Chemical denudation in the Yellow River and its geomorphological implications

Abstract

Chemical denudation plays an important role in regulating atmospheric CO2 balance and modulating global climate. With weekly collected water samples at three stations on the Yellow River mainstem from July 2011 to July 2012, we investigate its chemical denudation characteristics on the basis of water geochemistry and discuss the geomorphological implications. Because of limited atmospheric inputs into the Yellow River, chemical weathering is of first importance in affecting the chemical compositions of its water geochemistry. As a result of extensive carbonates within the watershed, carbonate dissolution is the major source of the dissolved solids, accounting for 28–33.7% of the total dissolved solids (TDS). In contrast, silicate weathering contributes only 9.9–10.9%. With a mean TDS concentration of 639mgl−1, the TDS flux into the ocean is estimated at 16Mtyr−1, corresponding to a specific chemical denudation rate of 21.3tkm−2yr−1. Comparative analysis with physical erosion suggests the dominance of physical erosion over chemical weathering in providing riverine loads. Rapid removal by physical erosion may have restrained the chemical denudation processes. Rock weathering consumes, on average, 2.3Mt of atmospheric CO2 during the one-year-long sampling campaign, accounting for 0.22–0.31% of the global annual CO2 consumption through chemical weathering. Of the CO2 consumed, 74% is caused by carbonate weathering and 26% by silicate weathering, indicating the predominance of carbonate weathering in consuming atmospheric CO2 within the watershed.