Particle formation mechanism assessment

The specific long-term environmental effects of increased trace element loading of the atmosphere continue to be difficult to assess. Specific areas of uncertainty requiring further investigation include the following 1) the mechanisms of particle formation and dispersion in the environment, 2) the chemical transformations and reactivity of the particles in various environmental compartments, 3) the physicochemical characteristics of individual particles, and 4) the specific interactions of the particles with living organisms (11). 

The subject of this particular volume relates to aerosol particle physics including aerosol characterisation, the formation mechanism, the aerodynamic size distribution of the activity and aerosol residence time, instrumentation techniques, aerosol collection and sampling, various kinds of environmental (atmospheric aerosols), particularly radioactive aerosols and the special case of radon decay product aerosols (indoors and outdoors) and the unattached fl ac-tion, thoron decay product aerosols, the deposition patterns of aerosol particles in the lung and the subsequent uptake into human subjects and risk assessment. 

Although it is not yet possible to assess the effect of photoionization in flames, this mechanism may well have an important contribution to ion formation, especially toward the end of the process when polyaromatic hydrocarbons are adsorbed on the surface of soot particles. 

Particle size analysis is useful for assessing attrition because both fragmentation and fine formation yield separate particle populations with different sizes. Production of midsize particles by means of shattering will lower the particle population s mean size and increase its size spread, as formation of fines through surface erosion will make the overall size distribution bimodal or multimodal. Barletta et al. (1993b) summarizes the different size distribution patterns in attrition resulting from the predominant attrition mechanisms and reviews the different models that fit these distributions. 

The quantitative assessment of nanocomposite formation is quite a challenge. The terms generally used, such as tactoid (= microcomposites), intercalated, and exfoliated, are rather oversimplifying models for some typical characteristics of different morphologies. The intercalation of silicate structures by polymer chains, the delamination of sihcate layers, the mixing of the various compounds, and the distribution of particles or single layers in the matrix are mechanisms that are... 

---