Abstract
Abstract. The southeastern coastal region is one of the most developed and populated areas in China. Meanwhile, it has been severely impacted by acid rain over many years. The chemical compositions and carbon isotope compositions of dissolved inorganic carbon (δ13CDIC) in river water in the high-flow season were investigated to estimate the chemical weathering and associated atmospheric CO2 consumption rates as well as the acid-deposition disturbance. Mass balance calculations indicated that the dissolved loads of major rivers in the Southeast Coastal River Basin (SECRB) were contributed to by atmospheric (14.3 %, 6.6 %–23.4 %), anthropogenic (15.7 %, 0 %–41.1 %), silicate weathering (39.5 %, 17.8 %–74.0 %) and carbonate weathering inputs (30.6 %, 3.9 %–62.0 %). The silicate and carbonate chemical weathering rates for these river watersheds were 14.2–35.8 and 1.8–52.1 t km−2 a−1, respectively. The associated mean CO2 consumption rate by silicate weathering for the whole SECRB was 191×103 mol km−2 a−1. The chemical and δ13CDIC evidence indicated that sulfuric and nitric acid (mainly from acid deposition) were significantly involved in the chemical weathering of rocks. There was an overestimation of CO2 consumption at 0.19×1012 g C a−1 if sulfuric and nitric acid were ignored, which accounted for about 33.6 % of the total CO2 consumption by silicate weathering in the SECRB. This study quantitatively highlights the role of acid deposition in chemical weathering, suggesting that the anthropogenic impact should be seriously considered in estimations of chemical weathering and associated CO2 consumption.
Highlights
Chemical weathering of rocks is the key process that links geochemical cycling of solid earth to the atmosphere and ocean
Carbonate weathering and anthropogenic inputs account for 30.6 % (3.9 %– 62.0 %) and 15.7 % (0 %–41.1 %), respectively
River water in the southeastern coastal region of China is characterized by high proportions of Na+, K+ and dissolved SiO2, indicating that the water chemistry of the rivers in the Southeast Coastal River Basin (SECRB) is mainly controlled by silicate weathering
Summary
Chemical weathering of rocks is the key process that links geochemical cycling of solid earth to the atmosphere and ocean. As a net sink of atmospheric CO2 on geologic timescales, estimations of silicate chemical weathering rates and the controlling factors are important issues that are related to long-term global climate change (e.g., Raymo and Ruddiman, 1992; Négrel et al 1993; Berner and Caldeira, 1997; Gaillardet et al, 1999; Kump et al, 2000; Amiotte-Suchet et al, 2003; Oliva et al, 2003; Hartmann et al, 2009; Moon et al, 2014). As an important component in the Earth’s critical zone (U.S National Research Council Committee, 2001), rivers serve as integrators of various natural and anthropogenic processes and products in a basin, and as carriers, transporting the weathering products from the continent to the ocean. Liu et al.: Geochemistry of the dissolved loads during high-flow season of rivers son et al, 1996; Galy and France-Lanord, 1999; Huh, 2003; Millot et al, 2002, 2003; Oliva et al, 2003; West et al, 2005; Moon et al, 2007; Noh et al, 2009; Shin et al, 2011; Calmels et al, 2011; Li et al, 2014)
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