| 251. |
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| 252. |
- Rummukainen, Markku, et al.
(author)
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Climate models go green
- 2014
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In: Today’s Great Explorers : New frontiers in Strategy Research at Lund University - New frontiers in Strategy Research at Lund University. ; , s. 31-46
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Book chapter (pop. science, debate, etc.)abstract
- The use of coal, oil and gas, and land use change, has caused emissions of carbon dioxide which equals to about 550 billion tons of carbon. Half of these have accumulated in the atmosphere, which warms our climate with profound effects on natural and human systems. The other half has been absorbed by the oceans and the biosphere. Climate change affects the strength of these ‘ carbon sinks’. Knowledge about their future capacity is important for informed action on climate stabilisation. MERGE’s research on a new generation of climate models aims for a greater understanding of vegetation, climate and climate change
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| 253. |
- Saqnati, Mehri, et al.
(author)
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Hygroscopic behaviour of aerosol particles emitted from biomass fired grate boilers
- 2005
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In: Aerosol Science and Technology. - : Taylor & Francis Group. - 0278-6826 .- 1521-7388. ; 39:91, s. 919-930
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Journal article (peer-reviewed)abstract
- This study focuses on the hygroscopic properties of submicrometer aerosol particles emitted from two small-scale district heating combustion plants (1 and 1.5 MW) burning two types of biomass fuels (moist forest residue and pellets). The hygroscopic particle diameter growth factor (Gf ) was measured when taken from a dehydrated to a humidified state for particle diameters between 30– 350 nm (dry size) using a Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA). Particles of a certain dry size all showed similar diameter growth and the Gf at RH = 90% for 110/100 nm particles was 1.68 in the 1MWboiler, and 1.5 in the 1.5MWboiler. These growth factors are considerably higher in comparison to other combustion aerosol particles such as diesel exhaust, and are the result of the efficient combustion and the high concentration of alkali species in the fuel. The observed water uptake could be explained using the Zdanovski-Stokes-Robinson (ZSR) mixing rule and a chemical composition of potassium salts only, taken from ion chromatography analysis of filter and impactor samples (KCl, K2SO4, andK2CO3). Agglomerated particles collapsed and became more spherical when initially exposed to a moderately high relative humidity. When diluted with hot particle-free air, the fractallike structures remained intact until humidified in the H-TDMA. A method to estimate the fractal dimension of the agglomerated combustion aerosol and to convert the measured mobility diameter hygroscopic growth to the more useful property volume diameter growth is presented. The fractal dimension was estimated to be ∼2.5.
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| 254. |
- Schkolnik, G., et al.
(author)
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Constraining the density and complex refractive index of elemental and organic carbon in biomass burning aerosol using optical and chemical measurements
- 2007
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 41:5, s. 1107-1118
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Journal article (peer-reviewed)abstract
- The role of biomass burning aerosols in the climate system is still poorly quantified, in part due to uncertainties regarding the optical properties of elemental and organic carbon (EC and OC, respectively), the main constituents of pyrogenic aerosols. In this study, we utilize comprehensive physical and chemical field measurements of biomass burning aerosols in Brazil to constrain the densities and refractive indices (RI) of EC and OC in these particles, by comparing their optically and chemically derived RI. The optically derived effective RI are retrieved from the measured absorption and scattering coefficients using a Mie scattering algorithm, and serve as a reference dataset, while the chemically derived effective RI are calculated from the measured chemical composition using electromagnetic mixing rules. The results are discussed in light of the observed combustion conditions, and in an effort to derive conclusions as to the chemical and optical properties of the usually less well-characterized components of biomass burning aerosols, namely, elemental carbon and organic matter. The best agreement between the optically and chemically derived RI was achieved by assigning a density of rho(EC) = 1.8 g cm(-3) and refractive index RIEC = 1.87 - 0.22i to the EC component, and rho = 0.9 g cm(-3) and RI = 1.4 - 0i to the unidentified organic matter fraction of the particles. These parameters suggest low graphitization levels for the EC, and a dominant proportion of aliphatic compounds in the unidentified organic matter. Combining the density and RI of the unidentified organic matter with the properties of the chemically characterized organic fraction yields rho = 1.1 g cm(-3) and RI = 1.3 - 0i for the total aerosol OC. (c) 2006 Elsevier Ltd. All rights reserved.
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| 255. |
- Schmid, Otmar, et al.
