Antti-pekka Hyvärinen | University of Eastern Finland (original) (raw)
Papers by Antti-pekka Hyvärinen
Geophysica
The Arctic Summer Cloud Ocean Study, ASCOS, was a six-week expedition in August-September 2008 no... more The Arctic Summer Cloud Ocean Study, ASCOS, was a six-week expedition in August-September 2008 north of the 87th latitude onboard the Swedish icebreaker Oden. The expedition was a contribution to the International Polar Year 2007/2008. ASCOS studies some of the controlling factors of the low-level cloud system, especially the formation of cloud condensation and ice nuclei, over the Arctic pack ice. This will improve the accuracy of the climate models in the Arctic area where the climate is expected to change faster than in any other part of the world. A distinct feature of ASCOS is its necessarily interdisciplinary nature, which includes physical oceanography, marine and sea ice biogeochemistry, surface microlayer chemistry, aerosol, gas-phase and cloud chemistry and physics, and meteorology. The expedition sailed from Longyearbyen, Svalbard, in the beginning of August. After a week's cruise the icebreaker was moored to a several square kilometres wide ice floe north of the 87th...
Nucleation and Atmospheric Aerosols, 2007
ABSTRACT New particle formation in the atmosphere still attracts both atmospheric scientists and ... more ABSTRACT New particle formation in the atmosphere still attracts both atmospheric scientists and aerosol researchers. New laminar flow chamber was recently built in Finnish Meteorological Institute to study particle formation of binary and ternary compounds such as sulfuric acid–water and sulfuric acid–ammonia–water, respectively. The laminar flow chamber and its experimental setup are presented here. Keywords Homogeneous nucleation, particle formation, sulfuric acid–water
Nucleation and Atmospheric Aerosols, 2007
Page 1. 561 CD O'Dowd and PE Wagner (eds.), Nucleation and Atmospheric Aerosols, 561–564. © ... more Page 1. 561 CD O'Dowd and PE Wagner (eds.), Nucleation and Atmospheric Aerosols, 561–564. © Springer 2007. ... These kinds of stations are, eg, the GAW (Global Atmospheric Watch) stations at Jungfraujoch in Switzerland and at Pallas in Finland. ...
The Journal of Physical Chemistry C, 2008
... Abdul-Razzak, H.; Ghan, SJ J. Geophys. Res. 2004 109 D03205 [CrossRef]. 14. Henning, S.; Rose... more ... Abdul-Razzak, H.; Ghan, SJ J. Geophys. Res. 2004 109 D03205 [CrossRef]. 14. Henning, S.; Rosenørn, T.; D'Anna, B.; Gola, AA; Svenningsson, B.; Bilde, M. Atmos. Chem. Phys. 2005 5 575 582 [ChemPort]. 15. Mmereki, BT; Hicks, JM; Donaldson, DJ J. Phys. Chem. ...
The Journal of Physical Chemistry A, 2007
The surface tension of adipic aqueous solutions was measured as a function of temperature (T=278-... more The surface tension of adipic aqueous solutions was measured as a function of temperature (T=278-313 K) and adipic acid mole fraction (X=0.000-0.003) using the Wilhelmy plate method. A parametrization fitted to these data is presented. The evaporation rates of binary water-malonic and water-adipic acid droplets were measured with a TDMA technique at different temperatures (T=293-300 K) and relative humidities (58-80%), and the saturation vapor pressures of subcooled liquid malonic and adipic acids were derived from the data using a binary evaporation model. The temperature dependence of the vapor pressures was obtained as least-squares fits to the derived vapor pressures: ln(Psat,l) (Pa)=220.2389-22634.96/T (K)-26.66767 ln T (K) for malonic acid and ln(Psat,l) (Pa)=140.6704-18230.97/T (K)-15.48011 ln T (K) for adipic acid.
