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Environmental fate & pathways

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Hydrolysis:

Hydrolysis is a reaction in which a water molecule or hydroxide ion substitutes for another atom or group of atoms present in a chemical resulting in a structural change of that chemical. Potentially hydrolyzable groups include alkyl halides, amides, carbamates, carboxylic acid esters and lactones, epoxides, phosphate esters, and sulfonic acid esters (Neely, 1985). The lack of a suitable leaving group renders compounds resistant to hydrolysis.

Icosane consists entirely of carbon and hydrogen and do not contain hydrolyzable groups. As such, it has a very low potential to hydrolyze. Therefore, this degradative process will not contribute to its removal from the environment.

Phototransformation in air:

Icosane half-life in air is 0.424 days. Therefore icosane is to be considered as not persistent in the atmospheric compartment (DT50 less than 2 days).

Phototransformation in water and soil:

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 approachto 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.

Biodegradation:

”Hydrocarbons C14-C20, aliphatics (≤2% aromatics)” were found to be readily biodegradable (biodegradation in natural seawater > 60% ThOD) in OECD 306 closed bottle test (van Ginkel, 2009a) as well as in OECD 301 ready biodegradability test (Cidaria, 1994). Therefore, the substances belonging to the category are considered readily biodegradable and no further biodegradation studies are deemed necessary.

 

Adsorption / Desorption

Koc of icosane has been estimated in the Concawe Library of Petrorisk using SPARC v4.2. Starting from a log Kow of 11.46, a Koc of 1.84x10^11 L/kg has been obtained.

Distribution modelling:

The distribution of the substance in the environmental compartments, air, water, soil, and sediment, has been calculated using the PETRORISK Model, version 5.3. Computer modeling is an accepted method for estimating the environmental distribution of chemicals. Distribution modeling results are included in the 'Multimedia distribution modeling results' tab in the PETRORISK spreadsheet attached to IUCLID section 13.