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

Walker, Brett D.; Beaupré, Steven R.; Griffin, Sheila; Druffel, Ellen R. M.

doi:10.1017/rdc.2019.9

Cited by 9 publications

(16 citation statements)

References 16 publications

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“…The CO 2 evolved from DOC was stripped with ultrahigh purity helium gas, cryogenically purified, and quantified. Reported DOC concentrations were corrected for CO 2 loss due to breakthrough from the Horibe glass trap cooled with liquid nitrogen during collection, whose mass was quantified via integration using an infrared CO 2 gas analyzer (LI‐COR Inc., model LI‐6252; Walker et al, ). The breakthrough does not affect the ∆ 14 C and δ 13 C measurements outside of the reported uncertainties.…”

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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“…Isotopic fractionation during the DOC extraction process cannot be ruled out and therefore we refrain from interpretation of the observed δ 13 C values. There is no consensus about the correction method for blank incorporation or isotopic fractionation for δ 13 C measurements 39 . However, isotopic fractionation, if it occurred, would not have affected the Δ 14 C values because they are fractionation-corrected values 43 .…”

Section: Methodsmentioning

confidence: 99%

Removal of Refractory Dissolved Organic Carbon in the Amundsen Sea, Antarctica

Fang

Lee

et al. 2020

Sci Rep

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the removal mechanism of refractory deep-ocean dissolved organic carbon (deep-Doc) is poorly understood. the Amundsen Sea polynya (ASp) serves as a natural test basin for assessing the fate of deep-Doc when it is supplied with a large amount of fresh-Doc and exposed to strong solar radiation during the polynya opening in austral summer. We measured the radiocarbon content of Doc in the water column on the western Amundsen shelf. the radiocarbon content of Doc in the surface water of the ASP reflected higher primary production than in the region covered by sea ice. The radiocarbon measurements of DOC, taken two years apart in the ASP, were different, suggesting rapid cycling of Doc. the increase in Doc concentration was less than expected from the observed increase in radiocarbon content from those at the greatest depths. Based on a radiocarbon mass balance, we show that deep-Doc is consumed along with fresh-Doc in the ASp. our observations imply that water circulation through the surface layer, where fresh-Doc is produced, may play an important role in global Doc cycling.The concentration of dissolved organic carbon (DOC) in the deep ocean (>1000 m, hereafter deep-DOC) is vertically uniform, but varies horizontally from ~34 to 48 μmol kg −1 (ref. 1 ). The 14 C ages of deep-DOC range from ~4000 yr in the North Atlantic to ~6500 yr in the North Pacific 2-6 . The old 14 C ages, together with its resistance to bacterial consumption 7 , imply that deep-DOC is refractory. A decrease in deep-DOC concentration of ~29% along the deep water circulation path is consistent with a very slow consumption rate 8 . Bacterial degradation, photochemical degradation, and adsorption to particles have been demonstrated as potential removal mechanisms 8-13 . However, the removal processes of deep-DOC are still not clearly understood.The Amundsen Sea in the west Antarctic is characterized by a relatively broad and deep continental shelf and extensive perennial sea ice cover 14 (Fig. 1). Circumpolar Deep Water (CDW) flows onto the Amundsen Shelf along the seafloor [15][16][17] . A part of the intruding CDW mixes with the overlying water to form modified CDW (MCDW). In the surface layer above ~400 m, water flows north, northwest, and off the shelf in general 18,19 . The western Amundsen Sea harbors a highly productive polynya, the Amundsen Sea Polynya (ASP) [20][21][22] . Peak annual production can be as high as ~3 gC m −2 d −1 with an average annual production of 105 gC m −2 yr −1 (ref. 22 ). High primary production in summer supplies considerable DOC (fresh-DOC) to the euphotic layer 20 . Deep-DOC supplied to the surface layer of the Amundsen Sea via CDW intrusion and mixing with the overlying water is subjected to biogeochemical processes such as the addition of extensive fresh-DOC 20 and microbial 23 and/or photochemical degradation 10 . The turnover time of the waters in the western Amundsen Sea embayment was suggested to be a few decades based on the 14 C content of dissolved inorganic carbon (DIC) 24 . Because of this unique enviro...

