title: Comparison of concentrations and stereoisomer ratios of mecoprop, dichlorprop and metolachlor in Ontario streams, 2006-2007 vs. 2003-2004.
abstract: Mecoprop, dichlorprop and metolachlor concentrations and enantiomer signatures were determined in Ontario streams in 2006-2007 and compared to results from 2003 to 2004. Median concentrations of dichlorprop and metolachlor were not significantly different between the two campaigns, but mecoprop was higher in 2006-2007. Concentrations of mecoprop and dichlorprop in Lake Ontario surface water were 1-2 orders of magnitude lower than stream averages. Enantiomer fractions (EFs) > 0.5 of mecoprop in high-concentration stream water samples during 2006-2007 were related to replacement of racemic mecoprop by single (+) enantiomer mecoprop-P after 2004. EFs <0.5 in low-concentration samples suggested enantioselective degradation and/or interconversion. Metolachlor profiles were expressed as SF, the fraction of herbicidally active/(active + inactive) stereoisomers. Samples with higher concentrations of metolachlor had SFs similar to S-metolachlor which is enriched in the active stereoisomers. Low concentrations were associated with lower and more variable SFs, suggesting mixed input of racemic and S-metolachlor or stereoselective degradation.
authors: Center for Atmospheric Research Experiments, Environment Canada, 6248 Eighth Line, Egbert, L0L 1N0 ON, Canada.
authors: Perihan Binnur
authors: PB
authors: Kurt-Karakus
authors: Terry F
authors: TF
authors: Bidleman
authors: Derek C G
authors: DC
authors: Muir
authors: John
authors: J
authors: Struger
authors: Ed
authors: E
authors: Sverko
authors: Steve J
authors: SJ
authors: Cagampan
authors: Jeff M
authors: JM
authors: Small
authors: Liisa M
authors: LM
authors: Jantunen
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D008456:2-Methyl-4-chlorophenoxyacetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D000081:Acetamides / Q000737:chemistry*; D004784:Environmental Monitoring; D006540:Herbicides / Q000737:chemistry*; D009864:Ontario; D045483:Rivers / Q000737:chemistry*; D013237:Stereoisomerism; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000081:Acetamides; D006540:Herbicides; D014874:Water Pollutants, Chemical; D015084:2,4-Dichlorophenoxyacetic Acid; C008340:mecoprop; D008456:2-Methyl-4-chlorophenoxyacetic Acid; C010571:dichlorprop; C051786:metolachlor