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Environmental fate & pathways

Endpoint summary

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Description of key information

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In a Japanese MITI test biodegradation of 2,4-Dinitrophenol reached 0% of its theoretical BOD in 4 weeks using an activated sludge inoculum (aerobic biodegradation) (NITE; Chemical Risk Information Platform (CHRIP).

However, biodegradation may be the most important process of loss for dinitrophenols in natural waters.

The only data of half-life is in aerobic and anaerobic waters reported were 68 days and 2.8 days of biodegradation, respectively (Capel PD, Larson SJ, 1995).

In general, complete or partial biodegradation of 2,4-DNP was observed in several aquatic systems, in aerobic conditions, as mixed microorganisms from activated sludge (Kincannon et al. 1983a, 1983b; Patil and Shinde 1989; Pitter 1976), enriched sewage (Brown et al. 1990; Wiggins and Alexander 19SS), adapted sediment from rivers or waste lagoons (Barth and Bunch 1979; Chambers et al. 1963; Tabak et al. 1964).

In several studies with activated sludge previously adapted to mineralize low concentrations of dinitrophenols (Jo KW, Silverstein J, 1998) and in methanogenic conditions with anaerobic digester sludge (Battersby and Wilson 1989; O’Connor and Young 1989) showed biodegradation, but this activity diminished at higher concentrations of 2,4-dinitrophenol.

The half-life of 2,4-dinitrophenol in an aquifer slurry was about 5 days under both methanogenic and sulfate-reducing conditions, but was not biodegraded under nitrate-reducing conditions (Krumholz LR, Suflita JM).

In natural waters in which the degrader populations are small, biodegradation of 2,4-DNP will be slow until microorganisms multiply to give a large enough degrader population to cause a detectable degradation.

2,4-DNP is also biodegrade by several pure cultures of microorganisms. Usually, the pure cultures were able to biodegrade 2,4-DNP after a certain adaptation period and as long as the concentration of 2,4-DNP was below a certain toxic level. The degradation pathway depended on the microorganisms and the conditions of aeration.

Typically, with aerobic organisms and aerobic conditions, the biodegradation proceeded by replacement of nitro groups by hydroxyl groups and liberation of nitrite, or by hydroxylation of the aromatic ring positions 3, 5, or 6 (Raymond and Alexander 1971).

Although these pure culture studies are important for establishing degradative pathways, they do not reflect real environmental situations where mixed microorganisms and different nutritional conditions are present.

Complete or partial biodegradation of 2,4-DNP was observed also in field condition, as in an aeration lagoons and settling ponds.


Biodegradation may be the most significant process for destroying dinitrophenols in soil.

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 by isolated culture proceeding of the reduction of the nitro group or displacement of a nitro group by a hydroxyl group with the release of nitrite ions (Kohping GW, Wiegel J. 1987, Shea PJ, Weber JB, Overcash MR., 1983).

However, high concentration 2,4-dinitrophenol (100 mg/kg ) may be toxic to the degrader microorganisms.

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).

The biodegradation of dinitrophenols in soils will occur also by bacteria in multiphasic mineralization kinetics (involving several slow types of anaerobic reaction anaerobic to methane and carbon dioxide) (Schmidt SK, Gier MJ. 1990, Young LY. 1986).

Also a pure culture of the fungus Fusarium oxysporum, pure cultures of Nocardia alba, Arthrobacter and Corynebacterium simplex are able to reduce 2,4-dinitrophenol (Overcash MR et al, 1982).