| 1. |
- Horst, Axel, et al.
(författare)
-
Compound-specific bromine isotope analysis of methyl bromide using gas chromatography hyphenated with inductively coupled plasma multiple-collector mass spectrometry
- 2011
-
Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 25:17, s. 2425-2432
-
Tidskriftsartikel (refereegranskat)abstract
- Methyl bromide is the most important natural bromine contributor to stratospheric ozone depletion, yet there are still large uncertainties regarding quantification of its sources and sinks. The stable bromine isotope composition of CH(3)Br is potentially a powerful tool to apportion its sources and to study both its transport and its reactive fate. A novel compound-specific method to measure (81)Br/(79)Br isotope ratios in CH3Br using gas chromatography hyphenated with inductively coupled plasma multiple-collector mass spectrometry (GC/MCICPMS) was developed. Sample amounts of >40 ng could bemeasured with a precision of 0.1 parts per thousand (1 sigma, n=3). The method results are reproducible over the long term as shown with 36 analyses acquired over 3 months, yielding a standard deviation ( 1s) better than 0.4 parts per thousand. This new method demonstrates for the first time Br isotope ratio determination in gaseous brominated samples. It is three orders of magnitude more sensitive than previously existing isotope ratio mass spectrometry methods for Br isotope determination of other organobromines, thus allowing applications towards ambient atmospheric samples.
|
|
| 2. |
- Horst, Axel
(författare)
-
Compound-specific bromine isotope analysis of methyl bromide using GC-multiple collector mass spectrometry
- 2012
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The isotopic composition of ozone depleting methyl halides may provide valuable information on the sources and sinks of these compounds. However, so far mostly stable carbon isotope analysis of methyl chloride and methyl bromide has been attempted. One obstacle to progress with their other isotope systems has been the challenge to obtain sufficiently large amounts of methyl halides to meet the detection limits of existing isotope analytical methods. A compound-specific technique using gas chromatography multiple-collector inductively-coupled plasma mass spectrometry (GC-MC-ICPMS) has in this work been developed to measure 81Br/79Br isotope ratios in CH3Br. This ICPMS method is three orders of magnitude more sensitive compared to existing gas source mass spectrometry methods (dual inlet and continuous flow) for Br isotope determination and thus opens up possibilities for applications toward ambient atmospheric samples to investigate the sources and sinks of methyl halides.
|
|
| 3. |
- Horst, Axel, et al.
(författare)
-
Stable bromine isotopic composition of atmospheric CH3Br
- 2013
-
Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 65, s. 21040-
-
Tidskriftsartikel (refereegranskat)abstract
- Tropospheric methyl bromide (CH3Br) is the largest source of bromine to the stratosphere and plays an important role in ozone depletion. Here, the first stable bromine isotope composition (delta Br-81) of atmospheric CH3Br is presented. The delta Br-81 of higher concentration Stockholm samples and free air subarctic Abisko samples suggest a source/background value of -0.04 +/- 0.28 parts per thousand ranging up to +1.75 +/- 0.12 parts per thousand. The Stockholm delta Br-81 versus concentration relationship corresponds to an apparent isotope enrichment factor of -4.7 +/- 3.7 parts per thousand, representing the combined reaction sink. This study demonstrates the scientific potential of atmospheric delta Br-81 measurements, which in the future may be combined with other isotope systems in a top-down inverse approach to further understand key source and sink processes of methyl bromide.
|
|
| 4. |
|
|
| 5. |
- Horst, Axel, 1975-
(författare)
-
Stable bromine isotopic composition of methyl bromide : Method development and applications
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The isotopic composition of ozone depleting methyl halides may provide valuable information on the sources and sinks of these compounds. However, so far mostly stable carbon isotope analysis of methyl chloride and methyl bromide (CH3Br) has been attempted. Especially halogen isotope analysis has been hindered by the challenge to obtain sufficiently large amounts of methyl halides to meet the detection limits of existing isotope analytical methods. The purpose of this doctoral thesis was to develop both a high-volume cryogenic collection system for methyl bromide (Article II) and an analytical technique being able to analyze the sampled amounts of CH3Br for its Br isotopic composition, which was accomplished by using gas chromatography multiple-collector inductively-coupled plasma mass spectrometry (Article I). These methods were applied in the field campaign from which we report the first bromine isotopic values of CH3Br in the atmosphere (Article III), being in the range of -0.47 to + 1.75 ‰ vs. SMOB (Standard Mean Ocean Bromide). A laboratory study on pectin and halophyte plant material (Article IV) gave an insight in Br isotope composition of abiotically formed CH3Br which may be a main source to the atmospheric budget. These plant experiments yielded δ81Br values of 0 to -2 ‰ SMOB. Atmospheric CH3Br and this potential source showed partly distinct δ81Br ranges and demonstrate the potential of Br isotopes for source apportionment.
|
|
| 6. |
- Horst, Axel, et al.
