whole_WalkerRachel2001_thesis.pdf (8.97 MB)
Ecological risk assessment in a Tasmanian agricultural catchment
thesisposted on 2023-05-27, 15:39 authored by Walker, R
In the Huon Valley, southern Tasmania, Australia, large volumes of pesticides are applied to the region's apple orchards. The broad objective of this study was to determine whether regional aquatic ecosystems are being adversely impacted by the use of orchard pesticides. The subcatchment of Mountain River was chosen as the study area, and a regional risk assessment was completed to gain an understanding of the environmental issues in the region. A Tier 1 risk assessment identified the insecticide, chlorpyrifos, as being of particular concern to aquatic ecosystems. The risk hypothesis for research on chlorpyrifos was that spray drift from chlorpyrifos applications in orchard located on river flats was resulting in aquatic ecosystems being exposed to potentially harmful concentrations of pesticide. Chlorpyrifos exposures in Mountain River were characterised using data from seasonal sampling and sampling at the time of spray application. Seasonal results showed intermittent, low-level detections of chlorpyrifos in Mountain River. Sampling at the time of spraying provided unique field data describing the magnitude and duration of pulse exposures at a site directly exposed to spray drift. The concentrations measured compared well with the spray drift model, AgDRIFT‚Äövë¬¢. Chlorpyrifos effects in Mountain River were characterised using multiple lines of evidence. Probabilistic risk assessments using cumulative frequency distributions of exposure and effects data, and @Risk¬¨vÜ software simulations of probability distributions functions fitted with BestFit¬¨vÜ software showed that aquatic species were not adversely impacted by the exposures measured. Field studies validated the outcomes of the probabilistic risk assessment for fish species. In situ investigations on the blood chemistry and acetykholinesterase activity of rainbow trout (Oncorhynchus mykzss) were used to assess acute effects. A maximum aquatic concentration of 0.163˜í¬¿g/L was measured soon after the commencement of spraying, but no significant changes in blood chemistry parameters or cholinesterase activity were detected. Body burdens and histology of native fish caught from localities surrounded by orchards confirmed exposure to pesticides but it was difficult to assess the severity of chronic effects, given the multiple stressors to which fish in agricultural areas are exposed.
Rights statementCopyright 2001 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s). Thesis (Ph.D.)--University of Tasmania, 2001. Includes bibliographical references