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Environmental fate & pathways

Biodegradation in soil

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Description of key information

Acrylic acid was readily biodegradable in a sandy loam soil under aerobic conditions at 25°C in the dark. The DT50 under these conditions was estimated to be < 1 day. 

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Additional information

A well-documented and reliable test on biodegradation in soil, performed according to U.S. EPA Pesticide Assessment Guidelines, Subdivision N, § 162- 1 is available (BAMM 1992). From the test design, the test can be rated as a simulation test in soil.

The metabolism of [14C]-acrylic acid (radiochemical purity 96 % by HPLC) in a Milton sandy loam soil from Somersham, Cambridgeshire, U.K. has been studied under aerobic conditions for up to 28 days after treatment. Soil samples were incubated in darkness at 25°C. The test substance was applied to the soil at a rate of 100 mg/kg dw. Total recoveries of radioactivity were in the range of 87 – 104 % of the amounts applied.

 

Under aerobic conditions acrylic acid was rapidly metabolised, after 3 days no acrylic acid was detected in soil extracts. The half-life for acrylic acid under these conditions was estimated to be less than 1 day. Carbon dioxide evolution accounted for 72.9 % of applied radioactivity by Day 3 and a total of 81.1 % over the 28-day study period. Non-extractable radioactivity peaked at 16.8 % of applied radioactivity by Day 3 and decreased to 10.1 % by Day 28. Chromatographic analysis of soil extracts revealed that most of the extractable radioactivity after Day 1 was associated with highly polar material which was not further analysed.

The trend exhibited by the metabolism of acrylic acid in soil was bi-phasic. In the first phase, by Day 3, the vast majority (if not all) of the [14C]-acrylic acid applied to the soil had been degraded. Most of the radioactivity was mineralised to carbon dioxide. The remainder probably became incorporated into soluble or insoluble organic material. The soluble material was extracted and visualised by HPLC analysis. The insoluble material remained bound. In the second phase the radiolabelled organic material appeared to remain bioavailable, but it was metabolised at a much slower rate (based on CO2 evolution data) so distinguishing it from, the more labile acrylic acid.

 

From the presented simulation test in soil it can be concluded that acrylic acid is readily biodegradable in this soil type (sandy loam).

The applicability of the comparatively short DT50 < 3 d to other soil types and environmentally more relevant lower temperatures is not clear. Based on all available data, also taking into account the low adsorption potential of acrylic acid to soil, rapid biodegradation in soil under environmental conditions can be expected.