The Journal of Physical Chemistry A, 2006
This work is an assessment of the capabilities of the FLUENT-FPM software package to simulate act... more This work is an assessment of the capabilities of the FLUENT-FPM software package to simulate actual nucleation experiments. In the first step, we verified the FPM condensation routine with the NEWALC code. Next, homogeneous nucleation of n-butanol, n-pentanol, and n-hexanol in a laminar flow diffusion chamber (LFDC) was simulated and the results were compared to experimental data and an earlier model, which was described by Lihavainen and Viisanen (2001) and will be called femtube2 in the following. Models based on classical nucleation theory typically give too small nucleation rates for alcohol vapors. Also, the FPM underestimates particle production by several orders of magnitude, the factor being a constant for each nucleation isotherm (i.e., at constant nucleation temperature). However, experimental observations beyond exact particle concentrations can be reproduced. We found a behavior similar to the experiment for the dependence of the concentration of nucleated particles N on the flow rate. After correcting the FPM nucleation rate by a constant factor, experimentally found vapor depletion effects could be simulated. Comparing the FPM and femtube2, we observed that the FPM systematically predicts lower saturation ratio values. Further investigation of vapor depletion showed significant differences between the FPM and the femtube2 model. Furthermore, FPM simulations confirm the earlier found carrier gas effect (Lihavainen and Viisanen,
Science, 2010
This copy is for your personal, non-commercial use only.
Physical Review Letters, 2008
The influence of the pressure of a chemically inert carrier gas on the nucleation rate is one of ... more The influence of the pressure of a chemically inert carrier gas on the nucleation rate is one of the biggest puzzles in the research of gas-liquid nucleation. Experiments can show a positive effect, a negative effect, or no effect at all. The same experiment may show both trends for the same substance depending on temperature, or for different substances at the same temperature. We show how this ambiguous effect naturally arises from the competition of two contributions: nonisothermal effects and pressure-volume work. Our model clarifies seemingly contradictory experimental results and quantifies the variation of the nucleation ability of a substance in the presence of an ambient gas. Our findings are corroborated by molecular dynamics simulations and might have important implications since nucleation in experiments, technical applications, and nature practically always occurs in the presence of an ambient gas.
Journal of Geophysical Research, 2009
The Journal of Chemical Physics, 2014
Nucleation rates of n-propanol were investigated in the Laminar Flow Diffusion Chamber. Nucleatio... more Nucleation rates of n-propanol were investigated in the Laminar Flow Diffusion Chamber. Nucleation temperatures between 270 and 300 K and rates between 10(0) and 10(6) cm(-3) s(-1) were achieved. Since earlier measurements of n-butanol and n‑pentanol suggest a dependence of nucleation rates on carrier gas pressure, similar conditions were adjusted for these measurements. The obtained data fit well to results available from literature. A small positive pressure effect was found which strengthen the assumption that this effect is attributed to the carbon chain length of the n-alcohol [D. Brus, A. P. Hyvärinen, J. Wedekind, Y. Viisanen, M. Kulmala, V. Ždímal, J. Smolík, and H. Lihavainen, J. Chem. Phys. 128, 134312 (2008)] and might be less intensive for substances in the homologous series with higher equilibrium vapor pressure. A comparison with the theoretical approach by Wedekind et al. [Phys. Rev. Lett. 101, 12 (2008)] shows that the effect goes in the same direction but that the intensity is much stronger in experiments than in theory.
