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Title: The Impact of Pesticides on River Ecology: Phase 2: A study of headwater streams
Author: D Sheahan
Author: H Bates
Author: M Hurst
Author: P Mattiessen
Author: A Smith
Author: C White
Author: R Williams
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1396, Representation ID: 461, Object ID: 2553; EAPRJOUT_1052, Representation ID: 316, Object ID: 2325
Previous pesticide transport studies have demonstrated that organisms in headwater streams may be exposed to transient but high concentrations of pesticides following storm events. The key objectives of this project were: (i)To identify headwater streams draining catchments most likely to be at risk from pesticide runoff. (ii) To monitor background and peak concentrations of pesticides known to be in use in the catchments. (iii) To develop appropriate sensitive bioassay procedures for deployment at selected field sites and to associate the measured pesticide concentrations in streams with effects in bioassays, and establish any links with effects observed in indigenous organisms. Four headwater streams draining cracking clay catchments with different agricultural usage were studied over a three-year period. A total of 71 storm events were sampled for the four sites over three years. Twenty-six compounds were analysed for across all four sites but only 12 pesticides were detected in water samples collected during storm events. Nine of these compounds were herbicides and the remaining three fungicides. In summary, some pesticides generally occur at sufficient concentration and frequency in headwater streams that drain agricultural catchments to produce chronic biological effects. This effect of contaminated drainflow with the occasional occurrence of higher pesticide contamination levels in streams following spray drift has almost certainly led to degradation in the biological communities present in the streams studied. A number of valuable biological monitoring techniques were developed. The combination of solid-phase extraction of storm event samples with subsequent testing using bioassay procedures provides a powerful approach for the identification of potential biological effects of pesticides upon stream communities. Multivariate analysis of invertebrate sample data allows more of the information collected using traditional survey methods to be included in an assessment of the impact of pesticides upon the stream fauna. Both approaches are recommended in future monitoring programmes.
Publisher: Environment Agency
Subject Keywords: RunoffBioassaysPesticides
Extent: 107
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