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Environmental fate & pathways

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Both TAME and MTBE are not expected to hydrolyse under environmentally relevant pH conditions (pH 4-10) based on their physical-chemical properties and the properties of other structurally related aliphatic ethers (Lyman et al., 1982; Prager, 1992). Since ETBE is structurally highly related to both substances it can be expected that also ETBE will not significantly hydrolyze in natural waters.

According to existing data, degradation half-life of ETBE in the air is 3-12 days depending on environmental conditions (predominantly OH-radical concentration).

Using a degradation rate constant of 3.0E-12 cm3/molecule/s and an OH –radical concentration of 5E05 radicals/cm3 a half-life of 5.35 days is calculated (Bennett and Kerr, 1990).

Direct photolysis will not be an important removal process since aliphatic ethers do not absorb light at wavelengths >290 nm. The UV-spectrum (max at 289 nm) indicates that direct photolysis in water may not occur.

The abiotic degradation rate constants used in the assessment are sumamrised in the following table:


Degradation for hydrolysis

0 d-1

Degradation for photolysis

0 d-1

Degradation in air

0.130 d-1