The Amazon River: behaviour of metals (Fe, Al, Mn) and dissolved organic matter in the initial mixing at the Rio Negro/Solimões confluence

Aucour, Anne‐Marie; Tao, Fenggang; Moreira-Turcq, Patrícia; Seyler, Patrick; Sheppard, Simon M.F.; Benedetti, Marc F.

doi:10.1016/s0009-2541(02)00398-4

Cited by 94 publications

(97 citation statements)

References 23 publications

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“…Dahlqvist et al carbon budget of the Amazon in the mixing zone (between sample D11 and D19) where low conductivity, organic rich water (D12) meets high conductivity, calcium rich water (D11). It was shown that during this mixing process 1.9 Tg of DOC was lost per year (Aucour et al, 2003) part of it may have been promoted by the colloidal Ca evidence here.…”

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confidence: 58%

Association of calcium with colloidal particles and speciation of calcium in the Kalix and Amazon rivers

Dahlqvist

Benedetti

Andersson

et al. 2004

Geochimica et Cosmochimica Acta

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Abstract-A considerable amount of colloidally bound Ca has been detected in water samples from Amazonian rivers and the Kalix River, a sub-arctic boreal river. Fractionation experiments using several analytical techniques and processing tools were conducted in order to elucidate the matter. Results show that on average 84% of the total Ca concentration is present as free Ca. Particulate, colloidal and complexed Ca constitute the remaining 16%, of which the colloidal fraction is significant. Ultrafiltration experiments show that the colloidal fraction in the sampled Amazonian rivers and the Kalix River range between 1% and 25%.In both the Amazonian and the Kalix rivers the technique of cross-flow ultrafiltration was used to isolate particles and colloids. The difference in concentration measured with ICP-AES and a Ca ion-selective electrode in identical samples was used to define the free Ca concentration and thus indirectly the magnitude of the particulate, colloidal and complexed fractions. Results from the Kalix and Amazonian rivers are in excellent agreement. Furthermore, the results show that the colloidal concentrations of Ca can be greatly overestimated (up to 227%) when conventional analysis and calculation of ultrafiltration data is used due to retention of free Ca ions during the ultrafiltration process. Calculation methods for colloidal matter are presented in this work, using complementary data from ISE analysis.In the Kalix River temporal changes in the fractionation of Ca were studied before, during and after a spring-flood event. Changes in the size distribution of colloidally associated Ca was studied using FlFFF (Flow Field-Flow Fractionation) coupled on-line to a HR ICP-MS. The FlFFF-HR ICP-MS fractograms clearly show the colloidal component of Ca, supporting the ultrafiltration findings. During winter conditions the size distribution of colloidally associated Ca has a concentration maximum at ϳ5 to 10 nm in diameter, shifting to smaller sizes (Ͻ5 nm) during and after the spring flood. This shift in size distribution follows a change in the river during this period from ironoxyhydroxy colloids being the most important colloidal carrier phase to humic substances during and after the spring flood.WHAM and NICA-Donnan models were used to calculate the amount of colloidally bound Ca. The results similar for both models, show that on average 16% of the Ca may be associated to a colloidal phase, which is in broad agreement with the measurements.

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confidence: 58%

Association of calcium with colloidal particles and speciation of calcium in the Kalix and Amazon rivers

Dahlqvist

Benedetti

Andersson

et al. 2004

Geochimica et Cosmochimica Acta

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“…Adsorption to or flocculation with colloidal Fe would encourage removal by increasing the size and mass of particulates in a process similar to that used by water industries for removal of DOC (Sharp et al 2006). This was one mechanism thought to remove both Fe and particulate organic matter in the Rio Negro/Solimões confluence in the Amzaon (Aucour et al 2003). Certainly this could have contributed to the large loss of POC in Nidd reach 1 in October 2012 that was accompanied by a decrease in Fe (0.855-0.661 mg L -1 ) and an increase in pH from pH 4.4-5.7, which is within the optimal range for Fe-organic matter coagulation (Sharp et al 2006).…”

