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短时间高强度旅游活动下洞穴CO的变化特征及对滴水水文地球化学的响应
张结1,2,, 周忠发1,2,, 汪炎林1,3, 潘艳喜1,3, 薛冰清1,3, 张昊天1,2, 田衷珲1,2
1. 贵州师范大学喀斯特研究院/地理与环境科学学院,贵阳 550001
2. 贵州省喀斯特山地生态环境国家重点实验室培育基地,贵阳 550001
3. 国家喀斯特石漠化防治工程技术研究中心,贵阳 550001

作者简介:张结(1988-), 男, 安徽安庆人, 硕士生, 主要从事喀斯特地貌与洞穴研究。E-mail: 975479386@qq.com

通讯作者:周忠发(1969-), 贵州遵义人, 教授, 博士生导师, 主要从事喀斯特资源环境、GIS与遥感研究。E-mail: fa6897@163.com
摘要

洞穴高强度旅游活动产生的CO2对洞穴滴水水文地球化学及洞穴沉积物沉积具有重要影响。本文于2017年9月30日-10月9日对贵州绥阳大风洞洞穴CO2、温度、相对湿度、游客数量及洞穴滴水水化学指标等进行连续监测,运用系统分析方法对各要素进行综合分析。结果发现:① 受游客数量和洞穴通风效应等因素影响,洞穴空气CO2分压(PCO2(A))在时间序列上呈现明显的昼夜变化和日际变化,表现为白昼高、夜间低,游客多的天数高,游客少的天数低。在空间变化上,由于通风程度和洞腔体积不同,不同监测点PCO2(A)存在明显差异,由洞内深处至洞口分别为3#(神泉玉露)>1#(时光隧道)>2#(夜明珠);② 通过比较PCO2(A)和滴水水温,前者对CO2溶解度影响比后者更为显著,表明PCO2(A)是洞穴沉积过程中最重要的驱动因素之一;③ 洞穴滴水水温、滴水PCO2分压(PCO2(W))与PCO2(A)变化趋势大体一致,也呈现出明显的昼夜变化和日际变化。pH、SIc和HCO3-变化趋势大体上与PCO2(A)相反,EC和Ca2+则无明显的昼夜变化,但存在一定的日际变化。随着旅游活动强度的增加,滴水水化学变化幅度逐渐增大。此外,不同滴水点所在洞腔结构、大小、封闭程度等不同,使PCO2(A)的扩散和通风程度存在差异,进而影响洞穴滴水水化学组分和洞穴沉积物沉积状况。因此,本研究对于洞穴环境保护和管理及其岩溶洞穴碳循环的研究具有重要意义。

关键词: 人为二氧化碳; 短时间尺度; 高强度旅游活动; 洞穴滴水; 水文地球化学; 大风洞;
Variation of CO2 and its response to the drip hydrogeochemistry in caves under the short-time high-strength tourism activities
ZHANG Jie1,2,, ZHOU Zhongfa1,2,, WANG Yanlin1,3, PAN Yanxi1,3, XUE Bingqing1,3, ZHANG Haotian1,2, TIAN Zhonghui1,2
1. School of Karst Science/College of Geography and Environmental Sciences, Guizhou Normal University, Guiyang 550001, China
2. The State Key Laboratory Incubation Base for Karst Mountain Ecology Environment of Guizhou Province, Guiyang 550001, China
3. State Engineering Technology Center of Karst Rock Desertification Rehabilitation, Guiyang 550001, China
Abstract

The presence of CO2 in the caves affected by intense tourism activities has a significant impact on the drip hydrogeochemistry and sedimentation. In this investigation, a continuous monitoring on the indexes such as CO2, temperature, relative humidity, tourist number and drip hydrochemistry was conducted in Guizhou Suiyang Dafeng Cave from 30 September 2017 to 9 October 2017. Following the collection of data, different methods were applied systematically to analyze a number of elements comprehensively. The observed results show that, under the influence of factors such as tourist number and ventilation effect of cave, the partial pressure of CO2 in the cave (PCO2 (A)) presented obvious diurnal and interdiurnal variations in the time sequence, and showed a higher value in daytime whereas a lower value at nighttime, and also a higher value on days with many tourists and a lower value on days with few tourists. In space variation, due to different ventilation degrees and cavity volumes, the PCO2(A) of different monitoring points had obvious differences, from the deep cave to the entrance of cave as 3# (Magical Spring and Dewdrop) >1# (Time Tunnel)>2# (Legendary Luminous Pearl). Through the comparison of PCO2(A) and drip temperature, the former had more significant influence on the solubility of CO2 than the latter did. Moreover, the drip temperature and drip partial pressure of CO2 (PCO2(W)) of cave generally had the same trend of variation with that of PCO2(A), and also presented obvious diurnal and interdiurnal variations. The pH, SIc, and HCO3- generally had a trend of variation in the opposite way to that of PCO2 (A), EC and Ca2+ had no obvious diurnal variation but certain interdiurnal variation. With an increase in the strength of tourism activities, the variation amplitude of drip hydrochemistry gradually increased. Furthermore, the differences in the factors such as cavity structure, size and closeness caused differences in the diffusion speed of PCO2(A) and cave ventilation degree, and further influenced the hydrochemistry of the constituents of cave drip and sedimentation conditions of cave. Overall, this study will have a significant impact on the research on protection and management of cave environment as well as its karst cave carbon cycle.

Keyword: anthropogenic CO2; short-time scale; high intensity tourism activity; cave drip water; hydrogeochemistry; Dafeng Cave;
1 引言

洞穴环境监测是了解洞穴沉积物生长过程[1]、古气候环境变化[2]、岩溶碳循环过程[3]及洞穴环境保护[4,5,6,7,8]的重要途径。其中洞穴空气CO2(PCO2(A))作为洞穴环境重要指标之一,在碳酸盐沉积物的溶解和沉积中扮演着关键的角色[9,10]。一般地,PCO2(A)的输入通量包括自然通量和人为通量,自然通量主要来源于洞穴上覆土壤或表层喀斯特的直接扩散,洞穴滴水脱气,洞穴有机质的微生物分解,动物呼吸和内生的CO2[11,12,13,14],人为通量来自于人的呼吸[5, 15-16]。PCO2(A)的输出通量与洞内外空气温度差产生的洞穴通风作用和洞穴几何形态控制有着密切的关系[17,18,19,20]。关于洞穴PCO2(A)的研究主要集中于CO2的时空变化[16, 21-26],旅游活动对PCO2(A)的影响等方面[27,28]。而对于洞穴PCO2(A)和水中CO2分压(PCO2(W))之间关系的研究,如宋林华[29]等在浙江瑶琳洞对水—气CO2机理进行实验研究,揭示出碱性溶液在静态和动态实验中吸收CO2的速度和程度存在明显差异;Pu等[30]对重庆雪玉洞PCO2(A)和PCO2(W)进行两年的研究,发现洞穴上覆土壤CO2的季节变化及洞外温度的波动是导致PCO2(A)和PCO2(W)存在明显季节变化的主要因素,并得出PCO2(A)和PCO2(W)的同步急剧变化受洞穴通风控制。Pracný等[31]在Punkva洞研究水—气PCO2的变化规律,也发现PCO2(A)和PCO2(W)呈现同步的季节变化。水—气PCO2与洞穴水文地球化学的关系方面,曹明达等[32]对贵州双河洞进行系统研究,发现洞穴滴水水—气CO2分压差与水中矿物饱和指数及pH等水文地球化学指标呈现出明显的相关性,并指出在天然洞穴中PCO2(A)对洞穴水文地球化学过程影响较小。Wang等[33]对雪玉洞PCO2(A)和滴水水文地球化学之间的关系进行研究,发现在日际变化尺度上,当PCO2(A)浓度增高时,滴水中pH和δ13CDIC降低,表明PCO2(A)是控制滴水水文地球化学的主导因素之一。Spötl等[19]对奥地利Obir洞进行系统研究,揭示出PCO2(A)控制滴水水文地球化学,并在积极性通风条件下对沉积物沉积产生影响。但以上研究主要侧重于季节或年际变化等长时间尺度,或者短时间尺度,但并未考虑人为活动产生的CO2对洞穴滴水水文地球化学的影响。Pu等[34]通过高分辨率的数据揭示了雪玉洞PCO2(W)与洞穴水水文地球化学的关系,并阐明其主要受活塞效应、稀释效应、土壤CO2效应和缓冲效应等因素的影响。此外PCO2(A)的变化在年际尺度上还对洞穴沉积物替代指标具有明显的影响[35,36,37],但主要是通过PCO2(W)起作用,如PCO2(A)通量增加,使HCO3-增加,pH降低,水溶液呈溶蚀状态,进而导致碳酸盐岩沉积驱动力减弱,反之,输入通量减少,驱动力则增强[38],这在旅游洞穴中表现尤为明显,因此旅游活动产生的过量CO2对洞内水—气环境的影响是洞穴管理和保护的一个潜在问题[39,40],尤其是短时间尺度(日际和小时尺度)、高强度人为CO2的贡献对洞穴环境具有明显影响,并使天然洞穴系统的CO2平衡遭到破坏,进而影响洞穴岩溶作用,尤其是水—岩—气之间的相互作用,导致洞穴岩溶碳循环发生变化。本文以贵州绥阳双河洞系中的大风洞为研究对象,在“十一”长假期间(2017年9月30日-10月10日)对PCO2(A)和洞穴滴水中的相关参数进行定点连续监测,探讨在短时间尺度高强度人为影响下CO2的变化特征,并分析人为CO2对洞穴滴水水文地球化学环境及洞穴沉积环境的影响,为洞穴环境保护和管理提供科学依据,对人为因素影响下岩溶洞穴碳循环的研究具有重要意义。

