Nuclei Aitken

W -IO"- Intermediate and large Aitken nuclei Dectron microscope Suspended — Vapor molecules — Diffusion... 

Aitken nuclei Particles, generally with diameters less than 0.1 xm, that are true aerosols when they form the nucleus for condensation or ice formation. 

Fine Aitken nuclei, transient lifetime High temperature combustion processes, condensation from the vapour... 

Table I presents the average aerodynamic distributions of Pb-212 and Pb-214, as well as the frequency with which Pb-214 or Pb-212 was the dominant isotope in each size range. The Aitken nuclei fraction (below 0.08 pm) contained a higher percentage of Pb-212 activity compared with Pb-214 in 69.6% of the measurements. The predominance of Pb-212 in this fraction is also illustrated by the distributions reported in Figure 1. In the remaining measurements, where Pb-214 was fractionally more abundant below 0.08 um, the disparity between the relative amounts of each isotope was not nearly as dramatic. Conversely, Figure 1 and Table I illustrate that Pb-214 is generally enriched in the accumulation mode aerosol, particularly between 0.11 and 0.52 ]xm, where most of the surface area and mass occurs.

Ultra fine or Aitken nuclei Accumulation Mechanically generated... 

Aitken Nuclei Accumulation Mode Coarse Particles... 

As we have seen in our earlier discussion of the size distribution of tropospheric particles, the chemical components are not generally distributed equally among all sizes but, rather, tend to be found in specific size ranges characteristic of their source. Generally, the smallest ultrafine particles are produced by homogeneous nucleation and hence tend to contain secondary species such as sulfate and likely organics (see Section A.2). Particles in the Aitken nuclei range are produced... 

Novakov and Penner (1993) measured the mass size distributions of sulfur, organic carbon, and chlorine (characteristic of sea salt) as well as the CCN concentration (at 0.5% supersaturation), nss, and Aitken nuclei concentrations at a mountain peak in Puerto Rico. 

Hegg, D. A., L. F. Radke, and P. V. Hobbs, Measurements of Aitken Nuclei and Cloud Condensation Nuclei in the Marine Atmosphere and Their Relation to the DMS-Cloud-Climate Hypothesis, J. Geophys. Res., 96, 18727-18733 (1991b). 

Andreae, M.O. et al. (1992) Ozone and Aitken nuclei over equatorial Africa Airborne observations during DECAFE 88, J. Geophys. Res., 97,6137. 

In the free atmosphere, the rate of production of small ions is in balance with the rate of neutralisation by recombination and the rate of attachment to condensation nuclei. Condensation nuclei, otherwise called Aitken nuclei, are submicrometric particles mainly produced by combustion processes. If slight differences in the rates of attachment of positive and negative ions are ignored,... 

Aitken nuclei -0.08 Accumulation of nuclei in laboratory air 212Pb... 

Podzimek, J., 1976 Possible correlation between ozone and Aitken nuclei count in the lower ftratosphere. Pure and Appl. Geophys. 114, 925-932. 

Podamek, J., Sedlacek, W. A. and Brooks Haberl, J., 1977 Aitken nuclei measurements in the lower stratosphere. Tellus 29, 116-127. 

Weickmann, H., 1957 Recent measurements of the vertical distribution of Aitken nuclei. In Artificial stimulation of rain (eds. H. Weickmann and W. Smith), Pergamon Press, New York, 81-88. 

The study of Reiter et al. (1976) at the Wank Mountain Observatory distinguished days with strong and weak vertical exchange by means of Aitken nuclei counts and concentrations of radon decay products. The main difference between both meteorological situations is a shift in the total aerosol concentration. Variations in chemical composition are minor. This indicates that at the height of the Wank Mountain [1780 m above sea level (a.s.l.)] the continental aerosol is already well homogenized. Gillette and Blifford (1971) and Delany et al. (1973) have reached similar conclusions from aircraft samples over the North American continent. 

Radford, H. E. (1980). The fast reaction of CH2OH with 02. Chem. Phys. Lett. 71, 195-197. Radke, L. F., and P. V. Hobbs (1969). Measurement of cloud condensation nuclei, light scattering coefficient, sodium-containing particles and Aitken nuclei in the Olympic Mountains of Washington. J. Atmos. Sci. 26, 281-288. 

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