Bacterial communities in batch and continuous-flow wetlands treating the herbicide S-metolachlor.
Although laboratory studies have revealed that many different neutral degradates of chloroacetamide herbicides can form during thermochemical, biological, and photochemical transformations, relatively few have been sought in the environment, despite their likely generation in appreciable amounts, relative persistence, and known or potential toxicity. The present paper describes a GC/ MS method for the analysis of 20 neutral chloroacetamide degradates, along with the four parent compounds, three triazine herbicides, and two neutral triazine degradates. Using large volume injections and 300:1 concentration via solid phase extraction, detection limits for most neutral chloroacetamide degradates were in the hundreds of pg/L range (low ng/L range for degradates possessing a hydroxy group). In a depth profile taken in midsummer from the upper Chesapeake Bay, 19 of the 20 neutral chloroacetamide degradates of interest were detected, along with three ionic oxanilic acid derivatives. Of those degradates encountered, eight do not appear to have been previously reported in natural or affected environmental samples. Concentrations of most neutral chloroacetamide degradates exceeded those of the parent compounds, while the total concentration of the neutral chloroacetamide degradates was 20-30 times that of the parents. These micropollutants therefore merit more detailed attention as contaminants of potential environmental concern.