Page 268 - Materials Chemistry, Second Edition

252 4 Life Cycle Impact Assessment

A selection of MIR factors (absolute and relative) has been listed in Table 4.13.
The data by Derwent et al. (1998) also include specifications for NO as demanded
2
by Finlayson-Pitts and Pitts (1986). Surprisingly SO is also part of smog formation.
2
As can be deduced from the data, POCP values calculated by different models do
not exactly match. The total range of all known POCP value does however not
exceed two to three orders of magnitude.
To be noted in Table 4.12 is the fact that absolute MIR values can also be negative
in exceptional cases if a specific VOC inhibits the smog reactions. This is the
case with benzaldehyde whose molecules react in the gasphase with NO without
x
radical formation and therefore interrupt the chain reaction forming ozone and
other photooxidants.
4.5.2.4.2 Characterisation/Quantification In the context of a uniform impact cat-
egory for the formation of photooxidants the quantification of the impact indicator
is accomplished as follows with the help of the POCP characterisation factors:
POCP = ∑ (m × POCP ) (kg ethene equivalents) (4.19)
i i
i
where m = load of the substance i involved in summer smog formation per fU.
i
A very extensive data record (96 substances) of Derwent, Jenkin and Saunders
(1996, loc. cit.) is in part reproduced in Table 4.12. The tropospheric ozone
formation with average European climate conditions is characterised and can also
be used for the quantification of a regional ozone formation as its own indicator
for this impact (POCP = POCP ) as has been proposed by SETAC Europe. 222)
reg
Alternatively the characterisation can be accomplished by MIR factors:
POCP = ∑ (m × MIR ) (kg ethene equivalents) (4.20)
loc i i
i
The characterisation with the help of MIR factors (Table 4.13) is suitable for
a quantification of summer smog in areas with particularly high solar radiation,
unfavourable emission conditions and slowly varying weather conditions. They
have rarely been used so far in LCIA practice, probably because of an altogether
small relation to space in the classical LCA. In the following, attempts to include
the space into the impact assessment of summer smog events are discussed.
4.5.2.4.3 Regionalisation of the Impact Indicator As already discussed, the for-
mation of summer smog depends on regional and meteorological factors like
‘background concentration’ of relevant precursors. The RAINS (regional air pollu-
tion information and simulation) model, developed on behalf of the UNECE (United
Nations Economic Commission for Europe)-convention with respect to extensive
and transnational air pollution, calculates the spatially dissolved ozone formation
for all of Europe and considers spatially varying meteorological conditions and
tropospheric chemistry. In addition, the spatially resolved ozone concentrations
are related to critical ozone limits for humans and the natural environment. This
model was used by Potting 223) to obtain simple factors which relate the release of an

222) Kl¨ opffer et al. (2001) and Potting et al. (2002).
223) Potting et al. (1998) and Hauschild and Potting (2001).