| 1. |
- Hwang, K.W., et al.
(author)
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Observation of difference in the size distribution of carbon and major inorganic compounds of atmospheric aerosols after the long-range transport between the selected days of winter and summer
- 2008
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 42:5, s. 1057-1063
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Journal article (peer-reviewed)abstract
- This paper presents the results from a study conducted in two urban areas in Korea to compare the size distributions of atmospheric aerosols, focusing on carbonaceous and certain major inorganic compounds, after long-range transport between selected days in winter and summer. Size segregated aerosols were sampled for 3 consecutive days each in February and July, 2004, and were analyzed to obtain the 24-h averaged concentrations of total mass, elemental carbon, organic carbon, nitrate, and sulfate. Backward trajectories from the receptor site on the sampling days were calculated to estimate the elapsed time for the air parcel to travel between Wonju and the Seoul metropolitan area. The averaged elapsed time on the sampling days was 3–12 h in the winter and 10–19 h in the summer. The enrichment of fine particles as expressed in particulate matter (PM)2/(PM10–PM2) was higher in the summer as compared to that in the winter. Size-fractionized concentration ratios of the organic to the elemental carbon at Wonju were two times as high as those at Seoul except for the particles with size <0.5 μm. This increasing trend was in proportional to the length of the elapsed time during the summer. Ultrafine particles in the summer were further enriched in carbon compounds, particularly in organic carbons and those in winter more enriched in the sulfates and nitrates. The mass fractions of organic carbon, elemental carbon, sulfate and nitrate became more significant with the decrease in the particle size.
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| 2. |
- Larsson, Per
(author)
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Atmospheric deposition of persistent pollutants governs uptake in freshwater zooplankton
- 1989
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844 .- 0004-6981. ; 23:10, s. 2151-2158
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Journal article (peer-reviewed)abstract
- The atmospheric fallout of PCBs, ∑DDT and γ-HCH (lindane) to a pond in southern Sweden was studied in relation to uptake by freshwater Zooplankton. The extent of the atmospheric deposition of PCBs and lindane was reflected in the uptake by the Zooplankton; high deposition in the spring and autumn resulted in high uptake by the organisms while a lower uptake during summer was a result of lower deposition. The atmospheric deposition of ∑DDT was dominated by p,p-DDT, p,p-DDE and o,p-DDT, while p,p-DDE and p,p-DDD were dominant in Zooplankton. These differences in ∑DDT composition are probably attributed to microbial conversion; as a result, levels in the Zooplankton appeared not to be governed by atmospheric deposition. The availability of the previously airborne, persistent pollutants to Zooplankton was a function of the compounds chemical properties, e.g. water solubility, and the form of deposition. The results show that atmospheric deposition is an important route by which persistent pollutants are transported to Holarctic, aquatic ecosystems.
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| 3. |
- Larsson, Per, et al.
(author)
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Atmospheric transport of chlorinated hydrocarbons to Sweden 1985 compared to 1973
- 1989
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844 .- 0004-6981. ; 23:8, s. 1699-1711
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Journal article (peer-reviewed)abstract
- The atmospheric fallout of DDT and DDE (ΣDDT) over Sweden has decreased during the last decade. Today long-range transport from southern sources outside the country dominates the inflow. This was reflected in a decreasing south-to-north gradient of the compounds in atmospheric deposition and in the lower atomosphere. The fallout of PCBs was similar in 1984–1985 and 1972–1973, and today local contamination by combustion is more prominent than it was 10 years ago, even though PCB restrictions have been in force during the interim. Since PCB deposition is higher in the coastal areas than in the inland regions, other sources, such as volatilization from the seas and long-range transport also contribute to PCBs in fallout. The levels of PCB and ΣDDT in the lower atmosphere were positively correlated with temperature. Consequently, the compounds tended to be in the gas phase during the warmer summer period whereas during winter they were more liable to be adsorbed to particles, partition to airborne water and contribute in fallout. From each sampling station a chromatographic 'fingerprint' of pollutants in airborne fallout and in the lower atmosphere was obtained. The fingerprint was the combined result of the station's location and climate. The results show that considerable amounts of chlorinated pollutants are being transported to and within Sweden via the atmosphere.
