Continuum regime motion of a growing droplet in opposing thermo-diffusiophoretic and gravitational fields of a thermal diffusion cloud chamber

A model for the motion of aerosol particles by Stefan flow, thermo-diffusiophoresis and gravity in a continuum regime is described, which considers a phase change on the particle surface. It is tested in a thermal diffusion cloud chamber where a droplet formed by nucleation quickly grows and simultaneously moves upwards due to vertical temperature and concentration gradients. Kinetic coefficients are assumed to be constant. Model predictions of the height where the droplet reverses its motion are in satisfactory agreement with the experimental results of Ždímal et al. ((1996). Colloids Surfaces A, 106, 119). The droplet motion seems to be predicted well at higher gradients and vapor fluxes, but model underestimates droplet motion at lower ones. For those cases also the free-molecule and transition regimes need to be included. Copyright © 2001 Elsevier Science B.V

Size resolved mass concentration and elemental composition of atmospheric aerosols over the Eastern Mediterranean area

International audienceA Berner low pressure impactor was used to collect size-segregated aerosol samples at Finokalia, located on the north-eastern coast of Crete, Greece during July 2000 and January 2001. Several samples were also collected during the summer campaign aboard the research vessel "AEGAIEO" in the Aegean Sea. Gravimetric analysis and inversion techniques yielded daily PM1 and PM10 mass concentrations. The samples were also analysed by PIXE giving the elemental size distributions of Al, Si, K, Ca, Ti, Mn, Fe, Sr, S, Cl, Ni, V, Cu, Cr, Zn, and Pb. The crustal elements and sea-salt had a unimodal supermicron size distribution. Sulphur was found predominantly in submicron fractions. K, V, and Ni exhibited a bimodal distribution with a submicron mode produced by forest fires and oil combustion. The anthropogenic elements had broad and not well-defined distributions. The time series for PM1 and PM10 mass and elemental concentrations showed both daily and seasonal variation. Higher mass concentrations were observed during two incursions of Saharan dust, whilst higher concentrations of S, Cu, Zn, and Pb were encountered in samples collected in air masses arriving from northern Greece or the western coast of Turkey. Elevated concentrations of chlorine were found in samples with air masses either originating above the Atlantic Ocean and arriving at Finokalia via western Europe or recirculating over the western coast of the Black Sea

Mesoscale modeling of combined aerosol and photo-oxidant processes in the eastern Mediterranean

International audienceParticulate matter and photo-oxidant processes in the Eastern Mediterranean have been studied using the UAM-AERO mesoscale air quality model in conjunction with the NILU-CTM regional model. Meteorological data were obtained from the RAMS prognostic meteorological model. The modeling domain includes the eastern Mediterranean area between the Greek mainland and the island of Crete. The modeling system is applied to study the atmospheric processes in three periods, i.e. 13?16 July 2000, 26?30 July 2000 and 7?14 January 2001. The spatial and temporal distributions of both gaseous and particulate matter pollutants have been extensively studied together with the identification of major emission sources in the area. The modeling results were compared with field data obtained in the same period. Comparison of the modeling results with measured data was performed for a number of gaseous and aerosol species. The UAM-AERO model underestimates the PM10 measured concentrations during summer but better comparison has been obtained for the winter data

Continuum regime motion of a growing droplet in opposing thermo-diffusiophoretic and gravitational fields of a thermal diffusion cloud chamber

A model for the motion of aerosol particles by Stefan flow, thermo-diffusiophoresis and gravity in a continuum regime is described, which considers a phase change on the particle surface. It is tested in a thermal diffusion cloud chamber where a droplet formed by nucleation quickly grows and simultaneously moves upwards due to vertical temperature and concentration gradients. Kinetic coefficients are assumed to be constant. Model predictions of the height where the droplet reverses its motion are in satisfactory agreement with the experimental results of Ždímal et al. ((1996). Colloids Surfaces A, 106, 119). The droplet motion seems to be predicted well at higher gradients and vapor fluxes, but model underestimates droplet motion at lower ones. For those cases also the free-molecule and transition regimes need to be included. Copyright © 2001 Elsevier Science B.V

Continuum regime motion of a growing droplet in opposing thermo-diffusiophoretic and gravitational fields of a thermal diffusion cloud chamber

A model for the motion of aerosol particles by Stefan flow, thermo-diffusiophoresis and gravity in a continuum regime is described, which considers a phase change on the particle surface. It is tested in a thermal diffusion cloud chamber where a droplet formed by nucleation quickly grows and simultaneously moves upwards due to vertical temperature and concentration gradients. Kinetic coefficients are assumed to be constant. Model predictions of the height where the droplet reverses its motion are in satisfactory agreement with the experimental results of Ždímal et al. ((1996). Colloids Surfaces A, 106, 119). The droplet motion seems to be predicted well at higher gradients and vapor fluxes, but model underestimates droplet motion at lower ones. For those cases also the free-molecule and transition regimes need to be included. Copyright © 2001 Elsevier Science B.V

Continuum regime motion of a growing droplet in opposing thermo-diffusiophoretic and gravitational fields of a thermal diffusion cloud chamber

A model for the motion of aerosol particles by Stefan flow, thermo-diffusiophoresis and gravity in a continuum regime is described, which considers a phase change on the particle surface. It is tested in a thermal diffusion cloud chamber where a droplet formed by nucleation quickly grows and simultaneously moves upwards due to vertical temperature and concentration gradients. Kinetic coefficients are assumed to be constant. Model predictions of the height where the droplet reverses its motion are in satisfactory agreement with the experimental results of Ždímal et al. ((1996). Colloids Surfaces A, 106, 119). The droplet motion seems to be predicted well at higher gradients and vapor fluxes, but model underestimates droplet motion at lower ones. For those cases also the free-molecule and transition regimes need to be included. Copyright © 2001 Elsevier Science B.V