Abstract
The dynamics of riverine solutes’ contents and sources reflect geological, ecological, and climatic information of the draining basin. This study investigated the influence of climatic variability on solute dynamics by the high-frequency hydrogeochemical monitory in the Liujiang River draining karst terrain of Guangxi Province, SW (Southwestern) China. In the study river, the content-discharge (C-Q) patterns of riverine solutes indicate that the majority of riverine solutes show similar dilution and near chemostatic behaviors responding to increasing discharge, especially geogenic solutes (such as weathering products from carbonate, silicate, and sulfide oxidation), whereas exogenous solutes (such as atmospheric input to riverine sulfate) and biological solutes (such as soil CO2) show higher contents with increasing discharge. Besides, the biological carbon is the main driver of the chemostatic behaviors of total dissolved inorganic carbon (DIC). The forward model results show that carbonate weathering dominates the water chemistry, and the weathering rates are intensified during high flow period due to additional inputs of weathering agents, i.e., the biologic carbonic acid from dissolution of soil CO2, indicated by δ13CDIC. In addition, there exists the strong capacity of CO2 consumption that is heavily dependent on climatic variables such as precipitation and air temperature in this study river. Our study highlights the impact of climatic variability on solutes dynamics and chemical weathering and thus must be better addressed in C models under future climate change scenarios.
Highlights
CO2 consumption during rock chemical weathering by reaction with carbonic and other strong acids are part of the important biogeochemical cycle of carbon and act on regulating the climate on Earth, even on shorter timescales [1,2,3]
We focused on temporal research to (1) explore the behaviors of riverine solutes in a hydrological year by means of C-Q relations; (2) understand the hydrological and the biogeochemical responses of chemical weathering, CO2 consumption, dissolved carbon, and sulfur dynamics in a typical karst river; (3) trace water, riverine sulfate, and dissolved inorganic carbon (DIC) sources and estimate their contributions constrained by stable isotopic tracers in the study catchment area under various climatic conditions
According to a high-frequency variation in riverine solutes contents and multiple sable isotopic tracers, this study investigated chemical weathering, CO2 consumption, and riverine solute sources and their contributions impacted by climatic variabilities in the typical monsoonal river
Summary
CO2 consumption during rock chemical weathering by reaction with carbonic and other strong acids (such as sulfuric and nitric acids) are part of the important biogeochemical cycle of carbon and act on regulating the climate on Earth, even on shorter timescales [1,2,3]. Numerous studies have focused on chemical weathering and CO2 consumption in carbonate-dominated catchments to understand local and even global carbon cycles [3,4]. Current estimation of global CO2 consumption by rock weathering varies from 0.1 to 0.44 Gt C a−1 [4,5]. These estimates have some uncertainty, largely due to the spatial variations (such as lithology, soil development, vegetation, precipitation, temperature, anthropogenic activity, etc.), which are inevitable on the continent [6]. A temporal rather than a spatial approach may be possible to obtain a stronger correlation between weathering flux and climate
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