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Capooci M, Seyfferth AL, Tobias C, Wozniak AS, Hedgpeth A, Bowen M, Biddle JF, McFarlane KJ, Vargas R. High methane concentrations in tidal salt marsh soils: Where does the methane go? GLOBAL CHANGE BIOLOGY 2024; 30:e17050. [PMID: 38273533 DOI: 10.1111/gcb.17050] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 10/18/2023] [Accepted: 10/18/2023] [Indexed: 01/27/2024]
Abstract
Tidal salt marshes produce and emit CH4 . Therefore, it is critical to understand the biogeochemical controls that regulate CH4 spatial and temporal dynamics in wetlands. The prevailing paradigm assumes that acetoclastic methanogenesis is the dominant pathway for CH4 production, and higher salinity concentrations inhibit CH4 production in salt marshes. Recent evidence shows that CH4 is produced within salt marshes via methylotrophic methanogenesis, a process not inhibited by sulfate reduction. To further explore this conundrum, we performed measurements of soil-atmosphere CH4 and CO2 fluxes coupled with depth profiles of soil CH4 and CO2 pore water gas concentrations, stable and radioisotopes, pore water chemistry, and microbial community composition to assess CH4 production and fate within a temperate tidal salt marsh. We found unexpectedly high CH4 concentrations up to 145,000 μmol mol-1 positively correlated with S2- (salinity range: 6.6-14.5 ppt). Despite large CH4 production within the soil, soil-atmosphere CH4 fluxes were low but with higher emissions and extreme variability during plant senescence (84.3 ± 684.4 nmol m-2 s-1 ). CH4 and CO2 within the soil pore water were produced from young carbon, with most Δ14 C-CH4 and Δ14 C-CO2 values at or above modern. We found evidence that CH4 within soils was produced by methylotrophic and hydrogenotrophic methanogenesis. Several pathways exist after CH4 is produced, including diffusion into the atmosphere, CH4 oxidation, and lateral export to adjacent tidal creeks; the latter being the most likely dominant flux. Our findings demonstrate that CH4 production and fluxes are biogeochemically heterogeneous, with multiple processes and pathways that can co-occur and vary in importance over the year. This study highlights the potential for high CH4 production, the need to understand the underlying biogeochemical controls, and the challenges of evaluating CH4 budgets and blue carbon in salt marshes.
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Affiliation(s)
- Margaret Capooci
- Department of Plant and Soil Science, University of Delaware, Newark, Delaware, USA
| | - Angelia L Seyfferth
- Department of Plant and Soil Science, University of Delaware, Newark, Delaware, USA
| | - Craig Tobias
- Department of Marine Sciences, University of Connecticut, Groton, Connecticut, USA
| | - Andrew S Wozniak
- School of Marine Science and Policy, University of Delaware, Lewes, Delaware, USA
| | - Alexandra Hedgpeth
- Department of Geography, University of California, Los Angeles, Los Angeles, California, USA
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Malique Bowen
- School of Marine Science and Policy, University of Delaware, Lewes, Delaware, USA
| | - Jennifer F Biddle
- School of Marine Science and Policy, University of Delaware, Lewes, Delaware, USA
| | - Karis J McFarlane
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Rodrigo Vargas
- Department of Plant and Soil Science, University of Delaware, Newark, Delaware, USA
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Radiocarbon isotope technique as a powerful tool in tracking anthropogenic emissions of carbonaceous air pollutants and greenhouse gases: A review. FUNDAMENTAL RESEARCH 2021. [DOI: 10.1016/j.fmre.2021.03.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
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Graven H, Keeling RF, Rogelj J. Changes to Carbon Isotopes in Atmospheric CO 2 Over the Industrial Era and Into the Future. GLOBAL BIOGEOCHEMICAL CYCLES 2020; 34:e2019GB006170. [PMID: 33380771 PMCID: PMC7757245 DOI: 10.1029/2019gb006170] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 09/18/2020] [Accepted: 10/16/2020] [Indexed: 05/19/2023]
Abstract
