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Environmental fate & pathways

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Sodium methanolate is a white to yellowish organic solid salt that decomposes above 300 °C (OECD SIDS 2006). Sodium methanolate has a calculated vapour pressure of 6.39 x 10-6 hPa (study director 2003). On contact with water the substance decomposes rapidly and exothermically under formation of methanol and sodium hydroxide (Leal & de Matos, 1991). For the partitioning in the environmental compartments the hydrolysis products are of relevance. Sodium hydroxide is an inorganic salt that partitions predominantly into the water phase and will not adsorb to particulate matter or surfaces. For sodium methanolate it was concluded that based on the Henry’s law constant of 0.304 Pa m3/mol it is not expected to significantly volatilise from the aquatic compartment and adsorption is not expected to be significant due to its high water solubility and low octanol-water partition coefficient. A distribution calculation performed with the Mackay level III model predicts that the air is the target environmental compartment for methanol. Photodegradation of methanol by hydroxyl radicals takes place with a half-life of 17 - 18 days (Atkinson, 1989). After rapid dissociation of the test substance in water the relevant organic reaction product, methanol, is readily biodegradable (76 – 82% BOD-removal after 5 days). For methanol the log KOWwas -0.77, indicating low bioaccumulation (study director 2009). This was confirmed by experimental BCF-values for methanol < 10 that have been determined in different fish species (Gluth et al., 1985; Freitag et al., 1985; Hansch and Leo, 1979). Sodium hydroxide will dissociate to sodium and hydroxide ions and can not bioaccumulate.