Sunlight Photodegradation of Metolachlor in Water

Environmental fate of S-Metolachlor: a review

“…Studies evaluating metolachlor photodegradation in water found monochloroacetic acid (MCA) as the main photoproduct (Kochany & Maguire, 1994;Wilson & Mabury, 2000). Although photodegradation has been shown to occur, metolachlor is considered relatively resistant to photolytic decomposition (Kochany & Maguire, 1994).…”

Effect of River and Wetland Sediments on Toxicity of Metolachlor

“…This value is higher than the toxicity (96 hr LC 50 , 2 mg/L) of metolachlor to rainbow trout (WSSA, 1983) but is comparable to the toxicity demonstrated for Daphnia magna (48 h LC 50 , 25 mg/L) (Mayer and Ellersieck, 1986). The toxicity (96-hr EC 50 ) of metolachlor to alga Selenastrum capricornutum is 50 g/L (Kochany and Maguire, 1994).…”

The Geochemistry of Pesticides

“…Because of this constraint, relatively few pesticide compounds undergo direct photolysis; those that have been observed to do so include several chlorophenoxy acids (and their esters), nitroaromatics, triazines, OPs, OCs, carbamates, polychlorophenols, ureas, and fumigants (e.g., Chu and Jafvert, 1994;Crosby and Leitis, 1973;Dilling et al, 1984;Harris, 1990b;Lam et al, 2003;Mansour and Feicht, 1994;Mill and Mabey, 1985;Zepp et al, 1984), as well as fipronil (Walse et al, 2004) and metolachlor (Kochany and Maguire, 1994). Most phototransformations of pesticide compounds occur through indirect photolysis, as a result of reaction with another species, known as a sensitizer, or a sensitizer-produced oxidant.…”

“…The photoproduction of hydrogen peroxide has also been shown to be catalyzed by algae (Zepp, 1988). In contrast with its tendency to increase the rates of indirect photolysis by acting as a sensitizer, NOM may also inhibit the rates of direct photolysis (Kochany and Maguire, 1994) through light attenuation and, in some cases, the quenching of reactive intermediates (Mill and Mabey, 1985;Walse et al, 2004). For some pesticide compounds, such as dinitroaniline herbicides (Weber, 1990), phototransformation occurs primarily in the vapor phase, rather than in the dissolved or sorbed phases.…”

“…However, since they are Brønsted acids and bases, pH buffers may also accelerate these reactions -or cause shifts in the relative rates of different transformation mechanismscompared to what occurs in unbuffered solution Reinhard, 1989a, 1992b;Burlinson et al, 1982;Deeley et al, 1991;Li and Felbeck, 1972;Smolen and Stone, 1997). Such effects, though, are not observed for all pesticide compounds (Hemmamda et al, 1994;Hong et al, 2001;Kochany and Maguire, 1994;Smolen and Stone, 1997). Indeed, the absence of buffer effects has been used as evidence for unimolecular reaction mechanisms (Bank and Tyrrell, 1984).…”