The availability and degradation of C-14-ring-labelled isoproturon in
soil was investigated over 140 days under controlled laboratory condit
ions. Degradation of the active ingredient followed and 65 days later
only a minor fraction (0.6%) of the parent molecule remained extractab
le. A demethylated-isoproturon metabolite was detectable in soil from
day 15 (2.6%). The amount of (CO2)-C-14 derived from the C-14 benzene
ring label and liberated over time indicated that a total of 13.6% iso
proturon was mineralized during the incubation period. In parallel, th
e amount of C-14 residue extracted from the soil by water followed by
methanol or remaining within the soil-analysed by combustion-was also
determined at intervals. After 140 days, 72% of the radiolabel added r
emained in the soil as non-extractable residue. The degradation half-l
ife of extractable isoproturon was an estimated 14 days.