The Journal of Chemical Physics, 2004
Nucleation rate isotherms of n-butanol, n-pentanol, n-hexanol, n-heptanol, and n-octanol were mea... more Nucleation rate isotherms of n-butanol, n-pentanol, n-hexanol, n-heptanol, and n-octanol were measured in a laminar flow diffusion chamber using helium as carrier gas. The measurements were made at 250-310 K, corresponding to reduced temperatures of 0.43-0.50, and at atmospheric pressure. Experimental nucleation rate range was from 10(3) to 10(7) cm(-3) s(-1). The expression and accuracy of thermodynamic parameters, in particular equilibrium vapor pressure, were found to have a significant effect on calculated nucleation rates. The results were compared to the classical nucleation theory (CNT), the self-consistency corrected classical theory (SCC) and the Hale's scaled model of the CNT. The average ratio between the experimental and theoretical nucleation rates for all alcohols used was 1.5x10(3) when the CNT was used, and 0.2x10(-1) when the SCC was used and 0.7x10(-1) when the Hale's scaled theory was used. The average values represent all the alcohols used at the same reduced temperatures. The average ratio was about the same throughout the temperature range, although J(exp)/J(the) calculated with the Hale's scaled theory increased slightly with increasing temperature. The saturation ratio dependency was predicted closest to experiment with the classical nucleation theory. The nucleation rates were compared to those found in the literature. The measurements were in reasonable agreement with each other. The molecular content of critical alcohol clusters was between 35 and 80 molecules. At a fixed reduced temperature, the number of molecules in a critical cluster decreased as a function of alcohol carbon chain length. The number of molecules in critical clusters was compared to those predicted by the Kelvin equation. The theory predicted the critical cluster sizes well.
The Journal of Chemical Physics, 2010
Homogeneous nucleation rates of water at temperatures between 240 and 270 K were measured in a la... more Homogeneous nucleation rates of water at temperatures between 240 and 270 K were measured in a laminar flow diffusion chamber at ambient pressure and helium as carrier gas. Being in the range of 10 2 -10 6 cm −3 s −1 , the experimental results extend the nucleation rate data from literature consistently and fill a pre-existing gap. Using the macroscopic vapor pressure, density, and surface tension for water we calculate the nucleation rates predicted by classic nucleation theory ͑CNT͒ and by the empirical correction function of CNT by Wölk and Strey ͓J. Phys. Chem. B 105, 11683 ͑2001͔͒. As in the case of other systems ͑e.g., alcohols͒, CNT predicts a stronger temperature dependence than experimentally observed, whereas the agreement with the empirical correction function is good for all data sets. Furthermore, the isothermal nucleation rate curves allow us to determine the experimental critical cluster sizes by use of the nucleation theorem. A comparison with the critical cluster sizes calculated by use of the Gibbs-Thomson equation is remarkably good for small cluster sizes, for bigger ones the Gibbs-Thomson equation overestimates the cluster sizes.
The Journal of Chemical Physics, 2008
Geophysical Research Letters, 2010
1] Nucleation theories typically neglect the influence of the ambient pressure on the condensatio... more 1] Nucleation theories typically neglect the influence of the ambient pressure on the condensation of droplets from a supersaturated vapor, despite increasing experimental evidence. We have applied a recently presented model that incorporates this effect to the homogeneous nucleation rates of water at tropospheric conditions. We measured experimental pressure dependent nucleation rates of water in helium at low to intermediate pressures and at temperatures from 240-270 K with the laminar flow diffusion chamber. The observed pressure effect shows a clear positive effect (increasing nucleation rate with increasing pressure) at 270 K and a weaker effect with lower temperatures, consistent with the theory. The experimental pressure effect was more pronounced than predicted by theory. The same principle of the pressure effect should also hold for heterogeneous nucleation of water, which implies that water vapor removal by droplet nucleation of water may be suppressed at tropospheric conditions. Citation: Hyvärinen, A.-P., D. Brus, J. Wedekind, and H. Lihavainen (2010), How ambient pressure influences water droplet nucleation at tropospheric conditions, Geophys. Res. Lett.,
Geophysical Research Letters, 2005
The static surface tensions and densities of ternary H2SO4 + NH3 + H2O solutions were measured at... more The static surface tensions and densities of ternary H2SO4 + NH3 + H2O solutions were measured at about 298 K using the Wilhelmy plate method. The mole fractions of H2SO4 ranged from 0 to 0.45 (0 to 82 wt%) and the mole fractions of NH3 from 0 to 0.26 (0 to 25 wt%). The available mole fractions were limited by the concentrations of the original aqueous ammonia solution and salt formation during mixing of sulfuric acid and ammonia. At constant mole fractions of H2SO4, the surface tension reaches its highest value when the mole fraction ratio between NH3 and H2SO4 is 2, corresponding to the binary solution of (NH4)2SO4 + water. The surface tensions and densities are presented, and expressed as polynomials as a function of sulfuric acid and ammonia mole fractions.
