Hydrological regulation of chemical weathering and dissolved inorganic carbon biogeochemical processes in a monsoonal river

Abstract

To better understand the mechanisms relating to hydrological regulations of chemical weathering processes and dissolved inorganic carbon (DIC) behaviours, high-frequency sampling campaigns and associated analyses were conducted in the Yu River, SouthChina. Hydrological variability modifies the biogeochemical processes of dissolved solutes, so major ions display different behaviours in response to discharge change. Most ions become diluted with increasing discharge because of the shortened reactive time between rock and water under high-flow conditions. Carbonate weathering is the main source of major ions, which shows strong chemostatic behaviour in response to changes in discharge. Ions from silicate weathering exhibit a significant dilution effect relative to the carbonate-sourced ions. Under high temperatures, the increased soil CO 2 influx from the mineralisation of organic material shifts the negative carbon isotope ratios of DIC (δ 13 C DIC ) during the high-flow season. The δ 13 C DIC values show a higher sensitivity than DIC contents in response to various hydrological conditions. Results from a modified isotope-mixing model (IsoSource) demonstrate that biological carbon is a dominant source of DIC and plays an important role in temporal carbon dynamics. Furthermore, this study provides insights into chemical weathering processes and carbon dynamics, highlighting the significant influence of hydrological variability to aid understanding of the global carbon cycle.

Hydrogeochemical Dynamics and Response of Karst Catchment to Rainstorms in a Critical Zone Observatory (CZO), Southwest China

“…HCO − 3 , Ca 2+ , and Mg 2+ in both SU and SP have near-zero b values and low CV C /CV Q ratios (<< 1), indicating chemostatic behaviors. The three ions in Yu River (Liu J. et al, 2020) and Xijiang River (Zhong et al, 2018) display similar export regime with this study, but their chemostatic behaviors are relatively weaker. Conversely, there are scenes of b > 0 for the three ions in the Bode River of central Germany (Musolff et al, 2015) and Ca 2+ in SU of Los Alamos (Koger et al, 2018), showing an enrichment trend.…”

Unravelling the hydrological effects on spatiotemporal variability of water chemistry in mountainous rivers from Southwest China

“…Hydrologic regulations were recognized as the main control on solute dynamics (Maher & Chamberlain, 2014; Torres et al, 2015; Zhong et al, 2020), by affecting both the chemical weathering processes and biogeochemical processes (Liu et al, 2020; Zhong et al, 2018). C ‐ Q relationships have been widely used to interpret changing biogeochemical processes under various hydrological conditions (Torres et al, 2015; Zhong et al, 2018).…”

“…There were negative power-law relationships between HCO 3 − and runoff ( Figure 6(a)), which were associated with the changing fluid transit time (Figure 7). As runoff increases, the reactive mineral surface in contact with fluids will increase ( Figure 7) (Liu et al, 2020;Zhong et al, 2020). Furthermore, carbonate weathering shows fast dissolution kinetics, which release HCO 3 − into the dissolved phase (Zhong et al, 2020).…”

Continuous production-degradation of dissolved organic matter provides signals of biogeochemical processes from terrestrial to marine end-members

“…This behavior is confirmed by radio-carbon dating, which shows an increase of 14 C ages from soil to inland waters and then to marine waters (Catalań et al, 2016). Importantly, photochemical and microbial degradation processes along with hydrological processes, particularly carbonate and silicate weathering, would play important roles in overall transformation processes along with transport of chemical species (Catalań et al, 2016;Igarza et al, 2019;Mostofa et al, 2019;Liu et al, 2020;Zhong et al, 2020;Yi et al, 2021).…”