Photo-lability of deep ocean dissolved black carbon

Stubbins, Aron; Niggemann, Jutta; Dittmar, Thorsten

doi:10.5194/bgd-9-485-2012

Cited by 71 publications

(155 citation statements)

References 45 publications

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“…This is verified by the higher O/C and H/C ratio as well as by the much lower aromaticity index than typically observed for black carbon compounds Koch and Dittmar, 2006). Stubbins et al (2012) previously demonstrated that highly condensed compounds are photolabile and degrade during exposition to UV-radiation in the surface ocean. This mechanism removes the black carbon from the analytical window, potentially preserving the old carbon as transformed DOM compounds.…”

Section: Chemical Information On the Most Persistent Dom: The Island mentioning

confidence: 70%

Molecular transformation and degradation of refractory dissolved organic matter in the Atlantic and Southern Ocean

Lechtenfeld

Kattner

Flerus

et al. 2014

Geochimica et Cosmochimica Acta

278

259

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More than 90% of the global ocean dissolved organic carbon (DOC) is refractory, has an average age of 4000-6000 years and a lifespan from months to millennia. The fraction of dissolved organic matter (DOM) that is resistant to degradation is a long-term buffer in the global carbon cycle but its chemical composition, structure, and biochemical formation and degradation mechanisms are still unresolved. We have compiled the most comprehensive molecular dataset of 197 Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses from solid-phase extracted marine DOM covering two major oceans, the Atlantic sector of the Southern Ocean and the East Atlantic Ocean (ranging from 50°N to 70°S). Molecular trends and radiocarbon dating of 34 DOM samples (comprising D 14 C values from À229& to À495&) were combined to model an integrated degradation rate for bulk DOC resulting in a predicted age of >24 ka for the most persistent DOM fraction. First order kinetic degradation rates for 1557 mass peaks indicate that numerous DOM molecules cycle on timescales much longer than the turnover of the bulk DOC pool (estimated residence times of up to~100 ka) and the range of validity of radiocarbon dating. Changes in elemental composition were determined by assigning molecular formulae to the detected mass peaks. The combination of residence times with molecular information enabled modelling of the average elemental composition of the slowest degrading fraction of the DOM pool. In our dataset, a group of 361 molecular formulae represented the most stable composition in the oceanic environment ("island of stability"). These most persistent compounds encompass only a narrow range of the molecular elemental ratios H/C (average of 1.17 ± 0.13), and O/C (average of 0.52 ± 0.10) and molecular masses (360 ± 28 and 497 ± 51 Da). In the Weddell Sea DOC concentrations in the surface waters were low (46.3 ± 3.3 lM) while the organic radiocarbon was significantly more depleted than that of the East Atlantic, representing average surface water DOM ages of 4920 ± 180 a. These results are in accordance with a highly degraded DOM in the Weddell Sea surface water as also shown by the molecular degradation index I DEG obtained from FT-ICR MS data. Further, we identified 339 molecular formulae which probably contribute to an increased DOC concentration in the Southern Ocean and potentially reflect an accumulation or enhanced sequestration of refractory DOC in the Weddell Sea. These results will contribute to a better understanding of the persistent nature of marine DOM and its role as an oceanic carbon buffer in a changing climate.

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Section: Chemical Information On the Most Persistent Dom: The Island mentioning

confidence: 70%

Molecular transformation and degradation of refractory dissolved organic matter in the Atlantic and Southern Ocean

Lechtenfeld

Kattner

Flerus

et al. 2014

Geochimica et Cosmochimica Acta

278

259

View full text Add to dashboard Cite

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“…This may indicate degradation processes that remove aromatic BC with transport to the open ocean (e.g. photo-oxidation; Stubbins et al, 2012a). Despite the limited number of BC 14 C studies, it is interesting to note the disparity between Δ 14 C values as isolated by SPE and UDOC.…”

