Size-composition distribution

The main statistical characteristic of the chemical structure of a heteropolymer among those pertaining to the first type is the distribution of molecules f( h, 12) for numbers l and h of their constituent monomeric units Mi and M2. In dealing with a high-molecular weight polymer, these numbers may be taken as continuous variables, uniquely specifying chemical size l=l + h and composition f = li/l of a macromolecule. Under such a consideration, it is more convenient instead of function /(Zi, l2) to use the equivalent function of Size-Composition Distribution (SCD) f(l, < ) This is possible to represent... 

A hypothetical aerosol size/composition distribution is shown in Figure 12.1, indicating that crustal materials (e.g., COf, Si, Al, Fe, Ca, and Mn), sea spray (e.g., Mg, Na, and Cl), and biogenic organic particles (e.g., pollen, spores, and plant fragments) are usually found in the coarse aerosol fraction (2.5 < r/ae < 10pm) (Meszaros et al., 1997 Krivacsy and Molnar, 1998 Matsumoto et al., 1998 Seinfeld and Pandis, 1998 Maenhaut et al., 2002 Smolik et al., 2003). Wind erosion, primary emissions, mechanical disruption, sea spray, and volcanic eruptions all contribute to the concentrations of these species (Seinfeld, 1986 Seinfeld and Pandis, 1998). 

Because of the difficulties associated with measurement of the aerosol size composition distribution, and then calculating from that their CCN properties, a series of empirical parametrizations have been developed based on atmospheric measurements. One of the most popular relates CCN(s) concentration to atmospheric supersaturation s (percent) with a power law... 

FIGURE 17.25 Predicted aerosol size-composition distributions before and after a fog episode (Pandis et al. 1990b). 

Table VIII summarizes the physical processes that affect the evolution of aerosol in a unit volxame of atmosphere. To develop the general dynamic.equation governing aerosol behavior let us assxime that the aerosol is composed of liquid droplets of M chemical species. We let c denote the concentration of species i in a droplet, i = 1,2,..., M, and Dp denote the diameter of the particle. We then define n(Dp, c, ..., cjyj,r,t) as the size-composition distribution function, such that n dDp dc. .. dcj is the n umber of particles per unit vol ume of atmosphere at location r at time t of diameter Dp to Dp + dDp and of composition c to spegies ...

The general equation governing the size composition distribution function was derived by Chu and Seinfeld (6T). The equation... 

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