Atmospheric Research, 2008
... For example, in the atmosphere, nucleation processes take place in formation of new ultrafine... more ... For example, in the atmosphere, nucleation processes take place in formation of new ultrafine particles in the planetary boundary layer and in free troposphere (Kulmala et al., 2004), and in ice crystal formation in cloud droplets (Cantrell and Heymsfield, 2005). ...
Atmospheric Environment, 2011
Polycyclic aromatic hydrocarbons (PAH compounds) were measured in the PM 10 fraction [from ambien... more Polycyclic aromatic hydrocarbons (PAH compounds) were measured in the PM 10 fraction [from ambient air] at Virolahti, Finland. The sampling site is located in a rural area in the south-eastern corner of Finland, near the Russian border. Altogether, 51 daily and 85 weekly filter samples were collected in 2007e2008. The yearly average concentration of benzo(a)pyrene at Virolahti in 2007 was 0.21 ng m À3 , which is well below the annual target value of 1 ng m À3 set by the European Union. The positive matrix factorization (PMF) method was applied in source apportionment for daily PAH data combined with other pollutant data. A three-factor solution of the PMF analysis with 28 components was chosen. These three factors were identified as long-range transported secondary particles (F1), combustion (F2) and a sea-salt factor (F3). The conditional probability function (CPF) was used to combine wind direction sectors with the PMF factors. In cases F1 and F2, pollutants mainly originated from the south-east, whereas pollutants in F3 came from the south-western sector.
Atmospheric Chemistry and Physics, 2013
Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical... more Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical and optical properties, resulting in more than 20 long-term (> 10 yr) aerosol measurement sites in the Northern Hemisphere and Antarctica. Most of these sites are located at remote locations and monitor the aerosol particle number concentration, wavelength-dependent light scattering, backscattering, and absorption coefficients. The existence of these multi-year datasets enables the analysis of long-term trends of these aerosol parameters, and of the derived light scatter-ingÅngström exponent and backscatter fraction. Since the aerosol variables are not normally distributed, three different methods (the seasonal Mann-Kendall test associated with the Sen's slope, the generalized least squares fit associated with an autoregressive bootstrap algorithm for confidence inter-vals, and the least-mean square fit applied to logarithms of the data) were applied to detect the long-term trends and their magnitudes. To allow a comparison among measurement sites, trends on the most recent 10 and 15 yr periods were calculated. No significant trends were found for the three continental European sites. Statistically significant trends were found for the two European marine sites but the signs of the trends varied with aerosol property and location. Statistically significant decreasing trends for both scattering and absorption coefficients (mean slope of −2.0 % yr −1 ) were found for most North American stations, although positive trends were found for a few desert and high-altitude sites. The difference in the timing of emission reduction policy for the Europe and US continents is a likely explanation for the decreasing trends in aerosol optical parameters found for most American Published by Copernicus Publications on behalf of the European Geosciences Union. 870 M. Collaud Coen et al.: Aerosol decadal trends -Part 1 sites compared to the lack of trends observed in Europe. No significant trends in scattering coefficient were found for the Arctic or Antarctic stations, whereas the Arctic station had a negative trend in absorption coefficient. The high altitude Pacific island station of Mauna Loa presents positive trends for both scattering and absorption coefficients. Atmos. Chem. Phys., 13, 869-894, 2013 www.atmos-chem-phys.net/13/869/2013/ Atmos. Chem. Phys., 13, 869-894, 2013 www.atmos-chem-phys.net/13/869/2013/ Atmos. Chem. Phys., 13, 869-894, 2013 www.atmos-chem-phys.net/13/869/2013/
Geophysica
The Arctic Summer Cloud Ocean Study, ASCOS, was a six-week expedition in August-September 2008 no... more The Arctic Summer Cloud Ocean Study, ASCOS, was a six-week expedition in August-September 2008 north of the 87th latitude onboard the Swedish icebreaker Oden. The expedition was a contribution to the International Polar Year 2007/2008. ASCOS studies some of the controlling factors of the low-level cloud system, especially the formation of cloud condensation and ice nuclei, over the Arctic pack ice. This will improve the accuracy of the climate models in the Arctic area where the climate is expected to change faster than in any other part of the world. A distinct feature of ASCOS is its necessarily interdisciplinary nature, which includes physical oceanography, marine and sea ice biogeochemistry, surface microlayer chemistry, aerosol, gas-phase and cloud chemistry and physics, and meteorology. The expedition sailed from Longyearbyen, Svalbard, in the beginning of August. After a week's cruise the icebreaker was moored to a several square kilometres wide ice floe north of the 87th...
