title: Dissipation of a commercial mixture of polyoxyethylene amine surfactants in aquatic outdoor microcosms: Effect of water depth and sediment organic carbon.
abstract: This study optimized existing analytical approaches and characterized the effect of sediment total organic carbon (0.05-2.05% TOC), and water depth (15, 30, and 90cm) on the fate of MON 0818, a commercial mixture of polyoxyethylene amine surfactants (POEAs), in outdoor microcosms. Mixtures of POEAs are commonly used as adjuvants in commercial herbicide formulations containing glyphosate. Until recently, analytical methods sensitive enough to monitor environmental concentrations of POEAs in aquatic systems were not available. After optimizing recently developed analytical methods, we found that the combined use of accelerated solvent extraction (ASE) and liquid chromatography-tandem mass spectrometry provided a reliable approach for determining the concentration of sediment-adsorbed POEAs. The surfactant showed strong affinity for sediment materials, with low maximum recoveries by ASE of 52%. Under microcosm conditions, water depth or sediment characteristics did not significantly affect the water-column half-life of POEA, which ranged from 3.2 to 5.3h. Binding of POEAs to suspended solids was observed, which dissipated via one- or two-phase exponential decay; when two-phase decay occurred, fast phase half-life values ranged from 0.71 to 1.3h and slow-phase values ranged from 18 to 44h. Concentrations of POEA increased in sediment shortly after application and decreased over the study period with a half-life of 5.8 to 71d. The concentrations of POEAs in the sediment of the shallow (15cm) ponds dissipated following a two-phase exponential decay model with an initial fast-phase half-life of 1.1 to 8.9d and a slower second-phase half-life of 21d. Our results suggest that aquatic organisms are unlikely to be exposed to POEAs in aqueous phase for periods of more than a few hours following an over-water application, and that sediment is a significant sink for POEAs in aquatic systems.
authors: Centre for Toxicology, School of Environmental Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada. Electronic address: joseluis.rodriguezgil@ucalgary.ca.
authors: Jose Luis
authors: JL
authors: Rodriguez-Gil
authors: Laboratory Services Division, University of Guelph, Guelph, ON N1G 2W1, Canada. Electronic address: llissemo@uoguelph.ca.
authors: Linda
authors: L
authors: Lissemore
authors: Centre for Toxicology, School of Environmental Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada. Electronic address: ksolomon@uoguelph.ca.
authors: Keith
authors: K
authors: Solomon
authors: Department of Environment and Geography, University of Manitoba, Winnipeg, MB R3T 2N2, Canada. Electronic address: mark.hanson@umanitoba.ca.
authors: Mark
authors: M
authors: Hanson
mesh_terms: D017753:Ecosystem; D005223:Fats / Q000032:analysis; D019015:Geologic Sediments / Q000737:chemistry; D006207:Half-Life; D011092:Polyethylene Glycols / Q000032:analysis; D013501:Surface-Active Agents / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D005223:Fats; C501118:MON 0818; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; D011092:Polyethylene Glycols
keywords: ANEOs; Fate; MON0818; Microcosm; POEA; Sediment