Page 312 - Materials Chemistry, Second Edition

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7.6.4 OVERALL IMPACT INDICATORS
The overall impact indicator, I total , is the sum of I near and I . Table 7.6 shows the
far
results for several pollutants, including the values for I , in order to show the long-
far
range contribution to I total . The impact indicators for the secondary pollutants nitrate
and sulfate refer to the mass of primary pollutant emitted, i.e., to NO and SO ,
x
2
respectively, and are represented by the results for the long-range exposure that show
only very slight variations for different stack heights. The average values for all
3
3
stack heights are 0.25 persons.mg/m .yr/kg for nitrate and 0.13 persons.mg/m .yr/kg
for sulfate, respectively.
Generally speaking, it can be said that the population exposure is smaller the
lower the population density is. Another general correlation is that an increasing
stack height leads to a decreasing impact indicator. Because Catalonia is quite
populated in comparison with other regions in Spain, because every pollutant depos-
ited on the Mediterranean does not lead to a human health effect via inhalation, and
because the modeling area of EcoSense is limited to Europe (therefore neglecting
harmful effects of Spanish emissions to North Africa, for instance), every molecule
or particle going into the long-range transport favors the decrease of the overall
population exposure.
Another obvious effect is that I total decreases with higher wind speeds. Moreover,
the influence of atmospheric residence time and decay can be derived. If one com-
pares the impact indicators for PM , PM , NO and SO , it can be seen that the
10
x
2
2.5
values decrease from PM over SO and PM to NO according to their atmospheric
2
10
2.5
x
residence time and decay rate. The span between the highest and the lowest value
of I total for each pollutant ranges from a factor of 10 for PM to a factor of 70 for
2.5
PM . This can be explained with the fact that PM accounts for a much greater
2.5
10
long-range contribution to the population exposure than PM due to its long atmo-
10
spheric residence time. Therefore, the lowest value of PM is determined by the
2.5
comparatively high long-range contribution, which leads to the comparatively small
span between highest and lowest value.
Using the dose–response and exposure–response functions, physical impacts
(e.g., cases of chronic bronchitis) per mass of pollutant can be calculated. Applying
these functions and the respective unit values, it is possible to convert the impact
indicators into DALY and external costs per kilogram of pollutant using the conver-
sion factors in Table 7.3.
7.6.5 ESTIMATES FOR ADJACENT REGIONS AND OTHER STACK
HEIGHTS
Process chains often comprise processes outside Catalonia, so an approximation
formula for other regions in Spain is presented in the following expression. It is
supposed that the long-range exposure for other regions in Spain does not vary
significantly from the values in Catalonia. Therefore, it holds that:

I far,other regions = I Catalonia . (7.11)

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