Nucleation and Atmospheric Aerosols, 2007
ABSTRACT New particle formation in the atmosphere still attracts both atmospheric scientists and ... more ABSTRACT New particle formation in the atmosphere still attracts both atmospheric scientists and aerosol researchers. New laminar flow chamber was recently built in Finnish Meteorological Institute to study particle formation of binary and ternary compounds such as sulfuric acid–water and sulfuric acid–ammonia–water, respectively. The laminar flow chamber and its experimental setup are presented here. Keywords Homogeneous nucleation, particle formation, sulfuric acid–water
Nucleation and Atmospheric Aerosols, 2007
Page 1. 561 CD O'Dowd and PE Wagner (eds.), Nucleation and Atmospheric Aerosols, 561–564. © ... more Page 1. 561 CD O'Dowd and PE Wagner (eds.), Nucleation and Atmospheric Aerosols, 561–564. © Springer 2007. ... These kinds of stations are, eg, the GAW (Global Atmospheric Watch) stations at Jungfraujoch in Switzerland and at Pallas in Finland. ...
The Journal of Physical Chemistry C, 2008
... Abdul-Razzak, H.; Ghan, SJ J. Geophys. Res. 2004 109 D03205 [CrossRef]. 14. Henning, S.; Rose... more ... Abdul-Razzak, H.; Ghan, SJ J. Geophys. Res. 2004 109 D03205 [CrossRef]. 14. Henning, S.; Rosenørn, T.; D'Anna, B.; Gola, AA; Svenningsson, B.; Bilde, M. Atmos. Chem. Phys. 2005 5 575 582 [ChemPort]. 15. Mmereki, BT; Hicks, JM; Donaldson, DJ J. Phys. Chem. ...
The Journal of Physical Chemistry A, 2007
The surface tension of adipic aqueous solutions was measured as a function of temperature (T=278-... more The surface tension of adipic aqueous solutions was measured as a function of temperature (T=278-313 K) and adipic acid mole fraction (X=0.000-0.003) using the Wilhelmy plate method. A parametrization fitted to these data is presented. The evaporation rates of binary water-malonic and water-adipic acid droplets were measured with a TDMA technique at different temperatures (T=293-300 K) and relative humidities (58-80%), and the saturation vapor pressures of subcooled liquid malonic and adipic acids were derived from the data using a binary evaporation model. The temperature dependence of the vapor pressures was obtained as least-squares fits to the derived vapor pressures: ln(Psat,l) (Pa)=220.2389-22634.96/T (K)-26.66767 ln T (K) for malonic acid and ln(Psat,l) (Pa)=140.6704-18230.97/T (K)-15.48011 ln T (K) for adipic acid.