2 研究区概况

研究区位于贵州省绥阳县温泉镇西北(107º02'30"E~107º25'00"E、28º08'00"N~28º20'00"N),属芙蓉江西支池武溪地下河系(图1)。双河洞洞穴系统目前为中国第一长洞,已探明长度超过200 km。是一座水洞、旱洞并存,结构复杂的超长白云岩洞穴系统,总体发育方向为SE-NE,平面展布形态总体呈枝状。地质构造上,洞系处于贵州北部宽缓箱状背斜翼部,由于受不同方向区域构造应力作用,所形成的NE、NW及SN向褶皱断裂带,将洞区围成一个相对上升的三角形地块[41]。研究区出露地层以中上寒武系娄山关组(∈2-3l)的白云岩、灰质白云岩及夹燧石和泥质的白云岩为主[42];喀斯特地貌类型齐全,有洞穴、落水洞、天坑、峡谷、地下河、盲谷等,洞内次生碳酸钙和硫酸钙沉积较发育,其中寒武系中上统娄山关组白云岩多形成地表分水岭或斜坡,在其底部约100 m厚度含有石膏层,溶蚀强烈。研究区气候总体属中亚热带季风气候,1月均温1.6 ℃,7月均温22.5 ℃,年均温l5.5 ℃;年平均降水量1210 mm,大多集中于4-10月,且降水强度大;植被以亚热带常绿阔叶林和阔叶落叶混交林为主,土壤垂直分带明显,低海拔区主要以黄壤、石灰土为主,相对高海拔区主要以山地黄棕壤为主。

图1 研究区概况图 Fig. 1 The sketch map of research area

本文以双河洞洞穴系统的支洞大风洞为研究对象,大风洞于1993年对外开放,其洞口海拔为734 m,洞口宽7.6 m,高4.5 m,主体洞道宽度在0.9~16.7 m之间,平均宽度为6.2 m;洞道高度在1.7~22.6 m 之间,平均高度为8.9 m,洞长约为696 m,总面积约为4805 m2,总体积为64518 m3。洞道水平起伏较小,洞道单一,向南逐渐变宽,距洞口440 m处右侧有一支洞,长度大约132 m。洞内发育众多的次生碳酸钙沉积物,如形态各异的石笋、石钟乳、石瀑和卷曲石等。沿着主洞道至564 m处为该洞段的终点,与响水洞相连。

3 数据来源与研究方法

在大风洞内由洞口至洞内深处依次设置3个CO2连续监测点,分别为1#(时光隧道)、2#(夜明珠)、3#(神泉玉露)(图2),具体监测点参数如表1所示。监测时间为2017年9月30日00:00至10月10日早上8:30左右。PCO2(A)、温度、相对湿度的连续监测选用美国Telaire-7001型便携式红外CO2仪3台同时外接美国ONSET公司HOBO自动记录仪(U12-012),时间间隔为1 min 45 s,其中温度测定量范围在-20 ℃~70 ℃,精度为±0.35 ℃,湿度5%~100%,CO2浓度范围在0~10000 mg/L,分辨率为1 mg/L,测量精度为±50 mg/L,实验前用标准(380 mg/L)气体进行校准,操作时将仪器放置在距操作者2 m外以避免人为影响。洞外气象使用美国Kestrel-4500型便携式小型气象站对洞穴内外空气中的风速、温度、相对湿度等进行连续监测,时间间隔为5 min,仪器分辨率分别为0.1 m/s、0.1 ℃和0.1%,测量精度分别是±3%、±1.0 ℃和±3%。再通过温度、湿度和CO2浓度计算虚拟温度(TV[43]。计算公式如下:

T V = T × ( 1 + 0.6079 r V - 0.3419 r C ) (1)

式中:T为温度(℃);rV为水汽混合比;rC为二氧化碳混合比率。

图2 大风洞监测点分布示意图 Fig. 2 Schematic diagram of the distribution of the monitoring points of Dafeng Cave

野外水样pH值、水温测定使用2台德国WTW公司生产的Multi 3430便携式多参数水质分析在2#和3#滴水点进行连续监测,监测前用标准溶液对pH和电导率进行校正,监测时间间隔为1 min(3#)和5 min(2#),测量精度分别为0.001 ℃和0.01 ℃。监测期间,每天08:00-18:00,采用德国Aquamerck公司生产的碱度计每隔2 h测定滴水中的HCO3-浓度,分辨率为1 mg/L。在现场每天取水样4次,取样时间分别在08:00、12:00、14:00和18:00。取样前用0.22 μm的滤膜过滤后再装入50 mL高密度聚乙烯瓶中。用于阳离子测定的样品加入1∶1硝酸酸化至pH<2以下,密封保存,阴离子样品则直接密封保存。室内实验分析在中国科学院地球化学研究所环境实验室测定完成。其中阴离子采用美国Dionex公司生产的ICS90型离子色谱仪测定,阳离子采用美国Varian公司生产的VISTA MPX型电感耦合等离子体—光发射光谱仪测定。监测点滴量利用不同量程的量筒(5 ml和500 ml)置于滴水点下方,并运用秒表测量1 min,每个滴水点均测量3次,测量时间与HCO3-的测定时间一致。“十一”期间大风洞开放时间为08:30-18:30,游客人数统计由专人在洞口检票处进行计数,游客类型分成人和儿童,儿童按成人1/2计算,每隔30 min记录1次。监测期间游客高峰基本位于11:00-12:00时段,次高峰基本位于14:00-15:00时段。运用激光测距仪对洞穴进行测量,测量精度为0.1 m。数据处理主要运用Origin 2016和SPSS 19.0等软件进行统计。

水化学数据集包括水温、pH、K+、Na+、Ca2+、Mg2+、Cl-、SO42-和HCO3-,并运用Phreeqc程序计算滴水中CO2分压[44](PCO2(w))和方解石饱和指数(Saturation indices calcite, SIc)。PCO2(w)SIc的计算公式为:

PC O 2 ( W ) = [ H + ] [ HC O 3 - ] K 1 K h (2)

式中:方括号中为离子活度,单位为mol/L;K1Kh是H2CO3的第一次离解常数和Henry定律常数。SIc计算运用公式:

SIc = log IAP K (3)

式中:IAP是方解石溶液中各离子的活度积;K是方解石溶解于水的平衡常数。如果SIc =0,水溶液处于热力学平衡状态;SIc<0,水溶液处于不饱和状态;SIc>0,水溶液中处于过饱和状态。

4 结果
4.1 洞穴空气CO浓度的时空变化特征

PCO2(A)变化的主要影响因素包括气候变化导致的植被和土壤生物活动产生的CO2浓度变化、通风效应和游客数量及其在洞内滞留的时间长短[45]。而洞穴短时间尺度CO2浓度变化主要与通风效应和游客数量及其滞留的时间长短等因素有关。图3所示,对3个监测点PCO2(A)进行10 d的连续自动监测,发现监测期间PCO2(A)浓度总体上呈现明显的昼夜变化,表现为白天CO2浓度出现明显的峰值,而夜间出现明显的低值。各监测点PCO2(A)最高值均出现在当天游客数量最多的14:00-14:30时间段。经过夜间的自净,CO2浓度逐渐降低与限制性通风时期(夏秋季)的背景值相近(约1000 mg/L)。日际变化上PCO2(A)的变化与进入洞穴的游客数量大体一致,即当进入洞穴的游客数量迅速增加时,PCO2(A)也出现显著地增加,增加幅度在不同监测点存在差异,分别为2.1 mg/L、1.2 mg/L和4.0 mg/L,这与其他旅游洞穴基本一致。至游客量达到最大值时,PCO2(A)出现高而尖的峰值,如10月3日1#、2#和3#分别为1481 mg/L、1455 mg/L和2351 mg/L(图4a、4c);而当游客数量较少时,CO2波动较小,出现宽缓的峰值,如10月9日1#、2#和3#分别约为1108 mg/L、1138 mg/L和1192 mg/L(图4b、4d)。此外,10月5日-10月6日CO2浓度出现异常低值,但1#(528 mg/L)和3#(948 mg/L)点低值均在8:30-9:00之间,而2#点最低值(874 mg/L)则在10:00左右,稍有一定的滞后。

图3 大风洞不同监测点CO2浓度短时间尺度变化 Fig. 3 Short-time scale variation in the concentration of CO2 at different monitoring points of Dafeng Cave

图4 游客在洞内滞留和游客出洞后CO2的变化趋势 Fig. 4 The trend of variation of CO2 when the tourists linger in the cave and exit the cave

不同监测点由于其在洞穴中的位置、洞腔大小、洞穴结构、洞道封闭性及通风程 度[2, 46]等因素的不同,其CO2浓度的空间变化也存在明显的差异。由表1可知,1#点由于距洞口较近,洞腔体积最小,通风程度最好;2#监测点距洞口较远,但洞腔体积较大,通风程度次之,3#监测点位于支洞内,距洞口距离最远,同时洞腔体积较小,封闭程度较好;因而3个监测点洞穴CO2浓度变化幅度存在明显的差异,如图3所示3#点PCO2(A)变化幅度最大(1403 mg/L),1#点次之(978 mg/L),2#点变化幅度最小(585 mg/L)。

