Factors contributing to the off-target transport of pyrethroid insecticides from urban surfaces.
Pyrethroid insecticides used in urban and suburban contexts have been found in urban creek sediments and associated with toxicity in aquatic bioassays. The objectives of this study were to evaluate the main factors contributing to the off-target transport of pyrethroid insecticides from surfaces typical of residential landscapes. Controlled rainfall simulations over concrete, bare soil, and turf plots treated individually with pyrethroid insecticides in a suspension concentrate, an emulsifiable concentrate, or a granule formulation were conducted at different rainfall intensities and different product set-time intervals. Pyrethroid mass washoff varied by several orders of magnitude between experimental treatments. Suspension concentrate product application to concrete yielded significantly greater washoff than any other treatment; granule product application to turf yielded the least washoff. Fractional losses at 10 L of runoff ranged from 25.9 to 0.011% of pyrethroid mass applied, and 10 L nominal mass losses ranged from 3970 to 0.18 μg. Mass washoff depended principally on formulation and surface type combination and, to a lesser degree, on set-time interval and rainfall intensity. Treatment effects were analyzed by ANOVA on main factors of formulation, surface type, and set time. Factor effects were not purely additive; a significant interaction between formulation and surface type was noted.
Agricultural and Environmental Chemistry Graduate Group and ‡Department of Civil and Environmental Engineering, University of California at Davis, One Shields Avenue, Davis, California 95616, United States.
Brant C
BC
Jorgenson
Christopher
C
Wissel-Tyson
Thomas M
TM
Young
D001681:Biological Assay; D002947:Cities; D007306:Insecticides / Q000032:analysis*; D011722:Pyrethrins / Q000032:analysis*; D011891:Rain; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis; D013499:Surface Properties; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
D007306:Insecticides; D011722:Pyrethrins; D012987:Soil; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical