Climate Variability Controls on CO₂ Consumption Fluxes and Carbon Dynamics for Monsoonal Rivers: Evidence From Xijiang River, Southwest China

Abstract

The feedbacks of climate variability on CO2 consumption fluxes and carbon dynamics are thought to play an important role in moderating the global carbon cycle. High‐frequency sampling campaigns and analyses were conducted in this study to investigate temporal variations of river water chemistry and the impacts of climate variability on CO2 consumption fluxes and carbon dynamics for the Xijiang River, Southwest China. Physical processes modify biogeochemical processes, so major ions display different responses to changing discharge. The annual CO2 consumption rate is (6.8 ± 0.2) × 106 ton/year by carbonate weathering and (2.4 ± 0.3) × 106 ton/year by silicate weathering. The annual CO2 consumption flux is much higher than most world rivers, and strong CO2 consumption capacities are observed in catchments in Southwest China. Lower negative δ13CDIC values are found in the high‐flow season which corresponds with high temperatures compared to those in the low‐flow season. High discharge will accelerate material transport, and high temperatures will increase primary production in the catchment, both of which can be responsible for the shift of δ13CDIC values in the high‐flow season. Increased mineral weathering and biological carbon influx in the catchment are the main factors controlling carbon dynamics. Overall, these findings highlight the sensitivity of CO2 consumption fluxes and carbon dynamics in response to climate variability in the riverine systems.

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

“…Rivers are primary conduits transporting terrestrial weathering loads from continents to the ocean (Li & Bush, 2015; McClanahan, Polk, Groves, Osterhoudt, & Grubbs, 2016; Schulte et al, 2011). In addition, chemical weathering is the main source of dissolved loads in rivers, which removes large amounts of atmospheric CO 2 and plays a critical role in the global carbon cycle (Clow & Mast, 2010; Gaillardet, Dupré, Louvat, & Allègre, 1999; Zhong et al, 2018). Carbonate dissolution consumes nearly 12.3 × 10 12 mol of carbon per year and is an important carbon sink in short‐term carbon balance (Gaillardet et al, 1999).…”

“…Carbonate dissolution consumes nearly 12.3 × 10 12 mol of carbon per year and is an important carbon sink in short‐term carbon balance (Gaillardet et al, 1999). Previous studies have established that hydrological processes govern riverine solute transport and carbon cycling by affecting biogeochemical reactions (Maher & Chamberlain, 2014; Zhong et al, 2018). Furthermore, the chemical weathering processes can be altered easily through changing hydrological conditions (Gareis & Lesack, 2017; Torres, West, & Clark, 2015; Zhong et al, 2018).…”

Spatial Variations of Trace Metals and Their Complexation Behavior with DOM in the Water of Dianchi Lake, China

“…After hydrochemical analysis, the water of DC was defined as HCO 3 -Ca type, and the highest HCO 3 − concentration was observed at lake inlet I-3. Water chemistry in Lake Dianchi was dominated by carbonate mineral weathering due to major cation and anions [25,26]. The hydrochemical parameters data have been exhibited in Table 1.…”

“…The milligram equivalent ratio of Mg 2+ /Ca 2+ also reflected the lithology of water erosion area. If this value is from 0.01 to 0.26, suggested a limestone source, and the lithology would be dolomite if this value is above 0.85 [25,26]. The lithology in central lake region predominated with dolomite, but predominated with dolomite limestone at inlets.…”

“…DOM is a mixture of diverse components, and metal-binding affinity is defined by the concentration ratio of DOM-bound metals relative to DOC. Cu and Fe in natural waters and effluents are significantly influenced not only by DOM concentration but also by the aromaticity of DOM [20,26]. The assessment of DOM optical properties may be useful to understand the trace metal-DOM interaction and metal bioavailability in natural and effluent water systems [10].…”