THE MIXING, DISTRIBUTION AND PERSISTENCE OF ESFENVALERATE WITHIN LITTORAL ENCLOSURES

The synthetic pyrethroid insecticide esfenvalerate was applied to the surface of 18 littoral enclosures (5 x 10 m) in a 2-ha pond near Duluth, Minnesota. The insecticide was applied as Asana(R) 1.9 emulsifiable concentrate (EC) at five nominal concentrations ranging from 0.01 to 5.0-mu-g/L active ingredient. Two applications were made 30 d apart. Samples of water, sediment, macrophytes, enclosure wall material, and fish were collected and analyzed for esfenvalerate residue. Maximum water concentrations occurred 1 to 3 h after application and rapidly decreased during the next 24 h. At 5.0-mu-g/L, 90% of the active ingredient was lost from the water column within 24 h and was below the detection limit (0.047-mu-g/L) within 4 d. A vertical concentration gradient was observed following application, with 95% of the measured esfenvalerate contained in the upper 75% of the enclosure water column 24 h after application. All other components of the pond ecosystem contained measurable amounts of esfenvalerate. Water and sediment, and, to a lesser extent, aquatic vegetation and macrophytes, were important reservoirs for esfenvalerate. Cumulative sorption of esfenvalerate to sediment and enclosure wall material was observed after two successive applications to littoral enclosures.