4.2 洞穴滴水水文地球化学特征分析

通过对2个滴水点的短时间尺度水文地球化学指标进行连续监测。由如图5所示,2#和3#滴水的滴量变化差异较大,分别在2.17~2.84 mg/L和318~395 mg/L之间,2#滴水点在10月5-6日达到高值,3#则是由10月3日开始逐渐增加,至4日逐渐稳定,5日开始逐渐变慢;表明降水至洞内在不同的滴水点位置所响应的时间长短不一。水温变化幅度相对较小,分别在15.2 ℃~15.5 ℃和15.5 ℃~16 ℃之间,两个滴水点水温大致呈现出有规律的白昼高而夜间低的变化特点;logPCO2(w)变化范围为10-3.21~10-2.8(617~1585 mg/L)和10-2..64~10-2.42(2291~3802 mg/L),变化趋势与滴水温度和PCO2(A)呈现较好的一致性;pH变化分别在7.98~8.43和7.68~7.91之间,其变化规律与水温变化趋势大致相反,呈现出白天低而夜间高的特征,最低值大致出现在每日午后18:00-22:00之间,并开始从晚上开始增加,最高值出现在早晨;SIc变化范围分别在0.47~0.93和0.2~0.43之间,除3#点9月30日和10月1日外,其他时间变化趋势与pH相似,也呈现出白天低而夜间高的特征;HCO3-变化范围分别在2.9~3.9 mmol/L和3.8~4.3 mmol/L之间,大体上变化趋势与pH和SIc相似。电导率在328~332 μs/cm和384~390 μs/cm之间,在10月2日和3日均出现较大波动,其他时间段相对稳定。Ca2+变化范围为50.5~52.13 mg/L和43.03~44.67 mg/L,2#点10月2日-3日及10月8日-9日Ca2+变化幅度相对较大,10月4日-7日变化幅度较小,呈现出先上升后下降的趋势。3#点Ca2+变化在9月30日-10月4日总体上呈上升趋势,而至5日呈现出突然升高然后再突然下降,在5日-7日出现低值,之后逐渐升高至稳定。

图5 2#和3#滴水点水文地球化学特征 Fig. 5 The characteristics of hydrology geochemistry of 2# and 3# drip points

5 讨论
5.1 短时间尺度PCO变化的驱动因素

5.1.1 游客量 游客数量及其在洞穴内滞留的时间是导致洞穴瞬时CO2浓度变化幅度较大的最直接原因[31]。其他条件不变的情况下,当一定数量的游客到达监测点时,PCO2(A)开始逐渐上升,随着滞留时间的增加和游客数量的增加,PCO2(A)开始处于快速上升阶段,当游客离开监测点后的一段时间内,由于CO2的累积效应,监测点的PCO2(A)继续缓慢升高至最大值,而后由于洞穴通风效应的影响,使洞内CO2不断扩散,稀释净化,最终回到自然背景值(Cn),由此日复一日地使PCO2(A)呈现出明显的昼夜变化(图6)。如图4a所示,在游客数量最多的10月3日,8:30游客还未进入洞穴,各监测点CO2浓度基本接近背景值,随着游客进入洞穴的数量增加,PCO2(A)逐渐增加,但由于受洞穴洞腔大小和洞穴通风效应的影响,不同监测点CO2浓度增加的幅度存在明显差异,分别为3#>1#>2#。由于CO2的累积效应,至16:00时洞穴PCO2(A)逐渐达到最大值,随后由于游客逐渐减少,CO2浓度梯度达到最大值,同时由于洞内外温差逐渐缩小,洞内外气流交换增强,CO2开始迅速扩散,至午夜或次日第一批游客来临之前达到自然背景值。而游客较少的10月9日与10月3日相比,CO2变化的模式相似,但是CO2在上升段和下降段的变化幅度明显较小。

图6 游客进入洞穴期间空气CO2浓度的演变过程[5] Fig. 6 The variation in the concentration of CO2 in the air during the period when the tourists enter the cave

5.1.2 洞穴通风效应 短时间尺度的洞穴通风过程主要受洞内外温度差[47,48]、洞穴形态[49]、气压和风[50,51]等因素的控制。目前对洞穴通风的估计忽略了高浓度二氧化碳和相对湿度的作用,因而一种更精确的浮力测量方法是虚拟温度(Tv),虚拟温度综合计算了洞穴气温、相对湿度和空气CO2,其包括每个气团的主要分子组成的变化对其浮力的影响[52]。因此通过计算洞内外虚拟温度差(△Tv =TvCave-TvOutside)来估算浮力差的变化,能够进一步准确估计洞穴通风情况。即当△Tv>0时,空气浮力差为正值,表明更多的暖而轻的洞穴空气离开洞穴并被洞外的冷重气流所取代;当△Tv<0时,空气浮力差为负值,则意味着洞穴空气将滞留在洞内,洞内外气流交换受到抑制,洞穴通风程度较弱。如图8所示,监测的绝大部分时间△Tv<0,空气浮力差为负值,说明在监测的大部分时间里,洞内外气流交换主要处于限制性通风状态,即洞内外气流交换受到限制,导致洞穴空气滞留于洞内。尤其是晴朗天气的午后,这种限制性通风状态尤为明显(图7a),而至夜间有所缓和,洞内外气流具有一定的交换,但此时洞内外气流交换可能主要受洞内外空气密度差控制(图7b),也就是当洞内外温差相近时,洞内由于旅游活动,PCO2(A)浓度增高,使洞穴空气密度增加,而洞外空气密度相对恒定,从而导致洞内外空气密度差产生,洞内气流缓慢流向洞外,最终经过夜间的自净,至第二天游客进入洞穴之前,达到自然背景值。但当旅游活动过于强烈,可能使PCO2(A)产生大量累积,导致洞穴空气无法在短时间内自净,进而可能抑制洞穴沉积物生长。

图7 监测期间大风洞洞穴通风模式图 Fig. 7 The mode chart for cave ventilation of Dafeng Cave during the monitoring period

图8 洞内外虚拟温度差(△Tv) Fig. 8 The virtual temperature difference between the inside and outside of cave

在降水期间(10月4日下午-6日早上),图8中10月5日午后时段△Tv<0,空气浮力差为负值,洞内外交换相对减弱,在此时间段洞穴PCO2(A)出现次一级峰值,分别为1048 mg/L、1345 mg/L和1785 mg/L(图3)。但是此结果似乎不合常理,因为游客进入洞穴将贡献一定的CO2,同时在洞内因运动释放一定的热量,而此时洞内温度应该更高,△Tv会更大,洞内外气流交换应更加顺畅。但是监测结果却恰恰相反,其中原因可能较为复杂。目前推断可能是由于大量游客进入洞内,在游览的过程中产生了大量的“脚风”,改变洞穴气流运动方式,导致洞内气流发生混合湍流作用,使洞内温度降低程度要高于游客本身的贡献。这表明旅游活动对洞穴通风过程具有一定的影响。

图8中的蓝色部分,△Tv>0,空气浮力差为正值,表明洞外温度低于洞内,洞外冷的空气进入洞内,使较暖的气流被置换出洞穴,被洞外的冷气流所取代(图7c、7d),此时洞内外通风明显增强。但同一日内,不同时间段,通风的程度不同。主要表现为雨天白昼期间△Tv<0,至雨天夜晚时段△Tv则明显大于0,即在由白昼至夜间,空气浮力差由负值转为正值,说明洞内外气流的方向也由洞内→洞外转向洞外→洞内,洞穴通风由限制性通风转向积极性通风。随着降水的继续,洞外降水因蒸发不断吸热,温度逐渐下降,使洞外温度比洞内更低,洞穴通风程度加剧,进而使PCO2(A)出现低值(图7d)。此外由洞口至洞内深处,地势相对较平缓,在积极性通风期间有利于洞内外气流的交换(除支洞外)。

洞穴的通风程度在不同监测点也存在一定差异。△Tv>0所占的面积由大到小分别为1#、3#和2#,1#点离洞口较近,洞腔相对较小(表1),但是洞穴通风率最高,2#点则由于洞腔最大,几乎是其他监测点的好几倍,虽然离洞口较远,但能容纳更多的空气,具有一定的缓冲作用,因此通风率相对较高,3#监测点位于支洞内,支洞洞腔均较小,形成了相对封闭的空间,因而洞穴通风率明显较低。因此不同监测点洞穴通风程度的差异主要是与洞口的距离、洞腔大小和洞穴封闭程度的相互耦合的结果。

5.2 PCO对洞穴碳酸钙沉积过程的驱动作用

洞穴次生碳酸钙沉积物是洞穴最重要的旅游景观之一,其形成是降水进入土壤溶解土壤CO2,生成碳酸水,在下渗的过程中与洞穴上覆基岩接触对其进行溶蚀,形成富含Ca2+的岩溶水,以滴水或裂隙水形式进入洞穴时,PCO2(W)和PCO2(A)之间产生分压差(ΔPCO2=PCO2(W)-PCO2(A))。根据亨利—胡克尔定理,CO2气体是由高分压位向低分压位运动,且分压差的绝对值越大,CO2运动越快[53]。当ΔPCO2>0时,溶液中的CO2在压力差的驱动下不断脱气,进而使水中碳酸钙过饱和而沉积,形成各种沉积景观;当ΔPCO2<0时,PCO2(A)被吸收进入水中,形成额外的碳酸,进一步溶蚀碳酸盐岩,不利于洞穴沉积物沉积;当ΔPCO2 = 0时,水中的CaCO3呈平衡状态,此时PCO2(W)的溶解度由环境温度决定,对洞穴景观形成亦能产生影响[54]。相关过程如下:

H2O+CO2=H2CO3 (4)

CaCO3+H2CO3=Ca2++2HCO3- (5)

Ca2++2HCO3-=CaCO3↓+CO2↑+H2O (6)

因此,在整个岩溶洞穴系统中,CO2是最活跃、最关键的因素,当地表环境变化相对稳定时,CO2溶解度的变化是水体中CaCO3变化的主要控制因素,对洞穴沉积景观的形成具有巨大的驱动作用,故而PCO2(A)在水溶液中溶解度是碳酸钙侵蚀与沉积的关键。如下式:

CO2(S)=Cab×PCO2×1.963 (7)

