The fate of acephate and carbaryl in water

Abstract

Acephate was resistent to hydrolysis in distilled, buffered water at pH 4.0 to 6.9, but not at pH 8.2, held for 20 days at 20 or 30 degrees C. The maximum conversion to methamidophos was 4.5% of the added acephate at pH 8.2 and 20 degrees C. The persistence of acephate in two natural waters, held at 9 degrees C for up to 42 and 50 days varied: 80% were recovered from pond water after 42 days, and 45% from creek water after 50 days. Rates of acephate degradation increased greatly when treated water samples were incubated in the presence of sediments, but not if water and sediment were autoclaved prior to treatment and incubation. The greatest conversion to methamidophos, 1.3% of the added acephate, had occurred after 42 days in pond water without sediment. Under the same conditions, carbaryl was less persistent than acephate in the natural waters: 18 to 20% were recovered from pond water after 42 days, and 37 to 40% from creek water after 50 days. The presence of sediment did not affect its degradation significantly. But more than 55% were recovered after 50 days if water and sediment were autoclaved prior to treatment and incubation. Neither acephate, methamidophos, nor carbaryl could be shown to escape from water into the atmosphere.

Use of activated charcoal in a solid-phase extraction technique for analysis of pesticide residues in tomatoes

“…This means that the sorbent chosen was very selective for the tomato pigments The use of ethyl acetate for extraction proved to be a good choice. Excellent results have been achieved in comparison to several solvents used for extraction and elution in analyses of fruits and vegetables, as has been reported by several authors [11][12][13][14][15]22,23 .…”

“…Finally, the activated charcoal was washed with ultra-pure water 17,19 . Before using the purified activated charcoal, it was washed with 20 mL of ethyl acetate in a vacuum system (Millipore membrane 0.45 µm, 47 mm diameter) and oven dried at 130 o C for 48 h 13 . During the filtering process, small particles of the activated charcoal were removed.…”

“…Sorbent activated charcoal is widely used for plant extract purification as well as for other matrices, especially for the recovery of more polar OPPs, like methamidophos and acephate [11][12][13][14][15][16][17] . On the other hand, experiments carried out by Kaipper 18 with the sorbents Florisil and C 18 , using the techniques of Matrix Dispersion of Solid Phase (MDSP) and Solid Phase Extraction (SPE), showed low recovery efficiency for methamidophos and acephate.…”

Aerobic microbial transformation of pesticides in surface water

“…5) was reported for carbaryl (22), depending either on the pesticide concentration or the type of water. 90,106,107) The type of surface water was found to be critical for the biodegradation of carbofuran (23). Insignificant biodegradation but rapid hydrolysis were observed for (23) in paddy water.…”

“…46,107,120,145,156) The catalytic hydrolysis by clay minerals and metal cations from sediments is assumed, but it is considered limited to some types of pesticides. 17) An insignificant sediment effect for an ionic pesticide that is slowly biodegraded was also observed.…”