The Journal of Physical Chemistry A, 2006
This work is an assessment of the capabilities of the FLUENT-FPM software package to simulate act... more This work is an assessment of the capabilities of the FLUENT-FPM software package to simulate actual nucleation experiments. In the first step, we verified the FPM condensation routine with the NEWALC code. Next, homogeneous nucleation of n-butanol, n-pentanol, and n-hexanol in a laminar flow diffusion chamber (LFDC) was simulated and the results were compared to experimental data and an earlier model, which was described by Lihavainen and Viisanen (2001) and will be called femtube2 in the following. Models based on classical nucleation theory typically give too small nucleation rates for alcohol vapors. Also, the FPM underestimates particle production by several orders of magnitude, the factor being a constant for each nucleation isotherm (i.e., at constant nucleation temperature). However, experimental observations beyond exact particle concentrations can be reproduced. We found a behavior similar to the experiment for the dependence of the concentration of nucleated particles N on the flow rate. After correcting the FPM nucleation rate by a constant factor, experimentally found vapor depletion effects could be simulated. Comparing the FPM and femtube2, we observed that the FPM systematically predicts lower saturation ratio values. Further investigation of vapor depletion showed significant differences between the FPM and the femtube2 model. Furthermore, FPM simulations confirm the earlier found carrier gas effect (Lihavainen and Viisanen,
Science, 2010
This copy is for your personal, non-commercial use only.
Physical Review Letters, 2008
The influence of the pressure of a chemically inert carrier gas on the nucleation rate is one of ... more The influence of the pressure of a chemically inert carrier gas on the nucleation rate is one of the biggest puzzles in the research of gas-liquid nucleation. Experiments can show a positive effect, a negative effect, or no effect at all. The same experiment may show both trends for the same substance depending on temperature, or for different substances at the same temperature. We show how this ambiguous effect naturally arises from the competition of two contributions: nonisothermal effects and pressure-volume work. Our model clarifies seemingly contradictory experimental results and quantifies the variation of the nucleation ability of a substance in the presence of an ambient gas. Our findings are corroborated by molecular dynamics simulations and might have important implications since nucleation in experiments, technical applications, and nature practically always occurs in the presence of an ambient gas.
Journal of Geophysical Research, 2009
The Journal of Chemical Physics, 2014
Nucleation rates of n-propanol were investigated in the Laminar Flow Diffusion Chamber. Nucleatio... more Nucleation rates of n-propanol were investigated in the Laminar Flow Diffusion Chamber. Nucleation temperatures between 270 and 300 K and rates between 10(0) and 10(6) cm(-3) s(-1) were achieved. Since earlier measurements of n-butanol and n‑pentanol suggest a dependence of nucleation rates on carrier gas pressure, similar conditions were adjusted for these measurements. The obtained data fit well to results available from literature. A small positive pressure effect was found which strengthen the assumption that this effect is attributed to the carbon chain length of the n-alcohol [D. Brus, A. P. Hyvärinen, J. Wedekind, Y. Viisanen, M. Kulmala, V. Ždímal, J. Smolík, and H. Lihavainen, J. Chem. Phys. 128, 134312 (2008)] and might be less intensive for substances in the homologous series with higher equilibrium vapor pressure. A comparison with the theoretical approach by Wedekind et al. [Phys. Rev. Lett. 101, 12 (2008)] shows that the effect goes in the same direction but that the intensity is much stronger in experiments than in theory.