In this "Grand Challenges" paper, we review how the carbon isotopic composition of atmospheric CO2 has changed since the Industrial Revolution due to human activities and their influence on the natural carbon cycle, and we provide new estimates of possible future changes for a range of scenarios. Emissions of CO2 from fossil fuel combustion and land use change reduce the ratio of 13C/12C in atmospheric CO2 (δ13CO2). This is because 12C is preferentially assimilated during photosynthesis and δ13C in plant-derived carbon in terrestrial ecosystems and fossil fuels is lower than atmospheric δ13CO2. Emissions of CO2 from fossil fuel combustion also reduce the ratio of 14C/C in atmospheric CO2 (Δ14CO2) because 14C is absent in million-year-old fossil fuels, which have been stored for much longer than the radioactive decay time of 14C. Atmospheric Δ14CO2 rapidly increased in the 1950s to 1960s because of 14C produced during nuclear bomb testing. The resulting trends in δ13C and Δ14C in atmospheric CO2 are influenced not only by these human emissions but also by natural carbon exchanges that mix carbon between the atmosphere and ocean and terrestrial ecosystems. This mixing caused Δ14CO2 to return toward preindustrial levels in the first few decades after the spike from nuclear testing. More recently, as the bomb 14C excess is now mostly well mixed with the decadally overturning carbon reservoirs, fossil fuel emissions have become the main factor driving further decreases in atmospheric Δ14CO2. For δ13CO2, in addition to exchanges between reservoirs, the extent to which 12C is preferentially assimilated during photosynthesis appears to have increased, slowing down the recent δ13CO2 trend slightly. A new compilation of ice core and flask δ13CO2 observations indicates that the decline in δ13CO2 since the preindustrial period is less than some prior estimates, which may have incorporated artifacts owing to offsets from different laboratories' measurements. Atmospheric observations of δ13CO2 have been used to investigate carbon fluxes and the functioning of plants, and they are used for comparison with δ13C in other materials such as tree rings. Atmospheric observations of Δ14CO2 have been used to quantify the rate of air-sea gas exchange and ocean circulation, and the rate of net primary production and the turnover time of carbon in plant material and soils. Atmospheric observations of Δ14CO2 are also used for comparison with Δ14C in other materials in many fields such as archaeology, forensics, and physiology. Another major application is the assessment of regional emissions of CO2 from fossil fuel combustion using Δ14CO2 observations and models. In the future, δ13CO2 and Δ14CO2 will continue to change. The sign and magnitude of the changes are mainly determined by global fossil fuel emissions. We present here simulations of future δ13CO2 and Δ14CO2 for six scenarios based on the shared socioeconomic pathways (SSPs) from the 6th Coupled Model Intercomparison Project (CMIP6). Applications using atmospheric δ13CO2 and Δ14CO2 observations in carbon cycle science and many other fields will be affected by these future changes. We recommend an increased effort toward making coordinated measurements of δ13C and Δ14C across the Earth System and for further development of isotopic modeling and model-data analysis tools.
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Affiliation(s)
- Heather Graven
- Department of PhysicsImperial College LondonLondonUK
- Grantham Institute for Climate Change and the EnvironmentImperial College LondonLondonUK
| | - Ralph F. Keeling
- Scripps Institution of OceanographyUniversity of California, San DiegoLa JollaCAUSA
| | - Joeri Rogelj
- Grantham Institute for Climate Change and the EnvironmentImperial College LondonLondonUK
- ENE ProgramInternational Institute for Applied Systems AnalysisLaxenburgAustria
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4
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Local variance of atmospheric 14C concentrations around Fukushima Dai-ichi Nuclear Power Plant from 2010 to 2012. J Radioanal Nucl Chem 2017; 314:1001-1007. [PMID: 29104341 PMCID: PMC5658471 DOI: 10.1007/s10967-017-5459-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Indexed: 11/06/2022]
Abstract
Radiocarbon (14C) has been measured in single tree ring samples collected from the southwest of the Fukushima Dai-ichi Nuclear Power Plant. Our data indicate south-westwards dispersion of radiocarbon and the highest 14C activity observed so far in the local environment during the 2011 accident. The abnormally high 14C activity in the late wood of 2011 ring may imply an unknown source of radiocarbon nearby after the accident. The influence of 14C shrank from 30 km during normal reactor operation to 14 km for the accident in the northwest of FDNPP, but remains unclear in the southwest.
