scholarly journals Carbon isotope anomaly in the major plant C<sub>1</sub> pool and its global biogeochemical implications

2004 ◽  
Vol 1 (1) ◽  
pp. 393-412 ◽  
Author(s):  
F. Keppler ◽  
R. M. Kalin ◽  
D. B. Harper ◽  
W. C. McRoberts ◽  
J. T. G. Hamilton
Keyword(s):  
Organic Matter ◽  
Biological Activity ◽  
Carbon Isotope ◽  
Plant Biomass ◽  
Plant Origin ◽  
Terrestrial Plants ◽  
Carbon Isotope Ratios ◽  
Volatile Organic ◽  
Extraterrestrial Origin ◽  
Global Carbon

Abstract. We report that the most abundant C1 units of terrestrial plants, the methoxyl groups of pectin and lignin, have a unique carbon isotope signature exceptionally depleted in 13C. Plant-derived C1 volatile organic compounds (VOCs) are also anomalously depleted in 13C compared with Cn+1 VOCs. The results confirm that the plant methoxyl pool is the predominant source of biospheric C1 compounds of plant origin such as methanol, chloromethane and bromomethane. Furthermore this pool, comprising ca. 2.5% of carbon in plant biomass, represents an important substrate for methanogenesis and could be a significant source of isotopically light methane entering the atmosphere. Our findings have significant implications for the use of carbon isotope ratios in elucidation of global carbon cycling. Moreover methoxyl groups could act as markers for biological activity in organic matter of terrestrial and extraterrestrial origin.

scholarly journals Carbon isotope anomaly in the major plant C<sub>1</sub> pool and its global biogeochemical implications

2004 ◽  
Vol 1 (2) ◽  
pp. 123-131 ◽  
Author(s):  
F. Keppler ◽  
R. M. Kalin ◽  
D. B. Harper ◽  
W. C. McRoberts ◽  
J. T. G. Hamilton
Keyword(s):  
Organic Matter ◽  
Biological Activity ◽  
Carbon Isotope ◽  
Plant Biomass ◽  
Plant Origin ◽  
Terrestrial Plants ◽  
Carbon Isotope Ratios ◽  
Volatile Organic ◽  
Extraterrestrial Origin ◽  
Global Carbon

Abstract. We report that the most abundant C1 units of terrestrial plants, the methoxyl groups of pectin and lignin, have a unique carbon isotope signature exceptionally depleted in 13C. Plant-derived C1 volatile organic compounds (VOCs) are also anomalously depleted in 13C compared with Cn+1 VOCs. The results confirm that the plant methoxyl pool is the predominant source of biospheric C1 compounds of plant origin such as methanol, chloromethane and bromomethane. Furthermore this pool, comprising ca 2.5% of carbon in plant biomass, could be an important substrate for methanogenesis and thus be envisaged as a possible source of isotopically light methane entering the atmosphere. Our findings have significant implications for the use of carbon isotope ratios in elucidation of global carbon cycling. Moreover methoxyl groups could act as markers for biological activity in organic matter of terrestrial and extraterrestrial origin.

Field evidence for coal combustion links the 252 My-old Siberian Traps with global carbon disruption

2021 ◽  
Author(s):  
Linda Elkins-Tanton ◽  
Steven Grasby ◽  
Benjamin Black ◽  
Roman Veselovskiy ◽  
Omid Ardakani ◽  
...  
Keyword(s):  
Organic Matter ◽  
Carbon Isotope ◽  
Flood Basalts ◽  
Siberian Traps ◽  
Field Evidence ◽  
Carbon Isotope Excursion ◽  
Show Evidence ◽  
Volcaniclastic Rocks ◽  
Atmospheric Changes ◽  
Global Carbon

&lt;p&gt;The Permo-Triassic Extinction was the most severe in Earth history. The Siberian Traps eruptions are strongly implicated in the global atmospheric changes that likely drove the extinction. A sharp negative carbon isotope excursion coincides within geochronological uncertainty with the oldest dated rocks from the Norilsk section of the Siberian flood basalts. The source of this light carbon has been debated for decades.&lt;/p&gt;&lt;p&gt;We focused on the voluminous volcaniclastic rocks of the Siberian Traps, relatively unstudied as potential carriers of carbon-bearing gases. Over six field seasons we collected rocks from across the Siberian platform and show the first direct evidence that the earliest eruptions particularly in the southern part of the province burned large volumes of a combination of vegetation and coal. Samples from the Maymecha-Kotuy region, from the Nizhnyaya Tunguska, Podkamennaya Tunguska, and Angara Rivers all show evidence of high-temperature organic matter carbonization and combustion.&lt;/p&gt;&lt;p&gt;Field evidence indicates a process in which ascending magmas entrain xenoliths of coal and carbonaceous sediments that are carbonized in the subsurface and also combusted either through reduction of magmas or when exposed to the atmosphere. We demonstrate that the volume and composition of organic matter interactions with magmas may explain the global carbon isotope signal, and have significantly driven the extinction.&lt;/p&gt;

