technical guidance documents - Institute for Health and Consumer ...

ENVIRONMENTAL EXPOSURE ASSESSMENT
The area fractions for water and for natural, agricultural and industrial/urban soils, are average
values obtained from ECETOC (1994b), supplemented with data received from Sweden and
Finland. Data for Norway and Austria are obtained from the FAO statistical databases
(http://apps.fao.org/). The residence time for air (defined as the time between air entering and
leaving the region) of 0.7 days is derived from the wind speed of 3 m/s and the area of the
region. The residence time of water of 40 days is selected as a reasonable average for the
European situation.
The amount of wastewater discharged, is the product of the amount of wastewater
discharged per person equivalent and the number of inhabitants of the system. Using a flow
per capita of 200 l .d -1 (equivalent to the value used in the SimpleTreat model, see Table 9)
and a population of 20 million, this results in an additional water flow through the model
environment of 4.0 .10 6 m 3 .d -1 . The inflow caused by inflowing riverwater, is 6.5 .10 7 m 3 .d -1 .
In addition to the environmental characteristics of the region, selected intermedia mass transfer
coefficients are required in the multimedia fugacity model to ensure comparability of the
outcome with other models. These transfer coefficients are summarised in Table 13.
Table 13 Intermedia mass transfer coefficients
Parameter Value
air-water interface: air side partial mass transfer coefficient 1.39 . 10 -3 m . s -1
air-water interface: water side partial mass transfer coefficient 1.39 . 10 -5 m . s -1
Aerosol deposition rate 0.001 m . s -1
air-soil interface: air side partial mass transfer coefficient 1.39 . 10 -3 m . s -1
air-soil interface: soilair side partial mass transfer coefficient 5.56 . 10 -6 m . s -1
air-soil interface: soilwater side partial mass transfer coefficient 5.56 . 10 -10 m . s -1
sediment-water interface: water side partial mass transfer coefficient 2.78 . 10 -6 m . s -1
sediment-water interface: pore water side partial mass transfer coefficient 2.78 . 10 -8 m . s -1
net sedimentation rate 3 mm . yr -1
Model parameters for the continental concentration
The continental box covers all 15 EU countries and Norway and similar percentages for
water and natural, agricultural and industrial/urban soils as given in Table 14. All other
parameters are similar to the ones given in the preceding tables. Emission estimation to this
continental box should be based on the EU-wide production volume of the substance. The
resulting concentrations in water and air must be used as background concentrations (i.e.
concentrations in water or air that enter the system) in the regional model. When the model is
built according to Figure 1 it is assumed that no inflow of the substance into the continental
system takes place. More recent versions of multimedia models do also contain so-called
global scales for different temperature regions, for instance moderate, tropic and arctic (see e.g.
Brandes et al., 1996). In this case the continent is embedded in the moderate scale just like the
region is embedded in the continent. The size of the total global scale is that of the northern
hemisphere. The global scales allow for a more accurate estimation of continental concentrations
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