Fungal degradation and metabolites of diuron
metabolites was observed, and analyses were therefore
carriedoutonthewholecontentofaconical¯askateach
time of the kinetic study, instead of taking samples;
however the same results were obtained. Moreover, cell
extractionwithethanolshowed thatnoretention incells
occurred. The mass balance might be explained by the
formation of metabolites not detected at 254nm or by
the mineralization of part of the herbicide.
that present a non-target toxicity higher than that of
the parent substance. Biodegradation studies must not
therefore be limited to the disappearance of the
pollutant if it is not mineralized: it is essential to
identify the intermediate products and compare their
toxicities with that of the pollutant.
ACKNOWLEDGEMENTS
This study was ®nanced by the Environmental
Research Program of the CNRS. The authors also
Â
thank the Conseil Regional d'Auvergne for the fellow-
ship of C Tixier.
Although diuron is degraded by both sunlight and
micro-organisms, the degradation is incomplete. As
the degradation products may be more toxic than
diuron itself, we determined their toxicity with four
biotests: Microtox1 test, T pyriformis population test,
T pyriformis FDA method and S teres test.
Thesefourteststhusfocusedontwodifferentcriteria:
fortheMicrotox1 testandtheFDAmethod,thetoxicity
wasdeterminedbytheevaluationofthedirectinhibition
of enzymatic activities. For the two other biotests, we
assessed a global effect on a series of processes involved
in cellular division. The degradation products showed
toxicities different from that of diuron.
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