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Environmental fate & pathways

Biodegradation in soil

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Description of key information

In tests on biological degradation in soil and compost, the structural analogue tributyl-O-acetylcitrate (CAS 77-90-7) was found to be readily biodegradable.

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Additional information

No experimental data is available to assess the biodegradation in soil of tributyl citrate (CAS 77-94-1).

From several test results on mineralisation in soil and compost, acetyl tributyl citrate can be classified as readily biodegradable in these substrates. The reduced degradation in one test with compost can probably be attributed to deficiencies in the applied method.

In a test on biodegradation in soil according to EPA OPPTS 835.3300 tributyl-O-acetylcitrate was found to be readily biodegradable. Decay rates decreased as a function of substrate concentration. However, ATBC is considered to be readily biodegradable at concentrations < 3.2 mg C/g soil, based on > 60 % ThCO2, observed within a 10- to 14-day window following the lag phase (lag, defined as the time required for net CO2-C evolution to reach 10% of the maximum amount of CO2-C evolved during mineralisation of the test substrate).

In a Respirometry test in ‘static’ compost biometer system, ATBC was found to be readily biodegradable. The higher test concentration (10.8 mg C/g soil), the conversion of substrate-C into CO2exceeded 50% (based on ThCO2) in about two weeks and 60% ThCO2in about three weeks. The lower test concentration (1.90 mg C/g soil), the conversion of substrate-C into CO2 exceeded 60% ThCO2 within about four days following the lag period. It can be assumed that the same applies to tributyl citrate (CAS 77-94-1) as it is a near analogue to the test substance acetyl tributyl citrate.

In a test on ultimate biodegradation in actively aerated compost, mineralization of the test substance reached 37 % (based on ThCO2 in 45 days. Microbial degradation of the test substance in the compost was, in part, retarded at the very high substrate loading used in this test. Further, problems with the aeration system were reported, particularly in the last two weeks of the test. Despite randomisation in bioreactor placement, the reduced air supply due to NaOH crystal formation in the air distribution manifold became more significant along the manifold and throughout the exposure period, potentially influencing the results achieved during this study.