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| 4. |
- Park, JM, et al.
(author)
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Performance evaluation of six different aerosol samplers in a particulate matter generation chamber
- 2009
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 43:2, s. 280-289
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Journal article (peer-reviewed)abstract
- The present study was carried out with the aim of evaluating the performance of six different aerosol samplers in terms of mass concentration, particle size distribution, and mass fraction for the international size-sampling conventions. The international size-sampling criteria were defined as inhalable, thoracic, and respirable mass fractions with 50% cutoff at an aerodynamic equivalent diameter of 100 μm, 10 μm, and 4 μm, respectively. Two Andersen, four total suspended particulate (TSP), two RespiCon, four PM10, two DustTrak, and two SidePak samplers were selected and tested to quantitatively estimate human exposure in a carefully controlled particulate matter (PM) test chamber. The overall results indicate that (1) Andersen samplers underestimate total suspended PM and overestimate thoracic and respirable PM due to particle bounce and carryover between stages, (2) TSP samplers provide total suspended PM as reference samplers, (3) TSP samplers quantified by a coulter counter multisizer provide no information below an equivalent spherical diameter of 2 μm and therefore underestimate respirable PM, (4) RespiCon samplers are free from particle bounce as inhalable samplers but underestimate total suspended PM, (5) PM10 samplers overestimate thoracic PM, and (6) DustTrak and SidePak samplers provide relative PM concentrations instead of absolute PM concentrations.
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| 5. |
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| 6. |
- Wierzbicka, Aneta, et al.
(author)
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Particle emissions from district heating units operating on three commonly used biofuels
- 2005
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 39:1, s. 139-150
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Journal article (peer-reviewed)abstract
- The aim of this study was to characterise particle emissions from district heating units operating on three commonly used biofuels: forest residues, pellets and sawdust. Boilers used in the three district heating units were of moving grate type, with the maximum thermal output between 1 and 1.5 MW. The measurements were done after multicyclones, the only particle removal devices installed, therefore the direct emissions to ambient air were characterised. Number and mass size distributions were determined. Elemental composition of the particles, was determined by particle induced X-ray emissions analysis (PIXE) and thermal-optical analysis. Particles' morphology was assessed on the basis of transmission electron microscopy (TEM). Total number concentration of emitted particles with aerodynamic diameter smaller than 5 pm (PM5) at medium operation load ranged from 6.3 to 7.7 x 10(7) particles/cm(n)(3), with the slightly higher values from combustion of forest residues. PM5 mass concentration at medium load from low pressure impactor measurements ranged between 51 and 120 mg./m(n)(3), with the highest values from unit operating on forest residues. Both PM5 mass and total number concentrations were dominated by fine mode contributions i.e. particles with aerodynamic diameter smaller than 1 mum (PM1). Elements determined by PIXE (Z > 12) contributed to 21-34% of PM1 mass, of which K, S, Cl and Ca contributed to 18-33% of PM1 mass, and Zn, Mn, Fe, Cr, Pb and Cd to 1-3%. Emitted concentrations of heavy metals depended on type of the fuel and operating load. Particulate organic (OC) and elemental (EC) carbon contribution to PM1 ranged from 1-19% and 0-56%. respectively. Particulate OC concentrations strongly depended on the operation load regardless the type of the fuel, while EC concentrations seemed to depend both on load and the type of the fuel. Considering the potential public health implications of the obtained results, further research is needed to carefully assess the impact of particle emissions from biofuels combustion on human health and environment.
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| 7. |
- Wiman, Bo, et al.
(author)
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Aerosol characteristics in a mature coniferous forest - methodology, composition, sources and spatial concentration variations
- 1985
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844 .- 0004-6981. ; 19:2, s. 349-362
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Journal article (peer-reviewed)abstract
- A forest site in southern Sweden representative of a wider range of coniferous forest Londscapes has been characterized with respect to aerosol composition (NO−3, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn. Br and Pb). In one series aerosol sampling was carried out simultaneously along a horizontal transect with four stations, one located in open field, one at the forest edge and two within the forest. In another series simultaneous sampling was performed along a vertical transect with four sampling points, one located below but near the canopy top and the others further downwards through the canopy (height c. 25 m). Sampling strategy and analytical methods are presented in detail. Statistical analyses of concentration data suggest that K, Ca, Ti, Mn and Fe in the coarse particle fractions originated from soil, whereas other components (S, V, Cu and Pb) were of mainly anthropogenic origin. Depletion of coarse fraction concentrations within the forest was detected for several elements, whereas spatial variations of fine fraction concentrations showed weak or no systematic trends. This result is interpreted as a net effect of counteracting mechanisms in the forest: losses due to deposition and inputs due to turbulence and gravitationally settling particles.