(author)
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Derivation of the Density and Refractive Index of Organic Matter and Elemental Carbon from Closure between Physical and Chemical Aerosol Properties
- 2009
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In: Environmental Science & Technology. - : American Chemical Society (ACS). - 1520-5851 .- 0013-936X. ; 43:4, s. 1166-1172
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Journal article (peer-reviewed)abstract
- Information on the density (p) and refractive index m(=n-ik) of elemental carbon (ECa) and organic matter (OMa), the main carbon components of atmospheric aerosols, has frequently been obtained from closure calculations between physical and chemical aerosol properties. However, this approach has suffered from large uncertainties since there were more unknown (or poorly known) parameters than defining equations. In this study, we propose a method that avoids this ambiguity mainly by considering both optical and mass closure and by expressing the three ECa parameters (p(Eca), n(Eca), k(ECa)) by a single (unknown) parameter. This allows mathematically rigorous determination of p(Eca), m(Eca), p(OMa) and m(OMa) from standard physico-chemical aerosol data and rigorous error analysis. The results are unambiguous and self-consistent, i.e., there is no difference between the chemically and physically derived p and m values of the atmospheric aerosol. Application of this method to our previously published data on biomass burning particles from Amazonia yields p(Eca) = 1.8(+/- 0.2) g/cm(3), m(ECa) = 1.9(+/- 0.1)-i0.20(-0.04/+0.02), p(OMa) = 1.39(+/- 0.13) g/cm(3) and m(OMa)=1.46(+/- 0.02), where the 1 sigma uncertainty limits given in parenthesis are based on the principles of error propagation. The relatively low imaginary part of mEca indicates the presence of only partially graphitized elemental carbon, which is consistent with biomass burning aerosol dominated bysmoldering combustion conditions.
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| 256. |
- Scott, C. E., et al.
(author)
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Impact of gas-to-particle partitioning approaches on the simulated radiative effects of biogenic secondary organic aerosol
- 2015
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324 .- 1680-7316. ; 15:22, s. 12989-13001
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Journal article (peer-reviewed)abstract
- The oxidation of biogenic volatile organic compounds (BVOCs) gives a range of products, from semi-volatile to extremely low-volatility compounds. To treat the interaction of these secondary organic vapours with the particle phase, global aerosol microphysics models generally use either a thermodynamic partitioning approach (assuming instant equilibrium between semi-volatile oxidation products and the particle phase) or a kinetic approach (accounting for the size dependence of condensation). We show that model treatment of the partitioning of biogenic organic vapours into the particle phase, and consequent distribution of material across the size distribution, controls the magnitude of the first aerosol indirect effect (AIE) due to biogenic secondary organic aerosol (SOA). With a kinetic partitioning approach, SOA is distributed according to the existing condensation sink, enhancing the growth of the smallest particles, i.e. those in the nucleation mode. This process tends to increase cloud droplet number concentrations in the presence of biogenic SOA. By contrast, an approach that distributes SOA according to pre-existing organic mass restricts the growth of the smallest particles, limiting the number that are able to form cloud droplets. With an organically mediated new particle formation mechanism, applying a mass-based rather than a kinetic approach to partitioning reduces our calculated global mean AIE due to biogenic SOA by 24 %. Our results suggest that the mechanisms driving organic partitioning need to be fully understood in order to accurately describe the climatic effects of SOA.
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| 257. |
- Sehlstedt, Maria, 1979-, et al.
(author)
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Antioxidant airway responses following experimental exposure to wood smoke in man
- 2010
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In: Particle and Fibre Toxicology. - : Springer Science and Business Media LLC. - 1743-8977. ; 7, s. 21-
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Journal article (peer-reviewed)abstract
- Background: Biomass combustion contributes to the production of ambient particulate matter (PM) in rural environments as well as urban settings, but relatively little is known about the health effects of these emissions. The aim of this study was therefore to characterize airway responses in humans exposed to wood smoke PM under controlled conditions. Nineteen healthy volunteers were exposed to both wood smoke, at a particulate matter (PM2.5) concentration of 224 +/- 22 mu g/m(3), and filtered air for three hours with intermittent exercise. The wood smoke was generated employing an experimental set-up with an adjustable wood pellet boiler system under incomplete combustion. Symptoms, lung function, and exhaled NO were measured over exposures, with bronchoscopy performed 24 h post-exposure for characterisation of airway inflammatory and antioxidant responses in airway lavages. Results: Glutathione (GSH) concentrations were enhanced in bronchoalveolar lavage (BAL) after wood smoke exposure vs. air (p = 0.025), together with an increase in upper airway symptoms. Neither lung function, exhaled NO nor systemic nor airway inflammatory parameters in BAL and bronchial mucosal biopsies were significantly affected. Conclusions: Exposure of healthy subjects to wood smoke, derived from an experimental wood pellet boiler operating under incomplete combustion conditions with PM emissions dominated by organic matter, caused an increase in mucosal symptoms and GSH in the alveolar respiratory tract lining fluids but no acute airway inflammatory responses. We contend that this response reflects a mobilisation of GSH to the air-lung interface, consistent with a protective adaptation to the investigated wood smoke exposure.
