Carbon and metal concentrations, size distributions and fluxes in major rivers of the Amazon basin

Benedetti, Marc F.; Mounier, Stéphane; Filizola, Naziano; Bénaïm, J.; Seyler, Patrick

doi:10.1002/hyp.1289

Cited by 38 publications

(37 citation statements)

References 27 publications

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“…This relationship corresponds with the observed temperature dependence of both bacterial decomposition and Colorado River Decrease in lower section 2300Miller, 2012 photochemical oxidation (Davidson and Janssens, 2006;Porcal et al, 2015)-the two major pathways for in situ DOC loss in aquatic systems (Cole et al, 2007). The lower coefficient of correlation between DOC concentration and temperature in the UMR (4c) was probably due to additional DOC loss pathways, such as sorption onto particles (Aufdenkampe et al, 2001), DOC flocculation (Benedetti et al, 2003) and exchanges with floodplains (Tockner et al, 1999). Meanwhile, we also found that contributions from tributary dilutions on DOC decreases were all positively correlated with water discharge in both river sections (Figures 4A,B).…”

Section: Tributary Inputs As a Dominant Control On The Doc Longitudinsupporting

confidence: 73%

Impact of Wetland Decline on Decreasing Dissolved Organic Carbon Concentrations along the Mississippi River Continuum

Duan

Kaushal

et al. 2017

Front. Mar. Sci.

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Prior to discharging to the ocean, large rivers constantly receive inputs of dissolved organic carbon (DOC) from tributaries or fringing floodplains and lose DOC via continuous in situ processing along distances that span thousands of kilometers. Current concepts predicting longitudinal changes in DOC mainly focus on in situ processing or exchange with fringing floodplain wetlands, while effects of heterogeneous watershed characteristics are generally ignored. We analyzed results from a 17-year time-series of DOC measurements made at seven sites and three expeditions along the entire Mississippi River main channel with DOC measurements made every 17 km. The results show a clear downstream decrease in DOC concentrations that was consistent throughout the entire study period. Downstream DOC decreases were primarily (∼63-71%) a result of constant dilutions by low-DOC tributary water controlled by watershed wetland distribution, while in situ processing played a secondary role. We estimate that from 1780 to 1980 wetland loss due to land-use alterations caused a ca. 58% decrease in in DOC concentrations in the tributaries of the Mississippi River. DOC reductions caused by watershed wetland loss likely impacted the capacity for the river to effectively remove nitrogen via denitrification, which can further exacerbate coastal hypoxia. These findings highlight the importance of watershed wetlands in regulating DOC longitudinally along the headland to ocean continuum of major rivers.

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Section: Tributary Inputs As a Dominant Control On The Doc Longitudinsupporting

confidence: 73%

Impact of Wetland Decline on Decreasing Dissolved Organic Carbon Concentrations along the Mississippi River Continuum

Duan

Kaushal

et al. 2017

Front. Mar. Sci.

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“…Dissolved and suspended phases were isolated immediately on board by filtration through 0Ð2 µm membrane filters using an ultra-clean procedure described elsewhere (Seyler and Elbaz-Poulichet, 1996). In addition, water samples were collected in the mixing zone at various depths (1, 6, 15, 25, 35, 45 m) and distances from the river bank ( Figure 3) and treated on board by a sequential cross-flow ultrafiltration (Eyrolle et al, 1996;Benedetti et al, 2003). For samples, 2 l of water were filtered using clean 0Ð2 µm (P 1 ) and 5 kDa (P 2 ) ultrafiltration membranes.…”

