Chemical weathering and atmospheric/soil CO2 uptake in the Andean and Foreland Amazon basins

Moquet, Jean-Sébastien; Crave, Alain; Viers, Jérôme; Seyler, Patrick; Armijos, Elisa; Bourrel, Luc; Chávarri, Eduardo; Lagane, Christelle; Laraque, Alain; Casimiro, Waldo Sven Lavado; Pombosa, Rodrigo; Noriega, Luis; Vera, Andrea; Guyot, Jean‐Loup

doi:10.1016/j.chemgeo.2011.01.005

Cited by 129 publications

(108 citation statements)

References 101 publications

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“…The original Be isotope data of most of these samples is published in . The discharge data used to calculate fluxes in Table 2 of the main text are from the following sources: Amazon at Obidos (Filizola and Guyot, 2009); Solimoes at Manacapuru (Coe et al, 2002); Negro at Manaus (Moreira-Turcq et al, 2003); Andean Rivers (Madre de Dios, Grande, upper Soli, Ucayali) (Moquet et al, 2011); Beni (Guyot et al, 1993).…”

mentioning

confidence: 99%

Earth surface erosion and weathering from the 10Be (meteoric)/9Be ratio

Blanckenburg

Bouchez

Wittmann

2012

Earth and Planetary Science Letters

105

142

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: Earth surface erosion and weathering from the 10Be (meteoric)/9Be ratio. v351-352, pp 295-305 2012, doi j/epsl.2012.07.022 AbstractThe isotope ratio of the meteoric cosmogenic nuclide 10 Be to the mineral-derived stable isotope 9 Be discloses both the Earth surfaces' denudation rate and its weathering intensity. We develop a set of steady state mass balance equations that describes this system from a soil column over the hillslope scale to an entire river basin. The prerequisites making this new approach possible are: 1) the 9 Be concentration of parent rock (typically 2.5 ± 0.5 ppm in granitic and clastic sedimentary lithologies) is known; 2) both Be isotopes equilibrate between the fluids decomposing rock and reactive solids formed during weathering; and 3) a critical spatial scale is exceeded at which the fluxes of both isotopes into and out of the weathering zone are at steady state over the time scale of weathering (typically ~10 kyr). For these cases the isotope ratios can be determined in bulk sediment or soil, on leachates from the reactive (adsorbed and pedogenic mineral-bound) phase in sediment or soil, and even on the dissolved phase in river water. The 10 Be/ 9Be ratio offers substantial advantages over the single-isotope system of meteoric 10 Be. The latter system allows to directly determine erosion rates only in the case that 10 Be is fully retentive in the weathering zone and that riverine sorting has not introduced grain size-dependent 10 Be concentration gradients in sediments. We show the feasibility of the 10 Be/ 9 Be tracer approach at the river scale for sediment and water samples in the Amazon basin, where independent estimates of denudation rates from in situ-produced 10 Be exist. We furthermore calculate meaningful denudation rates from a set of published 10 Be/ 9 Be ratios measured in the dissolved load of globally distributed rivers. We conclude that this isotope ratio can be used to reconstruct global paleodenudation from sedimentary records.

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mentioning

confidence: 99%

Earth surface erosion and weathering from the 10Be (meteoric)/9Be ratio

Blanckenburg

Bouchez

Wittmann

2012

Earth and Planetary Science Letters

105

142

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“…Carbonate lithologies are found mainly in the northern Andes in Maranon and Ucayali river catchments but smaller amounts of carbonate-bearing minerals are found in the Madre de Dios region (Moquet et al, 2011). The age of evasion became older as the calcium concentration increased and silicate weathering percentage decreased (Fig.…”

Section: Discussionmentioning

confidence: 99%

Old carbon contributes to aquatic emissions of carbon dioxide in the Amazon

et al. 2014

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Abstract. Knowing the rate at which carbon is cycled is crucial to understanding the dynamics of carbon transfer pathways. Recent technical developments now support measurement of the 14 C age of evaded CO 2 from fluvial systems, which provides an important "fingerprint" of the source of C. Here we report the first direct measurements of the 14 C age of effluxed CO 2 from two small streams and two rivers within the western Amazonian Basin. The rate of degassing and hydrochemical controls on degassing are also considered. We observe that CO 2 efflux from all systems except for the seasonal small stream was 14 C-depleted relative to the contemporary atmosphere, indicating a contribution from "old" carbon fixed before ∼ 1955 AD. Further, "old" CO 2 was effluxed from the perennial stream in the rainforest; this was unexpected as here connectivity with the contemporary C cycle is likely greatest. The effluxed gas represents all sources of CO 2 in the aquatic system and thus we used end-member analysis to identify the relative inputs of fossil, modern and intermediately aged C. The most likely solutions indicated a contribution from fossil carbon sources of between 3 and 9 % which we interpret as being derived from carbonate weathering. This is significant as the currently observed intensification of weather has the potential to increase the future release of old carbon, which can be subsequently degassed to the atmosphere, and so renders older, slower C cycles faster. Thus 14 C fingerprinting of evaded CO 2 provides understanding which is essential to more accurately model the carbon cycle in the Amazon Basin.

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“…The value for Nenjiang Basin (40.6 Â 10 3 mol km À2 a À1 ) is relatively lower, but is comparable with that of the Indus (60 Â 10 3 mol km À2 -a À1 , Gaillardet et al, 1999b). When compared with other mountain/ orogenic area rivers, CO 2 consumed by the weathering of silicate rocks within the whole Songhuajiang Basin (66.6 Â 10 3 mol km À2 -a À1 ) is much lower than that of the Amazon rivers draining Andes and sub-Andes areas (300 Â 10 3 mol km À2 a À1 , Moquet et al, 2011), but is comparable with that of the Amazon Basin (52.4 Â 10 3 mol km À2 a À1 ) and is higher than that of the Yukon (34.2 Â 10 3 mol km À2 a À1 ) (Gaillardet et al, 1999b).…”

Section: Chemical Weathering and Co 2 Consumption Ratementioning

confidence: 96%

“…This approach for estimating the atmospheric contribution has the advantage that it does not require corrections for evapo-transpiration if the samples are collected at the same time as its effect is already factored in by determining the Cl À abundance of rivers (Rai et al, 2010), while dry atmospheric inputs are also accounted for. The other method consists of dividing the mean Cl À concentration in rainwater by the evapo-transpiration factor (f et ), which is calculated as the ratio of the annual discharge over the annual precipitation received by the basin (Gaillardet et al, 1999b;Moquet et al, 2011).…”

Section: Atmospheric Inputsmentioning

confidence: 99%