典型白云岩洞穴水化学变化特征及其沉积差异对比研究

Comparative study on the characteristics of hydrochemical changes and sedimentary differences in typical dolomite caves

为揭示不同洞穴系统中水–气化学过程变化特征及其对沉积环境的影响,于2018年8月~2019年7月对绥阳县温泉镇双河洞穴系统一级支洞大风洞和麻黄洞内9个滴水点的空气及水化学指标开展了一个完整水文年的动态监测,并运用饱和指数法和水化学计量方法进行研究分析,结果表明:(1)大风洞和麻黄洞9个滴水点水化学类型除MH6#外均为HCO_(3)-Ca·Mg型,而MH6#因SO_(4)^(2-)浓度偏高,水化学类型为HCO_(3)·SO_(4)^(-)Ca·Mg型;(2)研究区内洞穴水水化学组分主要来源于岩石风化且受碳酸、硫酸和硝酸的共同作用;(3)通过水–气CO_(2)分压差数据和相关性分析可知,麻黄洞沉积环境整体优于大风洞;(4)大风洞和麻黄洞沉积环境主要受到气流交换模式、水–岩作用强度、稀释效应、先期方解石沉积(PCP)过程和人类旅游活动的影响,洞内沉积环境总体表现为旱季优于雨季、Ⅱ类滴水点优于Ⅰ类滴水点的特征。

To reveal the influence factors of water-gas chemical process on the sedimentary environment and its change characteristics in different cave systems,the dynamic monitoring of air and water chemical indexes at 9 dripwaters in the Shuanghe Cave system’s Dafeng Cave and Mahuang Cave was conducted for a complete hydrological year using the saturation index and water stoichiometry method for research and analysis,from August 2018 to July 2019.The results showed that:(1)the hydrochemical type of the 9 dripwaters in the Dafeng Cave and Mahuang Cave was HCO_(3)-Ca·Mg except for MH6#,whereas the hydrochemical type of MH6#was HCO3·SO_(4)-Ca·Mg due to the high concentration of SO_(4)^(2-).(2)The hydrochemical composition of the cave water in the study area mainly originates from rock weathering and is affected by the combined action of carbonic,sulfuric,and nitric acids.(3)Through the differential partial pressure of water-gas CO_(2) and correlation analysis,it was determined that the sedimentary environment of the Mahuang Cave is better than that of the Dafeng Cave.(4)The sedimentary environment of the Dafeng Cave and Mahuang Cave is mainly affected by the airflow exchange mode,water-rock interaction intensity,dilution effect,prior calcite precipitation(PCP)process,and tourism activities.The sedimentary environment of the Cave shows the characteristics of dry season better than rainy season,typeⅡdripwater better than typeⅠdripwater.