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Environmental fate & pathways

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Biodegradation is not a primary route of degradation for this substance. The substance is neither readily nor inherently biodegradable as indicated by numerous studies utilizing activated sludge. However, abiotic degradation studies demonstrate rapid degradation in water and air via oxidative and photolytic mechanisms. The substance is predicted to undergo rapid degradation after reaction with hydroxyl radicals with a DT50 value of 0.091 days (QSAR model AOPWIN, v1.93). It is unlikely to undergo hydrolysis, since the substance is an aromatic amine and cannot behave as an electrophile unless it is metabolically activated. Under natural or simulated sunlight, direct and indirect photodegradation in water is rapid (overall t½ = 0.12 d). It indicates that the substance is very photolabile, and both direct and indirect photolysis contribute significantly to its phototransformation. Rapid photodegradation and oxidation (CSR section 5.2.2) of the substance indicate that the substance is unlikely to persist in air. In addition, the vapour pressure (0.0104 Pa) and the Henry's law constant (3.63E-5 Pa m3/mol) of the substance indicate that the substance is not likely to volatilise extensively from surfaces into air under dry conditions or from water. Therefore, any concentrations of the substance in air are considered negligible.

Abiotic degradation occurs rapidly when the substance is exposed to light and oxygen and can lead either to the formation of higher molecular weight molecules (dimer, trimer and Bandrowski’s base) or to benzoquinone depending on concentration. Degradation pathways were identified in the buffered water studies by Picardo et al. (1990), with the primary degradative pathway being oxidation to p-benzoquinonediimine and subsequent hydrolysis to benzoquinone. Oxidation of the substance to p-benzoquinonediimine in aqueous solutions was also documented with Bandrowski’s base the primary rearrangement product (Corbett, 1972). Given the rapid oxidation of the substance, storage recommendations during and prior to use include keeping the substance in well-closed containers, protected from light (Merck Index, 1996). For the adsorption property of the substance, the Koc value (33.83 L/kg) is estimated to be 33.83 L/kg (log Koc=1.53) using KOCWIN (QSAR model).