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Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Based on the relevant physical-chemical properties, the known use pattern (release to water) and the assuming no biodegradability, HMDTMP and its salts will partition primarily to water and suspended sediments. In the sewage treatment plant the substance is not expected to degrade, but will be removed on sewage sludge (approximately 80%) and be present in the effluent (approximately 20%).

Additional information

Because HMDTMP and its salts behave in aqueous medium in accordance with the pH and composition of the medium, the conclusions in this section apply to both acid and salts.

The compartmental approaches expressed in the Mackay models at Level I and Level III have been used to give an indication of relative partition tendencies, but not predicted concentrations. This qualitative approach is sufficient for the present purpose.

Using fugacity based models HMDTMP (23605-74-5) is predicted to migrate primarily to sediment following release via water, and migrate primarily to soil when released by other pathways.

The acid, sodium and potassium salts in the HMDTMP category are freely soluble in water. The HMDTMP anion can be considered fully dissociated from its sodium or potassium cations when in dilute solution. Under any given conditions, the degree of ionisation of the HMDTMP species is determined by the pH of the solution. At a specific pH, the degree of ionisation is the same regardless of whether the starting material was HMDTMP-H, HMDTMP.4Na, HMDTMP.7K or another salt of HMDTMP.

Therefore, when a salt of HMDTMP is present in test media or the environment, the following is present (separately):

1. HMDTMP is present as HMDTMP-H or one of its ionised forms. The degree of ionisation depends upon the pH of the media and not whether HMDTMP (4-7K) salt, HMDTMP (4-7Na) salt, HMDTMP-H (acid form), or another salt was used for dosing. At pH 5.5 - 6, the HMDTMP anions would be present on average as the HMDTMP trivalent anion according to the pH curves.  At neutral pH (7), the HMDTMP anions would be present on average as the HMDTMP pentavalent anion according to the pH curves. At pH 8, the HMDTMP anions would be present on average as the HMDTMP hexavalent anion according to the pH curves.

2. Disassociated potassium or sodium cations. The amount of potassium or sodium present depends on which salt was dosed.

It should also be noted that divalent and trivalent cations would preferentially replace the sodium or potassium ions. These would include calcium (Ca2+), magnesium (Mg2+) and iron (Fe3+). These cations are more strongly bound by HMDTMP than potassium and sodium. This could result in HMDTMP-dication (e.g. HMDTMP-Ca, HMDTMP-Mg) and HMDTMP-trication (e.g. HMDTMP-Fe) complexes being present in solution.