The present study investigated the degradation of four pesticides by low-concentration of dissolved ozone in order to establish the effect of operational parameters. The results indicated that dissolved ozone (initial concentration of 1.4 mg/l) was effective to oxidize 60-99% of 0.1 mg/l aqueous diazinon, parathion, methyl-parathion and cypermethrin shortly within 30 min. The feasibilities of applying low dissolved levels of ozone in water (1.4-2.0 mg/l) to remove the target pesticides residing on vegetable surface (Brassica rapa) were studied. Ozonated water was mostly effective in cypermethrin removal (> 60%). The efficacy highly depended on the dissolved ozone levels. Higher temperature enhanced the efficacy in pesticide removal; however, the solubility of ozone in water is inversely proportional to temperature. The maximal efficacy for diazinon removal was detected to be at 15-20 degrees C. Major limitation factors for residual pesticide removal are temperature, concentration of ozone gas applied and concentration of dissolved ozone established. (c) 2006 Elsevier Ltd. All rights reserved.