Abstract

Abstract The chemical composition of river waters gives a measure of the atmospheric CO2 fixed by chemical weathering processes. Since the dominating factors controlling these processes are lithology and runoff, as well as uplift and erosion, we introduce a new simplified geo-lithological map of the Alps (Alpine-Geo-LiM) that adopted a lithological classification compliant with the methods most used in literature for estimating the consumption of atmospheric CO2 by chemical weathering. The map was used together with published alkalinity data of the 33 main Alpine rivers (1) to investigate the relationship between bicarbonate concentration in the sampled waters and the lithologies of the corresponding drained basins, and (2) to quantify the atmospheric CO2 consumed by chemical weathering. The analyses confirm (as known by the literature) that carbonates are lithologies highly prone to consuming atmospheric CO2. Moreover, the analyses show that sandstone (which could have a nonnegligible carbonate component) plays an important role in consuming atmospheric CO2. Another result is that in multilithological basins containing lithologies more prone to consuming atmospheric CO2, the contribution of igneous rocks to the atmospheric CO2 consumption is negligible. Alpine-Geo-LiM has several novel features when compared with published global lithological maps. One novel feature is due to the attention paid in discriminating metamorphic rocks, which were classified according to the chemistry of protoliths. The second novel feature is that the procedure used for the definition of the map was made available on the Web to allow the replicability and reproducibility of the product.

Highlights

  • Carbon is the fourth most abundant element in the universe (Morgan and Anders, 1980; Anders and Ebihara, 1982), and it plays a vital role in Earth’s environment

  • This criterion represents a novel feature when compared with other global lithologic maps (Gibbs and Kump, 1994; Amiotte-Suchet and Probst, 1995; Amiotte-Suchet at al., 2003; Dürr et al, 2005; Hartmann and Moosdorf, 2012; Moosdorf et al, 2010), where lithologies with very different behavior in the atmospheric CO2 consumption processes were included in the generic “metamorphic” class

  • Alpine-Geo-LiM is a high-resolution geo-lithological map of the Alps. It represents a novel map when compared with published global lithological maps (Gibbs and Kump, 1994; Amiotte-Suchet and Probst, 1995; Amiotte-Suchet at al., 2003; Dürr et al, 2005; Hartmann and Moosdorf, 2012; Moosdorf et al, 2010) for two main reasons

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Summary

Introduction

Carbon is the fourth most abundant element in the universe (Morgan and Anders, 1980; Anders and Ebihara, 1982), and it plays a vital role in Earth’s environment. This element migrates continuously among four sinks: oceans, atmosphere, ecosystems, and geosphere (Holland, 1978; Berner, 2003; Kump et al, 2009). In the “short-term” carbon cycle, carbon is rapidly exchanged within surficial systems, such as oceans, biosphere, soil, and atmosphere, where the anthropogenic CO2 production is taken into account. In the “long-term” carbon cycle, carbon is slowly exchanged between the geosphere and the ocean-atmosphere system. The concentration of atmospheric CO2 mainly derives from the balance between the CO2 produced by both volcanism and metamorphism, and the atmospheric CO2 consumed by weathering of silicates and carbonates (Berner et al, 1983; Berner, 1991, 1994, 2004, 2006; Berner and Kothavala, 2001; Gislason and Oelkers, 2011; Li and Elderfield, 2013)

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