Section: Discussionmentioning

confidence: 99%

Sporadic hotspots for physico-chemical retention of aquatic organic carbon: from peatland headwater source to sea

et al. 2015

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Few studies have quantified the role of instream processes on net dissolved and particulate organic carbon (DOC and POC, respectively) export from peatland catchments, and those that have offer conflicting evidence. In this study, we evaluated evidence for active organic matter processing under field conditions, via a coordinated campaign across four UK catchments with peatland headwaters, targeted on potential 'hotspots' and 'hot moments' of physico-chemical carbon cycling. We hypothesised that specific hotspots and hot moments would occur where waters enriched with DOC and POC sourced from headwaters are exposed to: (1) mixing with freshwaters of different pH, conductivity and metal concentrations; and (2) mixing with seawater during autumn when DOC concentrations were at their highest. We observed instances of POC removal in headwaters, and potential for rapid conversion between dissolved and particulate carbon forms and for net removal of peat-derived carbon at confluences further downstream (where observed, on the order of 52-75 % for POC, and 5-44 % for DOC). Estuary transect surveys indicated that up to 30 % of fluvial DOC can be removed under high flow conditions. However, in the majority of cases concentrations remained within the range that would be expected based on conservative transport. These findings indicate that rapid (e.g. solubility-related) processes within the river system may be important but sporadic, thus are unlikely to provide major removal pathways for peat-derived organic carbon.

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“…Vários autores têm avaliado a presença dos elementos químicos na bacia do rio Amazonas [5], [6]. Seyler & Boaventura [7] avaliaram a concentração e a variabilidade temporal de V, Cr, Mn, Co, Cu, Zn, As, Rb, Sr, Mo, Cd, Sb, Cs, Ba, U no rio Amazonas e seus afluentes principais (Negro, Madeira e Solimões) até a estação de Óbidos.…”

Section: Distribuição De Elementos Tóxicos No Estuário Do Rio Amazonasunclassified

Distribuição de elementos tóxicos no estuário do rio Amazonas

Pereira

Pires

Saraiva³

et al. 2011

Eclet. Quim.

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A presença de elementos não essenciais nas águas superficiais do rio Amazonas é uma preocupação global, o objetivo da pesquisa foi estudar a distribuição dos elementos As, Al, Mn, e Pb na água do estuário do rio Amazonas. As amostras foram coletadas em três regiões distintas: Canal Norte (AP), Canal Sul (PA) e rio Pará (PA) em três profundidades, com um total de 84 amostras. A espectrometria de emissão atômica com plasma indutivamente acoplado (ICPAES) foi utilizada para avaliar os teores de Al, Mn e Pb e a espectrofotometria de absorção atômica com geração de hidretos (HGAAS) foi usada para a análise do As. O As variou de <0,35 a 50,60 μg/L, o Al de <1,88 a 3347,70 μg/L, o Mn de 0,13 a 403,39 μg/L e Pb de <0,18 a 57,78 μg/L. Em média As (canal Sul), Al (todas as regiões), Mn (canal Norte e Sul) e Pb (canal Norte e Sul) se encontraram em valores acima do permitido pela legislação brasileira. Os elementos podem ter origem antrópica originária de atividade de mineração e industrial e origem natural proveniente de decomposição de rochas ígneas da bacia de drenagem do rio Amazonas que disponibilizam o elemento na forma ligada ao material particulado em suspensão.

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The Amazon River: behaviour of metals (Fe, Al, Mn) and dissolved organic matter in the initial mixing at the Rio Negro/Solimões confluence

Cited by 94 publications

References 23 publications

Association of calcium with colloidal particles and speciation of calcium in the Kalix and Amazon rivers

Association of calcium with colloidal particles and speciation of calcium in the Kalix and Amazon rivers

Sporadic hotspots for physico-chemical retention of aquatic organic carbon: from peatland headwater source to sea

Distribuição de elementos tóxicos no estuário do rio Amazonas

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