Chloride Methylation by Plant Pectin: An Efficient Environmentally Significant Process

Hamilton, John T. G.; McRoberts, W. Colin; Keppler, Frank; Kalin, Robert M.; Harper, David B.

doi:10.1126/science.1085036

Cited by 171 publications

(171 citation statements)

References 25 publications

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“…Sharma et al (2001) showed that only negligible amounts of methoxy groups are left after 10 min pyrolysis of plant material at 300ºC. This agrees with the studies of Hamilton et al (2003) and Keppler et al (2004) showing that pectin-related CH3Cl formation terminated at 300°C within the tested time span.…”

Section: Incubation Experimentssupporting

confidence: 78%

“…The same reaction pathway has been suggested for bromide salts (Hamilton et al, 2003). This abiotic reaction pathway was suggested to be an important source to the atmospheric methyl halide budget (Keppler et al, 2005;Wishkerman et al, 2008).…”

Section: Introductionmentioning

confidence: 82%

“…This method of quantitative cryo-trapping has been previously shown to preserve the isotope composition of the sample ) and breakthrough was not observed for flow rates up to 50mL/min. Hamilton et al (2003) demonstrated that incubation of pectin under nitrogen atmosphere yields the same amounts of CH3Cl as in air. Consequently incubations were accomplished with nitrogen as a carrier gas to avoid difficulties due to cotrapped O2.…”

Section: Incubation Experimentsmentioning

confidence: 99%

“…Pectin is the dominant source from non-woody plants at ambient and higher temperatures (up to ca. 300°C), and pectin-based sources such as decomposition of senescent plant material can be expected to be widespread (Hamilton et al, 2003).…”

Section: Isotopic Fingerprint Of a Potential Source Signaturementioning

confidence: 99%

“…Apart from biotic production of living plants, an abiotic reaction pathway has been described for CH3Br following a nucleophilic substitution reaction (SN2) (Hamilton et al, 2003;Keppler et al, 2004). The methoxy groups of pectin and lignin, both abundant cell-stabilizing macromolecules, react with halide ions dissolved in the tissue water of the plants (Khan et al, 2001) (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Stable bromine isotopic composition of methyl bromide released from plant matter

Horst

Holmstrand

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et al. 2014

Geochimica et Cosmochimica Acta

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Methyl bromide (CH3Br) emitted from plants constitutes a natural source of bromine to the atmosphere, and is a component in the currently unbalanced global CH3Br budget. In the stratosphere, CH3Br contributes to ozone loss processes.Studies of stable isotope composition may reduce uncertainties in the atmospheric CH3Br budget, but require well-constrained isotope fingerprints of the source end members. Here we report the first measurements of stable bromine isotopes (δ 81 Br) in CH3Br from abiotic plant emissions. Incubations of both KBr-fortified pectin, a ubiquitous cell-stabilizing macromolecule, and of a natural halophyte (Salicornia fruticosa), yielded an enrichment factor (ε) of -2.00±0.23‰ (1σ, n=8) for pectin and -1.82±0.02‰ (1σ, n=4) for Salicornia (the relative amount of 81 Br decreased in CH3Br compared to the substrate salt). For short incubations, and up to 10% consumption of the salt substrate, this isotope effect was similar for temperatures from 30 up to 300°C. For longer incubations of up to 100 hours at 180°C the δ 81 Br values increased from -2‰ to 0‰ for pectin and to -1‰ for Salicornia. These δ 81 Br source signatures of CH3Br formation from plant matter combine with similar data for carbon isotopes to facilitate multidimensional isotope diagnostics of the CH3Br budget.

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Section: Incubation Experimentssupporting

confidence: 78%

Section: Introductionmentioning

confidence: 82%

Section: Incubation Experimentsmentioning

confidence: 99%

Section: Isotopic Fingerprint Of a Potential Source Signaturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Stable bromine isotopic composition of methyl bromide released from plant matter

Horst

Holmstrand

Andersson

et al. 2014

Geochimica et Cosmochimica Acta

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Methyl chloride variability in the Taylor Dome ice core during the Holocene

2013

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[1] Methyl chloride (CH 3 Cl) is a naturally occurring, ozone-depleting trace gas and one of the most abundant chlorinated compounds in the atmosphere. CH 3 Cl was measured in air from the Taylor Dome ice core in East Antarctica to reconstruct an atmospheric record for the Holocene (11-0 kyr B.P.) and part of the last glacial period (50-30 kyr B.P.). CH 3 Cl variability throughout the Holocene is strikingly similar to that of atmospheric methane (CH 4 ), with higher levels in the early and late Holocene, and a well-defined minimum during mid-Holocene. The sources and sinks of atmospheric CH 3 Cl and CH 4 are located primarily in the tropics, and variations in their atmospheric levels likely reflect changes in tropical conditions. CH 3 Cl also appears to correlate with atmospheric CH 4 during the last glacial period (50-30 kyr B.P.), although the temporal resolution of sampling is limited. The Taylor Dome data provide information about the range of natural variability of atmospheric CH 3 Cl and place a new constraint on the causes of past CH 4 variability.

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Methyl chloride from the Aura Microwave Limb Sounder: First global climatology and assessment of variability in the upper troposphere and stratosphere

et al. 2013

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[1] Methyl chloride (CH 3 Cl) is by far the largest natural carrier of chlorine to the stratosphere. Its importance in stratospheric ozone chemistry is expected to increase in the coming decades as emission controls alter the relative contributions from natural and anthropogenic halogen sources. The Microwave Limb Sounder (MLS) on NASA's Aura satellite provides the first daily global observations of CH 3 Cl. Here we quantify the quality of the MLS version 3 CH 3 Cl data (single-profile precision of˙100 pptv; accuracy of 30-45%; vertical and horizontal resolution of 4-5 km and 450-600 km, respectively) and demonstrate their utility for scientific studies over the vertical range from 147 to 4.6 hPa. We exploit the unmatched scope of the 8 year MLS data set to investigate the spatial, seasonal, and interannual variations in the distribution of CH 3 Cl in the upper troposphere/lower stratosphere (UTLS). Like carbon monoxide, CH 3 Cl is a marker of pollution from biomass burning that can be lofted to the UTLS very rapidly by deep convection. The climatological seasonal cycle in CH 3 Cl reflects variability in regional fire activity and other surface sources as well as convection, and anomalous CH 3 Cl enhancements in the tropical upper troposphere are linked to specific episodes of intense burning. Methyl chloride is shown to be very useful as a tracer of large-scale dynamical processes, such as diabatic descent inside the stratospheric winter polar vortices, quasi-isentropic cross-tropopause transport associated with the summer monsoon circulations, and effects related to the quasi-biennial oscillation and the tropical "tape recorder".

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Chloride Methylation by Plant Pectin: An Efficient Environmentally Significant Process

Cited by 171 publications

References 25 publications

Stable bromine isotopic composition of methyl bromide released from plant matter

Stable bromine isotopic composition of methyl bromide released from plant matter

Methyl chloride variability in the Taylor Dome ice core during the Holocene

Methyl chloride from the Aura Microwave Limb Sounder: First global climatology and assessment of variability in the upper troposphere and stratosphere

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