式中:CO2(S)指CO2在水溶液中溶解度,单位为mg/L;PCO2为洞穴空气CO2分压,以大气压表示;1.963是指1升CO2在一个大气压在20 ℃时的重量,单位为g;Cab是不同温度下溶液对CO2的吸收系数,随溶液温度的升高而减小,因此CO2的溶解度受水体温度与空气PCO2的影响。但Ford等[55]的研究发现洞穴空气CO2对水中的CO2溶解度的影响要明显超过水温。在研究期间大风洞PCO2(A)在900~2400 mg/L之间,变化幅度为1500 mg/L(图3),洞穴水温变化幅度基本在0.5 ℃以内,这表明大风洞PCO2(A)浓度对CO2溶解度影响比温度更为显著,因此PCO2(A)是影响洞穴景观的主要因素,同时也是洞穴沉积物沉积过程的重要驱动力。

5.3 洞穴空气CO与洞穴滴水水化学

短时间尺度内,由于人为CO2的贡献量不同,洞穴滴水水化学也必然存在差异。如图9所示,洞穴PCO2(A)和滴水水文地球化学之间的关系。当PCO2(A)较高时,logPCO2(W)、HCO3-、Ca2+、pH、SIc和水温变化趋势较缓,但随着PCO2(A)减少,logPCO2(W)、HCO3-、Ca2+和水温下降的趋势明显,pH和SIc则呈现明显的上升趋势,主要是在晴天的夜间和雨天,洞内外气流交换增强,使洞内高浓度的PCO2(A)被稀释,导致水气之间的ΔPCO2增加,促进滴水中CO2脱气和方解石的沉积,从而消耗水中的HCO3-,使洞穴滴水pH升 高[9, 19, 56]。以PCO2(A)=1400 mg/L为拐点,当PCO2(A)<1400 mg/L时,两处滴水点的logPCO2(W)、HCO3-、Ca2+、pH、SIc和水温随PCO2(A)的变化存在明显差异,表明洞穴渗流水一旦遇到低的PCO2(A)就会发生瞬时脱气,这意味着洞穴上覆基岩内含有的水化学信号比洞穴滴水所含有的信号更精确。然而在降水期间,PCO2(A)均小于1100 mg/L,两处滴水点的PCO2(A)出现异常偏低,更加速了洞穴沉积过程,表明极端低的PCO2(A)能够导致洞穴滴水CO2脱气达到极致。因此在短时间尺度内,监测数据首次在洞穴发现了滴水水化学的异常趋势,这可能是大风洞低浓度的PCO2(A)条件下的水文地球化学的一般趋势。例如当游客数量较少时(10月8日和9日),洞穴空气CO2仅比背景值略高,分别为1244 mg/L和1177 mg/L,而pH则上升基本稳定至7.85左右,EC、logPCO2(W)和HCO3-及水温变化均较小。这说明当洞内人为活动强度在合理的范围内,洞穴环境的变化仍然相对稳定且趋于平衡,基本与自然环境相当;但高强度人为活动贡献的CO2对洞穴滴水水文地球化学洞穴沉积物的沉积有着显著的影响。

图9 PCO2(A)与洞穴滴水水文地球化学指标的关系 Fig. 9 Relationship between PCO2(A) and hydrogeochemical indicators of the cave dripping water

通过对比图10a和图10b中的概念模型表明,当大量游客进入洞穴,瞬时的CO2对洞内贡献增加,使PCO2(A)增高,水气之间的分压差减小,相应的PCO2(W)增加,水溶液中H+和HCO3-含量升高,pH值降低,滴水呈现侵蚀状态,碳酸钙不断溶解,最终不利于洞穴沉积景观的沉积。但当游客数量逐渐减少或几乎无游客时,洞穴空气中PCO2(A)大幅降低,水气之间的分压差增大,洞穴滴水脱气作用明显,使方解石水溶液呈现过饱和状态,进一步使洞穴沉积物的沉积趋势加强。

图10 洞穴CO2对洞内环境影响的概念模型 Fig. 10 Conceptual model of the influences of CO2 on the internal cave environment

此外,由于滴水点所在洞腔结构、大小、通风程度等因素的不同,使PCO2(A)的扩散速度和洞穴通风存在差异,进而影响PCO2(A)与洞穴滴水水化学之间的关系。如图10所示,2#点相对于3#点洞腔较大且封闭性较差(表1),因而在2#点CO2的扩散速度和通风程度均较3#点强,因此当其他条件不变时,洞腔愈小且愈封闭,游客产生的CO2在短时间尺度内升高就愈明显,洞穴滴水水文地球化学变化也越明显,反之亦然。

6 结论

通过对大风洞洞穴空气环境和水化学指标连续10 d的监测,运用系统分析方法对各要素进行综合分析,主要得出以下结论:

(1)监测期间,PCO2(A)在时间变化上呈现明显的昼夜变化和日际变化,主要受游客数量和短时间尺度的洞穴通风效应等因素的影响。在空间变化上,由于洞腔体积和通风程度不同,不同监测点PCO2(A)浓度存在明显差异,由洞内深处至洞口分别为3#>1#>2#。

(2)通过对PCO2(A)和洞穴滴水水温对溶解CO2的影响的比较,发现大风洞PCO2(A)变化幅度为1500 mg/L,洞穴水温变化幅度基本在0.5 ℃以内,表明PCO2(A)浓度变化对CO2溶解度影响比温度变化更为显著,也证明了PCO2(A)是洞穴沉积物沉积过程的最重要驱动因素之一。

(3)洞穴滴水水温和PCO2(w)变化趋势基本相似,表现为白昼高而夜间低,pH、SIc和HCO3-变化大体上呈现出白昼低而夜间高的特征,EC和Ca2+则无明显的昼夜变化。随着旅游活动强度的增大,PCO2(A)迅速增加,滴水水化学变化幅度也逐渐增大,但当CO2浓度达到一定阈值时,水化学变化幅度逐渐变小。PCO2(A)的扩散和通风程度的差异,会进一步影响洞穴滴水水化学的变化,表现为洞穴通风程度好,洞穴滴水水化学变化相对平稳;但洞穴通风程度差,使洞穴积聚大量CO2,对洞穴滴水水化学变化影响显著,也可能在一定程度上抑制洞穴沉积物的沉积。

(4)短时间尺度洞穴人为CO2变化对洞穴水化学影响的研究,有利于洞穴环境管理和保护,为旅游洞穴碳循环的深入研究提供了一定的理论依据。但由于洞穴是一个极其复杂的系统,现有的监测数据并不能完全揭示相关规律。因此洞穴环境监测研究需要分辨率更高的数据,才可能更加逼近实际的规律。

The authors have declared that no competing interests exist.