Carbon Isotope Ratios of Particulate Organic Matter in the Gulf of St. Lawrence

1979 ◽  
Vol 36 (6) ◽  
pp. 678-682 ◽  
Author(s):  
F. C. Tan ◽  
P. M. Strain
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
Organic Carbon ◽  
Carbon Isotope ◽  
Particulate Organic Matter ◽  
Surface Sediments ◽  
Isotope Ratios ◽  
Lawrence Estuary ◽  
Carbon Isotope Ratios ◽  
Surface Samples

Sixteen offshore surface samples within the Gulf of St. Lawrence show low δ13C values and are similar to eight offshore surface samples collected seaward of the Gulf of St. Lawrence. The δ13C surface values are consistent with δ13C values in plankton produced at the temperature found in the euphotic zone in the study area. Higher values are observed in four surface samples from the mouth of the St. Lawrence Estuary and probably result from high carbon demand during periods of high biological productivity. Lower values found in seven deep POC samples indicate changes in the nature of the POC caused by biological degradation of the organic matter. Significant differences (2–6‰) between the uniformly high δ13C values of the organic carbon in surface sediments and the low values of near-bottom water POC have been observed. The similarity between the δ13C values of surface water POC and the surface sediments suggest that surface water POC is an important source of organic carbon in surface sediments. Several observations of large vertical δ13C gradients in deep water POC suggest the presence of resuspended sediments 30–60 m above the sediment–water interface. Key words: particulate organic matter, carbon isotope ratios, isotope fractionation, sediment resuspension, sediment sources, Gulf of St. Lawrence

scholarly journals Dependence between the photochemical age of light aromatic hydrocarbons and the carbon isotope ratios of atmospheric nitrophenols

2019 ◽  
Vol 19 (8) ◽  
pp. 5495-5509
Author(s):  
Marina Saccon ◽  
Anna Kornilova ◽  
Lin Huang ◽  
Jochen Rudolph
Keyword(s):  
Carbon Isotope ◽  
Organic Compounds ◽  
Mechanistic Model ◽  
Isotope Effects ◽  
Isotope Ratios ◽  
Kinetic Isotope Effects ◽  
Laboratory Studies ◽  
Carbon Isotope Ratios ◽  
Kinetic Isotope ◽  
Volatile Organic

Abstract. Concepts were developed to establish relationships between the stable carbon isotope ratios of nitrophenols in the atmosphere and the photochemical processing of their precursors, light aromatic volatile organic compounds. These concepts were based on the assumption that nitrophenols are formed dominantly from the photo-oxidation of aromatic volatile organic compounds (VOCs). A mass balance model as well as various scenarios based on the proposed mechanism of nitrophenol formation were formulated and applied to derive the time-integrated exposure of the precursors to processing by OH radicals (∫[OH]dt) from ambient observations made between 2009 and 2012 in Toronto, Canada. The mechanistic model included the possibility of isotopic fractionation during intermediate steps, rather than only during the initial reaction step. This model takes kinetic isotope effects for the reaction of the precursor VOC with the hydroxyl radical and their respective rate constants into account, as well as carbon isotope ratio source signatures. While many of these values are known, there are some, such as the kinetic isotope effects of reactions of first- and second-generation products, which are unknown. These values were predicted in this study based on basic principles and published laboratory measurements of kinetic carbon isotope effects and were applied to the mechanistic model. Due to the uncertainty of the estimates based on general principles, three scenarios were used with different values for isotope effects that were not known from laboratory studies. Comparison of the dependence between nitrophenol carbon isotope ratios and ∫[OH]dt with published results of laboratory studies and ambient observations was used to narrow the range of plausible scenarios for the mechanistic model. The results also suggests that mass-balance-based models do not adequately describe the dependence between nitrophenol carbon isotope ratios and ∫[OH]dt.

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