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Environmental fate & pathways

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Half-lives for the direct and indirect photodegradation of 2,6-di-tert-butylphenol in the atmosphere and the top layer of surface water are short.

Photodegradation was assessed using the calculation method contained in AOPWin v 1.92 and revealed a half-life of 2.614 h (overall OH Rate Constant = 49.1082 E-12 cm3/molecule-sec).

The effects of sunlight on the degradation of aqueous solutions of 2,6-di-tert-butylphenol in synthetic humic water (SHW) and pure water (PW) (pH 7.0 buffer) were investigated. The ratio of (kP)shw / (kP)pw was 1.36 and suggests that 2,6 DTBP is marginally susceptible to indirect photolysis.

In preliminary tests, significant sorption of 2,6 DTBP to glass was observed as evidenced by the decrease in solution concentration seen in the dark controls. Silanization of the glassware (quartz) gave the least amount of adsorption. In the phase II study, 2,6-DTBP analysis of individual replicate test solutions using synthetic humic water or pure water in the media was conducted. The values for (kP)shw and (kP)pw were 2.94 day-1and 2.16 day-1respectively. The ration (R) of these values was 1.36 indicating marginal susceptibility for indirect photolysis and indicating the need for further testing. Phase III was conducted over a 29 hour period. A geometric correction factor for scattered light in tubes versus horizontal surfaces of 0.455 was applied to measured rate constants. The net photolysis rate constant (kPE) is thus 0.455 multiplied by (kP)shw resulting in 6.90 days-1. The direct photolysis rate constant (kDE) is 8.33 multiplied by (kA) resulting in 15.18 days-1. The photolytic half-life for environmental conditions resulted in a value of 2.41 hours based on corrected data.