Reference
[1] Fairchild I J, Baker A.Speleothem Science: From Process to Past Environments. Chichester: John Wiley & Sons, 2012: 416.
Abstract Speleothems (mineral deposits that formed in caves) are currently giving us some of the most exciting insights into environments and climates during the Pleistocene ice ages and the subsequent Holocene rise of civilizations. The book applies system science to Quaternary environments in a new and rigorous way and gives holistic explanations the relations between the properties of speleothems and the climatic and cave setting in which they are found. It is designed as the ideal companion to someone embarking on speleothem research and, since the underlying science is very broad, it will also be invaluable to a wide variety of others. Students and professional scientists interested in carbonate rocks, karst hydrogeology, climatology, aqueous geochemistry, carbonate geochemistry and the calibration of climatic proxies will find up-to-date reviews of these topics here. The book will also be valuable to Quaternary scientists who, up to now, have lacked a thorough overview of these important archives. Additional resources for this book can be found at: www.wiley.com/go/fairchild/speleothem.
DOI:10.1002/9781444361094      [本文引用:1]
[2] James E W, Banner J L, Hardt B.A global model for cave ventilation and seasonal bias in speleothem paleoclimate records. Geochemistry Geophysics Geosystems, 2015, 16(4): 1-12.
Abstract Erupting magma often contains crystals over a wide range of sizes and shapes, potentially affecting magma viscosity over many orders of magnitude. A robust relation between viscosity and the modality of crystal sizes and shapes remains lacking, principally because of the dimensional complexity and size of the governing parameter space. We have performed a suite of shear viscosity measurements on liquid-particle suspensions of dynamical similarity to crystal-bearing magma. Our experiments encompass five suspension types, each consisting of unique mixtures of two different particle sizes and shapes. The experiments span two orthogonal subspaces of particle concentration, as well as particle size and shape for each suspension type, thereby providing insight into the topology of parameter space. For each suspension type, we determined the dry maximum packing fraction and measured shear rates across a range of applied shear stresses. The results were fitted using a Herschel-Bulkley model and augment existing predictive capabilities. We demonstrate that our results are consistent with previous work, including friction-based constitutive laws for granular materials. We conclude that predictions for ascent rates of crystal-rich magmas must take the shear-rate dependence of viscosity into account. Shear-rate dependence depends first and foremost on the volume fraction of crystals, relative to the maximum packing fraction, which in turn depends on crystal size and shape distribution.
DOI:10.1002/2014GC005554      [本文引用:2]
[3] Peyraube N, Lastennet R, Villanueva J D, et al.Effect of diurnal and seasonal temperature variation on Cussac cave ventilation using CO2 assessment. Theoretiacl and Applied Climatology, 2017, 129(3/4): 1045-1058.
DOI:10.1007/s00704-016-1824-8      [本文引用:1]
[4] Song L H, Wang J, Liang F Y, et al.Effect of human and natural factors on the environment of show caves. Carsologica Sinica, 2004, 23(2): 91-99.
The environmental changes in show caves have been concerned by the show cave managers and speleo-scientists. Most scientists have recognized the speleo-activities and tourist facilities as the main factors to force the environment changes in the show caves. The show caves in carbonate rocks including the water caves and dried caves are strongly influenced by the visitor flow. Great number of visitors rushing into the show caves in a short periods causes the CO_2 content and temperature rapidly increase, especially in the narrow and small passages and chambers. The maximum CO_2 content was 7000 ppm (May 2, 2001) in the chamber about 20 m long, 2~5 m wide and 5~8 m high in Baiyun Cave, Hebei, after about 3000 people visited for 5 hours, the temperature increased from 16 8 ℃ to 19.6℃.In some cases, the natural factors may make great changes of the cave environment . For example, the heavy rain caused the great amount of drops in Yaolin Cave,Zhejiang.CO_2 concentration was obviously increased from 490~800 ppm on October 30 (before raining) to 740~1580 ppm on November 14, 1997 ( after raining). The measurement results show the temperature of drop water is 0.1~0.6℃ higher than the cave temperature, but it is not very clear that the temperature of cave was whether increased or not in the big chambers in Yaolin Cave. In Huangxian Cave, Hubei, in the wet season, most of 1833 rim pools were over flowing, the average CO_2 content in the Rim Pool Hall on October 6,2000 was 2050 ppm, in the range of 1800 ppm and 2300 ppm; the temperature varied from 17.6℃ to 19.1℃, average temperature was 18.5℃. While on August 20, 2001, when 90% of the rim pools were dried out,it was only 950 ppm of average CO_2 concentration varying from 900 ppm to 1100 ppm, and the average temperature was 17.9℃, fluctuated from 15.9℃ to 21.3℃.
DOI:10.1007/BF02911025      [本文引用:1]
[5] Lang M, Faimon J, Pracný P, et al.A show cave management: Anthropogenic CO2 in atmosphere of Výpustek Cave (Moravian Karst, Czech Republic). Journal for Nature Conservation, 2017, 35: 40-52.
DOI:10.1016/j.jnc.2016.11.007      [本文引用:3]
[6] Lario J, Soler V.Microclimate monitoring of Pozalagua Cave (Vizcaya, Spain): Application to management and protection of show caves. Journal of Cave and Karst Studies, 2010, 72(3): 169-180.
DOI:10.4311/jcks2009lsc0093      [本文引用:1]
[7] Calaforra J M, Fernández-Cortés A, Sánchez-Martos F, et al.Environmental control for determining human impact and permanent visitor capacity in a potential show cave before tourist use. Environmental Conservation, 2003, 30(2): 160-167.
DOI:10.1017/S0376892903000146      [本文引用:1]
[8] Cigna A A.An analytical study of air circulation in caves. International Journal of Speleology, 1968, 3(1): 41-54.
DOI:10.5038/1827-806X      [本文引用:1]
[9] Banner J L, Guilfoyle A, James E W, et al.Seasonal variations in modern speleothem calcite growth in Central Texas USA. Journal of Sedimentary Research, 2007, 77: 615-622.
Variations in growth rates of speleothem calcite have been hypothesized to reflect changes in a range of paleoenvironmental variables, including atmospheric temperature and precipitation, drip-water composition, and the rate of soil CO2 delivery to the subsurface. To test these hypotheses, we quantified growth rates of modern speleothem calcite on artificial substrates and monitored concurrent environmental conditions in three caves across the Edwards Plateau in central Texas. Within each of two caves, different drip sites exhibit similar annual cycles in calcite growth rates, even though there are large differences between the mean growth rates at the sites. The growth-rate cycles inversely correlate to seasonal changes in regional air temperature outside the caves, with near-zero growth rates during the warmest summer months, and peak growth rates in fall through spring. Drip sites from caves 130 km apart exhibit similar temporal patterns in calcite growth rate, indicating a controlling mechanism on at least this distance. The seasonal variations in calcite growth rate can be accounted for by a primary control by regional temperature effects on ventilation of cave-air CO2 concentrations and/or drip-water CO2 contents. In contrast, site-to-site differences in the magnitude of calcite growth rates within an individual cave appear to be controlled principally by differences in drip rate. A secondary control by drip rate on the growth rate temporal variations is suggested by interannual variations. No calcite growth was observed in the third cave, which has relatively high values of and small seasonal changes in cave-air CO2. These results indicate that growth-rate variations in ancient speleothems may serve as a paleoenvironmental proxy with seasonal resolution. By applying this approach of monitoring the modern system, speleothem growth rate and geochemical proxies for paleoenvironmental change may be evaluated and calibrated
DOI:10.2110/jsr.2007.065      [本文引用:2]
[10] Wang Aoyu, Pu Junbing, Shen Licheng, et al.Natural and human factors of CO2 concentration variations in Xueyu Cave, Chongqing. Tropical Geography, 2010, 30(3): 272-277.
[本文引用:1]
[王翱宇, 蒲俊兵, 沈立成, . 重庆雪玉洞CO2浓度变化的自然与人为因素探讨. 热带地理, 2010, 30(3): 272-277.]
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
[11] Faimon J, Ličbinská M, Zajíček P.Relationship between carbon dioxide in Balcarka Cave and adjacent soils in the Moravian Karst region of the Czech Republic. International Journal of Speleology, 2012, 41(1): 17-28.
[本文引用:1]
[12] Faimon J, Ličbinská M.Carbon dioxide in the soils and adjacent caves of the Moravian Karst. Acta Carsologica, 2010, 39(3): 463-475.
