Non-uniform vertical distribution of fine sediment in the Amazon River

Curtis, William F.; Meade, Robert H.; Nordin, Carl F.; Price, N.B.; Sholkovitz, Edward R.

doi:10.1038/280381a0

Cited by 48 publications

(32 citation statements)

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“…Activities of 222Rn were about an order of magnitude greater than activities of the parent 226Ra in both mainstem and tributary samples. However, due: to the non-uniform vertical distribution ofparticulate material in the Amazon River (Curtis et al 1979), 226Ra activities in olur surface samples could underestimate the depth-integrated average activity by a factor of about 2. Nevertheless, since the :226Ra values include both the dissolved and particulate fractions, they indicate that the bulk of the 222Rn in the Amazon River is not supported by decay of river 226Ra.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the differences between the two data sets probably results from less dilution of Andean source waters during the latter cruise. It should also be noted that these values are characteristic only of the early rising portion of the hydrograph since the concentrations of most major ions vary by a factor of 2-3 as a function of discharge (Gibbs 1972;Schmidt 1972), while discharge itself varies from about 100,000 to 200,000 m3 s-l (Oltman 1968;Meade et al 1979;Richey et al 1986).…”

Section: Resultsmentioning

confidence: 99%

“…) was f25%. Due to the non-uniform vertical distribution of particulate matter in the Amazon River-particulate matter concentrations increase with depth and tend to be higher near one bank than the other (Curtis et al 1979;Meade 1985)-respiration rates were determined on subsamples of the composite sample. Although the compositing procedure raised the dissolved oxygen concentration from the in situ concentration of about 170 PM to about 240 IAM, this should not have affected the respiration rate because at these relatively high oxygen concentrations respiration rates should not be limited by oxygen concentration (Devol 1978).…”

Section: Methodsmentioning

confidence: 99%

“…At the end of the incubation period (8-16 h) oxygen concentrations were determined with the oxygen meter. The three poisoned controls and the oxygen concenTotal suspended solids (TSS) were determined on composite samples by the method of Meade et al (1979).…”

Section: Methodsmentioning

confidence: 99%

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The role of gas exchange in the inorganic carbon, oxygen, and ²²²Rn budgets of the Amazon River1

Devol

Quay

Richey

et al. 1987

Limnology & Oceanography

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Dissolved oxygen, ***Rn, pC02, alkalinity, respiration rate, and discharge have been measured at eight mainstem and seven tributary stations during February-March 1984 in a 1,700-km stretch of the Amazon River between Vargem Grande and Obidos in Brazil. Air-water gas exchange rates were estimated two ways: measurements of the flux of 222Rn into floating domes yielded an average boundary layer thickness of 78 pm, and oxygen mass balance calculations resulted in an average of 38 pm. Given a boundary layer thickness on the order of 50 pm, CO, loss to the atmosphere in the entire reach would have been 37.4 kmol s-l, which is about equal to the total tributary dissolved inorganic carbon (DIC) input (43 kmol s-l) and is about half of the total fluvial DIC input to the section (97.7 kmol s-l). Thus, CO, evasion is a major component of Amazon River DIC balance. Because gas exchange within the section was rapid relative to water travel time through the section, a quasi-steady state was maintained between respiratory input and evasion of CO,. Dissolved ***Rn activities in the mainstem varied from 3.5 to 8.3 dpm liter-' and were always highly supersaturated with respect to the atmosphere. Dissolved radon was also not supported by decay ~f~*~Ra (0.59-0.70 dpm liter-') in the mainstem. A ***Rn mass balance indicated that direct groundwater input into this stretch of the Amazon mainstem probably accounted for no more than 1% of water discharge.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

The role of gas exchange in the inorganic carbon, oxygen, and ²²²Rn budgets of the Amazon River1