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5
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Wu S. Variation of atmospheric 14CO 2 and its spatial distribution. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2017; 169-170:116-121. [PMID: 28110198 DOI: 10.1016/j.jenvrad.2017.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 12/31/2016] [Accepted: 01/10/2017] [Indexed: 06/06/2023]
Abstract
The atmospheric 14CO2 is usually presented in the Δ14C notation, which cannot reflect its absolute quantity change. This article presents the atmospheric radiocarbon activity concentrations (aacn, reported in mBq/m3) in recent years at nine observation stations. The aacn at Schauinsland decrease from 1977 to 1993 but between 1993 and 2003 keeps at a relative steady state. Atmospheric aacns were higher in the northern hemisphere than that in the southern hemisphere. The aacns in the northern hemisphere show clear seasonal cycle with higher value in winter and lower value in summer, while this seasonality is not obvious in the southern hemisphere. Vegetation plays as a role of sink in summer and a role of source in winter, and atmosphere-biosphere radiocarbon exchange might be the main driver of the aacns seasonality. The annual mean aacns in both hemispheres show slightly increasing trends since 2002, which may be mainly caused by decreasing air-sea 14C flux as the air-sea 14C gradient decline.
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Affiliation(s)
- Shugang Wu
- SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710061, China; Xi'an AMS Center, Xi'an, 710061, China.
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6
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Verhulst KR, Karion A, Kim J, Salameh PK, Keeling RF, Newman S, Miller J, Sloop C, Pongetti T, Rao P, Wong C, Hopkins FM, Yadav V, Weiss RF, Duren RM, Miller CE. Carbon dioxide and methane measurements from the Los Angeles Megacity Carbon Project - Part 1: calibration, urban enhancements, and uncertainty estimates. ATMOSPHERIC CHEMISTRY AND PHYSICS 2017. [PMID: 30984251 DOI: 10.5194/acp-2016-850] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We report continuous surface observations of carbon dioxide (CO2) and methane (CH4) from the Los Angeles (LA) Megacity Carbon Project during 2015. We devised a calibration strategy, methods for selection of background air masses, calculation of urban enhancements, and a detailed algorithm for estimating uncertainties in urban-scale CO2 and CH4 measurements. These methods are essential for understanding carbon fluxes from the LA megacity and other complex urban environments globally. We estimate background mole fractions entering LA using observations from four "extra-urban" sites including two "marine" sites located south of LA in La Jolla (LJO) and offshore on San Clemente Island (SCI), one "continental" site located in Victorville (VIC), in the high desert northeast of LA, and one "continental/mid-troposphere" site located on Mount Wilson (MWO) in the San Gabriel Mountains. We find that a local marine background can be established to within ~1 ppm CO2 and ~10 ppb CH4 using these local measurement sites. Overall, atmospheric carbon dioxide and methane levels are highly variable across Los Angeles. "Urban" and "suburban" sites show moderate to large CO2 and CH4 enhancements relative to a marine background estimate. The USC (University of Southern California) site near downtown LA exhibits median hourly enhancements of ~20 ppm CO2 and ~150 ppb CH4 during 2015 as well as ~15 ppm CO2 and ~80 ppb CH4 during mid-afternoon hours (12:00-16:00 LT, local time), which is the typical period of focus for flux inversions. The estimated measurement uncertainty is typically better than 0.1 ppm CO2 and 1 ppb CH4 based on the repeated standard gas measurements from the LA sites during the last 2 years, similar to Andrews et al. (2014). The largest component of the measurement uncertainty is due to the single-point calibration method; however, the uncertainty in the background mole fraction is much larger than the measurement uncertainty. The background uncertainty for the marine background estimate is ~10 and ~15 % of the median mid-afternoon enhancement near downtown LA for CO2 and CH4, respectively. Overall, analytical and background uncertainties are small relative to the local CO2 and CH4 enhancements; however, our results suggest that reducing the uncertainty to less than 5 % of the median mid-afternoon enhancement will require detailed assessment of the impact of meteorology on background conditions.
