Seasonal variations of cave dripwater hydrogeochemical parameters and δC in the subtropical monsoon region and links to regional hydroclimate.

Stalagmites are considered natural archives of climate proxies. However, under the combined effects of atmospheric circulation patterns, precipitation, and karst environments, drip hydrogeochemical processes can be coupled and linked to each other to control cave sediment record information. Therefore, the evolution of chemistry and factors controlling the isotopic composition of the dripwater during regional precipitation migration from the surface to caves need to be evaluated. In this study, hydrogeochemical characteristics and the isotopic composition of the dripwater in the Mahuang Cave in Guizhou Province, Southwest China, including stable isotope (δC) and trace element ratios, were monitored from August 2018 to December 2020. The results showed seasonal variations in the δC, Mg/Ca, and Sr/Ca values of the dripwater in dry and wet seasons under the control of water-gas-rock reactions, such as soil CO concentrations and carbonate rock dissolution. In addition, the five monitored dripwater points in the Mahuang Cave showed fast and slow seepage due to the complex cave fractures and stratigraphy, reflecting the effects of precipitation variations to different degrees. Indeed, the δC were more sensitive to the recharge changes from extreme precipitation and drought events. Therefore, dripwater δC is a reliable indicator of the recorded hydrological signal in the southwest monsoon region.