Potassium salts of [hexane-1,6-diylbis[nitrilobis(methylene)]]tetrakisphosphonic acid (4-7 K:1)

Distribution modelling

Administrative data

Endpoint:

distribution modelling

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Data source

Reference

Reference Type:

other: Software model

Title:

Level III Fugacity-based multimedia environmental model

Author:

CEMC

Year:

2004

Bibliographic source:

Canadian Environmental Modelling Centre, Trent University, Peterborough, Ontario http://www.trentu.ca/cemc. Version 2.80.1

Materials and methods

Model:

calculation according to Mackay, Level III

Media:

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

Test material

Test material information

Constituent 1

Reference substance name:

[hexane-1,6-diylbis[nitrilobis(methylene)]]tetrakisphosphonic acid, potassium salt

EC Number:

254-135-7

EC Name:

[hexane-1,6-diylbis[nitrilobis(methylene)]]tetrakisphosphonic acid, potassium salt

Cas Number:

38820-59-6

Molecular formula:

C10H28N2O12P4.xK

IUPAC Name:

[hexane-1,6-diylbis[nitrilobis(methylene)]]tetrakisphosphonic acid, potassium salt

Test material form:

solid - liquid: aqueous solution

Study design

Test substance input data:

- Molar mass: 492
- Data temperature: 25
- Water solubility: 410000 mg/l
- Vapour pressure: 2.7E-09 Pa
- log Pow: 7.4 (note: adjusted value used, as the program does not allow input of Koc)
- Melting point:
- Reaction half-life estimates for
- Air: negligible
- Water: negligible
- Soil: negligible
- Sediment: negligible
- Suspended sediment: negligible
- Aerosols: negligible
- Aquatic biota: negligible

Environmental properties:

as default

Results and discussion

Percent distribution in media

Air (%):

0

Water (%):

2.6

Soil (%):

0

Sediment (%):

97.5

Any other information on results incl. tables

Using a fugacity based model (Mackay Level 1) HMDTMP is predicted to migrate to the soil and aquatic sediment compartments when modelling using a substitute log Kow (selected to generate an indicative Koc).

Table: level I outputs using an adjusted log Kow

Air	3E-15%
Soil	97.7%
Water	4.4E-03%
Sediment	2.2%

The Level III program has also been applied, with the default model, using the same input parameters and

the adjusted log Kow. The resulting distribution between compartments is as follows:

Table: Level III outputs using an adjusted log Kow

	Release to air only	Release to water only	Release to soil only
Distribution to air (%)	<0.1	<0.1	<0.1
Distribution to soil (%)	99.5	<0.1	99.6
Distribution to water (%)	<0.1	2.6	<0.1
Distribution to sediment (%)	0.5	97.5	0.4

For the known use pattern, the most likely emission route will be directly to water. Direct emission to soil via spreading of sludge from waste water treatment plants is also possible. The results reflect that most HMDTMP found in air would be precipitated to soil, and that there is very little movement between soil and water, because transfer via the air compartment is very slow, for a substance of low volatility. In water, the adsorption coefficient of HMDTMP results in significant adsorption to sediment.

The distribution in a sewage treatment plant has been estimated using the SimpleTreat model (implemented in EUSES 2.1.2) to be 0% degraded, 16% to water, 84% to sewage sludge. These outputs are based on non-biodegradability, and the properties given above for the fugacity-modelling of distribution. There is evidence from literature that wastewater treatment plants using a purification step with iron and aluminium salt additives to remove phosphorus, can be expected to achieve more than 90% removal of the analogous phosphonate complexing agent DTPMP, attributed largely to adsorption to amorphous precipitated iron oxides (Nowack, 2002).

Applicant's summary and conclusion

Conclusions:

Based on the relevant physical-chemical properties, the known use pattern (release to water) and the fact that it is non-biodegradable, HMDTMP and its salts will partition primarily to aquatic sediments. In the sewage treatment plant the substance is not expected to degrade, but will be removed on sewage sludge (84%) and be present in the effluent (16%).