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Affiliation(s)
- Kristal R Verhulst
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- University of California, Los Angeles, Joint Institute for Regional Earth System Science and Engineering, Los Angeles, CA, USA
| | - Anna Karion
- National Institute of Standards and Technology (NIST), Gaithersburg, MD, USA
| | - Jooil Kim
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Peter K Salameh
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Ralph F Keeling
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Sally Newman
- California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, USA
| | - John Miller
- NOAA/ESRL/GMD, Boulder, CO, USA
- CIRES, University of Colorado, Boulder, Boulder, CO, USA
| | | | - Thomas Pongetti
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Preeti Rao
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Clare Wong
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, USA
| | - Francesca M Hopkins
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Vineet Yadav
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Ray F Weiss
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Riley M Duren
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Charles E Miller
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
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7
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Verhulst KR, Karion A, Kim J, Salameh PK, Keeling RF, Newman S, Miller J, Sloop C, Pongetti T, Rao P, Wong C, Hopkins FM, Yadav V, Weiss RF, Duren RM, Miller CE. Carbon dioxide and methane measurements from the Los Angeles Megacity Carbon Project - Part 1: calibration, urban enhancements, and uncertainty estimates. ATMOSPHERIC CHEMISTRY AND PHYSICS 2017; 17:10.5194/acp-17-8313-2017. [PMID: 30984251 PMCID: PMC6459414 DOI: 10.5194/acp-17-8313-2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We report continuous surface observations of carbon dioxide (CO2) and methane (CH4) from the Los Angeles (LA) Megacity Carbon Project during 2015. We devised a calibration strategy, methods for selection of background air masses, calculation of urban enhancements, and a detailed algorithm for estimating uncertainties in urban-scale CO2 and CH4 measurements. These methods are essential for understanding carbon fluxes from the LA megacity and other complex urban environments globally. We estimate background mole fractions entering LA using observations from four "extra-urban" sites including two "marine" sites located south of LA in La Jolla (LJO) and offshore on San Clemente Island (SCI), one "continental" site located in Victorville (VIC), in the high desert northeast of LA, and one "continental/mid-troposphere" site located on Mount Wilson (MWO) in the San Gabriel Mountains. We find that a local marine background can be established to within ~1 ppm CO2 and ~10 ppb CH4 using these local measurement sites. Overall, atmospheric carbon dioxide and methane levels are highly variable across Los Angeles. "Urban" and "suburban" sites show moderate to large CO2 and CH4 enhancements relative to a marine background estimate. The USC (University of Southern California) site near downtown LA exhibits median hourly enhancements of ~20 ppm CO2 and ~150 ppb CH4 during 2015 as well as ~15 ppm CO2 and ~80 ppb CH4 during mid-afternoon hours (12:00-16:00 LT, local time), which is the typical period of focus for flux inversions. The estimated measurement uncertainty is typically better than 0.1 ppm CO2 and 1 ppb CH4 based on the repeated standard gas measurements from the LA sites during the last 2 years, similar to Andrews et al. (2014). The largest component of the measurement uncertainty is due to the single-point calibration method; however, the uncertainty in the background mole fraction is much larger than the measurement uncertainty. The background uncertainty for the marine background estimate is ~10 and ~15 % of the median mid-afternoon enhancement near downtown LA for CO2 and CH4, respectively. Overall, analytical and background uncertainties are small relative to the local CO2 and CH4 enhancements; however, our results suggest that reducing the uncertainty to less than 5 % of the median mid-afternoon enhancement will require detailed assessment of the impact of meteorology on background conditions.
