Abstract
ABSTRACT: Chemical weathering and soil removal rates are responsible for the Earth’s landscape, composition of surface and groundwater, producing the soils and buffering the composition of the atmosphere. This study aimed to assess the chemical weathering and soil removal rates in the Sorocaba River basin, Sao Paulo State, Brazil, allowing answering the questions about the dynamics of fluvial transport of dissolved and suspended solids, the chemical weathering processes and associated atmospheric/soil CO2 consumption, and the relationship between chemical weathering and soil erosion rates. The annual specific flux of total suspended solids and total dissolved solids were 49.59 and 60.97 t/km2/yr. The chemical weathering process dominant in the Sorocaba River basin was the monosiallitization (RE = 2.4), with an associated atmospheric/soil CO2 consumption of 2.3 × 105 mol/km2/yr. The chemical weathering and soil removal rates were 7.2 and 29.8 m/Myr, respectively, indicating a soil thickness reduction. Finally, the soil removal rate in the Sorocaba River basin is almost 3-fold higher than the Cenozoic soil removal rates, being this difference related to the current land use which increased the soil removal processes.
Highlights
Chemical weathering is typically a destructive process, which allows the development of new minerals from the weathering of primary minerals
The Friver of dissolved chemical species, total dissolved solids (TDS) and total suspended solids (TSS) were quantified in the specific transport form, the result of the product between CWAV and average discharge of the study period weighted by surface of study area, according to the stochastic methodology proposed by Probst (1992)
This study aimed to evaluate the chemical weathering of rocks and soil removal processes that occur in the Sorocaba River basin and allowed a better understanding of the dynamics of fluvial transport of dissolved and suspended solids, of the chemical weathering processes and the atmospheric/soil CO2 consumption and of the relationship between chemical weathering and soil removal rates
Summary
Chemical weathering is typically a destructive process, which allows the development of new minerals from the weathering of primary minerals. Many studies have been carried out to assess chemical weathering and soil erosion rates using mass-balance models adjusted to atmospheric and anthropogenic (mainly originating from domestic sewage and industrial and agricultural activities) contributions, once the total river fluxes integrate the contributions of these different sources (Probst 1986, 1992, Meybeck 1987, Lasaga et al 1994, White and Blum 1995, Boeglin and Probst 1996, 1998, Boeglin et al 1997, Gaillardet et al 1999, Semhi et al 2000, Millot et al 2002, Meybeck et al 2003, Walling and Fang 2003, Riebe et al 2004, Chakrapani 2005, Weijden and Pacheco 2006, Louvat et al 2008, Gurumurthy et al 2012, Laraque et al 2013, Li et al 2014). The interest in assessing the chemical weathering and soil removal rates in watersheds under different geological and climatic setting occurred in Brazil (Stallard and Edmond 1981, 1983, 1987, Moreira-Nordemann 1980, 1984, Mortatti et al 1997, 2008, Gaillardet et al 1997, Bortoletto Junior et al 2002, Conceição and Bonotto 2003, 2004, Mortatti and Probst 2003, Bonotto et al 2007, Sardinha et al 2010, Fernandes et al 2012, 2016a, Conceição et al 2015, Couto Júnior et al 2019, Spatti Júnior et al 2019)
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