Environmental Engineering Reference
In-Depth Information
applications, models can provide at best an estimate of indoor air concentrations
within an order of magnitude of measured values (Bradley, Patterson and Davis
2009
). However, measured indoor air concentrations using 24-h samples can also
show up to about one order of magnitude variability (Kuehster et al.
2004
), so in
this context, the model accuracy is often reasonable.
The available models are subdivided (see Table
10.1
) into models that use a mass
flux calculation to estimate indoor air concentration and models that use an attenua-
tion factor approach. The models based on mass flux calculations are further divided
into those that include diffusive transport of soil air and those that include both
diffusive and convective transport. Parameters that most strongly influence the pre-
dicted indoor air concentration for all models are source concentration and depth,
soil moisture content, building ventilation rate, and oxygen supply (where aero-
bic degradation is incorporated). For the dilution factor model from Norway and
the Johnson and Ettinger (
1991
) Model (J&E Model), the contribution of the soil
parameters is higher than for most of the other models mentioned in this chap-
ter. The exception is the Flemish Vlier-Humaan model, for which the building and
physical-chemical parameters equally influence to the predicted indoor air concen-
tration, while variation in the soil parameters does not result in much variation in
the indoor air concentration. Because of its appearance in regulation and guidance
in the US, much attention has been focused on testing the J&E Model.
Table 10.1
Overview of mathematical models
Vlier-
Humaan JEM
DF
Sweden
DF
Norway
Item
CSOIL
VOLASOIL RISC
Compartment/floor
- slab-on-grade
•
•
•
•
- concrete
basement
•
•
•
•
- crawl space
•
•
•
•
•
Transport
-diffusive
•
•
•
•
•
- diffusive plus
convective
•
•
•
- attenuation
factor/empirical
•
•
Source
- groundwater
•
•
•
•
•
•
•
•
•
•
•
•
•
- vadose zone
•
-soilgas
Application
- site specific
assessments
•
•
•
•
- derivation of
screening levels
•
•
•
•
•
JEM
Johnson and Ettinger model;
DF
Dilution Factor;
X
applies for model
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