Page 296 - Materials Chemistry, Second Edition

L1644_C07.fm Page 268 Monday, October 20, 2003 12:10 PM

This impact information should be based on a certain spatial differentiation with
regard to the processes in the chain and include a minimal amount of additional data
on the corresponding geographic situation. The site-dependent impact assessment
can be carried out for various compartments using a multimedia fate and exposure
model (see Chapter 4) or for only one release compartment n and one target com-
partment m by the application of a spatially explicit medium-specific model. In
accordance with Potting (2000), we believe that the relevance of LCIA can be
enhanced by the inclusion of a few general site parameters in the assessment pro-
cedure; we would call this site-dependent impact assessment.
For the effect analysis we propose to use the dose–response and expo-
sure–response functions described in Chapter 4. The fate information should be
obtained by using pollutant dispersion and long-range transport models and/or mul-
timedia fate models. The target information needed corresponds to the receptor
density that describes the sensitivity of the target, but we do not consider that
background information is necessary, assuming that residual risk is what we want
to address in LCIA and that linear dose–response and exposure–response functions
exist, at least for priority pollutants. For a further discussion of this issue, see Crettaz
et al. (2002), Nigge (2000) and Potting (2000).

7.3 STATISTICALLY DETERMINED GENERIC CLASSES
OF AIRBORNE EMISSIONS

Considering only one pollutant, p, and one receptor, r, as well as one release
compartment, n, and one target compartment, m, then I nm = I ( = DRE /M), the
pr i,, i i
incremental receptor exposure per mass of pollutant emitted (recep-
3
tors.(mg/m ).yr/kg), which represents the concentration increment multiplied by the
receptors during a certain time period divided through the mass of pollutant. In two-
dimensional polar coordinates (r,j) around the emission situation, i, within a suitable
cartographic projection of the Earth’s surface, this can be written as (Nigge 2000):

1 R 2p
)
I = Ú r Ú D c r ( ,jr r ( ,j ) d drj (7.5)
i i i
Q 0 0
where
Q = M /T is the constant emission rate (kg/yr) with M as mass of one pollutant
i
i
(kg) emitted at the emission situation i and T as the duration of the
emission (yr).
r is the radius (m).
R is the outer boundary of the modeling area (m).
Dc (r,j) is the concentration increment at a receptor point with the polar coordi-
i
3
nates (r, j) for the emission situation i (mg/m ).
ri(r, j) is the receptor density at a receptor point with the polar coordinates
2
(r, j) for the emission situation i (receptors/m ).

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