(författare)
-
Stable bromine isotopic composition of methyl bromide released from plant matter
- 2014
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 125, s. 186-195
-
Tidskriftsartikel (refereegranskat)abstract
- 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 (delta Br-81) 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 (epsilon) of -2.00 +/- 0.23 parts per thousand (1 sigma, n = 8) for pectin and -1.82 +/- 0.02 parts per thousand (1 sigma, n = 4) for Salicornia (the relative amount of the heavier Br-81 was 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 degrees C. For longer incubations of up to 90 h at 180 degrees C the delta Br-81 values increased from -2 parts per thousand to 0 parts per thousand for pectin and to -1 parts per thousand for Salicornia. These delta Br-81 source signatures of CH3Br formation from plant matter combine with similar data for carbon isotopes to facilitate multidimensional isotope diagnostics of the CH3Br budget.
|
|
| 7. |
- Hulme, Mike, et al.
(författare)
-
Letter: Science-Policy Interface: Beyond Assessments
- 2011
-
Ingår i: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 333:6043, s. 697-698
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 8. |
- Thornton, Brett F., et al.
(författare)
-
A High-Volume Cryosampler and Sample Purification System for Bromine Isotope Studies of Methyl Bromide
- 2013
-
Ingår i: Journal of Atmospheric and Oceanic Technology. - 0739-0572 .- 1520-0426. ; 30:9, s. 2095-2107
-
Tidskriftsartikel (refereegranskat)abstract
- A system was developed for collecting from the ambient atmosphere the methyl halides CH3Cl and CH3Br in quantities sufficient for chlorine and bromine isotope analysis. The construction and operation of the novel cryogenic collection system (cryosampler) and sample purification system developed for this task are described. This study demonstrates the capability of the cryosampler by quantifying the CH3Cl and CH3Br collected from atmospheric samples and the nonfractionating bromine isotope fingerprint of CH3Br from synthetic air samples of controlled composition. An optimized cryosampler operation time of 4 h at a flow rate of 15 L min(-1) is applied to yield the nearly 40 ng required for subsequent Br-81-CH3Br analyses. The sample purification system is designed around a packed column gas chromatography-quadropole-mass spectrometry (GCqMS) system with three additional cryotraps and backflushing capacity. The system's suitability was tested by observing both the mass recovery and the lack of Br-81 isotope fractionation induced during sample purification under varying flow rates and loading scenarios. To demonstrate that the entire system samples and dependably delivers CH3Br to the isotope analysis system without inducing isotope fractionation, diluted synthetic air mixtures prepared from standard gases were processed through the entire system, yielding a Br-81-CH3Br of +0.03 parts per thousand +/- 0.10 parts per thousand relative to their starting composition. Finally, the combined cryosampler-purification and analysis system was applied to demonstrate the first-ever Br-81-CH3Br in the ambient atmosphere with two samples collected in the autumn of 2011, yielding -0.08 parts per thousand +/- 0.43 parts per thousand and +1.75 parts per thousand +/- 0.13 parts per thousand versus standard mean ocean bromide for samples collected at a suburban Stockholm, Sweden, site.
|
|
| 9. |
- Thornton, Brett F., et al.
(författare)
-
Methyl chloride and methyl bromide emissions from baking : an unrecognized anthropogenic source
- 2016
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 551, s. 327-333
-
Tidskriftsartikel (refereegranskat)abstract
- Methyl chloride and methyl bromide (CH3Cl and CH3Br) are the largest natural sources of chlorine and bromine, respectively, to the stratosphere, where they contribute to ozone depletion. We report the anthropogenic production of CH3Cl and CH3Br during breadbaking, and suggest this production is an abiotic process involving the methyl ester functional groups in pectin and lignin structural polymers of plant cells. Wide variations in baking styles allow only rough estimates of this flux of methyl halides on a global basis. A simple model suggests that CH3Br emissions from breadbaking likely peaked circa 1990 at approximately 200 tonnes per year (about 0.3% of industrial production), prior to restrictions on the dough conditioner potassium bromate. In contrast, CH3Cl emissions from breadbaking may be of similar magnitude as acknowledged present-day CH3Cl industrial emissions. Because the mechanisms involve functional groups and compounds widely found in plant materials, this type of methyl halide production may occur in other cooking techniques as well.
|
|
| 10. |
- Wegener, Axel, et al.
(författare)
-
Hovering Data Clouds: A Decentralized and Self-organizing Information System.
- 2006
-
Ingår i: IWSOS/EuroNGI / Hermann de Meer, James P. G. Sterbenz. - 3540376585 ; 4124, s. 243-247
-
Konferensbidrag (refereegranskat)abstract
- With ever-increasing numbers of cars, traffic congestion on the roads is a very serious economic and environmental problem for our modern society. Existing technologies for traffic monitoring and management require stationary infrastructure. These approaches lack flexibility with respect to system deployment and unpredictable events (e.g., accidents). Moreover, the delivery of traffic reports from radio stations is imprecise and often outdated. In the project AutoNomos we aim at developing a decentralized system for traffic monitoring and managing, based on vehicular ad-hoc networks (VANETs). Our objective is to design a system for traffic forecasting that can deliver faster and more appropriate reactions to unpredictable events. In our design, cars collect traffic information, extract the relevant data, and generate traffic reports. A key concept are so-called Hovering Data Clouds (HDCs), which are based on the insight that many crucial structures in traffic (e.g., traffic jams) lead an existence that is independent of the individual cars they are composed of. The result is an elegant, robust and self-organizing distributed information system. In this paper we demonstrate first experimental results.
|
|
