Hydrocarbons, C4, steam-cracker distillate

Distribution modelling

Administrative data

Endpoint:

distribution modelling

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: QSAR calculation, acceptable with restrictions

Data source

Reference

Reference Type:

other: Computer model

Title:

EPI Suite v4.10

Author:

US EPA

Year:

2012

Bibliographic source:

USEPA OPPT Risk Assessment Division

Materials and methods

Model:

other: Water Volatilization Program

Calculation programme:

The Water Volatilization Program in the EPI Suite estimates volatilization half-lives from a model river and lake. The program methodology is based upon an adaptation of the recommended method outlined in chapter 15 of the "Handbook of Chemical Property Estimation Methods" (Thomas, 1990).

Media:

water - air

Test material

Test material information

Constituent 1

Reference substance name:

1,3-Butadiene

Cas Number:

106-99-0

Molecular formula:

C4H6

IUPAC Name:

1,3-Butadiene

Constituent 2

Reference substance name:

Butane

EC Number:

203-448-7

EC Name:

Butane

Cas Number:

106-97-8

Molecular formula:

C4H10

IUPAC Name:

butane

Constituent 3

Reference substance name:

2-butene

EC Number:

203-452-9

EC Name:

2-butene

Cas Number:

107-01-7

Molecular formula:

CH3CH=CHCH3

IUPAC Name:

but-2-ene

Study design

Test substance input data:

Henry's Law Constant: 0.0705 atm-m3/mole to 0.969 atm-m3/mole

Environmental properties:

River Water Depth = 1 meter
River Wind Velocity = 5 meters/sec
River Current Velocity = 1 meter/sec
Lake Water Depth = 1 meter
Lake Wind Velocity = 0.5 meters/sec
Lake Current Velocity = 0.05 meter/sec

Results and discussion

Percent distribution in media

Other distribution results:

Half-life in river: 45.4 minutes to 46.7 minutes
Half-life in lake: 69.9 hours to 72.42 hours

Applicant's summary and conclusion

Conclusions:

Based on the calculated Henry's Law Constant range of 7150 (1,3-butadiene) to 98200 (butane) Pa m³/mol, the estimated half-life of the streams in this category ranges from 45.4 to 46.7 minutes in a river and 69.9 to 72.4 hours in a lake.

Executive summary:

The half-life of representative components of the streams in this category have been estimated using a standard QSAR model and the calculated Henry's Law Constants.

The Henry's Law Constant indicates that volatilisation from aqueous media is expected to be rapid. According to Pedersen et al. (1995), the criteria for total degradation (95% removal by volatilisation, equivalent to 70% degradation in the aquatic environment in 28 days) corresponds to a half-life of 6 days (144 hours). The half-life of these representative components are significantly shorter than this indicating that they would meet the criteria for total degradation.

Pedersen F, Tyle H, Niemela JR, Guttmann B, Lander L, Wedebrand A. 1195. Environmental Hazard Classification – data collection and interpretation guide (2^ndedition). Tema Nord 1195:581. Nordic Council of Ministers