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Environmental fate & pathways

Biodegradation in soil

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Description of key information

The test substance is readily biodegradable.

Key value for chemical safety assessment

Additional information

No relevant data on the biodegradation in soil are available. However, since the test substance is readily biodegradable no further data are deemed necessary.

In accordance with Regulation (EC) No 1907/2006, Annex IX, Section 9.2.1.3, Column 2, soil simulation testing does not need to be conducted if the substance is readily biodegradable. The substance is readily biodegradable (see IUCLID Ch. 5.2.1). Therefore, no further soil simulation study will be provided.

In aerobic and anerobic experiments with soil from a contaminated site (Ndegwa et al., 2004), MEA (addition of 2000 mg/kg) was completely degraded in up to 20 days from the soil at low termperatures (5 -10 °C) and up to 11 days at 20 to 25 °C. As the soil used in these experiments was pre-exposed to MEA (contaminated site), this publication should only be used as supporting information.

In aerobic bench-scale reactor experiments the degradation of MEA was studied (Mrklas et al., 2004). The reactors contained a slurry which was composed of soil and groundwater from a contaminated site (initial MEA concentration = ca. 31000 mg/kg). As the material was pre-exposed, this publication should only be used as supporting information. Degradation of MEA was observed in the experiments and was enhanced by phosphate addition. After phosphate addition, MEA was completely degraded within 11 days.

Two supporting studies on the degradation of MEA in soil were performed by Sorensen et al. (1997). Experiments were performed using one soil in small bioreactor experiments. In one experiment MEA was tested at three concentrations (400 - 1500 mg/kg) at three temperatures (6, 14, 25 °C) for 120 d using a respirometric test assay with a water saturated soil (slurry). The CO2 evolution was followed to determine the biodegradation. The lag phase decreased with an increase in temperature (24 to 5.3 d at 1500 mg MEA/kg), while the degradation rate increased. Temperature was the most important variable affecting biodegradation.

In the second set of experiments, a comparison between aerobic and anaerobic degradation was set up. Water-unsaturated soil was incubated with a MEA solution (500 mg/kg) at 25 °C under either aerobic or anaerobic conditions for 82 days. Degradation under aerobic conditions showed a shorter lag phase (4.5 d) and higher degradation rate (54.9 mg MEA/kg*h) than under anaerobic conditions (0.11 mg MEA/kg*h). In addition, the results for anarobic conditions showed a higher variability (e.g. lag phase: 10 to 33 d).