重庆雪玉洞CO_2浓度变化的自然与人为因素探讨  

Natural and Human Factors of CO_2 Concentration Variations in Xueyu Cave, Chongqing

作　　者：王翱宇[1] 蒲俊兵[1] 沈立成[1,2] 何阳 

机构地区：[1]西南大学三峡库区生态环境教育部重点实验室,重庆400715 [2]西南大学地理科学学院,重庆400715 [3]重庆丰都龙河旅游开发公司,重庆401147

出　　处：《热带地理》2010年第3期272-277,共6页Tropical Geography

基　　金：国家自然科学基金项目(40672165);重庆市科委院士专项(CSTC2007BC7001;CSTC2005AB7006);西南大学博士基金项目(SWUB2008013)13)

摘　　要：通过对重庆雪玉洞洞穴CO2浓度、地下河CO2分压及地下河水、滴水次生沉积物稳定碳同位素δ13C等地球化学指标进行的完整水文年监测,并结合该洞以往的CO2短期观测记录,发现洞内与CO2相关的环境因子均存在显著的季变性,其总体特征是:CO2浓度夏高冬低,δ13C夏轻冬重。对比每月游客量变化,发现人为因素对洞穴CO2环境的改变远弱于自然因素,洞内发育的常年地下河在其中起主导作用。地下河的存在使不同相态的碳在洞内快速流动交换以达到平衡,从而在"质"上(同位素比)和"量"上(浓度)反映外部环境的季节变化,又使得各项地球化学指标在每年的4月和11月换季时呈现突变特征。可推断雪玉洞CO2的改变来源于地下河对洞穴上部土壤CO2的传递,最终归因于土壤层生物活动对季节气候条件变化的响应。而雪玉洞地下河在CO2变化过程中的传递作用十分突出,可作为同类型洞穴的借鉴,为旅游开发服务。Geochemical monitoring works on CO2 concentration of the cave air, CO2 partial pressure of the ground river and the stable carbon isotope ratio δ13C of the modern speleothems, which were taken through a complete hydrological year in Xueyu cave, revealed the significant seasonality of the CO2-related environmental factors. Some previous short-term cave CO2 records also corroborated the seasonal reproducibility. The general feature of the seasonality in Xueyu cave can be concluded as higher CO2 concentration in summer and lower CO2 concentration in winter, while more negative δ^13C value sediments in summer and less negative δ^13C value sediments in winter. Human factor was proved to have less influence on cave CO2 environment than the natural one by comparing the monthly tourist amount with CO2 concentration. Whereas, comparative analysis indicated that the ground river, which was developed in the bottom floor of the cave, was the dominant of CO2 variation process. The existence of the ground river induced a rapidly fluid carbon exchange among different phases, which led them to achieve a dynamic balance, and the carbon isotope ratio and the CO2 concentration could respond to the outer seasonal variation through this course. The existence of the ground river also led the cave geochemical index to behave in an abrupt change in every April and every November. Obviously in this case, CO2 variation of Xueyu cave can be derived from the upper soil CO2 variation, which is sensitive in responding seasonal climatic variation for its bioactivity. In conclusion, Xueyu cave is a typical example that the ground river plays a key role in CO2 transferring, and it is also a representative reference for the same style caves in their cave tourism exploitation.

关 键 词：重庆雪玉洞 二氧化碳浓度 稳定碳同位素 季节变化 人为因素 

分 类 号：P641.3[天文地球—地质矿产勘探]