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Affiliation(s)
- Kristal R. Verhulst
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- University of California, Los Angeles, Joint Institute for Regional Earth System Science and Engineering, Los Angeles, CA, USA
| | - Anna Karion
- National Institute of Standards and Technology (NIST), Gaithersburg, MD, USA
| | - Jooil Kim
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Peter K. Salameh
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Ralph F. Keeling
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Sally Newman
- California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, USA
| | - John Miller
- NOAA/ESRL/GMD, Boulder, CO, USA
- CIRES, University of Colorado, Boulder, Boulder, CO, USA
| | | | - Thomas Pongetti
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Preeti Rao
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Clare Wong
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, USA
| | - Francesca M. Hopkins
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Vineet Yadav
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Ray F. Weiss
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Riley M. Duren
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Charles E. Miller
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
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8
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Impact of fossil fuel emissions on atmospheric radiocarbon and various applications of radiocarbon over this century. Proc Natl Acad Sci U S A 2015. [PMID: 26195757 DOI: 10.1073/pnas.1504467112] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Radiocarbon analyses are commonly used in a broad range of fields, including earth science, archaeology, forgery detection, isotope forensics, and physiology. Many applications are sensitive to the radiocarbon ((14)C) content of atmospheric CO2, which has varied since 1890 as a result of nuclear weapons testing, fossil fuel emissions, and CO2 cycling between atmospheric, oceanic, and terrestrial carbon reservoirs. Over this century, the ratio (14)C/C in atmospheric CO2 (Δ(14)CO2) will be determined by the amount of fossil fuel combustion, which decreases Δ(14)CO2 because fossil fuels have lost all (14)C from radioactive decay. Simulations of Δ(14)CO2 using the emission scenarios from the Intergovernmental Panel on Climate Change Fifth Assessment Report, the Representative Concentration Pathways, indicate that ambitious emission reductions could sustain Δ(14)CO2 near the preindustrial level of 0‰ through 2100, whereas "business-as-usual" emissions will reduce Δ(14)CO2 to -250‰, equivalent to the depletion expected from over 2,000 y of radioactive decay. Given current emissions trends, fossil fuel emission-driven artificial "aging" of the atmosphere is likely to occur much faster and with a larger magnitude than previously expected. This finding has strong and as yet unrecognized implications for many applications of radiocarbon in various fields, and it implies that radiocarbon dating may no longer provide definitive ages for samples up to 2,000 y old.
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9
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Taylor AJ, Lai CT, Hopkins FM, Wharton S, Bible K, Xu X, Phillips C, Bush S, Ehleringer JR. Radiocarbon-Based Partitioning of Soil Respiration in an Old-Growth Coniferous Forest. Ecosystems 2015. [DOI: 10.1007/s10021-014-9839-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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10
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Chanton J, Zhao T, Rosenheim BE, Joye S, Bosman S, Brunner C, Yeager KM, Diercks AR, Hollander D. Using natural abundance radiocarbon to trace the flux of petrocarbon to the seafloor following the Deepwater Horizon oil spill. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:847-54. [PMID: 25494527 DOI: 10.1021/es5046524] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
In 2010, the Deepwater Horizon accident released 4.6–6.0 × 10(11) grams or 4.1 to 4.6 million barrels of fossil petroleum derived carbon (petrocarbon) as oil into the Gulf of Mexico. Natural abundance radiocarbon measurements on surface sediment organic matter in a 2.4 × 10(10) m(2) deep-water region surrounding the spill site indicate the deposition of a fossil-carbon containing layer that included 1.6 to 2.6 × 10(10) grams of oil-derived carbon. This quantity represents between 0.5 to 9.1% of the released petrocarbon, with a best estimate of 3.0–4.9%. These values may be lower limit estimates of the fraction of the oil that was deposited on the seafloor because they focus on a limited mostly deep-water area of the Gulf, include a conservative estimate of thickness of the depositional layer, and use an average background or prespill radiocarbon value for sedimentary organic carbon that produces a conservative value. A similar approach using hopane tracer estimated that 4–31% of 2 million barrels of oil that stayed in the deep sea settled on the bottom. Converting that to a percentage of the total oil that entered into the environment (to which we normalized our estimate) converts this range to 1.8 to 14.4%. Although extrapolated over a larger area, our independent estimate produced similar values.
