Current-use pesticide types and concentrations were predictably greatest in storm events following agricultural applications with discharge and suspended concentrations having a secondary role.

Historic-use pesticide and metabolite concentrations fluctuated with suspended sediment concentrations.

Pesticide contamination was transient within and among storm events.

Aquatic organisms in agricultural watersheds are exposed to transient pulses of pesticide mixtures that vary in frequency and magnitude depending upon agricultural practices, discharge and sedimentation.