Comparative study of thin film photodegradative rates for 36 pesticides

Abstract

interest during the past decade. See Zabik et al. (1976) for a comprehensive review on pesticide photochemistry. In the investigation on the degradative dynamics of pesticides on tea bush, Chen et al. (1983) regarded the sen-

Hexabromocyclododecane and Hexachlorocyclohexane: How Lessons Learnt Have Led to Improved Regulation

“…Among banned organochlorines, Brun et al (2008) reported α-and γ-HCH among the most frequently detected chemical substances in wetprecipitation across Atlantic Canada. Chen et al (1984) reported half-lives of 91 hours (3.79 days), 152 hours (6.33 days) and 104 hours (4.33 days) for α-HCH, β-HCH and γ-HCH, respectively, in the air. Hydrolytic half-lives of 0.8 year (292 days) (pH 8.0, 20 0 C) and 26 years (pH 7.8, 5 0 C) were estimated for α-HCH by Ngabe et al (1993).…”

“…On the basis of empirical data primarily, the half-life of HBCD in soil is ≥182 days (Environment Canada, 2011). Half-life in air >2 days 3.7 to 6.33 (Chen et al, 1984) 0.4 to 5.2 (Marvin et al, 2011) Half-life in water >60 days 3 to 300 days (Mackay et al, 1997) 60 to 130 days (Marvin et al, 2011) Half-life in aquatic sediments >180 days 90 days (WWFC, 1999) 0.9 to 12.6 years (Helm et al, 2002) 125-191 days (EC, 2008) Half-life in soil >180 days <180-1146<180- (IPCS, 1991 6.9 to 63 days (Davis et al, 2005) ≥182 days (Environment Canada, 2011) Half-life in biota (days/years) none 7 to 10 years (humans) (Zou and Matsumura, 2003) 23 to 219 days (humans) (Schecter et al, 2012) 1 to 17 days (mice) (Schecter et al, 2012) 53 to 136 days (fish) When released to the environment, HBCD isomers will adsorb onto solid particles of sediments and soil . Though there is a predominance (>90%) of γ-HCBD in the environment compared to α-and β-HBCD, α-HBCD often has the highest prevalence in biota, followed by β-HBCD (Birnbaum and Staskal, 2004).…”

A refined method for analysis of 4,4′-dicofol and 4,4′-dichlorobenzophenone

“…It has been reported that dicofol can undergo photolysis to form DCBP (Chen et al 1984) and also transform under alkaline conditions (Walsh and Hites 1979). In addition, it has been found that dicofol could be metabolically transformed to DCBP in rats and mice (Brown et al 1969; Brown and Casida 1987).…”

Environmental Fate and Toxicology of Methomyl

“…Methomyl was degraded most rapidly when placed on a glass slide ( fi lm thickness of 0.67 m g/cm 2 ) and irradiated in a photochemical reactor at an environmentally relevant wavelength (300 nm; 33-36°C). They also found that carbamates containing an electron-donating aliphatic group were more completely degraded than were those with an electron-withdrawing aromatic group (Chen et al 1984 ) . The authors identi fi ed the photodegradative t 1/2 for methomyl to be approx.…”

“…However, Mico et al ( 2010 ) concluded that oxidation via ozonation (10.5 mg/L O 3 ; pH 4.5) occurs more rapidly than the photo-Fenton reaction, with complete degradation occurring within 60 min. Chen et al ( 1984 ) measured the photodegradative rates of various carbamate insecticides. Methomyl was degraded most rapidly when placed on a glass slide ( fi lm thickness of 0.67 m g/cm 2 ) and irradiated in a photochemical reactor at an environmentally relevant wavelength (300 nm; 33-36°C).…”