Section: Methodsmentioning

confidence: 99%

Rare earth elements in the Amazon basin

Gérard¹,

Seyler²,

Benedetti³

et al. 2003

Hydrological Processes

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Abstract:The rare earth element (REE) concentrations of the dissolved and particulate fractions and bed sediment between Manaus and Santarém in the Amazon River, and in some major tributaries, were evaluated. A very important zone in the Amazon basin, the 'encontro das aguas' area where the Rio Solimões and the Rio Negro meet, was especially sampled. Different size fractions were isolated by ultrafiltration. Water samples were collected at different stages of the mixing. Three groups of waters are distinguished: group I has a low pH (<5Ð5) and is represented by the Negro basin rivers; group II has alkalinity less than 0Ð2 meq l 1 and is represented by the Rios Tapajós and Trombetas; group III has high alkalinity (>0Ð2 meq l 1 ) and higher pH (>6Ð5) and is represented by the Madeira basin rivers, the Solimões and the Amazon. The highest dissolved REE concentration is in the Rio Negro and the lowest in the Rio Tapajós (dissolved REEs vary by more than a factor of ten). The solubility of REEs is pH dependent: in river waters with a pH < 6 the Ce concentration is twice that of La, whereas in rivers with a higher pH the concentrations of Ce and La are similar. Dissolved REE concentrations are positively correlated with the dissolved organic carbon. Correlations between Fe, Al, and La suggest that La is associated with Al (Fe)-rich organic matter and/or related to dissolved Fe-rich inorganic material. Dissolved REEs normalized to North American shale composite show an enrichment in intermediate/heavy REEs (from Eu to Er), except for the shields rivers (such as Rio Negro and Rio Trombetas). Both of them are depleted in heavy REEs and show a relative Ce enrichment. In contrast, for the Andeans rivers (such as Rio Solimões), light REEs are slightly depleted and a negative Ce relative anomaly occurs. The pattern of the Amazon River atÓbidos confirms the major influence of the Rios Negro and Solimões with REE fractionation. For the Rio Negro, 60 to 70% of REEs are concentrated in the particulate fraction (>0Ð2 µm), 20 to 30% are in the colloidal fraction (0Ð2 µm to 5000 Da) and less than 10% are in solution (<5000 Da). For the Solimões the distribution is different. More than 95% of REEs are in the particulate fraction. In the mixing area, the colloidal fraction is enriched in heavy REEs.

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“…Floodplains and lakes often represent areas of enhanced primary production, providing the river with fresh autochtonous OM (Junk et al, 1989;Melack and Forsberg, 2001;Benedetti et al, 2003). High levels of algal and aquatic plant production (Junk and Howard-Williams, 1984;Junk et al, 1989) can considerably enhance the overall export of DOM from a river system (Tockner et al, 1999;Hedges et al, 2000).…”

Section: Conversion Of Om To Co 2 In Inland Watersmentioning

confidence: 99%

Where Carbon Goes When Water Flows: Carbon Cycling across the Aquatic Continuum

et al. 2017

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The purpose of this review is to highlight progress in unraveling carbon cycling dynamics across the continuum of landscapes, inland waters, coastal oceans, and the atmosphere. Earth systems are intimately interconnected, yet most biogeochemical studies focus on specific components in isolation. The movement of water drives the carbon cycle, and, as such, inland waters provide a critical intersection between terrestrial and marine biospheres. Inland, estuarine, and coastal waters are well studied in regions near centers of human population in the Northern hemisphere. However, many of the world's large river systems and their marine receiving waters remain poorly characterized, particularly in the tropics, which contribute to a disproportionately large fraction of the transformation of terrestrial organic matter to carbon dioxide, and the Arctic, where positive feedback mechanisms are likely to amplify global climate change. There are large gaps in current coverage of environmental observations along the aquatic continuum. For example, tidally-influenced reaches of major rivers and near-shore coastal regions around river plumes are often left out of carbon budgets due to a combination of methodological constraints and poor data coverage. We suggest that closing these gaps could potentially alter global estimates of CO 2 outgassing from surface waters to the atmosphere by several-fold. Finally, in order to identify and constrain/embrace uncertainties in global carbon budget estimations it is important that we further adopt statistical and modeling approaches that have become well-established in the fields of oceanography and paleoclimatology, for example.

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Carbon and metal concentrations, size distributions and fluxes in major rivers of the Amazon basin

Abstract: International audienc

Cited by 38 publications

References 27 publications

Impact of Wetland Decline on Decreasing Dissolved Organic Carbon Concentrations along the Mississippi River Continuum

Impact of Wetland Decline on Decreasing Dissolved Organic Carbon Concentrations along the Mississippi River Continuum

Rare earth elements in the Amazon basin

Where Carbon Goes When Water Flows: Carbon Cycling across the Aquatic Continuum

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