Rock Weathering Characteristics and the Atmospheric Carbon Sink in the Chemical Weathering Processes of Qingshuijiang River Basin

Abstract

Carbon sink produced during rock weathering is critical to global carbon cycles. In this work, the major ion chemistry and ion sources of Qingshuijiang River Basin were investigated. The principal component analysis, mass balance approach and deduction method were applied for estimating the weathering rate and atmospheric CO2 consumption via the chemical weathering of rocks. The results demonstrated that the chemical weathering of carbonate and silicate rocks within the drainage basin was the main source of the dissolved chemical substances in the Qingshuijiang River Basin, prior to carbonate rock weathering. Some 58.28% of the total dissolved chemical substances were derived from the chemical weathering of carbonate rock, 17.38% from the dissolution of silicate rock, and 17.74% from atmospheric CO2 contribution rates. The chemical weathering rate of this catchment was estimated to be 109.97t·(km2·a)-1, which was comparable to Wujiang River Basin, but higher than the average of global rivers. Furthermore, the atmospheric CO2 consumption rate was estimated to be 7.25×105 mol·(km2·a)-1. The CO2 flux consumed by the rock chemical processes within this catchment was 12.45×109 mol·a-1, of which about 63.13%(7.86×109 mol·a-1) was resulted from carbonate weathering and 36.87%(4.59×109 mol·a-1) from silicate weathering. The CO2 consumed by rock chemical weathering in the Qingshuijiang River reduced the atmospheric CO2 level and constituted a significant part of the global carbon budget. Correlation and spatial distribution analysis of SO42-, F-, NO3- showed that anthropogenic activities contributed remarkably to dissolved solutes and associated CO2 consumption worldwide, and anthropogenic inputs probably contributed some 4.87% to the dissolved solutes in the Qingshuijiang River.