Variations of soil/cave CO2 concentrations and further variablessuch as temperature, humidity, and cave visitor attendancewere studied in two sites of the Moravian Karst (Czech Republic). All the variables showed the same seasonality; they were strongly correlated with each other. The dependence of soil CO2 levels on soil air temperature and absolute humidity was confirmed. Individual effects could not be distinguished because of multicollinearity. The effect of vegetation on soil CO2 production was not recognized. Cave attendance was identified as the most significant predictor of cave CO2 levels. Other variables, soil CO2 and temperature gradients, were less significant. A spurious relationship was alternatively considered,in which external temperature was the universal predictorof cave CO2 levels.
DOI:10.3986/ac.v39i3.76      [本文引用:1]
[13] Faimon J, Ličbinská M, Zajíček P, et al.Partial pressures of CO2 in epikarstic zone deduced from hydrogeochemistry of permanent drips, the Moravian Karst Czech Republic. Acta Carsologica, 2012, 41(1): 47-57.
[本文引用:1]
[14] Holland H D, Kirsipu T V, Huebner J S, et al.On some aspects of the chemical evolution of cave water. Journal of Geology, 1964, 72(1): 36-67.
The evolution of cave waters can be divided naturally into three stages: a stage of carbonation in the soil zone, a stage of solution of calcite and/or dolomite, and a stage of equilibration with cave air. Much of the necessary physical-chemical data for the interpretation of the chemistry of cave waters is available: the solubility of $CO_{2}$ in water is well known, as is the solubility of calcite and aragonite in pure water and in solutions containing dissolved $CO_{2}$. Only the solubility of dolomite is still in doubt. Water samples from Indian Echo Cave and Carpenter Cave in Pennsylvania and from the Luray Caverns in Virginia were analyzed, and their composition was used to interpret their chemical evolution. The waters in each cave must have absorbed a large amount of $CO_{2}$ on their passage through the soil zone. Even so, the calcium and magnesium content of some of the water at Luray is so large that impossibly high $CO_{2}$ pressures would have had to prevail in the soil zone if the solubility data of Yanat''eva (1954) and of Garrels, Thompson, and Siever (1960) for dolomite were correct. We suggest that the solubility product of dolomite is probably near $10^{17}$, about two orders of magnitude higher than the value proposed by Garrels, Thompson, and Siever (1960). During the precipitation of $O_{3}$ from cave waters, the activity product $a_{Ca^{+2}}\cdot a_{CO_{3}^{-}}$ has been found to exceed the solubility product of calcite by as much as a factor of seven. In bodies of standing water from which no $CaCO_{3}$ is precipitating the activity product is very nearly equal to the accepted value of the solubility product of calcite. Precipitation of $O_{3}$ takes place essentially entirely by escape of $CO_{2}$ from cave water to the cave air. This is demonstrated convincingly by the observed constancy of the magnesium concentration in these waters during $O_{3}$ precipitation. At Luray nearly all of the water is supersaturated with respect to dolomite. However, no dolomite has been observed to precipitate in the cave even where the activity product $a_{Ca^{+2}}\cdot a_{Mg^{+2}}\cdot a_{CO_{3}^{-}}^{2}$ is in excess of $2 \times 10^{-15}$. The strontium content of $O_{3}$ precipitated from cave water depends on the mineralogy of the precipitate and on the ratio of the concentration of strontium to the concentration of calcium in the parent water. The strontium content of our Luray aragonites is always greater than the strontium content of the Luray calcites, and the absolute value of the strontium concentration can be related satisfactorily to the strontium-calcium ratio in the parent water via the distribution coefficients $k_{Sr}^{C}$ and $k_{Sr}^{A}$ determined in the laboratory. The strontium content of the cave waters at Luray is determined by the amount of dolomite dissolved by the carbonated rain water, by the strontium content of the dissolved dolomite, and by the amount and mineralogy of the $O_{3}$ deposited during equilibration with cave air.
DOI:10.1086/626964      [本文引用:1]
[15] Lang M, Faimon J, Ek C.A case study of anthropogenic impact on the CO2 levels in low-volume profile of the Balcarka Cave (Moravian Karst, Czech Republic). Acta Carsologica, 2015, 44(1): 71-80.
[本文引用:1]
[16] Faimon J, Štelcl J, Sas D.Anthropogenic CO2-flux into cave atmosphere and its environmental impact: A case study in the Císarská Cave (Moravian Karst, Czech Republic). Science of the Total Environment, 2006, 369(1-3): 231-245.
DOI:10.1016/j.scitotenv.2006.04.006      [本文引用:2]
[17] Lang M, Faimon J, Godissart J, et al.Carbon dioxide seasonality indynamic caves: The roles of ventilation modes and advective fluxes. Theoretical and Applied Climatology, 2017, 129(3/4): 1355-1372.
The seasonality in cave COlevels was studied based on (1) a new data set from the dynamically ventilated Comblain-au-Pont Cave (Dinant Karst Basin, Belgium), (2) archive data from Moravian Karst caves, and (3) published data from caves worldwide. A simplified dynamic model was proposed for testing the effect of all conceivable COfluxes on cave COlevels. Considering generally accepted fluxes, i.e., the direct diffusive flux from soils/epikarst, the indirect flux derived from dripwater degassing, and the input/output fluxes linked to cave ventilation, gives the cave COlevel maxima of 1.9 10mol m(i.e., 440 ppmv), which only slightly exceed external values. This indicates that an additional input COflux is necessary for reaching usual cave COlevel maxima. The modeling indicates that the additional flux could be a convective advective COflux from soil/epikarst driven by airflow (cave ventilation) and enhanced soil/epikarstic COconcentrations. Such flux reaching up to 170 mol sis capable of providing the cave COlevel maxima up to 3 10mol m(70,000 ppmv). This value corresponds to the maxima known from caves worldwide. Based on cave geometry, three types of dynamic caves were distinguished: (1) the caves with the advective COflux from soil/epikarst at downward airflow ventilation mode, (2) the caves with the advective soil/epikarstic flux at upward airflow ventilation mode, and (3) the caves without any soil/epikarstic advective flux. In addition to COseasonality, the model explains both the short-term and seasonal variations in C in cave air CO.
DOI:10.1007/s00704-016-1858-y      [本文引用:1]
[18] Fernández-Cortes A, Sanchez-Moral S, Cuezva S, et al.Annual and transient signatures of gas exchange and transport in the Castañar de Ibor Cave (Spain). International Journal of Speleology, 2009, 38(2): 153-162.
DOI:10.5038/1827-806X      [本文引用:1]
[19] Spötl C, Fairchild I J, Tooth A F.Cave air control on dripwater geochemistry, Obir Caves (Austria): Implications for speleothem deposition in dynamically ventilated caves. Geochimica et Cosmochimica Acta, 2005, 69(10): 2451-2468.
DOI:10.1016/j.gca.2004.12.009      [本文引用:3]
[20] Faimon J, Troppová D, Baldík V, et al.Air circulation andits impact on microclimatic variables in the Císařská Cave (Moravian Karst, Czech Republic). International Journal of Climatology, 2012, 32(4): 599-623.
DOI:10.1002/joc.v32.4      [本文引用:1]
[21] Ban Fengmei, Cai Binggui.Research on seasonal variations of the air's main environmental factors in the Shihua Cave, Beijing. Carsologica Sinica, 2011, 30(2): 132-137.
[本文引用:1]
[班凤梅, 蔡炳贵. 北京石花洞空气环境主要因子季节性变化特征研究. 中国岩溶, 2011, 30(2): 132-137.]
洞穴大气CO2浓度不仅是影响洞穴沉积物沉积(或者溶蚀)的重要 因素之一,而且在旅游洞穴,它关系到沉积物景观的稳定性以及旅游环境的舒适性.本文通过对石花洞洞穴大气温度、湿度及CO2浓度近4个水文年的观测,结果 表明:(1)洞穴温度在15℃上下波动,夏季约高1℃,主要与洞内外温差的季节性交化和旅游活动有关;(2)洞穴CO,浓度随着大气温度上升而缓慢升高, 至每年的7月上甸雨季来临时,气温、降水及土壤中CO,大幅提高,降水溶解大量的土壤CO2并渗入洞穴中,导致洞穴CO2浓度迅速上升,8月观测到的最高 浓度可达到4 334ppm,在雨季结束后,随着大气温度降低,CO2浓度缓慢下降,2月份平均值达到最低,为360~458 ppm.另外,在5月份和10月份的旅游黄金周,旅游人数的增加,洞穴CO2浓度异常增高.在进行洞穴管理与规划时,应综合考虑自然和人为因素对洞穴的影 响.
[22] Cai Binggui, Shen Linmei, Zheng Wei, et al.Spatial distribution and diurnal variationin CO2 concentration, temperature and relative humidity of the cave air: A case study from Water Cave, Benxi, Liaoning, China. Carsologica Sinica, 2009, 28(4): 348-354.
[本文引用:0]
[蔡炳贵, 沈凛梅, 郑伟, . 本溪水洞洞穴空气CO2浓度与温、湿度的空间分布和昼夜变化特征. 中国岩溶, 2009, 28(4): 348-354.]
[23] Zhang Ping, Yang Yan, Sun Zhe, et al.Comparisons between seasonal and diurnal patterns of cave air CO2 and control factors in Jiguan Cave, Henan Province, China. Environmental Science, 2017, 38(1): 60-69.
[本文引用:0]
[张萍, 杨琰, 孙喆, . 河南鸡冠洞CO2季节和昼夜变化特征及影响因子比较. 环境科学, 2017, 38(1): 60-69.]
岩溶洞穴空气CO_2变化影响次生沉积物沉积和溶蚀,它关系到洞穴旅游景观的稳定性及洞穴环境的舒适性,是岩溶作用发生的关键因素,进行洞穴空气CO_2变化的机制研究对于理解岩溶作用发生规律和现代洞穴合理保护具有重要意义.本文基于对我国南北地理分界区域河南西部鸡冠洞2011年12月至2016年5月近5年连续洞穴CO_2、水文地球化学指标、洞内外温度及湿度、大气降水和游客量等数据监测,并结合2016年5月19~20日洞穴CO_2等指标的昼夜的系统监测,分析了鸡冠洞洞穴空气CO_2时空变化特征和昼夜变化特征及其影响因素,结果表明:1在空间尺度上,越靠近洞口通风效应越强,洞穴空气p CO_2越低,越接近大气的p CO_2;洞穴结构及外界环境变化尤其是气候变化导致的土壤中p CO_2变化也会对鸡冠洞空气p CO_2变化产生影响.2在长时间尺度,鸡冠洞洞穴空气p CO_2夏季明显高于冬季,对比分析发现旅游活动和岩溶作用是其主要的影响因子.3在短时间尺度上(昼夜变化),鸡冠洞洞穴空气p CO_2变化主要受旅游活动的影响,建议景区在进行旅游开发的时候要考虑高峰期游客人数对CO_2的影响及岩溶景观的合理保护.
[24] He Haibo, Tang Jing, Liu Shuhua, et al.Spatial and temporal variation of environments and influencing factors in Loufang Cave, northeast of Sichuan Province. Tropical Geography, 2014, 34(5): 696-703.
[本文引用:0]
[贺海波, 汤静, 刘淑华, . 川东北楼房洞洞穴环境时空变化与影响因素. 热带地理, 2014, 34(5): 696-703.]
