Page 299 - Materials Chemistry, Second Edition

L1644_C07.fm Page 271 Monday, October 20, 2003 12:10 PM

the population density. Moreover, a simplification (Expression 7.7) can be introduced
into Expression 7.5 (Nigge 2000):

1 2p
Dcr () ∫ p Ú Dcr ( j, d ) j (7.7)
i i
2 0
According to Nigge (2000), Expression 7.5 then reads:

1 100 km 2p
I = Ú r Ú D c r () r r () 2 p dr (7.8)
C near, C C
Q 0 0
In Expression 7.8, 100 km is a value for orientation; it is proposed as the limit
between the short- and long-range contribution to I, the incremental receptor expo-
sure per mass of one pollutant emitted. The index C indicates that Expression 7.8
does not refer to a single emission situation, i, but to a generic class of emission
situations, statistically correlated with respect to dispersion conditions and popula-
tion density and with the same source characteristics. A further mathematical analysis
is given in Nigge (2000). Remembering that I i,far is calculated as a country or regional
average, the overall impact indicator for each class then reads:

I ∫ I C,near +I far (7.9)
C
where
I is the incremental population exposure per mass of one pollutant emitted
C
(persons.(mg/m ).yr/kg) at the generic class of emission situations that
3
are statistically correlated with respect to dispersion conditions and
receptor density and have the same source characteristics.

In order to compute the impact indicator for each class, the following elements of
Expression 7.8 must be calculated:

2
r (r) is the radial receptor density (receptors/m ) for each class (in our case
C
2
population density; persons/m ).
Dc (r) is the radial concentration increment profile for each class (mg/m ).
3
C
The definition of classes of meteorological conditions and the derivation of
generic meteorological data files to calculate the radial concentration increment
profile, Dc (r), are questions of fate analysis. The definition of classes of population
C
densities and the calculation of the radial population density, r (r), belong to the
C
exposure analysis.
7.4.1 FATE ANALYSIS TO CHARACTERIZE DISPERSION CONDITIONS

This section discusses the transport of airborne pollutants from the emission source
to the receptors. For the purpose of short-range dispersion modeling (dispersion up

© 2004 CRC Press LLC