Photolytic degradation of quinalphos in natural waters and on soil matrices under simulated solar irradiation

• Published in: Chemosphere (Oxford) Vol. 64; no. 8; pp. 1375 - 1382
• Main Authors: Gonçalves, C., Dimou, A., Sakkas, V., Alpendurada, M.F., Albanis, T.A.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2006; Elsevier
• Subjects: Applied sciences; Biological and physicochemical phenomena; Biological and physicochemical properties of pollutants. Interaction in the soil; Chromatography, Gas; Degradation products; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; environmental fate; Exact sciences and technology; Fate; Fresh Water - analysis; insecticide residues; Kinetics; Mass Spectrometry; Models, Chemical; Natural water pollution; Organothiophosphorus Compounds - analysis; Organothiophosphorus Compounds - radiation effects; pesticide persistence; Photolysis; Pollution; Pollution, environment geology; Quinalphos; Soil and sediments pollution; Soil Pollutants - analysis; Soil Pollutants - radiation effects; soil pollution; solar radiation; Sunlight; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - radiation effects; water pollution; Water treatment and pollution; Quinalphos; Sunlight; Degradation products; Photolysis; Fate; Insecticide; Pollutant behavior; Pesticides; Soil pollution; Chemical reaction kinetics; Persistence; Selfpurification; Organophosphorus compounds; Water pollution; Solar radiation; Degradation product; Organic compounds; Photochemical degradation
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2005.12.020

The photochemical persistence of quinalphos, one of the most widely used organophosphorous insecticides, was investigated in a variety of environmental matrices such as natural waters and soils of different composition. Simulated solar irradiation was obtained using a xenon arc lamp (Suntest CPS+ apparatus) giving an irradiation intensity of 750 W m −2 equivalent to a light dose per hour of irradiation of 2700 kJ m −2. The phototransformation rates were determined using solid-phase microextraction (SPME) and ultrasonic extraction (USE) coupled to GC-FTD, while the identification of photoproducts was carried out by GC–MS. In water samples, the degradation kinetics followed a pseudo-first-order reaction and photolysis half-lives ranged between 11.6 and 19.0 h depending on the constitution of the irradiated media. Dissolved organic matter (DOM) has a predominant retarding effect, while nitrate ions accelerated the photodegradation kinetics. In soil samples, the degradation kinetics was monitored on 1 mm soil layer prepared on glass TLC plates. The kinetic behaviour of quinalphos was complex and characterized by a double step photoreaction, fast in the first 4 h of irradiation followed by a slow degradation rate up to 64 h. The photolysis half-life of quinalphos was shorter in sandy soil compared to the rest of the soil samples, varying between 16.9 and 47.5 h, and showing a strong dependence on the composition of the irradiated media. Among the transformation products formed mainly through photohydrolysis and photoisomerization processes, some photoproduct structures were proposed according to their mass spectral information.