| 1. |
- Kramshöj, Magnus, et al.
(author)
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Biogenic volatile release from permafrost thaw is determined by the soil microbial sink
- 2018
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
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Journal article (peer-reviewed)abstract
- Warming in the Arctic accelerates thawing of permafrost-affected soils, which leads to a release of greenhouse gases to the atmosphere. We do not know whether permafrost thaw also releases non-methane volatile organic compounds that can contribute to both negative and positive radiative forcing on climate. Here we show using proton transfer reaction–time of flight–mass spectrometry that substantial amounts of ethanol and methanol and in total 316 organic ions were released from Greenlandic permafrost soils upon thaw in laboratory incubations. We demonstrate that the majority of this release is taken up in the active layer above. In an experiment using 14C-labeled ethanol and methanol, we demonstrate that these compounds are consumed by microorganisms. Our findings highlight that the thawing permafrost soils are not only a considerable source of volatile organic compounds but also that the active layer regulates their release into the atmosphere.
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| 2. |
- Peacock, Mike, et al.
(author)
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Understanding Dissolved Organic Matter Reactivity and Composition in Lakes and Streams Using Proton-Transfer-Reaction Mass Spectrometry (PTR-MS)
- 2018
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In: Environmental Science and Technology Letters. - : American Chemical Society (ACS). - 2328-8930. ; 5, s. 739-744
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Journal article (peer-reviewed)abstract
- Here, we present a novel approach for investigating dissolved organic matter (DOM) composition using thermal desorption proton- transfer-reaction mass spectrometry (PTR-MS), a technique that provides insight into the molecular composition of DOM < m/z 500 (termed “PTR- DOC”). The applicability of PTR-MS for understanding the relationship between DOM composition and reactivity has yet to be explored. We present results from a synoptic sampling campaign of streams and lakes in a Swedish forest catchment where we measured DOM composition using PTR-MS and traditional optical methods and conducted DOM biodegradability assays. PTR-DOC comprised ≤12% of the total DOC pool. We found significant relationships between PTR-DOC and DOM degradability; reduced chemo- diversity and low concentrations of PTR-DOC were both associated with the total DOM pool being more susceptible to microbial degradation. Furthermore, molecular differences were apparent among headwater lakes, headwater streams, and lakes further down the catchment. Direct linkages between PTR-DOC and optical methods were observed. Using the quantitative data that PTR-MS generates, it could become possible to identify the fluorescing components ofDOM, and the method may be particularly informative in low-DOC waters such as marine environments where PTR-DOC may dominate the total DOM pool.
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| 3. |
- Schmale, Julia, et al.
(author)
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Collocated observations of cloud condensation nuclei, particle size distributions, and chemical composition
- 2017
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In: Scientific Data. - : Springer Science and Business Media LLC. - 2052-4463. ; 4
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Journal article (peer-reviewed)abstract
- Cloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other international sites over multiple years. Here, harmonized data records from 11 observatories are summarized, spanning 98,677 instrument hours for CCN data, 157,880 for particle number size distributions, and 70,817 for chemical composition data. The observatories represent nine different environments, e.g., Arctic, Atlantic, Pacific and Mediterranean maritime, boreal forest, or high alpine atmospheric conditions. This is a unique collection of aerosol particle properties most relevant for studying aerosol-cloud interactions which constitute the largest uncertainty in anthropogenic radiative forcing of the climate. The dataset is appropriate for comprehensive aerosol characterization (e.g., closure studies of CCN), model-measurement intercomparison and satellite retrieval method evaluation, among others. Data have been acquired and processed following international recommendations for quality assurance and have undergone multiple stages of quality assessment.
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| 4. |
- Schmale, Julia, et al.
(author)
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Long-term cloud condensation nuclei number concentration, particle number size distribution and chemical composition measurements at regionally representative observatories
- 2018
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 18:4, s. 2853-2881
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Journal article (peer-reviewed)abstract
- Aerosol-cloud interactions (ACI) constitute the single largest uncertainty in anthropogenic radiative forcing. To reduce the uncertainties and gain more confidence in the simulation of ACI, models need to be evaluated against observations, in particular against measurements of cloud condensation nuclei (CCN). Here we present a data set - ready to be used for model validation - of long-term observations of CCN number concentrations, particle number size distributions and chemical composition from 12 sites on 3 continents. Studied environments include coastal background, rural background, alpine sites, remote forests and an urban surrounding. Expectedly, CCN characteristics are highly variable across site categories. However, they also vary within them, most strongly in the coastal background group, where CCN number concentrations can vary by up to a factor of 30 within one season. In terms of particle activation behaviour, most continental stations exhibit very similar activation ratios (relative to particles 20nm) across the range of 0.1 to 1.0% supersaturation. At the coastal sites the transition from particles being CCN inactive to becoming CCN active occurs over a wider range of the supersaturation spectrum. Several stations show strong seasonal cycles of CCN number concentrations and particle number size distributions, e.g. at Barrow (Arctic haze in spring), at the alpine stations (stronger influence of polluted boundary layer air masses in summer), the rain forest (wet and dry season) or Finokalia (wildfire influence in autumn). The rural background and urban sites exhibit relatively little variability throughout the year, while short-term variability can be high especially at the urban site. The average hygroscopicity parameter, calculated from the chemical composition of submicron particles was highest at the coastal site of Mace Head (0.6) and lowest at the rain forest station ATTO (0.2-0.3). We performed closure studies based on -Köhler theory to predict CCN number concentrations. The ratio of predicted to measured CCN concentrations is between 0.87 and 1.4 for five different types of . The temporal variability is also well captured, with Pearson correlation coefficients exceeding 0.87. Information on CCN number concentrations at many locations is important to better characterise ACI and their radiative forcing. But long-term comprehensive aerosol particle characterisations are labour intensive and costly. Hence, we recommend operating migrating-CCNCs to conduct collocated CCN number concentration and particle number size distribution measurements at individual locations throughout one year at least to derive a seasonally resolved hygroscopicity parameter. This way, CCN number concentrations can only be calculated based on continued particle number size distribution information and greater spatial coverage of long-term measurements can be achieved.
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