Partitioning and uptake of permethrin by stream invertebrates and periphyton

Abstract

Abstract Aqueous permethrin (Ambush®) containing 1.17 g in 0.705 litre was applied manually to the surface of a forest stream. Surface water, invertebrate drift and periphyton were sampled 280 m downstream from the treatment site at intervals of time, and analysed by gas‐liquid chromatography (GLC). The peak concentration in water was 2.71 ng/mL at 30 min post‐treatment, which dissipated to levels below the minimum detection limit (MDL = 0.005 ng/mL) within 270 min. The peak levels (ng/g) of permethrin residues in drifting invertebrates at 55 min after treatment varied inversely with the size of the insects and were 63.6 for the relatively small, 39.6 for medium and and 30.1 for large insects, thus indicating bioconcentration in all sizes. No residues were detected in the respective size categories after 48, 24 and 12 h post‐treatment. Periphyton exhibited a much greater capacity for sorption of permethrin than the invertebrates, and the peak residues were at least 100 times greater than the ambient water concentrations. The residues in algae persisted for about 7 d after treatment, and the dissipation was slow. The trans isomer was relatively more labile than the cis isomer. The biomagnification aspects together with the slow desorption from both types of organisms indicated that the two substrates acted as sinks for the chemical in the stream environment.