Drip water Geochemistry of Niah Great Cave, NW Borneo, Malaysia: a base line study

A base line study was conducted to understand the geochemical variations of drip waters in Niah Great Cave, Sarawak, NW Borneo of Malaysia. Drip waters were collected at three different sites within the cave (D6: SW entrance enroute to painted Cave; D5: centre of the Great Cave, and D8: west mouth Great Cave entrance). The collected samples were analysed for temperature, pH, EC, major elements, non purgeable organic carbon, δ13C and δ18O. Mg/Ca and Sr/Ca ratios, ionic strength, partial pressure of CO2 and saturation indices of carbonate minerals have been used to dictate the geochemical signatures of drip water compositions. The data reveal a wide range of major ion chemistry at three different sites within the cave. The δ13C values in drip waters range from −10.58 to −10.09 ‰. The enriched and the depleted δ13C values are noted at the entrances of the cave due to degassing of water CO2 and warmer air results in lighter fractions of δ13C. The δ18O values range from −6.89 to –6.16 ‰. Minor δ18O deviation in the drip waters are due to the variation in drip rates as faster drip rates show depleted isotopic composition and vice versa. The spatial variability of drip water chemistry results due to water–rock interaction at various conditions of subsurface flow path. This study gives a basis for interpreting the varying controls on drip water chemistry in the cave

Introduction

Mineral dust is a key player in the Earth system with important impacts on the global energy and carbon cycles, acting on timescales of minutes to millennia. Megatons of dust are lifted each year into the atmosphere by strong near-surface winds over the world's arid regions. Such winds can be generated by short-lived small-scale dust devils, cold outflow from thunderstorms up to continental-scale dust storms. The tiny dust particles can be lifted to great heights and transported thousands of kilometres across the globe. Once airborne, dust affects radiation and clouds and thereby also precipitation. Dust also alters chemical processes in the atmosphere and deteriorates air quality and visibility for aviation. Dust is removed from the atmosphere by gravitational settling, turbulence or precipitation. Deposition on plants, snow and ice changes the amount of reflected solar radiation. Iron and other nutrients contained in dust fertilise both terrestrial and marine ecosystems. Dust deposits in glaciers, soils and ocean or lake sediments constitute an important archive of past environmental changes. For the first time, this book gives a detailed account of the state of the art in the fascinating, highly interdisciplinary and dynamically evolving area of dust research including results from field campaigns, laboratory, aircraft, satellite, modelling and theoretical studies. This chapter gives a short introduction into the topic, placing several recent developments in dust research into a historical context