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Environmental fate & pathways

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Transport and distribution

Adsorption/desorption

A weight of evidence approach was used for evaluation, as the experimental determined values are used as training structure for the ACD calculated values.

In a screening study conducted according to OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC)) the log Koc values of C12 and C14 AAPB were determined. Based on a corrected dead time value, the log Koc of C12 and C14 AAPB were determined to be 2.5 (Koc: ca. 320; C12 derivate) and 3.5 (Koc: ca. 3200; C14 derivate), respectively. Based on these results and taking into account the classification scheme of Blume and Ahlsdorf (1993) a medium (C12 derivate) and high sorption (C14 derivate) onto soil organic matter is to be expected.

Based on the Koc value determined by measurement, C12 AAPB was used as training structure for the ACD software and Kow values were calculated for C8, C10, C14, C16 and C18 AAPB (for this calculation to the IUCLID the following justification documents are attached: QSAR prediction report format (QPRF) and QSAR model reporting format (QMRF)). The soil sorption coefficient of AAPB containing C8-, C10-, C12-, C14-, C16-, and C18 fatty acids was calculated using the guideline conform EUSES algorithm for non hydrophobics. The calculation yielded Koc values of 89.3 (C8 derivate), 303 (C10 derivate), 726 (C12 derivate), 4870 (C14 derivate), 16500 (C16 derivate), and 56000 (C18 derivate). According to the classification scheme of Blume & Ahlsdorf (1993), a low (C8 derivate), medium (C10 derivate), high (C12 and C14 derivates), and very high (C16 and C18 derivates) sorption onto soil organic matter is to be expected.

As reported in HERA (2007), the Koc values for AAPB containing C8-, C10-, C12-, C14-, C16-, and C18 fatty acids were calculated using EPIWIN v3.11, PCKOCWIN v1.67. The calculation yielded Koc values of 264.7 (C8 derivate), 900.5 (C10 derivate), 3063 (C12 derivate), 10420 (C14 derivate), 35450 (C16 derivate), and 120600 (C18 derivate). According to the classification scheme of Litz (1990) these values indicate a low to very high sorption potential to the organic matter of soils and sediments depending on the chain length.

Based on the experimental determined Koc values of C12 and C14 AAPB, the Koc values calculated with EPIWIN seem to overestimate soil sorption. The values calculated with ACD/EUSES (reasoned in separate documents (QPRF, QMRF attached to IUCLID)) Koc and Kow values were used for further calculations (environmental exposure and risk assessment).