Degradation of atrazine and several organophosphorus pesticides in oranges

The degradation of atrazine and four organophosphorus pesticides (chlorpyri phos. fenamiphos, methidathion and methyl-parathion) in oranges was studied . Oranges were immersed in a Milli-Q water solution spiked with 10 me litre (-1) of each pesticide for one day, allowing their adsorption on the orange peel. Then, the oranges were rinsed with Milli-Q water and left outdoors t o expose them to natural ambient conditions for two weeks. In parallel, an aqueous solution containing 1 mg litre(-1) of each pesticide was placed in a Pyrex flask, which was tightly closed, and exposed to the same ambient co nditions. Both samples (orange peel and Milli-Q water) were analyzed period ically by gas chromatography coupled to a nitrogen-phosphorus detector. The pesticide degradation in both samples could be described using a first-ord er degradation curve. Half-lives varied from 14.5 to more than 30 days in a queous solution and from 2.3 to 4.1 days in oranges for organophosphorus pe sticides, while those for atrazine were 3.1 days and 14.2 days, respectivel y. The presence of some organophosphorus degradation products in water samp les after storage under the above conditions was confirmed by gas chromatog raphy-mass spectrometry.