Chemical weathering and CO2 consumption rates of rocks in the Bishuiyan subterranean basin of Guangxi, China

Abstract

To investigate the influence of chemical weathering on CO₂ consumption, an analysis was performed of water chemistry by applying water chemistry equilibria methods in the Bishuiyan subterranean basin, SW China. The average value of total ion concentrations (TZ⁺) was 1,854.97 μEq/L, which was significantly higher than the global average value (TZ⁺ = 1,250 μEq/L). Ca²⁺ and HCO₃⁻ were the main ionic constituents in the waters. SO₄²⁻ and NO₃⁻ concentrations were relatively higher than other anion concentrations, and Cl⁻ concentrations were consistently the lowest. Dissolved load balance models result showed that carbonate weathering, silicate weathering, and atmospheric input were the primary ionic contributors, wherein the effects of carbonate weathering > silicate weathering > atmospheric input for the whole catchment, with the exception of Taiping, where silicate weathering was prominent over carbonate weathering. In addition, these analyses indicated that the erosion via rock weathering was also affected by atmospherically derived CO₂ and allogenic acids. The estimated yield by quantitative calculation for the carbonate weathering rate was 59.7 t/(km² year), which was 4.40 times higher than that of silicate weathering rate. Further, the carbonate and silicate weathering components of the carbon sink accounted for 71.2% and 28.8%, respectively, of the total basin rock weathering carbon sink.