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“…[14][15][16] We typically use this method for δ 13 C measurements of three sample types: (i) closed-tube combusted and purified CO 2 from NIST (Gaithersburg, MD, USA) Oxalic Acid I SRM-4990 standard (OX-I) added to Exetainer vials via a gas-tight syringe transfer (representing our secondary standard for our GB run), (ii) closed-tube combusted and purified sample CO 2 that is sealed into 3 mm Pyrex break-seals and cracked, and (iii) CO 2 purified from seawater DOC via UV photochemical oxidation. 11,13 To show the robustness of our sealedtube δ 13 C method, only the combusted OX-I CO 2 sealed-tube results are presented. These results also include C blank contributions from the processes of combustion and vacuum line extraction.…”

Section: Sample Co 2 Purification and Measurementmentioning

confidence: 99%

“…For example, recent developments in both atmospheric and aqueous methane 14 C dating can be used to generate methane δ 13 C data from the same sample without the need for collecting or extracting additional samples 9,10 . Another example is 14 C studies of marine dissolved organic carbon (DOC), which often require contemporaneous δ 13 C values for environmental interpretation 11–13 …”

Section: Introductionmentioning

confidence: 99%

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A sealed‐tube method for offline δ¹³C analysis of CO₂ via a Gas Bench II continuous‐flow isotope ratio mass spectrometer

Walker

Beaupré

Griffin

et al. 2021

Rapid Comm Mass Spectrometry

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Rationale The isotopic measurement of environmental sample CO2 via isotope ratio mass spectrometry (IRMS) can present many analytical challenges. In many offline applications, exceedingly few samples can be prepared per day. In such applications, long‐term storage (months) of sample CO2 is desirable, in order to accumulate enough samples to warrant a day of isotopic measurements. Conversely, traditional sample tube cracker systems for dual‐inlet IRMS offer a capacity for only 6–8 tubes and thus limit throughput. Here we present a simple method to alleviate these concerns using a Gas Bench II gas handling device coupled with continuous‐flow IRMS. Methods Sample preparation entails the cryogenic purification and quantification of CO2 on a vacuum line. Sample CO2 splits are expanded from a known volume to several sample ports and allowed to isotopically equilibrate (homogenize). Equilibrated CO2 splits are frozen into 3 mm outer diameter Pyrex break‐seals and sealed under vacuum with a torch to a length of 5.5 cm. Sample break‐seals are scored, placed into 12 mL Labco Exetainer® vials, purged with ultrahigh‐purity helium, cracked inside the capped helium‐flushed vials and subsequently measured via a Gas Bench equipped IRMS instrument using a CTC Analytics PAL autosampler. Results Our δ13C results from NIST and internal isotopic standards, measured over a time period of several years, indicate that the sealed‐tube method produces accurate δ13C values to a precision of ±0.1‰ for samples containing 10–35 μgC. The tube cracking technique within Exetainer vials has been optimized over a period of 10 years, resulting in decreased sample failure rates from 5–10% to <1%. Conclusions This technique offers an alternative method for δ13C analyses of CO2 where offline isolation and long‐term storage are desired. The method features a much higher sample throughput than traditional dual‐inlet IRMS cracker setups at similar precision (±0.1‰).

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

Cited by 9 publications

References 16 publications

Dissolved Organic Radiocarbon in the Central Pacific Ocean

Dissolved Organic Radiocarbon in the Central Pacific Ocean

Removal of Refractory Dissolved Organic Carbon in the Amundsen Sea, Antarctica

A sealed‐tube method for offline δ¹³C analysis of CO₂ via a Gas Bench II continuous‐flow isotope ratio mass spectrometer

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

Cited by 9 publications

References 16 publications

Dissolved Organic Radiocarbon in the Central Pacific Ocean

Dissolved Organic Radiocarbon in the Central Pacific Ocean

Removal of Refractory Dissolved Organic Carbon in the Amundsen Sea, Antarctica

A sealed‐tube method for offline δ13C analysis of CO2 via a Gas Bench II continuous‐flow isotope ratio mass spectrometer

Contact Info

Product

Resources

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A sealed‐tube method for offline δ¹³C analysis of CO₂ via a Gas Bench II continuous‐flow isotope ratio mass spectrometer