煌大厅"的气温稳定在16.4±0.4℃,而距离洞口约150 m处"莲花观音"受"通风效应"影响,月均温变化幅度约为5℃,其年均温为19.1±1.0℃;(2)"辉煌大厅"的相对湿度常年保持在95%～100%,"莲花观音"的相对湿度平均值为94%,呈现"夏季低,冬季高"的特征,与洞穴外部大气相对湿度季节变化特征相似;(3)芙蓉洞内pCO_2呈现"秋季最高,冬季最低"的季节变化特征,其最大值常出现在10～11月,比土壤pCO_2最大值出现滞后1～2个月,大气降水量和上覆基岩厚度是影响洞穴pCO_2滞后于土壤pCO_2的主要因素;(4)上覆土壤pCO_2、洞穴温度和相对湿度对洞穴不同区域pCO_2的影响存在差异,其原因是由于洞穴空间形态、结构以及游客活动强度具有空间差异性。因此,在洞穴监测和探讨洞穴pCO_2的主要影响因素的过程中,需要重视洞穴各区域空间结构的影响。

In order to explore the source of CO2 in karst cave and the relationship between cave pCO2 and cave environment,a constant cave monitoring study(including air temperature in and out the of cave,local precipitation,soil pCO2,cave air pCO2,and the relative humidity of cave air)had been carried out during 2012-2016 A.D,in Furong Cave,Chongqing,Southwest China.The results showed thatⅰ)The mean cave air temperature was stable at 16.4±0.4℃at'Great Hall'in the deep of the cave,while the mean temperature was 19.1±1.0℃and the changing amplitude of monthly average cave air temperature was about 5℃at the monitoring site named'Lotus Guanyin',approximately 150 m from the entrance.It was explained that ventilation effect was stronger near the entrance than the deep of cave.ⅱ)The air relative humidity changed from 95%to 100%at'Great Hall'.In contrast,the average relative humidity was 94%and was lower in summer and higher in winter at'Lotus Guanyin'which was in line with the seasonal variation characteristics out of the cave.ⅲ)There was a seasonal change in cave air pCO2,with maximum cave air pCO2 values in autumn and the minimum values in winter.The peak values of cave air pCO2 were measured in October or November,lagging 1-2 months behind the peak of overlying soil pCO2.It was considered that the local meteoric precipitation and the thickness of overlying bedrock were the main factors.ⅳ)The effects of overlying soil pCO2,cave temperature and relative humidity on pCO2 at different areas of cave were different because the cave shape,structure and tourist activity had spatial differences.Consequently,it is important to pay attention to the cave spatial structure in the process of cave monitoring and discussing the influencing factors of cave pCO2.