The Journal of Chemical Physics, 2004
Nucleation rate isotherms of n-butanol, n-pentanol, n-hexanol, n-heptanol, and n-octanol were mea... more Nucleation rate isotherms of n-butanol, n-pentanol, n-hexanol, n-heptanol, and n-octanol were measured in a laminar flow diffusion chamber using helium as carrier gas. The measurements were made at 250-310 K, corresponding to reduced temperatures of 0.43-0.50, and at atmospheric pressure. Experimental nucleation rate range was from 10(3) to 10(7) cm(-3) s(-1). The expression and accuracy of thermodynamic parameters, in particular equilibrium vapor pressure, were found to have a significant effect on calculated nucleation rates. The results were compared to the classical nucleation theory (CNT), the self-consistency corrected classical theory (SCC) and the Hale's scaled model of the CNT. The average ratio between the experimental and theoretical nucleation rates for all alcohols used was 1.5x10(3) when the CNT was used, and 0.2x10(-1) when the SCC was used and 0.7x10(-1) when the Hale's scaled theory was used. The average values represent all the alcohols used at the same reduced temperatures. The average ratio was about the same throughout the temperature range, although J(exp)/J(the) calculated with the Hale's scaled theory increased slightly with increasing temperature. The saturation ratio dependency was predicted closest to experiment with the classical nucleation theory. The nucleation rates were compared to those found in the literature. The measurements were in reasonable agreement with each other. The molecular content of critical alcohol clusters was between 35 and 80 molecules. At a fixed reduced temperature, the number of molecules in a critical cluster decreased as a function of alcohol carbon chain length. The number of molecules in critical clusters was compared to those predicted by the Kelvin equation. The theory predicted the critical cluster sizes well.
The Journal of Chemical Physics, 2010
Homogeneous nucleation rates of water at temperatures between 240 and 270 K were measured in a la... more Homogeneous nucleation rates of water at temperatures between 240 and 270 K were measured in a laminar flow diffusion chamber at ambient pressure and helium as carrier gas. Being in the range of 10 2 -10 6 cm −3 s −1 , the experimental results extend the nucleation rate data from literature consistently and fill a pre-existing gap. Using the macroscopic vapor pressure, density, and surface tension for water we calculate the nucleation rates predicted by classic nucleation theory ͑CNT͒ and by the empirical correction function of CNT by Wölk and Strey ͓J. Phys. Chem. B 105, 11683 ͑2001͔͒. As in the case of other systems ͑e.g., alcohols͒, CNT predicts a stronger temperature dependence than experimentally observed, whereas the agreement with the empirical correction function is good for all data sets. Furthermore, the isothermal nucleation rate curves allow us to determine the experimental critical cluster sizes by use of the nucleation theorem. A comparison with the critical cluster sizes calculated by use of the Gibbs-Thomson equation is remarkably good for small cluster sizes, for bigger ones the Gibbs-Thomson equation overestimates the cluster sizes.
The Journal of Chemical Physics, 2008
Geophysical Research Letters, 2010
1] Nucleation theories typically neglect the influence of the ambient pressure on the condensatio... more 1] Nucleation theories typically neglect the influence of the ambient pressure on the condensation of droplets from a supersaturated vapor, despite increasing experimental evidence. We have applied a recently presented model that incorporates this effect to the homogeneous nucleation rates of water at tropospheric conditions. We measured experimental pressure dependent nucleation rates of water in helium at low to intermediate pressures and at temperatures from 240-270 K with the laminar flow diffusion chamber. The observed pressure effect shows a clear positive effect (increasing nucleation rate with increasing pressure) at 270 K and a weaker effect with lower temperatures, consistent with the theory. The experimental pressure effect was more pronounced than predicted by theory. The same principle of the pressure effect should also hold for heterogeneous nucleation of water, which implies that water vapor removal by droplet nucleation of water may be suppressed at tropospheric conditions. Citation: Hyvärinen, A.-P., D. Brus, J. Wedekind, and H. Lihavainen (2010), How ambient pressure influences water droplet nucleation at tropospheric conditions, Geophys. Res. Lett.,
Geophysical Research Letters, 2005
The static surface tensions and densities of ternary H2SO4 + NH3 + H2O solutions were measured at... more The static surface tensions and densities of ternary H2SO4 + NH3 + H2O solutions were measured at about 298 K using the Wilhelmy plate method. The mole fractions of H2SO4 ranged from 0 to 0.45 (0 to 82 wt%) and the mole fractions of NH3 from 0 to 0.26 (0 to 25 wt%). The available mole fractions were limited by the concentrations of the original aqueous ammonia solution and salt formation during mixing of sulfuric acid and ammonia. At constant mole fractions of H2SO4, the surface tension reaches its highest value when the mole fraction ratio between NH3 and H2SO4 is 2, corresponding to the binary solution of (NH4)2SO4 + water. The surface tensions and densities are presented, and expressed as polynomials as a function of sulfuric acid and ammonia mole fractions.
