| 1. |
- Gierga, Merle, et al.
(author)
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Purification of fire derived markers for mu g scale isotope analysis (delta C-13, Delta C-14) using high performance liquid chromatography (HPLC)
- 2014
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In: Organic Geochemistry. - : Elsevier BV. - 0146-6380 .- 1873-5290. ; 70, s. 1-9
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Journal article (peer-reviewed)abstract
- Black carbon (BC) is the residue of incomplete biomass combustion. It is ubiquitous in nature and, due to its relative persistence, is an important factor in Earth's slow-cycling carbon pool. This resistant nature makes pure BC one of the most used materials for C-14 dating to elucidate its formation date or residence time in the environment. However, most BC samples cannot be physically separated from their matrices, precluding accurate C-14 values. Here we present a method for radiocarbon dating of the oxidation products of BC, benzene polycarboxylic acids, thereby circumventing interference from extraneous carbon. Individual compounds were isolated using high performance liquid chromatography (HPLC) and converted to CO2 via wet chemical oxidation for C-13 and C-14 isotope analysis. A detailed assessment was performed to identify and quantify sources of extraneous carbon contamination using two process standards with distinct isotopic signatures. The average blank was 1.6 +/- 0.7 mu g C and had an average radiocarbon content of 0.90 +/- 0.50 (FC)-C-14. We successfully analyzed the C-14 content of individual benzene polycarboxylic acids with a sample size as small as 20-30 mu g C after correcting for the presence of the average blank. The combination of delta C-13 and (FC)-C-14 analysis helps interpret the results and enables monitoring of extraneous carbon contribution in a fast and cost efficient way. Such a molecular approach to radiocarbon dating of BC residues enables the expansion of isotopic BC studies to samples that have either been too small or strongly affected by non-fire derived carbon.
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| 2. |
- Preiner, Martina, et al.
(author)
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Serpentinization : Connecting Geochemistry, Ancient Metabolism and Industrial Hydrogenation
- 2018
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In: Life. - : MDPI AG. - 2075-1729.
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Research review (peer-reviewed)abstract
- Rock-water-carbon interactions germane to serpentinization in hydrothermal vents have occurred for over 4 billion years, ever since there was liquid water on Earth. Serpentinization converts iron(II) containing minerals and water to magnetite (Fe3O4) plus H-2. The hydrogen can generate native metals such as awaruite (Ni3Fe), a common serpentinization product. Awaruite catalyzes the synthesis of methane from H-2 and CO2 under hydrothermal conditions. Native iron and nickel catalyze the synthesis of formate, methanol, acetate, and pyruvate-intermediates of the acetyl-CoA pathway, the most ancient pathway of CO2 fixation. Carbon monoxide dehydrogenase (CODH) is central to the pathway and employs Ni-0 in its catalytic mechanism. CODH has been conserved during 4 billion years of evolution as a relic of the natural CO2-reducing catalyst at the onset of biochemistry. The carbide-containing active site of nitrogenase-the only enzyme on Earth that reduces N(2)is probably also a relic, a biological reconstruction of the naturally occurring inorganic catalyst that generated primordial organic nitrogen. Serpentinization generates Fe3O4 and H-2, the catalyst and reductant for industrial CO2 hydrogenation and for N-2 reduction via the Haber-Bosch process. In both industrial processes, an Fe3O4 catalyst is matured via H-2-dependent reduction to generate Fe5C2 and Fe2N respectively. Whether serpentinization entails similar catalyst maturation is not known. We suggest that at the onset of life, essential reactions leading to reduced carbon and reduced nitrogen occurred with catalysts that were synthesized during the serpentinization process, connecting the chemistry of life and Earth to industrial chemistry in unexpected ways.
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| 3. |
- Wiedemeier, Daniel B., et al.
(author)
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Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids (BPCA)
- 2016
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In: Journal of Visualized Experiments. - : MyJove Corporation. - 1940-087X. ; :111
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Journal article (peer-reviewed)abstract
- Fire-derived, pyrogenic carbon (PyC), sometimes called black carbon (BC), is the carbonaceous solid residue of biomass and fossil fuel combustion, such as char and soot. PyC is ubiquitous in the environment due to its long persistence, and its abundance might even increase with the projected increase in global wildfire activity and the continued burning of fossil fuel. PyC is also increasingly produced from the industrial pyrolysis of organic wastes, which yields charred soil amendments (biochar). Moreover, the emergence of nanotechnology may also result in the release of PyC-like compounds to the environment. It is thus a high priority to reliably detect, characterize and quantify these charred materials in order to investigate their environmental properties and to understand their role in the carbon cycle. Here, we present the benzene polycarboxylic acid (BPCA) method, which allows the simultaneous assessment of PyC's characteristics, quantity and isotopic composition (C-13 and C-14) on a molecular level. The method is applicable to a very wide range of environmental sample materials and detects PyC over a broad range of the combustion continuum, i.e., it is sensitive to slightly charred biomass as well as high temperature chars and soot. The BPCA protocol presented here is simple to employ, highly reproducible, as well as easily extendable and modifiable to specific requirements. It thus provides a versatile tool for the investigation of PyC in various disciplines, ranging from archeology and environmental forensics to biochar and carbon cycling research.
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| 4. |
- Xiao, Kai, et al.
(author)
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Large CO2 release and tidal flushing in salt marsh crab burrows reduce the potential for blue carbon sequestration
- 2021
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In: Limnology and Oceanography. - : Wiley. - 1939-5590 .- 0024-3590. ; 66:1, s. 14-29
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Journal article (peer-reviewed)abstract
- © 2020 Association for the Sciences of Limnology and Oceanography Abundant crab burrows in carbon-rich, muddy salt marsh soils act as preferential water flow conduits, potentially enhancing carbon transport across the soil–water interface. With increasing recognition of blue carbon systems (salt marshes, mangroves, and seagrass) as hotspots of soil carbon sequestration, it is important to understand drivers of soil carbon cycling and fluxes. We conducted field observations and flow modeling to assess how crab burrows drive carbon exchange over time scales of minutes to weeks in an intertidal marsh in South Carolina. Results showed that continuous advective porewater exchange between the crab burrows and the surrounding soil matrix occurs because of tidally driven hydraulic gradients. The concentrations of dissolved inorganic (DIC) and organic (DOC) carbon in crab burrow porewater differ with that in the surrounding soil matrix, implying a diffusive C flux in the low-permeability marsh soil. Gas-phase concentrations of CO2 in ∼ 300 crab burrows were approximately six times greater than ambient air. The estimated total C export rate via porewater exchange (1.0 ± 0.7 g C m−2 d−1) was much greater than via passive diffusion transport (6.7 ± 2 mg C m−2 d−1) and gas-phase CO2 release (1.8 mg C m−2 d−1). The burrow-related carbon export was comparable to the regional salt marsh DIC export, groundwater-derived DIC export, and the net primary production previously estimated using ecosystem-scale approaches. These insights reveal how crab burrows modify blue carbon sequestration in salt marshes and contribute to coastal carbon budgets.
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