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Environmental fate & pathways

Biodegradation in soil

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Description of key information

Imidazole biodegrades rapidly in soil.

Key value for chemical safety assessment

Half-life in soil:
2.5 d
at the temperature of:
20 °C

Additional information

The biodegradation potential of imidazole in soil was determined in a study according to OECD guideline 307 and in compliance with GLP criteria (BASF, 2009). In this study, the rate of degradation of 14C radio-labelled imidazole was investigated under aerobic conditions in three soils with ranging ratios of sand, sit and clay, and different pH and organic carbon content. The soils, at portions of 100 g dw and adjusted to 40% of the maximum water holding capacity, were incubated at room temperature in the dark in a batch application at a substance test concentration of 0.4 mg/kg soil dw. The tested concentration was determined to correspond to a field application rate of 150 g/ha (assuming a soil density of 1.5 g/mL and equal distribution in the upper 2.5 cm soil layer). The test vessels were continuously aerated and the exiting air was passed through a system for trapping organic volatiles and 14CO2. Samples were taken after 0, 1, 2, 4, 7, and 10 days. Soil aliquots were extracted 4 times, the extracts measured for radioactivity by liquid scintillation counting (LSC) and then concentrated and subjected to radio-HPLC analysis. The non-extractable residues were determined by combustion and LSC analysis. A total balance of radioactivity in soil was established for each sampling interval and the total mean recoveries for the three soils were in the range from 96.0-99.1% of the total applied radioactivity (TAR). The amount of extractable radioactivity decreased very fast during the study, reaching 0.9-2.5% TAR after 10 days of incubation. The non-extractable residues increased from 6-8% TAR at day 0 to maximum amounts of 14.5-19.0% TAR after 2-4 days and decreased again reaching 6.1-11.5% TAR after 10 days. The mineralization was very high in all three soils reaching 82-91% TAR within 10 days. No other volatile products than CO2 were detected. Overall, imidazole was degraded very rapidly reaching amounts of <3% TAR within 7-10 days in all three soils. The calculated DT50 values ranged from 1.8-2.5 days.