Aerosol ultrafine aerosols

Chu et al. (1987) present results of laboratory studies of the formation of an ultrafine aerosol by converting SO- to sulfuric acid using measurement methods described by Holub and Knutson (1987) and Kulju et al. (1987). It was found that the size of the resulting activity distributions is dependent on the S02 concentration. The role of humidity is still unclear and more studies are needed, but it appears that both future theoretical models and laboratory studies will be extremely fruitful in elucidating the behavior of Po-218 from shortly after its formation until its incorporation into the existing accumulation mode aerosol. 

Thus, there is a size threshold that must be reached before a cluster of atoms becomes big enough to be detected and turns into a "condensation nuclei". Recent work by Madelaine and coworkers (Perrin, et al, 1978 Madelaine, et al., 1980) have extended the size of measurable ultrafine particles to the order of 0.003 ym. They find rapid coagulation of this ultrafine aerosol to a larger average diameter one that is easily observable. 

Tippe AH, U. Roth, C. (2002) Deposition of fine and ultrafine aerosol particles during exposure at the air/cell interface. J Aerosol Sci 207-218... 

Phares, D. J. Collection of Ultrafine Aerosols by Electrostatic Classification for Size-Resolved Chemical Analysis. Proceedings of the 233rd American Chemical Society National Meeting, Chicago, IL, March 25-29, 2007. 

Carson, P. G., M. V. Johnston, and A. S. Wexler, Laser Desorp-tion/Ionization of Ultrafine Aerosol Particles, Rapid Commun. Mass Spectrosc., 11, 993-996 (1997b). 

Saros, M. T., R. J. Weber, J. J. Marti, and P. H. McMurry, Ultrafine Aerosol Measurement Using a Condensation Nucleus Counter with Pulse Height Analysis, Aerosol Sci. Techno , 25, 200-213 (1996). 

Wiedensohler, A., P. Aalto, D. Covert, J. Heintzenberg, and P. McMurry, Intercomparison of Three Methods to Determine Size Distributions of Ultrafine Aerosols with Low Number Concentrations, J. Aerosol Sci, 24, 551-554 (1993). 

Thus, while there are copious data showing that ultrafine aerosols nucleate in a wide range of situations (e.g., boundary layer air [3], cloud outflows [27], upper troposphere[31,32]), and that particle production is often coherent over regional scales, and not confined to local sources, the underlying nucleation processes have not yet been identified. An alternative explanation for some of these observations, outlined in the following sections, considers the role of background ionization in the generation of new particles in the troposphere [19,33]. 

Figure 1. Measured aircraft ultrafine aerosol emissions are compared with equivalent model predictions. The aerosol emission index (El) is given as the total number of particles generated for each kilogram of fuel burned, at particle sizes exceeding d>5 nm or d> 14 nm (open and filled symbols, respectively). Data were collected in the SULFUR-5 field campaign. In the simulations (lines), different initial chemiion concentrations, nio, were assumed, as indicated in the legend at the left of the figure (the first number is the value of n in /cmJ, and the second is the lower particle size cutoff diameter, nm. From [84],...

Phase 1. Low precursor supersaturation leads to slow nucleation at average rates <0.1-10 2/cm3s, connected with the formation of stable neutral clusters following the recombination of large ambient ions generates ultrafine aerosol densities of up to 100 s-1000 s/cm3 [19]. 

B. Karcher, F. Yu, F. P. Schroder and R. P. Turco, Ultrafine aerosol particles in aircraft plumes Analysis... 

Birmili W, Weinhold K, Nordmann S et al (2009) Atmospheric aerosol measurements in the German ultrafine aerosol network (GUAN). Part 1. Soot and particle number size distributions. Gefahrst Reinhalt Luft 69 137-145... 

Notably, the instruments used in the European Supersites for Atmospheric Aerosol Research (EUSAAR)/Aerosols, Clouds, and Trace gases Research Infrastructure Network (ACTRIS) and German Ultrafine Aerosol Network (GUAN) measurements used in this chapter are from intercalibrated measurements, where the abilities of the instruments were determined in common intercalibration workshops [15]. Overall, the instruments agree well on particle sizes between 20 and 200 nm, with the differences above 200 nm still relatively minor for number concentrations. In smallest particles sizes the instrument deviation is large, and for this reason we only consider particles larger than 30 nm in diameter in this chapter. 

Kumar P, Fennell P, Symonds J, Britter R (2008) Treatment of losses of ultrafine aerosol particles in long sampling tubes during ambient measurements. Atmos Environ... 

Laser-excited AFS with flame atomization or laser-induced plasma as atom source have also benefited from direct USNn. One example is the method used to obtain on-line and size-segregated information on the elemental ohemical oomposition of ultrafine aerosols [12]. In oontrastto plasma-based deteotors, laser-excited AFS instruments afford miniaturization for field applications. 

Carson PG, Johnston MV, Wexler AS (1997) Laser desorption/ionization of ultrafine aerosol particles. Rapid CommunMass Spectrom 11 993-996... 

Ma kela JM, Aalto P, Jokinen V, Pohja T, Nissinen A, Palmroth S, Markkanen T, Seitsonen K, Lihavainen H, Kulmala M (1997) Observations of ultrafine aerosol particle formation and growth in boreal forest. Geophys Res Lett 24 1219-1222... 

Stark JV, Park DG, Lagadic I, Klabunde KJ (1996) Nanoscale metal oxide particles/clusters as chenucal reagents-tJnique surface chemistry on magnesium oxide as shown by enhanced adsorption of acid gases (sulfur dioxide and carbon dioxide) and pressure dependence. Chem Mater 8 1904-1912 Stolzenburg MR, McMurry PH (1991) An ultrafine aerosol condensation nucleus counter. Aerosol Sci Tech 14 48-65... 

Ultrafine aerosols are commonly defined as particles with diameters less than 0.1 /rm fine particles have diameters of approximately 0.1 to 2 /xm. Fine particles may be formed by coagulation of ultrafine particles or through gas to particle conversion processes. In industrialized areas, fine particles tend to be mainly composed of SO -, NO3, NFff (all from gas to particle conversion processes), elemental carbon, organic carbon, and trace metals. Particles formed from gases are typically less than 1 ptm in diameter and cause reduced... 

The deposition in the mouth is largely due to impaction (except for ultrafine aerosols). This mode of deposition therefore increases with particle size and velocity. The reduction of oropharyngeal deposition is desirable both to improve the efficiency of lung deposition and to reduce its variability [26]. To accomplish this, the velocity of the particles must be sufficiently low. The lower bound for the particle velocity is dictated by the inspiratory flow carrying the aerosol cloud. But some aerosol generators impart high velocity to the particles in the course of formation of the aerosol cloud. 

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