Dibromomethane

Distribution modelling

Administrative data

Endpoint:

distribution modelling

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Results are based on QSAR model

Justification for type of information:

QSAR prediction: migrated from IUCLID 5.6

Materials and methods

Model:

calculation according to Mackay, Level III

Calculation programme:

EPI suite V4.1

Release year:

2 011

Media:

air - biota - sediment(s) - soil - water

Test material

Test material information

Constituent 1

Reference substance name:

Dibromomethane

EC Number:

200-824-2

EC Name:

Dibromomethane

Cas Number:

74-95-3

Molecular formula:

CH2Br2

IUPAC Name:

dibromomethane

Study design

Test substance input data:

- Molar mass:173.84 gr/mol
- Data temperature:25 oC
- Water solubility:8600 mg/L
- Vapour pressure:0.0578947 atm
- log Pow:1.68
- Biomass to water partition coefficient:10.3726
-Half-Lives (hr), (based upon Biowin (Ultimate) and Aopwin):
Air: 2272
Water: 360
Soil: 720
Sediment: 3240

Environmental properties:

Table 1. Compartment Dimensions and Properties of the Multimedia Fate Model
Air Water Soil Sediment
Volume (m3) 1x1014 2x1011 1.8x1010 5x108
Depth (m) 1000 20 0.2 0.05
Area (m2) 1x1011 1x1010 9x1010 1x1010


Table 2. Volume Fraction and Density Default Values of the Multimedia Fate Model
Air Water Soil Sediment
Volume fraction
Aerosol 2.00E-11
Suspended 5.00E-06
particles
Fish 1.00E-06
Air 0.2
Water 0.3 0.8
Solid 0.5 0.2

Density (kg/m3)
Bulk 1.19 1000 1500 1280
Pure air 1.19
Aerosol 2000
Liquid 1000
Suspended
particles 1500
Fish 1000
Air 1.19
Water 1000 1000
Solid 2400 2400

Results and discussion

Percent distribution in media

Air (%):

33.9

Water (%):

35.9

Soil (%):

30.1

Sediment (%):

0.01

Any other information on results incl. tables

If released to air, a vapor pressure of 35.3 mm Hg at 25^oC indicates dibromomethane will exist solely as a vapor in the ambient atmosphere. This tendency is predicted by Level III Fugacity Model:

	Mass Amount (%)	Emissions (kg/hr)
Air	97.3	1000
Water	2.33	0
Soil	0.378	0
Sediments	0.00638	0

If released to soil, dibromomethaneis expected to have very high mobility based upon an estimated Koc of 29.86. Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 8.22X10^-4atm m³/mole. Dibromomethanemay volatilize from dry soil surfaces based upon its vapor pressure. This tendency is predicted by Level III Fugacity Model:

	Mass Amount (%)	Emissions (kg/hr)
Air	27.5	0
Water	4.86	0
Soil	67.6	1000
Sediments	0.0133	0

If released into water, dibromomethaneis not expected to adsorb to suspended solids and sediment in water based upon the Koc and by Level III Fugacity Model. Volatilization from water surfaces is expected to be a significanttransport mechanismbased upon Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 2 hours and 6 days, respectively. On the other hand, Level III Fugacity Model predicted 84% of the substance remains in water and thus, dibromomethane can be available to biotic and abiotic degradations processes in water.

	Mass Amount (%)	Emissions (kg/hr)
Air	15.6	0
Water	84.2	1000
Soil	0.0605	0
Sediments	0.231	0

 If released to air soil and water dibromomethane is tending to distribute among these three compartments almost equally as predicted by Level III Fugacity Model:

	Mass Amount (%)	Emissions (kg/hr)
Air	33.9	1000
Water	35.9	1000
Soil	30.1	1000
Sediments	0.0983	0

Applicant's summary and conclusion

Conclusions:

As predicted by Level III Fugacity Model dibromomethane is tending to distribute among water soil and air compartments almost equally. Thus, dibromomethane is expected to undergo biotic and abiotic degradations processes in each of these three compartments.