Thesis
A probabilistic ecological risk assessment of chlorpyrifos to aquatic organisms in an agricultural drain
Washington State University
Master of Science (MS), Washington State University
2010
Handle:
https://hdl.handle.net/2376/102399
Abstract
The Yakima River Basin of eastern Washington State is located mainly in Yakima County. This watershed provides a valuable water resource to the areas' farmers and is federally recognized as a critical habitat for middle Columbia Steelhead. A possible conflict could arise between agriculture's crop protection needs and water quality when pesticides are carried to streams from irrigation and ground water return canals that feed the Yakima River, potentially endangering human health and the environment. Recent state and federal agency sampling campaigns show detection of numerous pesticides in waters of this Basin. This assessment focuses on water inputs into the Yakima River from the Marion Drain, which is a nineteen mile highly canalized ground water return that runs through the cities of Harrah, Toppenish and Granger. The organophosphorus insecticide chlorpyrifos has been detected in the lower Yakima River Basin at levels exceeding state and federal water quality limits, thus placing the Marion Drain on the Federal Clean Water Act 303(d) list. Marion Drain is listed as a category 5 water, i.e., impaired, and it now requires determination of a TMDL (Total Maximum Daily Load). A deterministic risk assessment by the Washington State Department of Ecology (ECY) indicates several chlorpyrifos concentrations contributed to significant risk for aquatic organisms in Marion Drain. The purpose of this study was to assess chlorpyrifos residues in surface water and to probabilistically characterize their risks to the aquatic animals. Chlorpyrifos 96-h lethal effects on an assemblage of aquatic animals and lotic invertebrates were assessed. Exposure was probabilistically determined using a Monte Carlo simulation of risk quotients and joint probability analysis techniques. Risk criteria were taken from EPA procedures for determining ambient water quality criteria as applied to pesticides like chlorpyrifos (Stephan et al. 1985; Urban and Cook 1986). The probabilistic analysis of exposure indicated that risk to an assemblage of aquatic animals and lotic invertebrates were moderate to high between March and October. These results agree with the NOAA (2008) and Burke et al (2006) deterministic assessments and conflict with the Geisy et al. (1999) probabilistic risk assessment.
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Details
- Title
- A probabilistic ecological risk assessment of chlorpyrifos to aquatic organisms in an agricultural drain
- Creators
- Jerry D. Jorden
- Contributors
- Allan S. Felsot (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525069901842
- Language
- English
- Resource Type
- Thesis