| 1. |
- Brus, David, et al.
(författare)
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Temperature-Dependent Diffusion of H2SO4 in Air at Atmospherically Relevant Conditions : Laboratory Measurements Using Laminar Flow Technique
- 2017
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Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 8:7
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Tidskriftsartikel (refereegranskat)abstract
- We report flow tube measurements of the effective sulfuric acid diffusion coefficient at ranges of different relative humidities (from similar to 4 to 70%), temperatures (278, 288 and 298 K) and initial H2SO4 concentrations (from 1 x 10(6) to 1 x 10(8) molecules.cm(-3)). The measurements were carried out under laminar flow of humidified air containing trace amounts of impurities such as amines (few ppt), thus representing typical conditions met in Earth's continental boundary layer. The diffusion coefficients were calculated from the sulfuric acid wall loss rate coefficients that were obtained by measuring H2SO4 concentration continuously at seven different positions along the flow tube with a chemical ionization mass spectrometer (CIMS). The wall loss rate coefficients and laminar flow conditions were verified with additional computational fluid dynamics (CFD) model FLUENT simulations. The determined effective sulfuric acid diffusion coefficients decreased with increasing relative humidity, as also seen in previous experiments, and had a rather strong power dependence with respect to temperature, around proportional to T-5.6, which is in disagreement with the expected temperature dependence of similar to T-1.75 for pure vapours. Further clustering kinetics simulations using quantum chemical data showed that the effective diffusion coefficient is lowered by the increased diffusion volume of H2SO4 molecules via a temperature-dependent attachment of base impurities like amines. Thus, the measurements and simulations suggest that in the atmosphere the attachment of sulfuric acid molecules with base molecules can lead to a lower than expected effective sulfuric acid diffusion coefficient with a higher than expected temperature dependence.
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| 2. |
- Ferm, Martin, et al.
(författare)
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Final report from NMR project 'Test of a filter pack combined with a PM10 inlet'. Project number 04FOX5
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The EMEP filter pack for measuring gaseous and particulate reduced and oxidised nitrogen compounds in air has been modified with a PM10 inlet to meet the EU air quality directive for particle measurements. The filter pack also collects sulphur compounds as well as base cations and sodium chloride. The EMEP filter pack has been used for 20 years now and it is important that the PM10 inlet doesn't affect the results. The cut-off for the filter pack recommended by EMEP is unknown and may be affected by wind. Here it was found that the cut-off for the EMEP filter pack is larger than it is for PM10. This implies that higher calcium concentrations will be obtained with the original EMEP filter pack without a PM10 inlet. All comparisons of the two filter packs show excellent agreement for sulphur dioxide and man made sulphate particles. Some losses of total nitrate have been found with the PM10 inlet especially of particulate nitrate. Some losses of particulate ammonium also take place but do not affect the total concentration.
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| 3. |
- Ferm, Martin, et al.
(författare)
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Measurements of PM1, PM2.5 and PM10 in air at Nordic background stations using low-cost equipment
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Mass concentrations of PM1, PM2.5 and PM10 in air were measured at four EMEP stations in the Nordic countries during 2006. All stations used the same low-cost equipment for sampling PM1, but used different techniques for the other size fractions. The PM1 filters were analysed for inorganic ions for the first half of June. PM1 constituted on average more than half of the PM2.5 concentrations, but was on average less than half of the PM10 concentrations. There were two episodes of high PM1 concentrations during the year, one in May-June and another one in August-September. The highest PM1 concentrations were found during South-Easterly wind trajectories and lowest concentrations during northerly trajectories. Even though the annual average mass relations between the three size fractions were rather independent of the trajectory sectors, the fine and the coarse particle masses were not correlated on a daily basis. The PM2.5 concentration, which is the parameter that should be measured within EU, correlated fairly well with the concentration of accumulation mode particles (PM1). In June only a minor fraction of PM1 consisted of inorganic ions. Only ammonium and sulphate ions of the measured ions in PM1 were well correlated with one another.
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| 4. |
- Kulmala, Markku, et al.
(författare)
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Direct Observations of Atmospheric Aerosol Nucleation
- 2013
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 339:6122, s. 943-946
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric nucleation is the dominant source of aerosol particles in the global atmosphere and an important player in aerosol climatic effects. The key steps of this process occur in the sub-2-nanometer (nm) size range, in which direct size-segregated observations have not been possible until very recently. Here, we present detailed observations of atmospheric nanoparticles and clusters down to 1-nm mobility diameter. We identified three separate size regimes below 2-nm diameter that build up a physically, chemically, and dynamically consistent framework on atmospheric nucleation-more specifically, aerosol formation via neutral pathways. Our findings emphasize the important role of organic compounds in atmospheric aerosol formation, subsequent aerosol growth, radiative forcing and associated feedbacks between biogenic emissions, clouds, and climate.
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| 5. |
- Mayer, Ludovic, et al.
(författare)
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Widespread Pesticide Distribution in the European Atmosphere Questions their Degradability in Air
- 2024
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Ingår i: Environmental Science and Technology. - 0013-936X. ; 58:7, s. 3342-3352
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Tidskriftsartikel (refereegranskat)abstract
- Risk assessment of pesticide impacts on remote ecosystems makes use of model-estimated degradation in air. Recent studies suggest these degradation rates to be overestimated, questioning current pesticide regulation. Here, we investigated the concentrations of 76 pesticides in Europe at 29 rural, coastal, mountain, and polar sites during the agricultural application season. Overall, 58 pesticides were observed in the European atmosphere. Low spatial variation of 7 pesticides suggests continental-scale atmospheric dispersal. Based on concentrations in free tropospheric air and at Arctic sites, 22 pesticides were identified to be prone to long-range atmospheric transport, which included 15 substances approved for agricultural use in Europe and 7 banned ones. Comparison between concentrations at remote sites and those found at pesticide source areas suggests long atmospheric lifetimes of atrazine, cyprodinil, spiroxamine, tebuconazole, terbuthylazine, and thiacloprid. In general, our findings suggest that atmospheric transport and persistence of pesticides have been underestimated and that their risk assessment needs to be improved.
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| 6. |
- Yli-Juuti, Taina, et al.
(författare)
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Effect Of Salt Formation On Condensation Of Organic Compounds On Atmospheric Nanoparticles
- 2013
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Ingår i: NUCLEATION AND ATMOSPHERIC AEROSOLS. - : AIP. - 9780735411524 ; , s. 445-448
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Konferensbidrag (refereegranskat)abstract
- Freshly formed atmospheric nanoparticles have been observed to contain also such organic compounds which have too high saturation vapor pressure to condense on nanoparticles reversibly. The condensation of these compounds on the particles may be facilitated by particle phase processes that transform the compounds into less-volatile form. Here we use particle growth model MABNAG to study the effect of particle phase acid-base chemistry on the condensation of organic acids and bases.
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