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Environmental fate & pathways

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Additional information

No experimental data concerning the Henry´s Law constant for the substance dimethylamine is available.

Due to the importance of the value (for instance for the Equilibrium Assumption for PNECsoil calculation) the US-EPA computer tool EPIWIN was used to determine the constant by calculation, although it is no mandatory requirement under REACH. The Bond method gives a result of 1.69 Pa*m³/mol, whereby the Group method shows a value of 1.84 Pa*m³/mol. The predicted values are representative for the uncharged molecule. At environmental conditions the molecule is expected to be ionized; therefore, a pH-corrected HLC was calculated according to REACH Guidance document (2008). The resulting HLC was 3.43 x 10E-4 Pa*m³/mol at pH 7 indicating that the molecule will not evaporate from the water surface into the atmosphere.

A publication is available about a batch-equilibrium method according to OECD Guideline 106 (von Oepen, Kördel and Klein, 1991). Three types of soil were used: Podzol with an organic carbon content of 4.85 %, Alfisol with 1.25 % organic carbon and Sediment with 1.58 % organic carbon, respectively. Although several interactions contributing to the sorption process are known, it was not possible to determine the quantitative contribution of each sorption mechanism. For the test substance, the Koc values were reported as followed for Podzol, Alfisol and Sediment: 4, 163 and 508, respectively. Therefore, the geometric mean of the Koc for soil is determined as 25.53.

Supporting information on soil adsorption coefficient is given by a calculation with the US-EPA computer tool EPIWIN (software: KOCWINv2.00). The program uses two different methods: the traditional method, which gave a value of 4.692 L/kg and the MCI method, which resulted in 8.158 L/kg. In this case the traditional method is taken more seriously into account.

Additional experimental data concerning adsorption coefficients as well as desorption coefficients to different soil types (Montmorillonite, Kaolinite, and marine sediment) are available (Wang and Lee, 1993). For marine sediment the scientists found adsorption coefficient range of 2.4 - 4.7 (Wang and Lee, 1990) for the substance dimethylamine.

Moreover, the amine is readily biodegradable, indicating, that the substance decomposes rapidly.