OECD 308: Aerobic and Anaerobic Transformation in Aquatic Sediment Systems

The purpose of this test is to measure the time course of biodegradation of a test substance in aquatic sediment systems under aerobic and anaerobic conditions and to quantify the observations in the form of kinetic rate expressions. Degradation of the test substance will be followed for the parent substance and its potential (known) transformation products. Degradation rate, mass balancing and transformation product pattern will be determined for the test substance. Degradation kinetics will also be followed for any major transformation product, if possible.

Study Design

Test setup

Typically, the test will be carried out with 14C-labelled test substance. Incubation in two (aerobic) and one (anaerobic) sediment system will be accomplished in the dark at a temperature of 20°C. The test will be conducted using multiple flask and flow throgh (aerobic) or static (anerobic) design.  A moderate stream of air will be used as carrier gas to collect CO2 and other volatiles in distinct traps consisting of different solutions.

Course of the test

One concentration of the test substance will be used for the test. Microbial activity of the sediment systems will be verified by substrate induced respiration (control samples). For examining possible abiotic degradation or other non-biological removal of the test substance (e.g. hydrolysis or adsorption to the test vessel), sterile samples will be prepared.

The test will run for a maximum of 100 days. Apart from samples taken directly after application, at least 5 sampling time points will be included. Time intervals will be chosen in such a way that the pattern of decline of the test substance and possible transformation products can be established.

Analysis of the test substance and transformation products

In case of the 14C-labelled test substance the analytical methods will base on LSC and HPLC coupled with UV and radio detection. LC-MS/MS can be carried out as additional analytical method. The analytical method and sample preparation will be established to allow a limit of quantification of ≤ 5% of the applied radioactivity.

Special test setup

  • Non-labelled test substance can also be used for the test to investigate the degradation kinetics (e.g. DT50) of the test substance.
  • Sediment systems from different sources can be utilised.


  • Kinetic analysis and calculations of DT50 and DT90 values
  • Transformation product pattern including characterisation/ identification of major products.

Guidelines and Literature

  • OECD Guideline for the Testing of Chemicals, No. 308, ” Aerobic and Anaerobic Transformation in Aquatic Sediment Systems”; adopted April 24, 2002.