Seed aerosol

I) A gas-phase product of the OH-aromatic reaction simply forms a liquid particle because of its vapor pressure, in the absence of any "seed" aerosol. 

II) A "seed" aerosol exists and the gas is taken up onto, but not into the aerosol. 

Ice particle measurements in the expansion experiment with 40% OC soot aerosol markedly differ from the 16% OC sample. Note that the optical particle spectrometer hardly detects any ice particles. Additionally, extinction signatures of ice are barely visible in the infrared spectra and diere is only a weak intensity increase of the back-scattered laser light in course of the expansion. The number concentration of ice crystals is less than 10 cm, thus < 1% of the seed aerosol particles act as deposition ice nuclei. In contrast to the 16% OC experiment, no precise critical ice saturation ratio can be specified for the 40% OC soot sample. RHi continues to increase to 190% because very little water vapour is lost on the small surface area of the scarce ice crystals. In summary, die comparison of the two expansion experiments provides first evidence that a higher fraction of organic carbon notably suppresses the ice nucleation potential of flame soot particles. 

Figure 6- Measured time profiles of pressure, gas temperature, relative humidity with respect to ice, back-scattered laser light intensity, as well as ice particle number concentration for two expansion cooling experiments with different flame soot aerosol samples from the CAST burner as seed aerosol (Mdhler et al, 2004b). See text for details.

Seed aerosol neutral acidic neutral acidic neutral acidic... 

Galloway, M. M., P. S. Chhabra, A. W. H. Chahn, J. D. Surrat, R. C. Flagan, J. H. Seinfeld and F. N. Keutsch (2009) Glyoxal uptake on ammonium sulphate seed aerosol Reaction products and reversibility of uptake under dark and irradiated conditions. Atmospheric Chemistry and Physics 9, 3331-3345... 

Recently we studied the effect of surfactants like methylglyoxal and acetaldehyde by exposing deliquesced ammonium sulfate seed aerosols (65% RH) 8 ppb or 250 ppb of the organic gas in a 3.5-m continuous flow aerosol reaction chamber [238]. The CCN activity was measured using a Continuous-Flow Streamwise... 

Schreier H, Gagne L, Conary JT, Laurian G (1998) Simulated lung transfection by nebulization of liposome cDNA complexes using a cascade impactor seeded with 2-CFSMEO-cells. J Aerosol Med 11 1-13... 

Smog chamber studies have documented similar aerosol growth mechanisms. For example, in the photochemical oxidation of dimethyl sulfide, the formation and growth of particles in an initially particle-free system was observed. However, if seed particles with 34-nm mean size were present, an oscillation in the... 

However, care must be taken to ensure that seed nuclei are present on which condensation can occur. If a very clean system is used in which nuclei are not present, spontaneous nucleation may occur this process is such that nuclei do not appear uniformly either in space or in time, and the initial particle growth rate depends on the degree of supersaturation. As a result, a polydisperse aerosol is produced under these conditions. 

Aerosols, fog and smog, foams, water purification and sewage treatment cloud seeding and clean room technology (see also Vignettes 1.1 and VIII)... 

In later experiments, Izumi et al. (47, 48) examined aerosol formation during photooxidation of a variety of hydrocarbons in an evacuable smog chamber. No seed particles were used in these experiments, but good estimates of the yield of aerosol from photochemical oxidation of the hydrocarbon precursors were obtained by using EAA data. In some cases, the volumetric yield was found to decrease with decreasing precursor concentration (Figure 4), so the finite vapor pressure of the reaction products limited nucleation, particle growth, or both. 

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