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| 8. |
- Wiman, Bo, et al.
(author)
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Aerosol concentration profiles within a mature coniferous forest - model versus field results
- 1985
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844 .- 0004-6981. ; 19:2, s. 363-367
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Journal article (peer-reviewed)abstract
- Aerosol mass concentration profiles along a horizontal and a vertical transect in a forest are modelled from field site information on aerosol particle size distributions, forest structure and aerodynamics. Model outputs are compared with concentration profiles obtained from field measurements at the site. The comparisons suggest that model properties are qualitatively valid. Though field data are insufficient for a systematic quantitative test of model behaviour, the investigation does not indicate any quantitatively fundamental model deficiencies.
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| 9. |
- Wiman, Bo, et al.
(author)
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Aerosol depletion and deposition in forests - a model analysis
- 1985
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844 .- 0004-6981. ; 19:2, s. 335-347
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Journal article (peer-reviewed)abstract
- A system of partial differential equations is developed to describe an aerosol entering from an open field into a downwind forest, where deposition and turbulent transfer affect particle concentration. The model considers the interplay between forest structure, open field and forest aerodynamics and aerosol characteristics. The modelling problem is broken down into a set of simpler submodels which can be refined or simplified individually. Model results suggest, basically, significant horizontal (vertical) depletion of super-μm particles downwind from the forest edge (downwards from the canopy top). Distinct edge effects in deposition rates are common. In certain cases vertical exchange processes predominate, leading to enrichment of the aerosol. Sub-μm particles (unless extremely small) are subject to almost negligible depletion and edge effects. Deposition of super-μm particle oriented aerosols are governed by a complex interaction between particle size, forest structure and aerodynamics whereas deposition of sub-μm particles is simply controlled by particle concentration and forest structure. Under certain conditions (dense homogenous forests) aerosol particle concentration across the open field to forest roughness transition increases again after initial depletion.
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| 10. |
- Öberg, Tomas, 1956-
(author)
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A QSAR for the hydroxyl radical reaction rate constant : Validation, domain of application, and prediction
- 2005
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 39:12, s. 2189-2200
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Journal article (peer-reviewed)abstract
- A large number of anthropogenic organic chemicals are emitted into the troposphere. Reactions with the hydroxyl radical are a dominant removal pathway for most organic compounds, but experimentally determined gas-phase reaction rate constants are only available for about 750 compounds. The lack of experimental data increases the importance of applying structure-activity relationships (QSAR) to evaluate and predict reactivities. It is generally acknowledged that these empirical relationships are valid only within the same domain for which they were developed. However, model validation is sometimes neglected and the application domain is not always well defined. The purpose of this paper is to outline how validation and domain definition can facilitate the modeling and prediction of the hydroxyl radical reaction rates for a large database. A substantial number of theoretical descriptors (867) were generated from 2D molecular structures for compounds present in the Syracuse Research Corporationﾒs PhysProp Database. A QSAR model was developed for the hydroxyl radical reaction rate constant using a projection-based regression technique, PLSR (partial least squares regression). The PLSR model was subsequently validated with an external test set. The main factors of variation could be attributed to two reaction pathways, hydrogen atom abstraction and addition to double bonds or aromatic systems. A set of 17 293 compounds, drawn from the PhysProp Database, was projected onto the PLSR model and 74% were inside the applicability domain. The predicted hydroxyl reaction rates for 25% of these compounds were slow or negligible, with atmospheric half-lives in the range from days to years. Finally, the list of persistent organic compounds was matched against the OECD list of High Production Volume Chemicals (HPVC). Together with the experimental data, nearly three hundred compounds were identified as both persistent and in high volume production.
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