Indirect photolysis of acetochlor: Rate constant of a nitrate-mediated hydroxyl radical reaction

The second order rate constant, k2, for reaction of the corn herbicide acetochlor with OH radicals was found to be 7.5 (±2.0) × 109 M−1 s−1, in close agreement with the value reported for a similar herbicide, alachlor, based on structure-activity relationships. Summer-time half-lives of 1–20 days for acetochlor were estimated for the Blue Earth River (southern Minnesota), an agriculturally impacted river with high nitrate levels (the primary source of •OH in surface waters).