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11
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Yin J, Yang X, Zheng Y. Influence of increasing combustion temperature on the AMS 14C dating of modern crop phytoliths. Sci Rep 2014; 4:6511. [PMID: 25288281 PMCID: PMC4187008 DOI: 10.1038/srep06511] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 09/10/2014] [Indexed: 12/03/2022] Open
Abstract
Several attempts have been made to directly date phytoliths, but most (14)C results are not consistent with other independent chronologies. Due to the limited dataset, there is not a clear explanation for these discrepancies. Herein, we report the (14)C ages of phytolith-occluded carbon (PhytOC) from contemporary rice and millet crops that were combusted at different temperatures to investigate the relationship between the combustion temperature and resulting (14)C age. Our results show that the (14)C age of PhytOC increases directly with combustion temperature (up to 1100°C) and results in age overestimations of hundreds of years. Considerably older ages are observed at higher temperatures, suggesting that it may be possible to distinguish between two fractions of organic carbon in phytoliths: labile and recalcitrant carbon. These findings challenge the assumption that PhytOC is homogeneous, an assumption made by those who have previously attempted to directly date phytoliths using (14)C.
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Affiliation(s)
- Jinhui Yin
- State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
- State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China
| | - Xue Yang
- State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
| | - Yonggang Zheng
- State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
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12
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Cappuccio JA, Falso MJS, Kashgarian M, Buchholz BA. 14C Analysis of protein extracts from Bacillus spores. Forensic Sci Int 2014; 240:54-60. [PMID: 24814329 DOI: 10.1016/j.forsciint.2014.04.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 03/28/2014] [Accepted: 04/01/2014] [Indexed: 10/25/2022]
Abstract
Investigators of bioagent incidents or interdicted materials need validated, independent analytical methods that will allow them to distinguish between recently made bioagent samples versus material drawn from the archives of a historical program. Heterotrophic bacteria convert the carbon in their food sources, growth substrate or culture media, into the biomolecules they need. The F(14)C (fraction modern radiocarbon) of a variety of media, Bacillus spores, and separated proteins from Bacillus spores was measured by accelerator mass spectrometry (AMS). AMS precisely measures F(14)C values of biological materials and has been used to date the synthesis of biomaterials over the bomb pulse era (1955 to present). The F(14)C of Bacillus spores reflects the radiocarbon content of the media in which they were grown. In a survey of commercial media we found that the F(14)C value indicated that carbon sources for the media were alive within about a year of the date of manufacture and generally of terrestrial origin. Hence, bacteria and their products can be dated using their (14)C signature. Bacillus spore samples were generated onsite with defined media and carbon free purification and also obtained from archived material. Using mechanical lysis and a variety of washes with carbon free acids and bases, contaminant carbon was removed from soluble proteins to enable accurate (14)C bomb-pulse dating. Since media is contemporary, (14)C bomb-pulse dating of isolated soluble proteins can be used to distinguish between historical archives of bioagents and those produced from recent media.
