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Environmental fate & pathways

Biodegradation in soil

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Description of key information

Data have been obtained from secondary source.

The biodegradation half-life of 2,4-dinitrophenol in an acidic soil was reported as 32.1 days and the biodegradation half-life in a basic soil as 4.6 days.

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Additional information

The biodegradation half-life of 2,4-dinitrophenol in an acidic soil was reported as 32.1 days and the biodegradation half-life in a basic soil as 4.6 days (Loehr RC, 1989). 2,4-DNP biodegrades due to anaerobic activity.

It disappeared within hours due to reduction of the nitro groups to yield diaminophenol (Kohping GW, Wiegel J. 1987).

In fact, it has been tested that in isolated culture studies the biodegradation in soil of 2,4-dinitriohenol may proceed either by reduction of the nitro group or displacement of a nitro group by a hydroxyl group with the release of nitrite ions (Shea PJ, Weber JB, Overcash MR. 1983)

The biodegradation of dinitrophenols in soils will occur also by bacteria in multiphasic mineralization kinetics(involving several types of reaction kinetics) (Schmidt SK, Gier MJ. 1990). Slow and partial mineralization of 2,4-DNP at low concentrations (<20 mg/kg) to methane was observed under anaerobic conditions after a suitable adaptation period, in contrast to the fast initial reductive biotransformation. The rate of conversion of 2,4-DNP to methane and carbon dioxide was found to be slow (Young LY. 1986.)

The biodegradation will occur as long as the initial concentrations of DNP in soils and sediments do not exceed the level of ≈100 mg/kg. Above this level, DNP may be toxic to the degrader microorganisms.

pH is important for the 2,4-dinitrophenol biodegradation. The optimum pH for microbial degradation is near neutrality because of the low rate of sorption of DNP to soils and sediment (increasing bioavailability to microorganisms) and low toxicity of DNP towards microorganisms at this pH.

Depending on the soil (pH, organic matter content), the length of acclimation phase, as well as the initial concentration, the residence time of dinitrophenols for the aerobic biodegradation of soil may vary from 8 to 120 days (Kincannon and Lin 1985; Loehr 1989; O’Connor et al. 1990).

A pure culture of the fungus Fusarium oxysporum was found to reduce 2,4-dinitrophenol to 2-amino-4-nitrophenol and 4-amino-2-nitrophenol. Nitrite release has been observed during the metabolism of 2,4-dinitrophenol by pure cultures of Nocardia alba, Arthrobacter and Corynebacterium simplex (Overcash MR et al, 1982).