Division 1.5 PRINCIPLE OF THE TEST METHOD

The method described in this test employs an aerobic and an anaerobic aquatic sediment (see Annex 1} system which allows:

1. (i)

   the measurement of the transformation rate of the test substance in a water-sediment system,

2. (ii)

   the measurement of the transformation rate of the test substance in the sediment,

3. (iii)

   the measurement of the mineralisation rate of the test substance and /or its transformation products (when ¹⁴C-labelled test substance is used),

4. (iv)

   the identification and quantification of transformation products in water and sediment phases including mass balance (when labelled test substance is used),

5. (v)

   the measurement of the distribution of the test substance and its transformation products between the two phases during a period of incubation in the dark (to avoid, for example, algal blooms) at constant temperature. Half-lives, DT₅₀, DT₇₅ and DT₉₀ values are determined where the data warrant, but should not be extrapolated far past the experimental period (see section 1.2).

At least two sediments and their associated waters are required for both the aerobic and the anaerobic studies respectively (7). However, there may be cases where more than two aquatic sediments should be used, for example, for a chemical that may be present in freshwater and/or marine environments.