Carbon isotope analysis

Experimental determination of the proportion of a given stable carbon isotope (C12 or C13) in a sample.
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12 results listed by similarity [list alphabetically]
Comparison of methane concentration and stable carbon isotope data for natural samples analyzed by discrete sample introduction module - cavity ring down spectroscopy (DSIM-CRDS) and traditional methods

A discrete sample introduction module (DSIM) was developed and interfaced to a cavity ring-down spectrometer to enable measurements of methane and CO2 concentrations and 13C values with a commercially available cavity ring-down spectrometer (CRDS). The DSIM-CRDS system permits the analysis of limited volume (5 - 100-ml) samples ranging six orders-of-magnitude from 100% analyte to the lower limit of instrument detection (2 ppm). We demonstrate system performance for methane by comparing concentrations and ...

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Static chamber gas fluxes and carbon and nitrogen isotope content of age-dated sediment cores from a Phragmites wetland in Sage Lot Pond, Massachusetts, 2013-2015

Coastal wetlands are major global carbon sinks; however, quantification of carbon flux can be difficult in these heterogeneous and dynamic ecosystems. To characterize spatial and temporal variability in a New England salt marsh, static chamber measurements of greenhouse gas (GHG) fluxes were compared among major plant-defined zones (high marsh dominated by Distichlis spicata and a zone of invasive Phragmites australis) during 2013 and 2014 growing seasons. Two sediment cores were collected in 2015 from the ...

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Collection, analysis, and age-dating of sediment cores from mangrove and salt marsh ecosystems in Tampa Bay, Florida, 2015

Coastal wetlands in Tampa Bay, Florida, are important ecosystems that deliver a variety of ecosystem services. Key to ecosystem functioning is wetland response to sea-level rise through accumulation of mineral and organic sediment. The organic sediment within coastal wetlands is composed of carbon sequestered over the time scale of the wetland’s existence. This study was conducted to provide information on soil accretion and carbon storage rates across a variety of coastal ecosystems that was utilized in ...

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Parent and alkylated polycyclic aromatic hydrocarbons (PAHs) and per- and polyfluoroalkyl substances (PFAS) in north San Francisco Bay, Napa River, and Sonoma Creek in 2018 and 2019

Sediment grain-size distributions, stable carbon isotope ratios (d13C), total carbon to total nitrogen ratios (C:N), short-lived radionuclides (Beryllium-7, Cesium-137, and Lead-210), concentrations of 76 parent and alkylated polycyclic aromatic hydrocarbons (PAHs) and concentrations of 33 per- and polyfluoroalkyl substances (PFAS) were measured in the northern reach of San Francisco Bay (San Pablo and Suisun Bays), and in stream beds of the lower reaches of Napa River and Sonoma Creek, 5 months and 20 ...

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Collection, analysis, and age-dating of sediment cores from natural and restored salt marshes on Cape Cod, Massachusetts, 2015-16

Nineteen sediment cores were collected from five salt marshes on the northern shore of Cape Cod where previously restricted tidal exchange was restored to part of the marshes. Cores were collected in duplicate from two locations within each marsh complex: one upstream and one downstream from the former tidal restriction (typically caused by an undersized culvert or a berm). The unaltered, natural downstream sites provide a comparison against the historically restricted upstream sites. The sampled cores ...

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Collection, analysis, and age-dating of sediment cores from Herring River wetlands and other nearby wetlands in Wellfleet, Massachusetts, 2015–17

The Herring River estuary in Wellfleet, Cape Cod, Massachusetts, has been tidally restricted for more than a century by a dike constructed near the mouth of the river. Upstream from the dike, the tidal restriction has caused the conversion of salt marsh wetlands to various other ecosystems including impounded freshwater marshes, flooded shrub land, drained forested upland, and brackish wetlands dominated by Phragmites australis. This estuary is now managed by the National Park Service, which plans to ...

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Data and calculations to support the study of the sea-air flux of methane and carbon dioxide on the West Spitsbergen margin in June 2014

A critical question for assessing global greenhouse gas budgets is how much of the methane that escapes from seafloor cold seep sites to the overlying water column eventually crosses the sea-air interface and reaches the atmosphere. The issue is particularly important in Arctic Ocean waters since rapid warming there increases the likelihood that gas hydrate--an ice-like form of methane and water stable at particular pressure and temperature conditions within marine sediments--will break down and release its ...

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Collection, Analysis, and Age-Dating of Sediment Cores from Salt Marshes on the South Shore of Cape Cod, Massachusetts, From 2013 Through 2014

The accretion history of fringing microtidal salt marshes located on the south shore of Cape Cod, Massachusetts, was reconstructed from sediment cores collected in low and high marsh vegetation zones. The location of these marshes within protected embayments and the absence of large rivers on Cape Cod result in minimal sediment supply and a dominance of organic matter contribution to sediment peat. Age models based on 210-lead and 137-cesium were constructed to evaluate how vertical accretion and carbon ...

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Collection, analysis, and age-dating of sediment cores from mangrove wetlands in San Juan Bay Estuary, Puerto Rico, 2016

The San Juan Bay Estuary, Puerto Rico, contains mangrove forests that store significant amounts of organic carbon in soils and biomass. There is a strong urbanization gradient across the estuary, from the highly urbanized and clogged Caño Martin Peña in the western part of the estuary, a series of lagoons in the center of the estuary, and a tropical forest reserve (Piñones) in the easternmost part with limited urbanization. We collected sediment cores to determine carbon burial rates and vertical ...

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Vertical chemical profiles collected across haloclines in the water column of the Ox Bel Ha cave network within the coastal aquifer of the Yucatan Peninsula in January 2015 and January 2016

Natural cave passages penetrating a coastal aquifer in the Yucatan Peninsula (Mexico) were accessed to test the hypothesis that chemoclines associated with salinity gradients (haloclines) within the flooded cave networks of the karst subterranean estuary are sites of methane oxidation. Two field trips were carried out to the fully-submerged cave system located 6.6 km inland from the coastline in January 2015 and January 2016. Vertical chemical profiles across the water column haloclines were obtained using ...

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Globorotalia truncatulinoides Sediment Trap Data in the Gulf of Mexico

Modern observations of planktic foraminifera from sediment trap studies help to constrain the regional ecology of paleoceanographically valuable species. Results from a weekly-resolved sediment trap time series (2008–2014) in the northern Gulf of Mexico demonstrate that 92% of Globorotalia truncatulinoides flux occurs in winter (January, February, and March), and that encrusted and non-encrusted individuals represent calcification in distinct depth habitats. Individual foraminiferal analysis (IFA) of G. ...

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Temporal hydrologic and chemical records from the Ox Bel Ha cave network within the coastal aquifer of the Yucatan Peninsula, from January 2015 to January 2016

Natural cave passages penetrating a coastal aquifer in the Yucatan Peninsula (Mexico) were accessed to investigate how regional meteorology and hydrology control methane dynamics in karst subterranean estuaries. Three field trips were carried out in January 2015, June 2015, and January 2016 to obtain year-long high-resolution temporal records of water chemistry and environmental parameters below and above the surface at a site (Cenote Bang) within the Ox Bel Ha cave network. These efforts resulted in ...

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