Registration Dossier

Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Magnesium methanolate decomposes very rapidly upon contact with water by hydrolysis. The environmental fate and pathways are determined by the degradation products methanol and magnesium hydroxide.

The hydrolysis product methanol is a naturally occuring substance and readily biodegradable in water, soil and sediments, both under aerobic and anaerobic conditions.

Compared to other loss mechanisms identified, including volatilization and chemical degradation, biodegradation is expected to be the dominant process controlling the fate of methanol in the soil, groundwater, and surface water environments

Methanol is degraded in the atmosphere by photochemical, hydroxyl-radical dependent reactions. The estimated elimination half-life is calculated to be about 17.2 days.

Due to the high solubility of methanol in water and its low octanol-water partition coefficient adsorption to soil is considered to be negligible. Given the value of the Henry's Law constant, once in water, methanol is likely to remain in the aqueous phase. No bioaccumulation is expected.

Hydrolysis product magnesium hydroxide:

Magnesium hydroxide is a naturally occuring mineral (Brucite)

The molecular structure of Magnesium hydroxide does not contain any hydrolysable functional groups and therefore, the test on the hydrolysis of Magnesium hydroxide could not be performed. The substance is an inorganic hydroxide and as such is not subject to biodegradation, the study is technical not feasible.

Magnesium hydroxide has a very low potential for adsorption to sediment based on a derived Kd value of 1.65. The Forum of European Geological Surveys (FOREGS) Geochemical Atlas of Europe ('Salminen, R. (ed.) 2005) [1]provided paired sediment-water concentrations of Magnesium and Magnesium oxide from which sediment partition coefficients (Kd values) could be derived.

The sediment-water partition coefficients were calculated for each of the pairs using the following equation:

Kd = Cs / Caq

Where Cs = the total concentration of the test substance in the solid phase (mg/kg) and Caq = concentration of test substance in aqueous phase (mg/L). The detection limit for Magnesium and Magnesium oxide in water was 0.001 mg/L.

The median Kd value along with the 10thand 90thpercentiles for the dataset are reported in Table 1.

 

Table4. Sediment-water partition coefficients (Kd) for Magnesium/Magnesium oxide compounds (L/kg)

Min

Max

Median

10th Percentile

90th Percentile

806

0

562.5

1.65

3.5

12.23

1]Salminen, R. (ed.) 2005. Geochemical Atlas of. Part 1: Background Information, Methodology and Maps.: Geological Survey of

 Magnesium hydroxide is an inorganic substance, it is unlikely to cross biological membranes. Magnesium hydroxide has no bioaccumulation potential.

 

Additional information