An improved method for the sealed-tube zinc graphitization of microgram carbon samples and 14C AMS measurement

Walker, Brett D.; Xu, Xiaomei

doi:10.1016/j.nimb.2018.08.004

Cited by 27 publications

(27 citation statements)

References 17 publications

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“…Samples were converted from CO 2 to graphite, by reduction on an iron catalyst using the closed-tube, zinc method (Walker & Xu, 2019;Xu et al, 2007). Δ 14 C measurements were performed by us at the Keck Carbon Cycle AMS Laboratory at University of California, Irvine (Santos et al, 2010;Southon et al, 2004).…”

Section: Setting and Methodsmentioning

confidence: 99%

Dissolved Organic Radiocarbon in the Central Pacific Ocean

Druffel

Griffin

Wang

et al. 2019

Geophysical Research Letters

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We report marine dissolved organic carbon (DOC) concentrations, and DOC ∆14C and δ13C values in seawater collected from the central Pacific. Surface ∆14C values are low in equatorial and polar regions where upwelling occurs and high in subtropical regions dominated by downwelling. A core feature of these data is that 14C aging of DOC (682 ± 86 14C years) and dissolved inorganic carbon (643 ± 40 14C years) in Antarctic Bottom Water between 54.0°S and 53.5°N are similar. These estimates of aging are minimum values due to mixing with deep waters. We also observe minimum ∆14C values (−550‰ to −570‰) between the depths of 2,000 and 3,500 m in the North Pacific, though the source of the low values cannot be determined at this time.

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Section: Setting and Methodsmentioning

confidence: 99%

Dissolved Organic Radiocarbon in the Central Pacific Ocean

Druffel

Griffin

Wang

et al. 2019

Geophysical Research Letters

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“…All isotopic measurements were performed by the Keck Carbon Cycle Accelerator Mass Spectrometry (KCCAMS) laboratory at UCI. Aliquots of CO 2 extracted from DOC, DIC, and mPMA OM were reduced to graphite using the closed-tube, zinc method ( 40 , 41 ) before 14 C analyses by accelerator mass spectrometry (AMS). The δ 13 C values of DOC and DIC were measured on separate aliquots of CO 2 using a Thermo Electron DELTA Plus IRMS equipped with a Gas Bench II.…”

Section: Methodsmentioning

confidence: 99%

Oceanic efflux of ancient marine dissolved organic carbon in primary marine aerosol

et al. 2019

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“…Following manometry, equilibrated gas splits of CO 2 are taken for Fm and δ 13 C measurements at UCI's Keck Carbon Cycle AMS (KCCAMS) Laboratory. One split (2-800 μgC) is graphitized via sealed-tube Zn reduction (Xu et al 2007;Walker and Xu 2019) for accelerator mass spectrometry radiocarbon (AMS 14 C) measurements. The other split is cryogenically transferred to 3 mm diameter, 5.5 cm length, Pyrex tubes for δ 13 C analysis with a Gas Bench II and Finnigan Delta Plus IRMS (Walker et al 2017).…”

Section: Methods Uv Photochemical Oxidation At Uc Irvinementioning

confidence: 99%

“…There are many reasons users should move towards the direct method of blank correction, because it: (1) can be more easily implemented given recent advances in ultra-small mass (2-25 μgC), sealed tube Zn graphitization (Walker and Xu 2019), (2) does not overestimate C contributions from MQ diluent, (3) can effectively correct for ubiquitous system line blanks underlying all UVox measurements, (4) yields more representative [DOC] and isotopic values with propagated uncertainties, and (5) can be applied with sample matrix matching (i.e. the addition of pre-combusted salt to seawater standards and blanks), which should control for possible UVox fractionation due to halides in solution.…”

Section: Doc Line Extraneous C Sources and Use Of Standards For Blankmentioning

confidence: 99%

UV Photochemical Oxidation and Extraction of Marine Dissolved Organic Carbon at UC Irvine: Status, Surprises, and Methodological Recommendations

et al. 2019

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The first ultraviolet photochemical oxidation (UVox) extraction method for marine dissolved organic carbon (DOC) as CO2 gas was established by Armstrong and co-workers in 1966. Subsequent refinement of the UVox technique has co-evolved with the need for high-precision isotopic (Δ14C, δ13C) analysis and smaller sample size requirements for accelerator mass spectrometry radiocarbon (AMS 14C) measurements. The UVox line at UC Irvine was established in 2004 and the system reaction kinetics and efficiency for isolating seawater DOC rigorously tested for quantitative isolation of ∼1 mg C for AMS 14C measurements. Since then, improvements have been made to sampling, storage, and UVox methods to increase overall efficiency. We discuss our progress, and key UVox system parameters for optimizing precision, accuracy, and efficiency, including (1) ocean to reactor: filtration, storage and preparation of DOC samples, (2) cryogenic trap design, efficiency and quantification of CO2 break through, and (3) use of isotopic standards, blanks and small sample graphitization techniques for the correction of DOC concentrations and Fm values with propagated uncertainties. New DOC UVox systems are in use at many institutions. However, rigorous assessment of quantitative UVox DOC yields and blank contributions, DOC concentrations and carbon isotopic values need to be made. We highlight the need for a community-wide inter-comparison study.

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An improved method for the sealed-tube zinc graphitization of microgram carbon samples and 14C AMS measurement

Cited by 27 publications

References 17 publications

Dissolved Organic Radiocarbon in the Central Pacific Ocean

Dissolved Organic Radiocarbon in the Central Pacific Ocean

Oceanic efflux of ancient marine dissolved organic carbon in primary marine aerosol

UV Photochemical Oxidation and Extraction of Marine Dissolved Organic Carbon at UC Irvine: Status, Surprises, and Methodological Recommendations

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