Appendix D - Dossier (PDF) - Tera

date: 20–JUL–2005
3. Environmental Fate and Pathways Substance ID: 71–43–2
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Media: air – biota – sediment(s) – soil – water
Method: other (calculation): model following first Mackay model
Method: An environmental modelling exercise was conducted to
estimate benzene’s distribution in the UK environment. The
computer model used by the Building Research Establishment,
developed from Mackay’s original model (Mackay D., Envir.
Sci. Technol. 13, 1218–1223, 1979; Mackay D. & Paterson S.,
Envir. Sci. Technol. 15, 1006–1014, 1981) was used. For the
model, it was assumed that 38,000 tonnes benzene are
released in the UK per year. Other factors required for the
model were molecular weight (78.11), water solubility (1780
mg/l at 20 degree C or 22.8 mg/m3), vapour pressure (1.01E2
hPa at 20 degree C), octanol–water partition
coefficient (2.13, log; 135, non–log) and the rate constants
for photo–oxidation in air (0.03/hour, t1/2 = 24 hr in
polluted air and 4.8E–3/hour,t1/2 = 6 days in ambient air),
photo–oxidation in water (3.6E–4/hour, t1/2 = 80 days) and
biodegradation in water (1.8E–3/hour, t1/2=16 days).
Result: The distribution of benzene in the environment was estimated
to be 0.08–0.49 ug/m3 in air, 0.42–2.64 ng/l in water,
1.17–7.30 ng/kg in soil, 2.80–17.5 ng/kg in sediment,
2.80–17.5 ng/kg in suspended sediment and 2.73–17.1 ng/kg in
biota.
Source: Deutsche Shell Chemie GmbH Eschborn
German Rapporteur
Reliability: (2) valid with restrictions
16–MAR–2004 (827)
Media: air – biota – sediment(s) – soil – water
Method: Calculation according Mackay, Level III
Method: The method is described in detail in Mackay, D. et al.,
Chemosphere 14, 335–374, 1985. Ideally mixed compartments
and photolysis (water and air) and biodegradation (water)
are as important degradation mechanisms are assumed.
Result: For the Netherlands, the model calculation gave following
results:
air water soil sediment
(fresh)
concentration 2.1 ug/m3 58 ng/l 12 ng/kg 130 ng/kg
distribution 99.0% 0.9% 0.1% < 0.1%
removal by 4.6% 0.2% n.c.* n.c.
reaction
removal by 95.2% < 0.1% n.c. n.c.
advection
* n.c. = not calculated
Transportation through the air seemed to be the most
important removal mechanism.
Source: Deutsche Shell Chemie GmbH Eschborn
German Rapporteur
Test condition: Model parameters: 41000 km2 total surface (88% soil/12%
water), 1000 m air column, 2.5 m water column, 0.03 m
sediment column, 0.15 m soil column, 2.3 d residence time
inair, 55% sea air with a benzene level of 0.1 ug/m3 and 45%
land air (mainly from south east direction, i.d. from
Belgium and Germany) with a benzene level of 1.8 ug/m3.
Appendix D: Benzene SIDS Dossier
– 192/957 –