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Chlorpyrifos is an organophosphate pesticide, widely used on fruit and vegetable crops. Here, we report on the oxidative degradation of standard chlorpyrifos by individual and combined effects of ultrasonic irradiation (US) and ozone (O 3 ). A standard chlorpyrifos solution (1 mg L -1 ) was treated with 1 MHz US, O 3 and its combination (US/O 3 ) for 0, 10, 20, 30, 40, 50 and 60 min. Reduction of residual chlorpyrifos was determined by gas chromatography with flame photometric detection (GC-FPD) while ion chromatography (IC) was used to determine the concentration of anions as major degradation products. US/O 3 combined treatment had a synergistic effect in reducing chlorpyrifos concentrations, with the highest rate of degradation occurring within the first 10 min. Moreover, chloride, nitrate and sulphate anion concentrations obtained from chlorpyrifos treated with US/O 3 combination, were significantly higher, compared to those treated with ultrasonic irradiation or ozone alone. A sharp decrease in pH from 7.46 to 4.49 was also observed for the combined treatment. The degradation pathway of chlopyrifos, after treatment, was confirmed by gas chromatography mass spectrometry (GC-MS). All treatments resulted in similar main fragment ions at m/z 351, 314, 286, 258, 197 and 97. The lethal concentration (LC 50 ), over a series (0-100) mg L -1 of standard chlorpyrifos solutions, was estimated and compared to the treated chlorpyrifos. All the treatments directly detoxified chlorpyrifos with LC 50 values against brine shrimps (Artemia salina L.) of 10.21, 103.54 and 234.09 mg L -1 for US, O 3 and US/O 3 treated chlorpyrifos solutions, respectively. The brine shrimp test showed highest toxicity in standard chlorpyrifos with an LC 50 value of 7.22 mg L -1 .

Ethion residue removal efficiency using individual and combined effects of ultrasonication (US), ozonation (O 3 ), ultrasonication and ozonation (US/O 3 ) was investigated. A 1 mg·L -1 standard ethion was subjected to an ultrasonic irradiation (3W input power) device with different frequencies of 108, 400, 700, 1000 kHz, and to an ozone with a concentration of 200 mg· mL -1 with various exposure times (0, 15, 30, 45 and 60 minutes). Reduction of residual ethion was determined by gas chromatography with flame photometric detection (GC-FPD). It was found that 1000 kHz ultrasonic irradiation for 60 minutes was the most effective treatment for reducing ethion concentration. Additionally, ozone could reduce the concentration of standard ethion after 60 minutes of exposure. Ultrasonic irradiation in combination with ozone had a synergistic effect in reducing standard ethion concentration, with the highest rate occurring within the first 15 minutes. Ethion concentration was reduced to 75.43% after ultrasonic irradiation at 1000 kHz and ozone exposure for 60 minutes. The effectiveness of the combined scheme for reducing of ethion residues on tangerine was also determined by GC-FPD. The ethion residue on fresh tangerines after ultrasonic irradiation and ozone washing was reduced by 73.03% after 60 minutes. The present study demonstrates that ultrasonic irradiation and ozone exposure could be used to reduce ethion residues in treated tangerine in order to meet the Standards for Pesticide Residue Limits.

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