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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

In aerobic water/sediment systems, Benzenepropanoic acid, 3,5-bis(1,1 -dimethylethyl)-4-hydroxy-,C7-9-branched alkyl esters disappears rapidly. The process involved are degradation and formation of bound residues. The main degradation product identified is Metilox acid (CAS: 20170-32-5). Concentrations of Metilox acid are also subject to degradation and formation of bound residues.

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Degradation in aerobic water/sediment systems (OECD 308):

The route and rate of degradation of the substance in two aquatic systems (river and pond) under aerobic conditions was investigated at 20'°C in the dark according to OECD 308 (2002) at a concentration of 15 μg/L.

The substance disappeared rapidly in water and sediment in the river and pond systems:

Total recoveries (material balances) of the applied radioactivity (AR) averaged 93.3 ± 2.3% and 93.7 ± 2.6% in the river and pond systems.

After 2 days only 30% of the radioactivity was related to the parent substance in the total systems (water and sediment for pond and river system), whereas 50% of the radioactivity refers to transformation products. Up to nineteen radioactive fractions were detected of which one of the major ones (M1) was identified as Metilox acid. M1 increased rapidly to maximum levels of 34.2% AR and 42.4% AR in the river and pond total systems, respectively, after 2 days of incubation and equally rapidly declined.

 

Therefore, it can be concluded that 50% of the substance was degraded after 2 days.

The mineralisation of the test item was very low, not exceeding 6% of the applied radioactivity for both systems after 100 days of incubation. Other organic volatile compounds did not exceed 1 % of the applied radioactivity.

 

The amount of non-extractable radioactivity was high for both test systems. Bound radioactivity in the sediment was ca. 35% in the river system and ca. 43% in the pond system after 14 days and reached maximum mean levels of 52% and 54% AR in the river and pond systems, respectively, at the end of the study (day 100).

 

For further details, please see attachment below (Endpoint summary, IUCLID chapter 5.2.2) 

DT50 (parent, water) = 0.2 – 0.3 days

DT50 (parent, sediment) = 4.5 – 5.5 days

DT50 (patent, total system) = 1.3-1.7 days

DT50 (M1, Metilox, total system) = 6.8 – 7.6 days