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Affiliation(s)
- Jenny A Cappuccio
- Biosciences & Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94551, United States
| | - Miranda J Sarachine Falso
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94551, United States
| | - Michaele Kashgarian
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94551, United States
| | - Bruce A Buchholz
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94551, United States.
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13
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Millar CI, Heckman K, Swanston C, Schmidt K, Westfall RD, Delany DL. Radiocarbon dating of American pika fecal pellets provides insights into population extirpations and climate refugia. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2014; 24:1748-1768. [PMID: 29210235 DOI: 10.1890/13-0520.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The American pika (Ochotona princeps) has become a species of concern for its sensitivity to warm temperatures and potential vulnerability to global warming. We explored the value of radiocarbon dating of fecal pellets to address questions of population persistence and timing of site extirpation. Carbon was extracted from pellets collected at 43 locations in the western Great Basin, USA, including three known occupied sites and 40 sites of uncertain status at range margins or where previous studies indicated the species is vulnerable. We resolved calibrated dates with high precision (within several years), most of which fell in the period of the mid-late 20th century bomb curve. The two-sided nature of the bomb curve renders far- and near-side dates of equal probability, which are separated by one to four decades. We document methods for narrowing resolution to one age range, including stratigraphic analysis of vegetation collected from pika haypiles. No evidence was found for biases in atmospheric 14C levels due to fossil-derived or industrial CO2 contamination. Radiocarbon dating indicated that pellets can persist for >59 years; known occupied sites resolved contemporary dates. Using combined evidence from field observations and radiocarbon dating, and the Bodie Mountains as an example, we propose a historical biogeographic scenario for pikas in minor Great Basin mountain ranges adjacent to major cordillera, wherein historical climate variability led to cycles of extirpation and recolonization during alternating cool and warm centuries. Using this model to inform future dynamics for small ranges in biogeographic settings similar to the Bodie Mountains in California, extirpation of pikas appears highly likely under directional warming trends projected for the next century, even while populations in extensive cordillera (e.g., Sierra Nevada, Rocky Mountains, Cascade Range) are likely to remain viable due to extensive, diverse habitat and high connectivity.
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Etminan N, Buchholz BA, Dreier R, Bruckner P, Torner JC, Steiger HJ, Hänggi D, Macdonald RL. Cerebral aneurysms: formation, progression, and developmental chronology. Transl Stroke Res 2013; 5:167-73. [PMID: 24323717 DOI: 10.1007/s12975-013-0294-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Revised: 10/06/2013] [Accepted: 10/08/2013] [Indexed: 02/08/2023]
Abstract
The prevalence of unruptured intracranial aneurysms (UIAs) in the general population is up to 3%. Existing epidemiological data suggests that only a small fraction of UIAs progress towards rupture over the lifetime of an individual, but the surrogates for subsequent rupture and the natural history of UIAs are discussed very controversially at present. In case of rupture of an UIA, the case fatality is up to 50%, which therefore continues to stimulate interest in the pathogenesis of cerebral aneurysm formation and progression. Actual data on the chronological development of cerebral aneurysm has been especially difficult to obtain and, until recently, the existing knowledge in this respect is mainly derived from animal or mathematical models or short-term observational studies. Here, we review the current data on cerebral aneurysm formation and progression as well as a novel approach to investigate the developmental chronology of cerebral aneurysms.
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Affiliation(s)
- Nima Etminan
- Department of Neurosurgery, Medical Faculty, Heinrich-Heine-University, Moorenstrasse 5, 40225, Dusseldorf, Germany,
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Graven HD, Gruber N, Key R, Khatiwala S, Giraud X. Changing controls on oceanic radiocarbon: New insights on shallow-to-deep ocean exchange and anthropogenic CO2uptake. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012jc008074] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Graven HD, Guilderson TP, Keeling RF. Observations of radiocarbon in CO2at seven global sampling sites in the Scripps flask network: Analysis of spatial gradients and seasonal cycles. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2011jd016535] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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