<p>基于2011年8月―2012年6月的实地监测数据,文章报道了川东北楼房洞溶洞系统气温、相对湿度(RH)、CO2体积分数、水体电导率(EC)和pH值等为期近1年的监测结果,并对其影响因素进行了分析。结果显示楼房洞洞穴系统环境存在明显的空间变化和季节变化:1)洞穴内的气温变化幅度比洞穴外小,洞穴内夏季气温比冬季高出3~5℃;2)在洞穴内,相对湿度在地下河附近小于在水池附近,显示了地下河对洞穴环境的显著影响;3)洞内监测点SLPB和QCMY处的相对湿度与空气温度出现明显相反的变化趋势,反映主要受气温控制的特点;4)雨季期间SLPB、QCMY和LZLY处的CO2体积分数出现峰值,是较强的生物呼吸作用、&ldquo;泵&rdquo;效应和较弱的通风效应等因素综合影响的结果;5)pH值的变化趋势在洞穴内外各监测点一致,原因可能是夏秋季节基岩溶蚀较强所致。6)洞内各监测点的EC值也是夏秋季节高于冬春季节,反映了气候变化导致的化学溶蚀作用可能是影响离子含量的主要因素。</p>
[25] Tong Xiaoning, Zhou Houyun, Huang Ying, et al.Spatio-temporal variation of air CO2 concentration in Baojinggong Cave, Guangdong, China. Tropical Geography, 2013, 33(4): 439-443.
[本文引用:0]
[童晓宁, 周厚云, 黄颖, . 广东英德宝晶宫CO2浓度的时空变化特征. 热带地理, 2013, 33(4): 439-443.]
于2011年12月至2013年4月每月一次对广东英德宝晶宫溶洞洞穴空气CO2浓度进行监测,结果显示洞穴空气CO2浓度存在明显的空间变化和季节变化。洞内空气CO2浓度在201×10-6?3 450×10-6之间变化,年平均值为1 018×10-6。在空间上,越靠近洞口或者通风效应越强的地方洞穴空气CO2浓度越低。在季节变化上,表现为洞穴空气CO2浓度在夏半年(5-10月)高而在冬半年(11-4月)低的特点。洞穴空气CO2浓度变化主要受洞穴通风效应和气候变化导致的植被呼吸作用和土壤微生物活动变化的影响。此外,宝晶宫特殊的洞穴结构及游客等因素也对该溶洞CO2浓度变化形成了一定的影响。
[26] Pan Yanxi, Zhou Zhongfa, Li Po, et al.Characteristics of spatial temporal variation of air environment in tourism cave and its cause analysis: A case study of the Dafeng Cave in Suiyang County, Guizhou Province. Carsologica Sinica, 2016, 35(4): 425-431.
[本文引用:1]
[潘艳喜, 周忠发, 李坡, . 旅游洞穴空气环境时空变化特征及其影响因素: 以贵州省绥阳大风洞为例. 中国岩溶, 2016, 35(4): 425-431.]
[27] Zhou Changchun, Wang Xiaoqing, Sun Xiaoyin, et al.A test analysis of environmental changes of tourism karst caves and study on influencing factors: A case of Jiutian Cave in Yiyuan County, Shandong Province. Tourism Tribune, 2009, 24(2): 81-86.
[本文引用:1]
[周长春, 王晓青, 孙小银, . 旅游洞穴环境变化监测分析及其影响因素研究: 以山东沂源九天洞为例. 旅游学刊, 2009, 24(2): 81-86.]
研究旅游洞穴的环境变化,关键是要弄清洞穴开放后,人为因素对洞穴环境的影响。通过实地测量沂源九天洞洞穴空气温度、湿度、CO2浓度、水化学特征和游客量的变化,研究旅游洞穴环境变化中的人为影响,并把它与自然影响做简单的比较。沂源溶洞环境变化研究将为洞穴景观的保护提
[28] Song Linhua, Wei Xiaoning, Liang Fuyuan.Effect of speleo-tourism on the CO2 content and temperature in Baiyun Cave, Lincheng, Hebei. Carsologica Sinica, 2003, 22(3): 230-235.
[本文引用:1]
[宋林华, 韦小宁, 梁福源. 河北临城白云洞洞穴旅游对洞穴CO2浓度及温度的影响. 中国岩溶, 2003, 22(3): 230-235.]
河北临城白云洞碳酸钙景观极其丰富但风化严重.2000年"五一"黄金周对白云洞的客流量、 温度、洞穴空气中的CO2浓度进行了系统的观测研究,并在8月、10月旅游淡季进行了对比观测.研究结果表明,洞穴旅游活动对洞穴的温度和CO2浓度的变 化有主控作用.白云洞在"五一"长假游开始前最低CO2浓度为600ppm, "五一"这一天当游客量达到 5800人时,大洞厅中的CO2达到4400ppm,温度提高了1.1℃,而狭小洞厅中CO2浓度可达到5800ppm,温度提高了2.3℃.当洞穴旅游 高峰连续维持多日时,洞穴中的CO2还会累积增加.如5月2日的游客达到4000多人时,狭小洞厅CO2达到7000ppm.旅游高峰期,洞穴CO2往往 经过一个晚上的扩散和流动后,也回不到本底值.但洞穴温度的累积不很明显.
[29] Song Linhua, Yang Jingrong, Lin Junshu, et al.Dynamically of absorbing CO2 in the recovering experiment of weathered speleothem in Yaolin Cave, Zhejiang, China. Carsologica Sinica, 1999, 18(4): 297-307.
[本文引用:1]
[宋林华, 杨京蓉, 林钧枢, . 浙江瑶琳洞风化碳酸钙景观复生试验中CO2吸收动力学研究. 中国岩溶, 1999, 18(4): 297-307.]
在H2O-CO2-CaCO3的系统中,因喀斯特水中逸出CO2,导致CaCO3沉积,形成千姿百态、琳琅满目的洞积物,如石笋、钟乳石、石林、石葡萄、卷曲石等等.由于洞穴环境的变化,使洞穴沉积石产生严重的风化作用.然而,我们试用钙碱性溶液吸收CO2,产生CaCO3沉积,可使风化的洞穴碳酸钙景观恢复其美学价值.碱性溶液吸收CO2的静态试验表明,溶液CO2的吸收过程主要发生在前8个小时,对浓碱溶液来讲,前4个小时最重要.动态试验结果说明,碱性溶液吸收CO2,沉积CaCO3的过程主要发生在60 cm流程内.试验中,滴水速度小的吸收CO2及沉积CaCO3率高于滴水速度快的碱性溶液.当一滴溶液变成薄膜流时,它吸收CO2的能力将提高24.34倍.
[30] Pu J B, Wang A Y, Yin J J, et al.PCO2 variations of cave air and cave water in a subtropical cave, SW China. Carbonates Evaporites, 2017: 1-11.
Cave CO2 is an important part of the carbon cycle in a karst system. From 2008 to 2009 the partial pressure of CO2 (PCO2) of the cave air and cave water (cave stream and dripwater) in Xueyu Cave was s
DOI:10.1007/s13146-017-0359-0      [本文引用:1]
[31] Pracný P, Faimon J, Kabelka L, et al.Variations of carbon dioxide in the air and dripwaters of Punkva Caves (Moravian Karst, Czech Republic). Carbonates Evaporites, 2016, 31(4): 375-386.
DOI:10.1007/s13146-015-0259-0      [本文引用:2]
[32] Cao Mingda, Zhou Zhongfa, Zhang Jie, et al.Effects of partial pressure of CO2 of water/gas on hydrochemical process of cave water: a case study indolomite cave system of shuanghe cave in Guizhou province. Environmental Science & Technology, 2017, 40(3): 54-60.
[本文引用:1]
[曹明达, 周忠发, 张结, . 白云岩洞穴系统中水—气CO2分压对洞穴水水文化学过程的影响: 以贵州双河洞为例. 环境科学与技术, 2017, 40(3): 54-60.]
[33] Wang X X, Wu Y H, Shen L C.Influences of air CO2 on hydrochemistry of drip waterand implications for paleoclimate study in a stream-developed cave, SW China. Acta Geochimica, 2016, 35(2): 172-183.
DOI:10.1007/s11631-015-0085-z      [本文引用:1]
[34] Pu J B, Yuan D X, Zhao H P, et al.Hydrochemical and PCO2 variations of a cave streamin a subtropical karst area, Chongqing, SW China: Piston effects, dilution effects, soil CO2 and buffer effects. Environmental Earth Science, 2014, 71(9): 4039-4049.
DOI:10.1007/s12665-013-2787-z      [本文引用:1]
[35] Wong C I, Banner J L, Musgrove M.Seasonal dripwater Mg/Ca and Sr/Ca variations driven by cave ventilation: Implications for and modeling of speleothem paleoclimate records. Geochimica et Cosmochimica Acta, 2011, 75(12): 3514-3529.
DOI:10.1016/j.gca.2011.03.025      [本文引用:1]
[36] Baldini J U L, Mc Dermot F, Hoffmann D L, et al. Very high-frequency and seasonal cave atmosphere PCO2 variability: Implications for stalagmite growth and oxygen isotope-based paleoclimaterecords. Earth and Planetary Science Letters, 2008, 272(1/2): 118-129.
DOI:10.1016/j.epsl.2008.04.031      [本文引用:1]
[37] Deininger M, Fohlmeister J, Scholz D, et al.Isotope disequilibrium effects: The influence of evaporation and ventilation effects on the carbon and oxygen isotope composition of speleothems: A model approach. Geochimica et Cosmochimica Acta, 2012, 96(11): 57-79.
DOI:10.1016/j.gca.2012.08.013      [本文引用:1]
[38] White W B.Geomorphology and Hydrology of Karst Terrains. New York: Oxford University Press, 1988.
[本文引用:1]
[39] Milanolo S, Gabrovšek F.Analysis of carbon dioxide variations in the atmosphere of Srednja Bijambarska Cave: Bosna and Herzegovina. Boundary-Layer Meteorology, 2009, 131(3): 479-493.
DOI:10.1007/s10546-009-9375-5      [本文引用:1]
[40] Liñán C, Vadillo I, Carrasco F.Carbon dioxide concentration in air within the Nerja Cave (Malaga, andalusia, Spain). International Journal of Speleology, 2008, 37(2): 99-106.
From 2001 to 2005 the CO2 concentration of the air in the interior and exterior of the Nerja Cave was studied and its relation with the air temperature and visitor number. The average annual CO2 concentration outside of the cave is 320 ppmv, whilst inside, the mean concentration increases to 525 ppmv during autumn and winter, and in the order of 750 ppmv during spring and summer. The temporal variation of CO2 content in the air of the cave is strongly influenced by its degree of natural ventilation which is, in turn, determined by the difference between external and internal air temperatures. During autumn, winter and spring, a positive correlation between the CO2 content of the air inside the cave and the temperature difference between the external and internal air was observed, such that when this difference increased, there was a higher level of CO2 within the cave. Then, the ventilation is high and CO2 levels are mainly of human origin. During summer, there was a negative correlation between CO2 and the temperature difference between the air outside and that inside the cave: when the temperature difference increases, the CO2 content within the cave is lower. At this time of the year, the renovation of the air is much slower due to the lower ventilation. A positive correlation between CO2 concentration of the air in the cave and the visitor number can only be observed during August, the month that receives the most visits throughout the year averaging 100,000.
DOI:10.5038/1827-806X.37.2.2      [本文引用:1]
[41] Chen Jiangeng, Zhang Yingjun.Formation and development of Shuanghe Cave System, Suiyang, Guizhou. Carsologica Sinica, 1994, 13(3): 247-255.
[本文引用:1]
[陈建庚, 张英骏. 贵州绥阳双河洞系的发育与成因探讨. 中国岩溶, 1994, 13(3): 247-255.]
[42] Li Po, He Wei, Qian Zhi, et al.Shuanghe Cave Geopark Research. Guiyang: Guizhou People's Publishing House, 2008: 58-101.
[本文引用:1]
[李坡, 贺卫, 钱治, . 双河洞地质公园研究. 贵阳: 贵州人民出版社, 2008: 58-101.]
[43] Sánchez-Cañete E P, Serrano-Ortiz P, Domingo F, et al. Cave ventilation is inf luenced by variations in the CO2 -dependent virtual temperature. International Journal of Speleology, 2013, 42(1): 1-8.
Dynamics and drivers of ventilation in caves are of growing interest for different fields of science. Accumulated CO2 in caves can be exchanged with the atmosphere, modifying the internal CO2 content, affecting stalagmite growth rates, deteriorating rupestrian paintings, or creating new minerals. Current estimates of cave ventilation neglect the role of high CO2 concentrations in determining air density - approximated via the virtual temperature (T-v) - affecting buoyancy and therefore the release or storage of CO2. Here we try to improve knowledge and understanding of cave ventilation through the use of T-v in CO2-rich air to explain buoyancy for different values of temperature (T) and CO2 content. Also, we show differences between T and T-v for 14 different experimental sites in the vadose zone, demonstrating the importance of using the correct definition of T-v to determine air buoyancy in caves. The calculation of T-v (including CO2 effects) is currently available via internet using an excel template, requiring the input of CO2 (%), air temperature (degrees C) and relative humidity (%).
