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Environmental fate & pathways

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Degradation in air

The following text was copied from the EU Risk Assessment Report (2003), pg. 30:

"In polluted urban air half-lives of few hours have been reported (Sakugawa et al., 1990). No clear figures of overall photolysis rates have been presented in the literature. A study done by Olzyna in Whitetop Mountain indicates that in unpolluted air at night time (during 8-10 hours) indirect photolytic degradation decreases H2O2 levels by about 25% and consequently 50% decrease would take 16-20 hours (it is assumed that the night time production rate of H2O2 is low or negligible). In polluted air diurnal variations in concentrations seem to be more or less larger than in unpolluted air.

According to the existing test data from different atmospheric conditions (Olszyna, 1988; Sakugawa et al., 1990; Kleinman 1986) a half-life of 24 hours (rate constant of 0.029 h-1) will be chosen to represent the average degradation half-life in the atmosphere."

Decomposition in natural waters

Hydrogen peroxide is not hydrolysed, due to its molecular structure. Furthermore, no direct photolysis of hydrogen peroxide is expected based on the following text copied from the EU Risk Assessment Report (2003), pg. 30:

"Direct photolysis is not expected to be an important degradation process in the aquatic environment. Hydrogen peroxide has absorption bands in the infrared, but is not decomposed by the light of these frequencies. The UV absorption spectrum is a continuous spectrum but the measured molar extinction coefficient values are low. Highest value is ε = 4.2 l/ (at 280 nm) decreasing continuously to 0.22 l/ (at 320 nm) and 0.00066 l/ (at 400 nm) (Schumb et al., 1955)."

Degradation in soil

The following text was copied from the EU Risk Assessment Report (2003), pp. 34/35:

In soil H2O2 is normally a short-lived substance. Rapid degradation will occur due to high concentration of catalytic material like transition metals, enzymes, easily oxidised/reduced organic substances and living microbes (Spain et al., 1989).

Hydrogen peroxide is used as a source of oxygen (for aerobic microbes) in polluted groundwater sites (enhanced bioremediation). Therefore specific information on degradability in soil is available. The problem in these applications where hydrogen peroxide is introduced directly into the ground is linked to a too rapid degradation. Observed half-lives of H2O2 in soil vary from 15 hours (soil without microbiological activity and few minerals) to several minutes (soils with 108-109 cells/g total solids, and in the presence of iron and manganese (Aggarwal et al., 1991; ECETOC 1993; Hinchee and Downey 1988 ; Pardieck et al., 1992).

In the assessment it is estimated that the degradation half-life in soil is 12 hours.