Metabolism and balance studies of [14C]monolinuron after use in spinach followed by cress and potato cultures

[¹⁴C]Monolinuron was added to soil which was then successively cropped with spinach, cress, and potatoes. Incubation was carried out in a closed system which allowed recoveries even of volatile degradation products and gave an overall recovery of 96% of the applied radioactivity at the end of the experiment. The spinach was found to contain 4.1% of the applied activity; the cress, 5.6%; old potatoes + leaves, 9.5%; new tubers, 1%; and the soil, 68.6%. The total amount of [¹⁴C]carbon dioxide liberated was 5.3%. The quantitative separation and characterization of the extractable radioactivity in spinach yielded 10.6% as unaltered monolinuron, 12% as 4-chlorophenylurea plus 4-chlorophenyl-hydroxymethylurea, 3.7% as 4-chlorophenylmethylurea, 1.4% as 4-chlorophenyl-hydroxymethyl-methoxyurea, 1.1% as 4-chlorophenyl-methoxyurea, and 71.2% as polar metabolites. Of these polar metabolites, 67.1% were cleaved with β-glucosidase, resulting in 2.9% unknown aglucone, 48.1% 4-chlorophenyl-hydroxymethyl-methoxyurea, and 16.1% 4-chlorophenyl-hydroxymethylurea. Similar results have been obtained in cress and potatoes. The soil contained 58% of monolinuron residues and 4.7?6.5% of the same types of metabolites as were found in plants. Twenty-one percent were found as polar metabolites.