Atmospheric Research, 2008
... For example, in the atmosphere, nucleation processes take place in formation of new ultrafine... more ... For example, in the atmosphere, nucleation processes take place in formation of new ultrafine particles in the planetary boundary layer and in free troposphere (Kulmala et al., 2004), and in ice crystal formation in cloud droplets (Cantrell and Heymsfield, 2005). ...
Atmospheric Environment, 2011
Polycyclic aromatic hydrocarbons (PAH compounds) were measured in the PM 10 fraction [from ambien... more Polycyclic aromatic hydrocarbons (PAH compounds) were measured in the PM 10 fraction [from ambient air] at Virolahti, Finland. The sampling site is located in a rural area in the south-eastern corner of Finland, near the Russian border. Altogether, 51 daily and 85 weekly filter samples were collected in 2007e2008. The yearly average concentration of benzo(a)pyrene at Virolahti in 2007 was 0.21 ng m À3 , which is well below the annual target value of 1 ng m À3 set by the European Union. The positive matrix factorization (PMF) method was applied in source apportionment for daily PAH data combined with other pollutant data. A three-factor solution of the PMF analysis with 28 components was chosen. These three factors were identified as long-range transported secondary particles (F1), combustion (F2) and a sea-salt factor (F3). The conditional probability function (CPF) was used to combine wind direction sectors with the PMF factors. In cases F1 and F2, pollutants mainly originated from the south-east, whereas pollutants in F3 came from the south-western sector.
Atmospheric Chemistry and Physics, 2013
Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical... more Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical and optical properties, resulting in more than 20 long-term (> 10 yr) aerosol measurement sites in the Northern Hemisphere and Antarctica. Most of these sites are located at remote locations and monitor the aerosol particle number concentration, wavelength-dependent light scattering, backscattering, and absorption coefficients. The existence of these multi-year datasets enables the analysis of long-term trends of these aerosol parameters, and of the derived light scatter-ingÅngström exponent and backscatter fraction. Since the aerosol variables are not normally distributed, three different methods (the seasonal Mann-Kendall test associated with the Sen's slope, the generalized least squares fit associated with an autoregressive bootstrap algorithm for confidence inter-vals, and the least-mean square fit applied to logarithms of the data) were applied to detect the long-term trends and their magnitudes. To allow a comparison among measurement sites, trends on the most recent 10 and 15 yr periods were calculated. No significant trends were found for the three continental European sites. Statistically significant trends were found for the two European marine sites but the signs of the trends varied with aerosol property and location. Statistically significant decreasing trends for both scattering and absorption coefficients (mean slope of −2.0 % yr −1 ) were found for most North American stations, although positive trends were found for a few desert and high-altitude sites. The difference in the timing of emission reduction policy for the Europe and US continents is a likely explanation for the decreasing trends in aerosol optical parameters found for most American Published by Copernicus Publications on behalf of the European Geosciences Union. 870 M. Collaud Coen et al.: Aerosol decadal trends -Part 1 sites compared to the lack of trends observed in Europe. No significant trends in scattering coefficient were found for the Arctic or Antarctic stations, whereas the Arctic station had a negative trend in absorption coefficient. The high altitude Pacific island station of Mauna Loa presents positive trends for both scattering and absorption coefficients. Atmos. Chem. Phys., 13, 869-894, 2013 www.atmos-chem-phys.net/13/869/2013/ Atmos. Chem. Phys., 13, 869-894, 2013 www.atmos-chem-phys.net/13/869/2013/ Atmos. Chem. Phys., 13, 869-894, 2013 www.atmos-chem-phys.net/13/869/2013/