An experimental design for outdoor water/sediment studies using C-14-labelled pesticides

Annex VI to Directive 91/414/EEC requires evaluation of the possibility of a plant protection product reaching non-target areas under proposed use con ditions, where it must be shown that the environment is adequately protecte d prior to authorisation. This process uses fate and behaviour information on the active substance from Annex II. Subsequently a risk assessment is ma de in Annex III by comparing environmental concentrations with ecotoxicolog ical end-points for non-target organisms, and demonstrating acceptable safe ty margins. Surface water must be considered where exposure may occur via spray-drift d uring application or from soil run-off. The laboratory studies (with C-14-p esticide) used in the assessment are hydrolysis, aqueous photolysis and wat er/sediment, which investigate the route and rate of degradation of the act ive substance under controlled conditions, and identify major degradates fr om chemical or biological routes. However, laboratory degradates may not al ways be relevant under field conditions, e.g. photolysis in surface water m ay be reduced by turbidity or enhanced by indirect photolysis, or sediment sorption may reduce the availability of residues. Presently, no semi-field approach exists for carrying out a higher tier test. This paper describes m ethodology for an outdoor water/sediment study using C-14-pesticide and pre sents data for an experimental fungicide, designated Compound X.