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| 258. |
- Sjödin, Åke, et al.
(author)
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Wear particles from road traffic : A field, laboratory and modelling study - final report
- 2010
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Reports (other academic/artistic)abstract
- This report is an outcome of a major research effort within the Swedish National Road Vehicle Emission Research Programme EMFO, carried out 2005-2008 in collaboration between IVL, Lund University, the City of Stockholm and VTI. Within the project extensive data have been collected by a variety of methods for measuring, sampling and analysing the chemical composition of primarily three different fractions of particulate matter - PM10, PM2.5, PM1. Emphasis has been on the PM10 fraction, in the case of which preferably the major Swedish cities experience significant problems with complying with the legally binding air quality standards. The collected data originate from indoor measurements in controlled runs with the VTI circular road simulator as well as ambient air measurements at both street and roof level in a variety of Swedish cities. Based on elemental (metals etc.) source profiles of various sources to the different particle fractions, derived from the literature or from measurements carried out within the project, several different receptor models (e.g. COPREM, PMF) were applied to the collected data to derive the contributions from exhaust, brake wear, tyre wear, road surface wear, long-range transport etc., to the measured concentrations of PM10 and other particle fractions in urban environments. Furthermore, from the measurements, emission factors (expressed in grams per vehkm) for the various particle fractions, as well as for a large number of contained metals (about 30 metals) were derived for a major city street in Stockholm. Total emission factors as well as emission factors for each of the different source types (exhaust, brake wear, tyre wear and road surface wear) have also been derived from the measurements.
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| 259. |
- Sjödin, Åke, et al.
(author)
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Wear particles from road traffic - a field, laboratory and modelling study. Final report
- 2010
-
Reports (other academic/artistic)abstract
- The present report forms the final report from a major research project within the Swedish National Road Vehicle Emission Research Programme EMFO, carried out during the period 2005-2008. The project was carried out in collaboration between IVL, Lund University, SLB analys and VTI. Within the project extensive data have been collected by a variety of methods for measuring, sampling and analysing the chemical composition of different fractions of airborne particulate matter, with emphasis on the PM10 fraction. Collected data originate from indoor measurements in controlled runs with a circular road simulator as well as ambient air measurements at both street and roof level in a variety of Swedish cities. Based on elemental (metals etc.) source profiles of various sources to the different particle fractions, derived from the literature or from measurements carried out within the project, several different receptor models (e.g. COPREM, PMF) were applied to the collected data to derive the contribution from exhaust, brake wear, tyre wear, road surface wear, long-range transport etc., to the measured concentrations of PM10 and other particle fractions in urban environments. An important result of the project is the evidence for the great importance of studded tyres for the high PM10 concentration levels that occur in many Swedish cities during winter and early spring. According to the controlled indoor experiments with the road simulator studded tyres give rise to ten times higher emissions of PM10 than non-studded (friction) winter tyres, while PM10 emissions caused by summer tyres is almost negligible
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| 260. |
- Sporre, Moa, et al.
(author)
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A long-term satellite study of aerosol effects on convective clouds in Nordic background air
- 2014
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:4, s. 2203-2217
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Journal article (peer-reviewed)abstract
- Aerosol-cloud interactions constitute a major uncertainty in future climate predictions. This study combines 10 years of ground-based aerosol particle measurements from two Nordic background stations (Vavihill and Hyytiala) with MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data of convective clouds. The merged data are used to examine how aerosols affect cloud droplet sizes and precipitation from convective clouds over the Nordic countries. From the satellite scenes, vertical profiles of cloud droplet effective radius (r(e)) are created by plotting retrieved cloud top r(e) against cloud top temperature for the clouds in a given satellite scene. The profiles have been divided according to aerosol number concentrations but also meteorological reanalysis parameters from the ECMWF (European Centre for Medium-Range Forecasts). Furthermore, weather radar data from the BALTEX (Baltic Sea Experiment) and precipitation data from several ground-based meteorological measurement stations have been investigated to determine whether aerosols affect precipitation intensity and amount. Small r(e) throughout the entire cloud profiles is associated with high aerosol number concentrations at both stations. However, aerosol number concentrations seem to affect neither the cloud optical thickness nor the vertical extent of the clouds in this study. Cloud profiles with no or little precipitation have smaller droplets than those with more precipitation. Moreover, the amount of precipitation that reaches the ground is affected by meteorological conditions such as the vertical extent of the clouds, the atmospheric instability and the relative humidity in the lower atmosphere rather than the aerosol number concentration. However, lower precipitation rates are associated with higher aerosol number concentrations for clouds with similar vertical extent. The combination of these ground-based and remote-sensing datasets provides a unique long-term study of the effects of aerosols on convective clouds over the Nordic countries.
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