Aitken formation

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. 

Geological Setting The IRAC is hosted in folded and faulted sedimentary rocks of Cambrian to lower Ordovician age (Currie 1975). These units are the slaty-limestone of the McKay Group (Cambro-Ordovician), massive limestone of the Ottertail Formation (Cambrian), and the sheared argillaceous rocks of the Cambrian Chanceller Formation (Allan 1914, Aitken Norford 1967). 

Aitken, J.D. Norford, B.S. 1976. Lower Ordovician Survey Peak and Outram Formations, southern Rocky Mountains of Alberta. Bulletin of Canadian Petroleum Geology, 15, 150-207. 

Condensation particle counter (CPC) Very small particles in the Aitken range act as condensation nuclei for the formation of larger particles in a supersaturated... 

The most common way in aerosol science to represent PND data is in terms of various modes. Generally, these modes are nucleation (typically in the 1-30 nm range), Aitken (typically in the 20-100 nm range), accumulation (typically in the 30-300 nm range) and coarse (typically over 300 nm size range). Each mode contains different sources, size range, formation mechanisms, and chemical compositions [30],... 

The first evidence of in situ particle formation in the atmosphere was provided by John Aitken at the end of the nineteenth century (Aitken 1897). He built the first apparatus to measure the number of dust and fog particles in the atmosphere. However, little progress was made in understanding what causes new particle formation or how widespread it might be for almost a century. In the 1990s the development of instruments capable of measuring the size distribution of particles as small as 3 nm led to the discovery that nucleation and growth of new particles is a rather common event in many areas around the world (Kulmala ct al. 2004). Areas where frequent nucleation bursts have been observed include... 

Washout by rain greatly reduces the Aitken nuclei mode and the coarse particle mode but has little effect on the accumulation mode in the trimodal size distribution (Whitby, 1975). The origin of each mode of atmospheric aerosol size distribution can be associated with various aerosol formation mechanisms, such as Brownian motion of the particles smaller than 0.1 pm in diameter, which causes the particles to diffuse and by collisions to coagulate to larger sizes. Coagulation generates multimodal distributions and affects the shape and the chemical composition of the particles. 

Wang, T.L., S.N. Aitken, P. Rozenberg and F. Millier. 2000. Selection for improved growth and wood density in lodgepole pine effects on radial patterns of wood formation. Wood and Fiber Science 32 391-403. 

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