Aged black carbon identified in marine dissolved organic carbon

Ziolkowski, Lori A.; Druffel, Ellen R. M.

doi:10.1029/2010gl043963

Cited by 170 publications

(221 citation statements)

References 37 publications

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“…This figure compiles data from surface horizons of 20 long-term field experiments (up to 23 years) in temperate climate, using 13 C labelling to trace the residence time of bulk SOM and of individual molecular compounds. The variation in turnover time is also seen in the compounds of microbial origin analysed for 13 fire-derived carbon does undergo oxidation and transport, as we now know from archaeological settings 28 , soils 29,30 , and from breakdown products in river 31 and ocean water 32,33 . In a field experiment, firederived residues were even observed to decompose faster than the remaining bulk organic matter, with 25% lost over 100 years (ref.…”

Section: Soil Humic Substancesmentioning

confidence: 99%

Persistence of soil organic matter as an ecosystem property

Schmidt

Torn

Abiven

et al. 2011

Nature

4,420

102

3,035

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Globally, soil organic matter (SOM) contains more than three times as much carbon as either the atmosphere or terrestrial vegetation. Yet it remains largely unknown why some SOM persists for millennia whereas other SOM decomposes readily-and this limits our ability to predict how soils will respond to climate change. Recent analytical and experimental advances have demonstrated that molecular structure alone does not control SOM stability: in fact, environmental and biological controls predominate. Here we propose ways to include this understanding in a new generation of experiments and soil carbon models, thereby improving predictions of the SOM response to global warming.Understanding soil biogeochemistry is essential to the stewardship of ecosystem services provided by soils, such as soil fertility (for food, fibre and fuel production), water quality, resistance to erosion and climate mitigation through reduced feedbacks to climate change. Soils store at least three times as much carbon (in SOM) as is found in either the atmosphere or in living plants 1 . This major pool of organic carbon is sensitive to changes in climate or local environment, but how and on what timescale will it respond to such changes? The feedbacks between soil organic carbon and climate are not fully understood, so we are not fully able to answer these questions 2-7 , but we can explore them using numerical models of soil-organic-carbon cycling. We can not only simulate feedbacks between climate change and ecosystems, but also evaluate management options and analyse carbon sequestration and biofuel strategies. These models, however, rest on some assumptions that have been challenged and even disproved by recent research arising from new isotopic, spectroscopic and molecularmarker techniques and long-term field experiments.Here we describe how recent evidence has led to a framework for understanding SOM cycling, and we highlight new approaches that could lead us to a new generation of soil carbon models, which could better reflect observations and inform predictions and policies.

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Section: Soil Humic Substancesmentioning

confidence: 99%

Persistence of soil organic matter as an ecosystem property

Schmidt

Torn

Abiven

et al. 2011

Nature

4,420

102

3,035

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“…Druffel et al (1992) calculated that 80% of the deep ocean DOC is recycled within every deep ocean mixing cycle, allowing for very long residence times of individual compounds. The presence of much older DOM fractions, such as lipid-like components ($À880&; Loh et al, 2004) or black carbon (À918&; Ziolkowski and Druffel, 2010) imply much longer apparent residence times for these components than the mean age of the bulk DOC, suggesting a broad continuum of residence times and degradation rates. Note that it is not possible to calculate the C-abundance of our molecular formulae in the bulk DOC because the FT-ICR mass spectra do not provide quantitative data.…”

Section: The Dom Degradation Continuummentioning

confidence: 99%

“…Black carbon adds a very old source component to the deep-sea DOM (Ziolkowski and Druffel, 2010), affecting the radiocarbon mass balance and therefore reservoir age. However, IOS compounds are not primary black carbon molecules.…”

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

confidence: 99%

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

248

249

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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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“…While most DOC is believed to be produced by phytoplankton in the surface ocean, marine DOC is surprisingly thousands of 14 C years old (Williams and Druffel, 1987). The presence of ancient BC in the marine DOC pool may explain this mystery (Ziolkowski and Druffel, 2010;Masiello and Druffel, 1998) and was the motivation for this work. The structural composition and Δ…”

Section: Introductionmentioning

confidence: 99%

“…After a fire, large amounts of charcoal in soils are oxidized and transported to river sheds (Myers-Pigg et al, 2015;Kim et al, 2004;Hockaday et al, 2007;Mannino and Harvey, 2004;Preston and Schmidt, 2006). BC is transported to the ocean by rivers, and is ubiquitous in the water column and sediments (Jaffe et al, 2013;Dittmar and Paeng, 2009;Ziolkowski and Druffel, 2010;Masiello and Druffel, 1998;Coppola et al, 2014;Middelburg et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

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 identified in marine dissolved organic carbon

Cited by 170 publications

References 37 publications

Persistence of soil organic matter as an ecosystem property

Persistence of soil organic matter as an ecosystem property

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

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