Studies on the Atmospheric Degradation of Chlorpyrifos-Methyl

Abstract

The gas-phase atmospheric degradation of chlorpyrifos-methyl (a widely used organophosphate insecticide in Southern European regions) has been investigated at the large outdoor European Photoreactor (EUPHORE) in Valencia, Spain. Photolysis under sunlight conditions and reaction with ozone were shown to be unimportant. The rate constant for reaction of chlorpyrifos-methyl with OH radicals was measured using a conventional relative rate method with cyclohexane and n-octane employed as reference compounds with k = (4.1 ± 0.4) × 10(-11) cm(3) molecule(-1) s(-1) at 300 ± 5 K and atmospheric pressure. The available evidence indicates that tropospheric degradation of chlorpyrifos-methyl is mainly controlled by reaction with OH radicals and that the tropospheric lifetime is estimated to be around 3.5 h. Significant aerosol formation was observed following the reaction of chlorpyrifos-methyl with OH radicals, and the main carbon-containing products detected in the gas phase were chlorpyrifos-methyl oxone and 3,5,6-trichloro-2-pyridinol.

Instrument intercomparison of glyoxal, methyl glyoxal and NO<sub>2</sub> under simulated atmospheric conditions

“…This program is based on a classical least squares fitting which also removes the spectral interfering broadband (formed due to the presence of aerosols, equipment instabilities or unknown broadband products) by including a curve that models and subtracts it locally. The software has been tested and used in previous works (Muñoz et al, 2011(Muñoz et al, , 2012.…”

Fate in the Environment and Long-Range Atmospheric Transport of the Organophosphorus Insecticide, Chlorpyrifos and Its Oxon

“…Monitoring data suggest that CPYO might have a shorter half-life. Half-lives, based on experimental data for CPY-methyl (CPY-methyl), have been reported to be in the range of 3.5 h for reactions between CPY-methyl and •OH, 15 h for direct photolysis, >8 d for reactions with ozone (O 3 ) and a half-life of 20 d for transformation of CPY-methyl through reactions with nitrate radicals (Munoz et al 2011). Given the structural similarity between CPY and CPY-methyl, it is likely that similar proportions apply to both substances for reactions in the atmosphere, but not necessarily in other media such as rainwater and surface water where rates are pH-dependent.…”

A smog chamber comparison of a microfluidic derivatisation measurement of gas-phase glyoxal and methylglyoxal with other analytical techniques

“…Detailed descriptions of this methodology can be found in the previously published literature (Muñoz et al, 2011;Gomez Alvarez et al, 2012). Briefly, the fibres were conditioned in the injector of a GC at 250 • C, and loaded with PFBHA derivatisation reagent through the headspace of a 4 mL opaque amber vial containing a 17 mg mL −1 solution of PFBHA in water.…”

“…The techniques of Solid Phase Microextraction (SPME) using PFBHA on-fibre (Muñoz et al, 2011;Gomez Alvarez et al, 2012) and a mist chamber with PFBHA solution (Spaulding et al, 2002) can significantly reduce sampling times to 10 minutes with detection limits of 0.003 ppbV for GLY and 0.01 ppbV for MGLY, respectively. However, the preparation processes for PFBHA-coated fibres are complicated and labour intensive and the mist chamber derivatisation requires a large sample gas volume (200 L).…”