Degradation of fluridone in submersed soils under controlled laboratory conditions

The experimental, aquatic herbicide fluridone (1-methyl-3-phenyl-5-3-(trifluoromethyl)phenyl]-4(1H)-pyridinone) was degraded in two submersed soils and in the water above those soils to one acidic metabolite (identified as 1,4-dihydro-1-methyl-4-oxo-5-3-(trifluoromethyl)phenyl]-3-pyridinecarboxylic acid by mass spectrometry). A sandy and a silt loam soil were treated with ¹⁴C]fluridone, immersed in water, and analyzed after 1, 3, 5, 7, 9, and 12 months. Seven to fifteen percent of the ¹⁴C applied to the soils was recovered in the water on each of the various collection dates. The acidic metabolite accounted for 86 to 93% of the radioactivity in the water fraction 7 months after treatment. The metabolite was absorbed strongly by both soils and comprised about 60% of the total ¹⁴C in each soil after 12 months. The remainder of the ¹⁴C in the soils after 12 months was either the parent compound (～30%) or an undefined insoluble residue (～10%).