Determination of insecticide contamination in agricultural headwater streams

A headwater stream in an agricultural catchment in Northern-Germany was intensively monitored for insecticide occurrence (lindane, parathion-ethyl, fenvalerate). Brief insecticide inputs following precipitation with subsequent surface runoff result in high concentrations in water and suspended matter (e.g. fenvalerate: 6.2 μg l−1, 302 μg kg−1). These transient insecticide contaminations are typical for headwater streams with an agricultural catchment area, but have been rarely reported in such extent. Event controlled sampling methods for the determination of this runoff related contamination with a time resolution of up to 1 h are introduced. The temporal distribution of the insecticide concentration is shown on different time scales (years, months, hours) over a period of 4 years. The measured concentrations are compared with other references. Insecticide losses due to surface water runoff were calculated between 0.01–0.07% of the applied insecticide.