Beschreibung:
<jats:title>Abstract</jats:title><jats:p>This paper describes the residue analysis of water and hydrosoil samples taken from two separate large‐scale aquatic ecotoxicology trials designed to assess the environmental fate and effects of the pyrethroids lambda‐cyhalothrin and cypermethrin. Comparison of the results demonstrates the high degree of reproducibility of the chemical residue found the day after treatment using experimental mesocosms (lambda‐cyhalothrin) as opposed to an in‐use farm pond (cypermethrin). Both studies showed that pyrethroid residues were rapidly lost from the water column: residues of lambda‐cyhalothrin were less than 2 ng litre<jats:sup>−1</jats:sup> following the final application of a cumulative seasonal exposure equivalent to twelve ‚drift’︁ and six ‚run‐off’︁ events, each delivering a dose equivalent to that expected from a typical event under field conditions. Hydrosoil appeared to act as a sink for pyrethroid residues and, under the stringent test conditions of the mesocosm study, lambda‐cyhalothrin residues reached 3.2 μg kg<jats:sup>−1</jats:sup> following the seasonal exposure described above. The cypermethrin farm‐pond study illustrated the localised pattern of exposure expected under natural field conditions, with site topography and cultivation practices which represent an average ‚worst case’︁. Residues in hydrosoil reached a maximum level of approximately 25 μg kg<jats:sup>−1</jats:sup> in one sampling zone at one interval, and thereafter declined to a level of < 9 μg kg<jats:sup>−1</jats:sup> within four months.</jats:p>