Driving Factors and Hydrological Response of DOC Dynamics in Karst Cave Water under Different Hydrological Pathways

<p indent="0mm">To investigate the hydrological responses of dissolved organic carbon (DOC) in cave water under different flow paths, this study conducted systematic field monitoring at five cave water sites in Mahuang Cave. The driving factors behind the dynamic variations in DOC under different hydrological pathways were analyzed, and their potential implications for paleoclimate reconstruction were explored. The results show that DOC concentrations in cave water followed the order: MH2 <sc>(1.81 mg/L)</sc> &gt; MHJJ <sc>(1.66 mg/L)</sc> &gt; MH5 <sc>(1.46 mg/L)</sc> &gt; MH3 (1.26 mg/L) &gt; MH4 <sc>(1.17 mg/L),</sc> indicating higher DOC levels in cave drip water compared to underground river water and fissure water. The DOC dynamic was primarily driven by meteorological factors such as rainfall and temperature, as well as water–rock interactions caused by climatic changes. Differences in residence time, water storage and recharge capacity of heterogeneous aquifers, connectivity of karst conduits, and recharge sources of karst water among the hydrological pathways led to varying DOC responses to external hydrological changes. Among the sites, MH2 (slow infiltration drip water) exhibited a slower response to environmental changes, whereas MH3 (rapid infiltration drip water) and MH4 (shaft flow drip water) responded more significantly. Meanwhile, MHJJ (seasonal drip water) and MH5 (underground river) showed rapid responses to external climatic variations.Additionally, variations in peak DOC concentrations among different hydrological pathways may influence the formation of organic layers in speleothems. Therefore, when reconstructing paleoclimate records based on speleothem laminae, it is indispensable to consider the impacts of hydrological pathways in heterogeneous aquifers on DOC dynamics.