DOI:10.5038/1827-806X.42.1.1      [本文引用:1]
[44] Milanolo S, Gabrovšek F.Estimation of carbon dioxide flux degassing from percolating waters in a karst cave: Case study from Bijambare Cave, Bosnia and Herzegovina. Chemie der Erde, 2015, 75(4): 465-474.
DOI:10.1016/j.chemer.2015.10.004      [本文引用:1]
[45] Chen Lin, Huang Jiayi, Liu Shuhua, et al.Spatial and temporal variation of environments of Baojinggong Cave, Guangdong Province, China and it's influencing factors. Earth and Environment, 2017, 45(2): 164-170.
[本文引用:1]
[陈琳, 黄嘉仪, 刘淑华, . 广东英德宝晶宫洞穴微环境时空变化特征及其主要影响因素探究. 地球与环境, 2017, 45(2): 164-170.]
[46] Benavente J, Vadillo I, Liñan C, et al.Ventilation effects in a karstic show cave and in its vadose environment, Nerja, southern Spain. Carbonates Evaporites, 2011, 26(1): 11-17.
This study deals with the process of CO 2 exchange between karst systems and the atmosphere, which is an important issue in the global carbon cycle and in climate change estimations. The study is focused on CO 2 measurements in the Nerja Cave (south Spain) and in a number of research boreholes located nearby during the 2006 2008 period. Nerja is an important show cave, with some 500,000 visitors per year. Tourists are only allowed to visit the part of the cavity nearest to the entrance. In 2006, monitoring of environmental variables began in the area closed to visits. Some anthropogenically induced peaks in the CO 2 content inside the cavity were used as a tracer to asses the ventilation patterns, which are mainly convection-driven, as in many other Mediterranean show caves. Air circulation is especially active during winter when the inflow of external precedence is important. The record from boreholes allowed identification of CO 2 concentrations of some tens of thousands of ppm in the vadose zone (<60 m). The highest CO 2 contents are shallower in summer and deeper in winter. This can be explained both by gas dissolution by downward percolation water in winter and by the increase of upward gas diffusion in summer. The overall influence of the external atmosphere, by way of the cave ventilation is presumed to mask incoming flows from the CO 2 -rich vadose environment.
DOI:10.1007/s13146-011-0050-9      [本文引用:1]
[47] Breitenbach S F M, Lechleitner F A, Meyer H, et al. Cave ventilation and rainfall signals in dripwater in a monsoonal setting: A monitoring study from NE India. Chemical Geology, 2015, 402: 111-124.
DOI:10.1016/j.chemgeo.2015.03.011      [本文引用:1]
[48] Ridley H E, Prufer K M, Walczak I W, et al.High-resolution monitoring of Yok Balum Cave, Belize: An investigation of seasonal ventilation regimes and the atmospheric and drip-flow response to a local earthquake. Journal of Cave and Karst Studies, 2015, 77(3): 183-199.
DOI:10.4311/2014ES0117      [本文引用:1]
[49] Cowan B D, Osborne M C, Banner J L, et al.Temporal variability of cave-air CO2 in central Texas. Journal of Cave and Karst Studies, 2013, 75(1): 38-50.
The growth rate and composition of cave calcite deposits (speleothems) are often used as proxies for past environmental change. There is, however, the potential for bias in the speleothem record due to seasonal fluctuations in calcite growth and drip-water chemistry. It has been proposed that the growth rate of speleothem calcite in Texas caves varies seasonally in response to density-driven fluctuations in cave-air CO2, with lower growth rates in the warmer months when cave-air CO2 is highest. We monitored CO2 in three undeveloped caves and three tourist caves spread over 130 km in central Texas to determine whether seasonal CO2 fluctuations are confined to tourist caves, which have been modified from their natural states, and the extent to which cave-air CO2 is controlled by variations in cave geometry, host rocks, cave volume, and soils. Nearly 150 lateral transects into six caves over three years show that CO2 concentrations vary seasonally in five of the caves monitored, with peak concentrations in the warmer months and lower concentrations in the cooler months. The caves occur in six stratigraphic units of lower Cretaceous marine platform carbonate rocks and vary in volume (from 100 to >100,000 m(3)) and geometry. Seasonal CO2 fluctuations are regional in extent and unlikely due to human activity. Seasonal fluctuations are independent of cave geometry, volume, depth, soil thickness, and the hosting stratigraphic unit. Our findings indicate that seasonal variations in calcite deposition may introduce bias in the speleothem record, and should be considered when reconstructing paleoclimate using speleothem proxies.
DOI:10.4311/2011ES0246      [本文引用:1]
[50] Mattey D P, Atkinson T C, Barker J A, et al.Carbon dioxide, ground air and carbon cycling in Gibraltar karst. Geochimica et Cosmochimica Acta, 2016, 184: 88-113.
We put forward a general conceptual model of CO2behaviour in the vadose zone of karst aquifers, based on physical principles of air flow through porous media and caves, combined with a geochemical interpretation of cave monitoring data. This ibraltar model links fluxes of water, air and carbon through the soil with the porosity of the vadose zone, the circulation of ground air and the ventilation of caves. Gibraltar hosts many natural caves whose locations span the full length and vertical range of the Rock. We report results of an 8-year monitoring study of carbon in soil organic matter and bedrock carbonate, dissolved inorganic carbon in vadose waters, and gaseous CO2in soil, cave and ground air. Results show that the regime of cave air CO2results from the interaction of cave ventilation with a reservoir of CO2-enriched ground air held within the smaller voids of the bedrock. ThepCO2of ground air, and of vadose waters that have been in close contact with it, are determined by multiple factors that include recharge patterns, vegetation productivity and root respiration, and conversion of organic matter to CO2within the soil, the epikarst and the whole vadose zone. Mathematical modelling and field observations show that ground air is subject to a density-driven circulation that reverses seasonally, as the difference between surface and underground temperatures reverses in sign. The Gibraltar model suggests that cave airpCO2is not directly related to CO2generated in the soil or the epikarstic zone, as is often assumed. Ground air CO2formed by the decay of organic matter (OM) washed down into the deeper unsaturated zone is an important additional source ofpCO2. In Gibraltar the addition of OM-derived CO2is the dominant control on thepCO2of ground air and the Ca-hardness of waters within the deep vadose zone. The seasonal regime of CO2in cave air depends on the position of a cave in relation to the density-driven ground air circulation pattern which is itself determined by the topography, as well as by the high-permeability conduits for air movement provided by caves themselves. In the steep topography of Gibraltar, caves in the lower part of the Rock act as outflow conduits for descending ground air in summer, and so have higherpCO2in that season. Caves in the upper Rock have highpCO2in winter, when they act as outflow conduits for rising currents of CO2-enriched ground air. Understanding seasonal flows of ground air in the vadose zone, together with the origins and seasonal regimes of CO2in cave air underpins robust interpretation of speleothem-based climate proxy records.
DOI:10.1016/j.gca.2016.01.041      [本文引用:1]
[51] Baldini J U L, Baldini L M, Mc Dermott F, et al. Carbon dioxide sources, sinks, and spatial variability in shallow temperate zone caves: Evidence from Ballynamintra Cave, Ireland. Journal of Cave and Karst Studies, 2006, 68(1): 4-11.
[本文引用:1]
[52] Vieten R, Winter A, Warken S F, et al.Seasonal temperature variations controlling cave ventilation processes in Cueva Larga, Puerto Rico. International Journal of Speleology, 2016, 45(3): 259-273.
DOI:10.5038/1827-806X      [本文引用:1]
[53] Wang Jing, Song Linhua, Xiang Changguo, et al.The impact of the soil CO2 concentration under different types of vegetation on landscape in caves. Geographical Research, 2004, 23(1): 71-77.
[本文引用:1]
[王静, 宋林华, 向昌国, . 不同植被类型覆盖下土壤CO2浓度对洞穴景观的影响. 地理研究, 2004, 23(1): 71-77.]
[54] Wang Jing.The effect of tourist activities on the speleothems and conservation strategy in the show caves. Resources Science, 2006, 28(5): 140-144.
[本文引用:1]
[王静. 旅游活动对溶洞碳酸钙沉积景观影响及保护性研究. 资源科学, 2006, 28(5): 140-144.]
随着旅游业发展,越来越多的溶洞旅游资源在我国被开发,其中的碳酸钙沉积景观是主要的旅游吸引物之一,由于其形成环境比较封闭,随着开放时间的推移,都不同程度出现了风化、破损现象,因此溶洞景区一般被视为生命周期较短。为了实现旅游资源的可持续发展,在溶洞旅游资源开发的过程中体现“在保护中开发,在开发中保护”的理念,本文从碳酸钙沉积景观形成的水文地球化学过程入手,通过分析洞穴水溶液中CO<sub>2</sub>溶解度影响因子,即水溶液温度和水溶液与洞穴环境之间的CO<sub>2</sub>分压差(ΔPCO<sub>2</sub>),从旅游活动的影响角度,对游客的热源与CO<sub>2</sub>源效应进行分析,提出了基于游客影响和景观形成过程研究的措施,即采用分流游客和水文地球化学实验方法进行景观保育以及科学的开发管理作为旅游溶洞碳酸钙沉积景观保护的有效措施。
[55] Ford D, Williams P.Karst Geomorphology and Hydrology. London: Unwin Hyman, 1989: 50-95.
[本文引用:1]
[56] Boch R, Spötl C, Risia S.Origin and palaeoenvironmental significance of lamination in stalagmites from Katerloch Cave, Austria. Sedimentology, 2011, 58(2): 508-531.
DOI:10.1111/sed.2011.58.issue-2      [本文引用:1]
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