Devol

Quay

Richey

et al. 1987

Limnology & Oceanography

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“…Further, interpreting point measurements at one location of the river network is limiting because large rivers systems like the Amazon are heterogeneous in space and time. Within the Amazon cross-section, hydrodynamic sorting causes large grain-size sediments to settle faster and thus concentrate at deeper depths (Rouse 1950;Gibbs, 1967;Curtis et al, 1979;Bouchez et al, 2011b), leading to compositional differences between the deeper, coarser sediments and the shallower, finer sediments (Bouchez et al, 2011a;Bouchez et al, 2014). Finally, seasonality presents another challenge to measuring fluxes.…”

Section: Introductionmentioning

confidence: 99%

Novel analytical strategies for tracing the organic carbon cycle in marine and riverine particles

Rosengard¹

2017

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Particulate organic carbon (POC) in the ocean and mobilized by rivers on land transfers ~0.1% of global primary productivity to the deep ocean sediments. This small fraction regulates the long-term carbon cycle by removing carbon dioxide from the atmosphere for centuries to millennia. This thesis investigates mechanisms of POC transfer to the deep ocean by analyzing particles collected in transit through two globally significant carbon reservoirs: the Southern Ocean and the Amazon River Basin. These endeavors test the hypothesis that organic matter composition controls the recycling and transfer efficiency of POC to the deep ocean, and illustrate new applications for ramped pyrolysis/oxidation (RPO), a growing method of POC characterization by thermal stability. By coupling RPO to stable and radiocarbon isotope analyses of riverine POC, I quantify three thermally distinct soil organic carbon pools mobilized by the Amazon River, and evaluate the degradability and fate of these different pools during transport to the coastal Atlantic Ocean. More directly, RPO analyses of marine samples suggest that POC transfer in the water column is in fact selective. Observations of consistent biomolecular changes that accompany transport of phytoplankton-derived organic matter to depth across the Southern Ocean support the argument for preferential degradation of specific POC pools in the water column. Combining discussions of POC recycling and transfer across both marine and terrestrial systems offer new perspectives of thermal stability as a proxy for diagenetic stability and POC degradation state. The challenges of interpreting RPO data in these two environments set the stage for applying the technique to more controlled experiments that trace POC from source to long-term sink.

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Sediment Load Measurements

Erskine¹

2004

Water Encyclopedia

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Two modes of sediment transport by rivers, suspended load and bed load, are usually recognized on behavioral grounds. Suspended load refers to the relatively fine part of the total sediment load that is transported in continuous or intermittent suspension. For sediment to remain in suspension, flow turbulence and velocity must be sufficiently great to counter the tendency of suspended sediment to settle to the riverbed. The two main factors determining sediment settling velocity are grain size and density. Bed or traction load refers to the relatively coarse part of the total sediment load that is transported along or close to the riverbed by rolling, sliding, or saltation. The latter term refers to sand movement in a series of hops across a riverbed in a distinct, concentrated layer.

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Non-uniform vertical distribution of fine sediment in the Amazon River

Cited by 48 publications

References 2 publications

The role of gas exchange in the inorganic carbon, oxygen, and ²²²Rn budgets of the Amazon River1

The role of gas exchange in the inorganic carbon, oxygen, and ²²²Rn budgets of the Amazon River1

Novel analytical strategies for tracing the organic carbon cycle in marine and riverine particles

Sediment Load Measurements

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Non-uniform vertical distribution of fine sediment in the Amazon River

Cited by 48 publications

References 2 publications

The role of gas exchange in the inorganic carbon, oxygen, and 222Rn budgets of the Amazon River1

The role of gas exchange in the inorganic carbon, oxygen, and 222Rn budgets of the Amazon River1

Novel analytical strategies for tracing the organic carbon cycle in marine and riverine particles

Sediment Load Measurements

Contact Info

Product

Resources

About

The role of gas exchange in the inorganic carbon, oxygen, and ²²²Rn budgets of the Amazon River1

The role of gas exchange in the inorganic carbon, oxygen, and ²²²Rn budgets of the Amazon River1