人类活动影响下亚热带岩溶区河流水化学驱动机制与化学风化增强机制OA

Taking the Wengjiang River Basin,a first-order tributary of the Beijiang River in the Pearl River system,as a case study,this study unravels the hydrogeological processes and chemical weathering regimes synergistically driven by anthropogenic activities and bedrock lithology.It accurately identifies the controlling factors of solute sources across wet and dry seasons and quantifies the anthropogenic imprint.By integrating hydrochemical isotopic,and ionic ratio analyses,this study systematically elucidates the hydrogeochemical evolution patterns characteristics of subtropical karst regions under monsoon climate conditions. This study reveals that hydrogeological processes in the Wengjiang River Basin are strongly governed by the dominant subtropical monsoon climate,exhibiting pronounced seasonal variability.During the high-flow season,river discharge is primarily recharged by meteoric precipitation characterized by depleted isotopic signatures,resulting in a rapid hydrological responses dominated by quickflow pathways.Conversely,baseflow during the low-flow season is sustained by groundwater subjected to significant evaporative fractionation,as evidenced by reduced d-excess values.This clearly signals intensified evaporation,leading to a marked evaporative concentration effect on the river's hydrochemistry.Furthermore,reservior regulation and agricultural irrigation further attenuates flow velocities and weaken water cycle intensity during the dry season.Lithology serves as the primary controll on the spatial distribution of hydrochemistry;carbonate weathering dominates the solute composition,establishing a Ca-HCO3 hydrochemical type.In areas underlain by silicate rocks,Total Dissolved Solids(TDS)are significantly lower,and chemical compositions are more susceptible to precipitation inputs.While carbonate weathering remains the principal source of solutes year-round,the contribution of anthropogenic activities escalates markedly during the low-flow season. A key finding of this study is the quantification of anthropogenic contributions to catchment-scale chemical weathering rates.Calculation indicate that the total chemical weathering rate in the Wengjiang River Basin is 78.7 t·km-2·a-1.Notably,sulfuric acid-induced carbonate weathering accounts for an approximate 19.8％increase in the weathering rate,identifying human activities as a significant geochemical agent driving the intensification of weathering processes.Anthropogenic disturbances-exemplified by the introduction of allochthonous acids from mining activities-not only alter natural weathering trajectories but also perturb riverine ionic compositions.This effect is particularly pronounced during the low-flow season when the hydrological buffering capacity diminishes.The results further demonstrate that the hydrogeochemical characteristics of the Wengjiang River Basin emerge from the synergistic interplay of lithological background,seasonal hydrological dynamics,and high-intensity human activities.These findings underscore the pivotal regulatory role of anthropogenic disturbances in governing geochemical cycling and weathering mechanisms within karst systems. Collectively,this study systematically deciphers the hydrochemical drivers and ion sources in the Wengjiang River Basin through three interconnected perspectives:bedrock lithological control,seasonal hydrological variability,and anthropogenic disturbance.The findings not only provide a critical scientific basis for water resource protection and sustainable watershed management under intense human disturbance,but also advance the understanding of geochemical cycling in subtropical monsoon regions with complex geological settings.Furthermore,this study underscores the imperative to integrate anthropogenic impacts into future hydrogeochemical modeling and management strategies.