Department of Applied Sciences, Faculty of Engineering and Science, Curtin University Malaysia, CDT 250, 98009, Miri, Sarawak, Malaysia.
Environ Monit Assess. 2024 Sep 19;196(10):954. doi: 10.1007/s10661-024-13133-9.
Relict caves in fenglin karst may typically have numerous entrances and openings. Hence, they host a variety of environments in which parameters such as light, airflow, humidity, and temperature may vary significantly over short distances. Similarly, drip water hydrochemistry, including isotopic values, may vary due to different contributions of various sources and residence time in the karst. This study investigated environmental parameters, including radiation, using hand-held instruments, along a transect within several major caves in the Niah karst of Sarawak (Malaysia). This has led to a baseline data set which showed an inverse relationship between humidity and temperature, gamma radiation levels that are about 25% of that in surrounding non-karst region, and high percentages of twilight zones in the studied caves. Airflow was found to be variable, with high values of 530 m/s in Painted Cave and 122 m/s in parts of Gan Kira passage, with flow towards the southeast at the time of the study. The hydrochemistry of the drip water and surface water was also analyzed and found to be dominantly Ca-Mg-Cl water type which indicates dissolution of minerals through water-rock interaction. In addition, the cave environment, particularly air temperature, humidity, and ventilation, also influences the drip water composition and isotopic values. Three different origins (precipitation, evaporation, and paleo-recharge) of drip water have been identified through the δO-δH diagram. Enriched isotopic values were observed in the cave entrance due to increased evaporation caused by lower humidity and higher air temperature. Factor analysis identifies the key geochemical processes responsible for the drip water chemistry. The outcome of this study provides the first baseline environmental data for the Niah caves, which could support future initiatives for sustainable management of this famous archeological site in southeast Asia.
在峰林喀斯特中，残余洞穴通常有许多入口和开口。因此，它们拥有各种环境，其中光照、气流、湿度和温度等参数在短距离内可能会有很大差异。同样，由于不同来源的贡献和在喀斯特中的停留时间不同，滴水水化学（包括同位素值）也可能会有所不同。本研究使用手持式仪器在砂拉越尼亚洞穴（马来西亚）的几个主要洞穴内的一条横切线上调查了环境参数，包括辐射。这导致了一个基线数据集，显示出湿度和温度之间的反比关系，伽马辐射水平约为周围非喀斯特地区的 25%，以及在所研究的洞穴中存在高比例的黄昏带。发现气流是可变的，在彩绘洞穴中有高达 530 m/s 的高值，在 Gan Kira 通道的某些部分有 122 m/s 的高值，在研究时气流向东南方向流动。还分析了滴水和地表水的水化学性质，发现主要是 Ca-Mg-Cl 水类型，这表明通过水岩相互作用溶解了矿物质。此外，洞穴环境，特别是空气温度、湿度和通风，也会影响滴水的组成和同位素值。通过 δO-δH 图确定了滴水的三个不同来源（降水、蒸发和古补给）。由于湿度较低和空气温度较高导致蒸发增加，在洞穴入口处观察到同位素值富集。因子分析确定了导致滴水化学的关键地球化学过程。这项研究的结果为尼亚洞穴提供了第一个环境基线数据，这可能为未来东南亚这个著名考古遗址的可持续管理提供支持。
