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Environmental fate & pathways

Adsorption / desorption

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Description of key information

No specific Koc value can be determined for AOH due to the complexity of its composition. The mean of the Koc values estimated for the key constituents phenanthrene, anthracene, fluoranthene and pyrene is considered to represent best the overall distribution properties of AOH.

Key value for chemical safety assessment

Koc at 20 °C:
52 250

Additional information

Due to the complex composition of the substance distillates (coal tar), heavy oils (anthracene oil >50 ppm BaP, AOH), a specific Koc value cannot be determined for the substance following standard procedures. Main components (all PAH) will have their individual Koc values. An extract on Koc values for individual PAH and an estimated Koc value for AOH is presented in the following paragraphs.

Koc values of PAH have been estimated by calculations based on Pow/log Pow values using different relations between Pow/log Pow and Koc/log Koc. Well established is the equation by Karickhoff et al. (1979) derived from experimental data: log Koc = log Pow - 0.21 (or Koc = 0.63 Kow). Koc data quoted will originate from this equation. Koc data derived using this equation have also been used in the EU Risk Assessment Report for Coal-tar pitch, high temperature (European Union 2008).

Overall properties of AOH will best be represented by the range of Koc values corresponding to the main PAH present in the substance (phenanthrene to pyrene, see Chapter 1.). The estimated adsorption coefficients (Koc) extend from approx. 23,000 to 100,000 (range of log Koc = 4.36 - 4.99) for the key constituents in AOH. It is considered that an average Koc will best represent the distribution properties of the substance AOH. Therefore, the arithmetic mean of the Koc values of the four main constituents in AOH (phenanthrene, anthracene, fluoranthene, pyrene) is calculated. This way, a Koc of 52,250 for AOH is estimated. Log Koc is 4.718.

(For Log Pow values of AOH and of relevant PAH see CSR Chapter 1.3 and IUCLID Sect. 4.7).

[LogKoc: 4.718]