The Response of Hydrogeochemical Dynamics of Cave Drip Water to Intense Precipitation Event

The hydrochemical parameters of cave drip water serve as valuable archives of external environmental signals and climatic variations. Short-term heavy precipitation events provide drip water datasets with superior temporal resolution compared to annual or monthly-scale studies, offering critical insights into fracture network evolution, hydrochemical dynamics, and hydrological response mechanisms. This study examines the hydrochemical responses of drip water parameters and elemental ratios to intense rainfall events in Guangshun Cave, Guizhou Province, through systematic monitoring of four drip sites (GS-0, GS-1, GS-3, GS-5) during a 43.60 mm/3-hour precipitation episode (June 16-18, 2024). High-resolution sampling at 4-hour intervals, combined with meteorological data, enabled characterization of hydrochemical variations and hydrological classification of drip points. Results demonstrate distinct response patterns: the percolation-dominated GS-0 site, exhibiting higher drip rate variability and extreme values, responded more rapidly to rainfall than infiltration-dominated sites (GS-1, GS-3, GS-5) with lower variability. Contrasting fracture densities and water storage capacities in the vadose zone drove differential hydrochemical processes—dissolution dominated GS-0 and GS-1, dilution controlled GS-3, while GS-5 exhibited alternating dissolution-dilution regimes. Infiltration-dominated sites showed Mg2+ and Sr2+ depletion via dilution, contrasting with percolation-dominated sites where dissolution enhanced cation concentrations; Although dissolution and dilution effects exhibit variations among individual drip sites, both Mg/Ca and Sr/Ca ratios across all monitoring points demonstrate coherent variability during intense precipitation episodes, displaying strong inverse correlations with Ca2+ concentrations, as evidenced by correlation coefficients of –0.96 to –0.64 and –0.91 to –0.68, respectively. These ratios exhibited weaker correlations with Mg2+/Sr2+ concentrations and inversely covaried with Ca2+.