Registration Dossier

Environmental fate & pathways

Distribution modelling

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Administrative data

Endpoint:
distribution modelling
Adequacy of study:
key study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2003

Materials and methods

Model:
other: Calculation according to Mackay Level 1 and Level III

Test material

Reference
Name:
Unnamed
Type:
Constituent

Results and discussion

Percent distribution in media

Air (%):
99.93
Water (%):
0.07
Soil (%):
0.01
Sediment (%):
0

Any other information on results incl. tables

EQC level III (Emission to air alone)

Applicant's summary and conclusion

Conclusions:
HFC-134a released to air would remain almost exclusively in that compartment and, when released to, water would be expected to partition ultimately partition predominantly to the ambient air. Moreover, any HFC-134a present in surface or ground waters would have little tendency to partition to biota or soil.
Executive summary:

The environmental partitioning of HFC-134a has been assessed (Franklin, 2003) using the EQC Level I and Level III models (Mackay et al, 1996).

In the Level I model, a fixed quantity of a supposedly non-degradable chemical is introduced into a closed evaluative environment and equilibrium achieved between the various environmental compartments (air, water, soil, sediment). The Level III model simulates a situation in which a chemical is emitted at a constant rate into one or more of the compartments, in each of which it may degrade; the steady-state distribution between compartments is then calculated. Due to the resistance to mass transfer between compartments, the various phases are not in equilibrium and the steady-state partitioning depends on its "mode of entry", i.e. the compartment(s) into which the chemical is injected. EQC modelling has been performed for HFC-134a using the physical properties and an atmospheric lifetime of 14.0 years, corresponding to a half-life of 9.7 years. Degradation in other media was not taken into account. The table below gives the percentage of HFC-134a calculated for each compartment.

 Compartment  EQC Level 1  EQC level III  EQC Level III
     Enmission to air alone  Emmission to water alone
 Air  99.91  99.93  19.9
 Water  0.092  0.067  79.9
 Soil  0.00094  0.0070  0.0014
 Sediment  0.00002  0.00015  0.18

The Level III simulation with emissions of HFC-134a to air alone leads to a distribution close to the Level I equilibrium situation as far as the air and water compartments are concerned. However, a much greater steady-state proportion of HFC-134a is found in the water compartment when the emissions are to water alone. This is due to the resistances to inter-media transfer (in particular from water to air) introduced in the Level III model. Thus, HFC-134a released to air would remain almost exclusively in that compartment and, when released to, water would be expected to partition ultimately partition predominantly to the ambient air. Moreover, any HFC-134a present in surface or ground waters would have little tendency to partition to biota or soil.