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Phototransformation in soil

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phototransformation in soil
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Description of key information

The available data and available weight of evidence demonstrate that the hydrocarbons contained by this substance do not absorb light within a range of 290 to 750 nm, the range in which photolysis occurs. Therefore, direct photolysis will not contribute to the degradation of these substances in the terrestrial environment.

Key value for chemical safety assessment

Additional information

The direct photolysis of an organic molecule occurs when it absorbs sufficient light energy to result in a structural transformation. The absorption of light in the ultra violet (UV)-visible range, 110-750 nm, can result in the electronic excitation of an organic molecule. The stratospheric ozone layer prevents UV light of less than 290 nm from reaching the earth's surface. Therefore, only light at wavelengths between 290 and 750 nm can result in photochemical transformations in the environment.


A conservative approach to estimating a photochemical degradation rate is to assume that degradation will occur in proportion to the amount of light wavelengths >290 nm absorbed by the molecule. This substance contains hydrocarbon molecules that absorb UV light below 290 nm, a range of UV light that does not reach the earth's surface. Therefore, this substance does not have the potential to undergo photolysis in water and soil, and this fate process will not contribute to a measurable degradative loss of this substance from the environment.


Zepp RG and Schlotzhauer PF.(1977). Photoreactivity of Selected Aromatic Hydrocarbons in Water. In: Polynuclear Aromatic Hydrocarbons. Jones PW and Leber P, eds., pp. 141-158. Ann Arbor Science Publishers, Inc., Ann Arbor, Miami, USA.

Zepp R and Cline D. (1977). Rates of direct photolysis in the aqueous environment. Environ. Sci. Technol. 11: 359-366.

USEPA - OPPT (1999). EPIWIN Estimation Program Interface for Windows, version 3.04.EPA - OPPT.Testing laboratory: Syracuse Research Corporation, NY, USA.

Harris J (1982). Chapter 8: Rate of Aqueous Photolysis. in: Handbook of Chemical Property Estimation Methods.McGraw-Hill Book Company, New York, NY, USA.