Section: Spe-doc and Bc Cyclingmentioning

confidence: 99%

“…We assume BC at Station M is representative of open ocean BC (with small contributions from riverine anthropogenic sources) (Coppola et al, 2014;Masiello and Druffel, 1998). UV oxidation plays a role in degrading highly aromatic BC in the land-to-ocean transit and may remove these structures upon entering the open ocean (Stubbins et al, 2012a;Masiello and Louchouarn, 2013;Myers-Pigg et al, 2015). Coastal BC may be influenced by anthropogenic riverine BC more directly, as urban water discharge is a primary source of Southern California coastal water pollution (Dwight et al, 2002).…”

Section: Spe-doc and Bc Cyclingmentioning

confidence: 99%

“…This BC extraction method is an improvement over UDOC, because SPE recovers approximately half of the total DOC pool based on the sample type (Louchouarn et al, 2010;Dittmar et al, 2008). Two studies have reported concentrations of BC in SPE-DOC of 0.6-0.8 µM in the Southern Ocean (Dittmar and Paeng, 2009) and 1.0 ± 0.2 µM in surface water at the Bermuda Atlantic Time Series site (Stubbins et al, 2012a).…”

mentioning

confidence: 99%

“…C values of SPE-BC provide insight into the composition of recalcitrant DOC, which escapes biological decomposition for thousands of years (Hansell et al, 2012;Ziolkowski and Druffel, 2010;Jiao et al, 2010;Stubbins et al, 2012a). Ziolkowski and Druffel (2010) reported the first BC Δ 14 C measurements in ultrafiltered DOC (UDOC) from river and seawater.…”

mentioning

confidence: 99%

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Solid phase extraction method for the study of black carbon cycling in dissolved organic carbon using radiocarbon

2015

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a b s t r a c t a r t i c l e i n f oRadiocarbon analysis is a powerful tool for understanding the cycling of individual components within carbon pools, such as black carbon (BC) in dissolved organic carbon (DOC). Radiocarbon (Δ 14 C) measurements of BC in DOC provide insight into one source of aged, recalcitrant DOC. We report a modified solid phase extraction (SPE) method to concentrate 43 ± 6% of DOC (SPE-DOC) from seawater. We used the Benzene Polycarboxylic Acid (BPCA) method to isolate BC from SPE-DOC (SPE-BC) for subsequent 14 C analysis. We report SPE-BC Δ 14 C values, SPE-BC concentrations, and the relative BPCA distributions from Milli-Q water process blanks, two riverine reference standards, as well as a coastal and an open ocean surface water sample. The composition of BC is less aromatic in the ocean samples than those in the river standards. We find higher BC Δ 14 C values in the river standards (+148 to −462‰) than BC in the ocean samples (−592 to −712‰), suggesting that BC ages within oceanic DOC. We report that BC is 4.2 ± 1.0% of SPE-DOC in the open ocean surface sample, or 1.4 ± 0.1 μM C. This work provides the methodological basis by which global BC concentrations, compositions (e.g. relative abundances of BPCA marker compounds) and Δ 14C values can be assessed.

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Aged black carbon in marine sediments and sinking particles

Coppola

Ziolkowski

Masiello

et al. 2014

Geophys. Res. Lett.

105

174

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We report measurements of oceanic black carbon (BC) to determine the sources of BC to abyssal marine sediments in the northeast Pacific Ocean. We find that the average 14 C age of BC is older (by 6200 ± 2200 14 C years) than that of the concurrently deposited non-BC sedimentary organic carbon. We investigate sources of aged BC to sediments by measuring a sample of sinking particulate organic carbon (POC) and find that POC may provide the main transport mechanism of BC to sediments. We suggest that aged BC is incorporated into POC from a combination of resuspended sediments and sorption of ancient dissolved organic carbon BC onto POC. Our BC flux estimate represents~8-16% of the global burial flux of organic carbon to abyssal sediments and constitutes a minimum long-term removal estimate of 6-32% of biomass-derived BC using the present day emission flux.

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Photo-lability of deep ocean dissolved black carbon

Cited by 71 publications

References 45 publications

Molecular transformation and degradation of refractory dissolved organic matter in the Atlantic and Southern Ocean

Molecular transformation and degradation of refractory dissolved organic matter in the Atlantic and Southern Ocean

Solid phase extraction method for the study of black carbon cycling in dissolved organic carbon using radiocarbon

Aged black carbon in marine sediments and sinking particles

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