ABSTRACT

Water samples were collected and analyzed for major ions in the dry season and wet season in the Qingshuijiang River Basin, to understand ion compositions and solute fluxes as related to rock weathering and associated CO₂ consumption rates. The total dissolved solids (TDS) varied from 35.29 to 740.90 mg·L^–1, and the mean value (217.5 mg·L^–1) was significantly higher than the global rivers. Ca²⁺ and HCO₃^–, dominated the ionic composition, accounting for approximately 61.95% of the total ionic budgets. TDS and major element concentrations decreased from the upstream to the downstream. Correlation and spatial distribution analysis showed that anthropogenic activities had a significant effect on water chemistry, probably contributed some 4.87% of the dissolved solutes. The chemical weathering rates were estimated to be 65.43 t·(km²·a)^–1 (55.01 t·(km²·a)^–1 and 10.42 t·(km²·a)^–1 by carbonate and silicate weathering, respectively), comparable to the Changjiang River in China, but significantly higher than the average of world rivers. Atmospheric CO₂ consumption rates by rock weathering within the basin was 72.57 × 10⁴ mol·(km²·a)^–1, 2.95 times the global average. Furthermore, the atmospheric CO₂ consumption by the rock weathering was estimated to be 12.45 × 10⁹ mol·a^–1 (7.86 × 10⁹ mol·a^–1 by carbonate weathering and 4.59 × 10⁹ mol·a^–1 by silicate weathering, respectively), accounting for 0.11% of the global total consumption fluxes. The CO₂ consumed by rock chemical weathering in the Qingshuijiang River Basin may constitute a significant part of the global carbon budget due to the intense CO₂ consumption even though with the small area in the world.