Page 311 - Materials Chemistry, Second Edition

L1644_C07.fm Page 283 Monday, October 20, 2003 12:10 PM

exposure must be subtracted from the calculated population exposure. Because the
short-range population exposure is calculated using the BEEST software, the pop-
ulation exposure within the radius of 100 km from the stack must be subtracted as
well. For this purpose, the population exposure of the emission cell as well as the
population exposure of part of the adjacent cells is subtracted.
After summing up the population exposure of each grid cell and subtracting the
background and the short-range exposure, the sum is divided by the emitted mass.
The result is the population exposure per mass of emitted pollutant for the long-
range transport I for each pollutant, emission cell and stack height considered.
far
Because the modeling area is comparatively small (which explains the existence of
only eight emission cells), the long-range exposure per mass of emitted pollutant
does not differ very much for the considered emission cells. The variation coefficient
for the different emission cells lies between 7.75 and 23.49%. Therefore, an average
Catalonian value is calculated for every pollutant and every stack height and applied
as I for the whole of Catalonia.
far
I for pollutants such as acetaldehyde and 1,3-butadiene that are not included
far
in the EcoSense software is approximated by their atmospheric residence time. For
that purpose I is calculated for a set of particles with different diameters and
far
atmospheric residence times (Table 7.5). A linear regression is carried out and an
approximation formula is calculated:

I = exp (–0.2043 • ln t) + 2.3916 • ln (– 7.3174) (7.12)
2
far
where
I is the long-range contribution to the population exposure per mass of emitted
far
3
pollutant (persons.mg/m yr/kg).
.
t is the atmospheric residence time (h).

TABLE 7.5
Diameter and Atmospheric Residence Time t of Several
Particles
Pollutant (diameter) t (h)
135
PM 2.5
22
PM 10
PM (d = 4 to 10 mm) 15
PM (d = 10 to 20 mm) 11
PM (d > 20 mm) 3
Source: Nigge, K.M., Life-Cycle Assessment of Natural Gas Vehicles, Develop-
ment and Application of Site-Dependent Impact Indicators, Springer-Verlag,
Berlin.

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