New estimate of chemical weathering rate in Xijiang River Basin based on multi-model

Abstract

Hydrochemistry and Sr isotope compositions were measured in water samples collected during high- and low-water periods from the main stream and tributaries of the Xijiang River Basin in southern China. The primary weathering end-members were analyzed and calculated using the multi-model combination and classic hydrogeochemical method. During the high-water period, structural factors were found to be the main factors controlling chemical weathering in the basin, whereas anthropogenic activity and other random factors had a negligible influence. During the low-water period, both structural and random factors controlled chemical weathering. Through path-model and semi-variance analyses, we determined and quantified the relationship between the main weathering sources, whose results were stable; this is consistent with the inversion model. The total dissolved substances were mainly derived from carbonate weathering, which was approximately 76% (0–96%) while silicate weathering accounted for only 14% (5–19%). The inversion model results showed that the optimum silicate weathering rate was 7.264–35.551 × 103 mol/km2/year, where carbonic acid was the main factor that induces weathering. The CO2 flux consumed by rock weathering in the basin during the study period was 150.69 × 109 mol/year, while the CO2 flux consumed by carbonic acid weathering of carbonate (CCW) and silicate rocks (CSW) was 144.47 and 29.45 × 109 mol/year, respectively. The CO2 flux produced by H2SO4 weathered carbonate (SCW) was 23.23 × 109 mol/year.

The effects of rainfall on groundwater hydrogeochemistry and chemical weathering

“…A set of a priori parameters values was chosen to constrain different sources. Some of these parameters for the carbonate and evaporite were obtained from (Millot et al, 2003;Chetelat et al, 2008;Zhang et al, 2021). The rainwater collected in this monitoring was used as the parameters for rain.…”

Chemical Weathering and CO2 Consumption Inferred from Riverine Water Chemistry in the Xi River Drainage, South China

“…The chemical weathering of terrestrial silicate rocks constitutes a significant carbon sink in global biogeochemical cycles on geological time scales [ 1 , 2 , 3 , 4 , 5 , 6 ]. The CO 2 consumption flux by silicate rock weathering controls the long-term global carbon cycle time scales of millions of years [ 7 , 8 , 9 , 10 ]. This consumed CO 2 is chemically locked in marine sediments and cannot be easily released back into the atmosphere on short timescales.…”

“…This consumed CO 2 is chemically locked in marine sediments and cannot be easily released back into the atmosphere on short timescales. Silicate rock weathering, along with organic carbon burial, thus controls the atmospheric CO 2 content on million- to 100-million-year geological time scales and drives the evolution of the global climate [ 10 , 11 ]. The chemical weathering of carbonate, perhaps surprisingly, also consumes atmospheric CO 2 .…”

“…Carbonate dissolution consumes approximately 12.3 × 10 12 mol of carbon per year [ 11 ]. The inorganic carbon fluxes from carbonate rock weathering are carbon sinks on the 10 2 - to 10 3 -year geological timescale [ 10 , 12 ]. For further research into the carbon sink associated with chemical weathering and their controlling mechanisms, the contribution of each end-member must be more accurately determined, especially in rivers as they represent short circuits between the terrestrial and marine water cycles.…”

“…When carbonate minerals precipitate, half of HCO 3 − reacts to form gaseous CO 2 in the atmosphere and aqueous CO 2 in the ocean. Unless gypsum or barite can precipitate, the participation of sulfuric acid in carbonate weathering is essentially a net release of CO 2 into the atmosphere [ 10 , 15 ]. If the sulfuric acid weathering of carbonate rocks is ignored, the CO 2 consumption involved in silicate weathering will be overestimated.…”