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Environmental fate & pathways

Distribution modelling

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Administrative data

Endpoint:
distribution modelling
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented publication which meets basic scientific principles.

Data source

Reference
Reference Type:
publication
Title:
Assessment of chemical fate in the environment using evaluative, regional and local scale models: Illustrative application to chlorobenzene and linear alkylbenzene sulfonates.
Author:
Mackay, D., Di Guardo, A., Paterson, S., Kicsi, G., Cowan, C. and Kane, D.
Year:
1996
Bibliographic source:
Environ. Toxicol. Chem. 15:1638-1648.

Materials and methods

Model:
calculation according to Mackay, Level III
Calculation programme:
Mackay models levels I, II, and III, also the ChemCAN level III model, and the WW-TREAT, GRiDS, and ROUT models.
Media:
air - biota - sediment(s) - soil - water

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): LAS

Study design

Test substance input data:
Level I, II, and III models:
Molecular mass 348
Air-water partition coefficient 0
Aerosol-water partition coefficient 100
Soil-water partitition coefficient (L/kg) 20
Sediment-water partitition coefficient (L/kg) 570
Fish-water partitition coefficient (L/kg) 250
Half-life in air (h) --
Half-life in water (h) 24
Half-life in soil (h) 480
Half-life in sediment (h) 96

ChemCAN model:
Total discharge to the environment (kg/yr) 1,444,000
Discharge to the air --
Discharge to water 144,000
Discharge to soil 1,296,000
Total input in the region (kg/year) 1,440,000
Total input in the region (kg/hour) 164.4

Results and discussion

Percent distribution in media

Air (%):
0
Water (%):
0.64
Soil (%):
99.35
Sediment (%):
0.004
Other distribution results:
Using the ChemCAN 4 model, of the total amount of LAS released to the environment assuming the discharge rates above, the distribution and concentrations were predicted to be:
to air: 0% (0 mg/m³)
dissolved in water: 0.64% (0.44 ¿g/m³)
in soil: 99.35% (7.06 ¿g/kg)
in sediment: 0.0036% (0.00347 ¿g/kg)

Any other information on results incl. tables

The level I and II models each resulted in LAS partitioning to air, water, soil, and sediment at percentages of 0%, 25.97%, 56.09%, and 17.76%, respectively. The overall residence time of LAS is 100 hours and removal is primarily by biodegradation in water (76%) and partitioning in sediment (13%). Thus, the impacts of LAS will be restricted to local receiving waters and their sediments and biota. In level III, when discharges are directly to water, the residence time is 33 hours and more than 99% remains in the water, though in shallower receiving waters more partitioning to sediments might be expected. When the discharge is to soil, as was assumed in the ChemCAN model, the residence time is 28 days because of the slower biodegradation rate and little transfers to other media. Based on these findings, the dominant fate processes are degradation rates in water and soil, and water-sediment transfer.

Based on an estimated total discharge to the environment of 1.44 x 106kg/year (1.44 x 105 kg to water and 1.296 x 106kg to soil). It should be noted that the discharge assumptions used by the authors are highly conservative and likely overpredict the amount of LAS entering various compartments, for example, the soil compartment. This study was conducted by the model developer and acknowledged expert on fugucity to demonstrate that the approach was appropriate for different types of chemicals.

Applicant's summary and conclusion

Conclusions:
Based on the results of the fugacity modeling, the dominant fate processes for LAS are degradation rates in water and soil, and water-sediment transfer.
Executive summary:

Fugacity modeling of LAS was done using several different models: level I, II, and III, the ChemCAN model, and the WW-TREAT, GRiDS, and ROUT models. Based on these findings, the dominant fate processes are degradation rates in water and soil, and water-sediment transfer.