Page 294 - Materials Chemistry, Second Edition

L1644_C07.fm Page 266 Monday, October 20, 2003 12:10 PM

ecosystem area, or fish population. The effective receptor density r m is introduced
eff r,
into the expression in order to relate the distribution of receptors r to the distribution
of the respective pollutant in the environment. Expression 7.1 then reads as follows:

DD nm = E m ◊ m ◊ r F nm ◊ M n (7.2)
pr, pr, eff r, p p
where
DD nm is the incremental damage caused (damage) due to the emission of pol-
pr,
lutant p into the initial medium n (air, water or soil) on the receptor
r in the target compartment m (air, water, soil or food chain).
2
r m is the effective density of receptor r (receptors/m ) in target medium m
eff r,
(air, water, soil or food chain), that is, for the receptor human popu-
2
2
lation (persons/m ) and for material surface (m maintenance sur-
2
face/m ), while this means for the fish population in the compartment
3
water (fishes/m ), i.e., we do not need to consider a density, but a
concentration.
3
E m is the effect factor (damage/receptors.(mg/m ).yr) representing the severity
pr,
of the impact due to the substance p in medium m (air, water, soil or
food chain) on receptor r.
In the context of this framework the incremental receptor exposure (DRE) is
then defined as the product of the number of receptors exposed to a certain concen-
tration during a certain period of time, as shown in the following expression:

DRE nm = DD nm / E m = m ◊r F nm ◊ M n (7.3)
pr, pr, pr, eff r , p p
where
DRE nm is the incremental receptor exposure during a certain period of time
pr,
3
(receptors.( mg/m ).yr) due to the emission of pollutant p into the initial
medium n (air, water or soil) on the receptor r in the target compart-
ment m (air, water, soil or food chain) — for example, for airborne
3
emissions with the receptor human population (persons.mg/m air.yr)
and for the receptor material surface (maintenance surface.
3
mg/m air.yr) and for water with the receptor fish population
3
(fishes.mg/m water.yr).
If the dose–response or exposure–response function is linear or the emission
source contributes only marginally to the background concentration, the incremental
damage becomes independent of the time pattern of the emission and only depends
on the total mass emitted. For a detailed mathematical derivation, see Nigge (2000)
and for the general idea of marginality and linearity see Potting (2000). For the
purpose of this study, it is assumed that the incremental damage DD nm is independent
pr,
of the time pattern of the emission. The incremental damage can then be calculated
by Expression 7.4, using an incremental receptor exposure per mass of pollutant

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