Spelling suggestions: "subject:"chlorpyrifos -- 0nvironmental aspects"" "subject:"chlorpyrifos -- anvironmental aspects""
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Biochemical and physiological indicators of behavioral impairment in salmonids exposed to chlorpyrifos and copperSandahl, Jason 17 September 2003 (has links)
The purpose of this work was to determine if environmentally-relevant
concentrations of chlorpyrifos and copper, two commonly detected chemicals in
Western surface waters, can negatively impact the biological health of salmonids.
Both compounds are highly neurotoxic to fish, but each with distinct biological target
sites and mechanisms of action. We used common biochemical and physiological
indicators of toxicity, and correlated these effects with potentially significant
behavioral alterations. For chlorpyrifos, the mechanism of toxic action is the inhibition
of acetylcholinesterase (AChE) throughout the peripheral and central nervous system.
Here, we conducted biochemical assays of AChE activity in brain and muscle tissues
after exposing steelhead trout (Oncorhynchus mykiss) and coho salmon (0. kisutch) to
chlorpyrifos for 96 hours. We then correlated the AChE inhibition with behavioral
impairment in swimming and feeding activities. In juvenile steelhead and coho
exposed to 0.6-2.5 ��g/L chlorpyrifos, AChE activity was inhibited between ~10-65%.
This biochemical indicator was significantly correlated with changes in behavioral
patterns. Spontaneous swimming rates were reduced ~30-80% in the exposed fish,
and strikes at food items (brine shrimp) were reduced ~10-70%. For copper and some
other neurotoxicants, the olfactory nervous system is a sensitive target site in fish. The
highly-developed olfactory system in salmonids is particularly susceptible to toxic
insult by dissolved chemicals since receptor neurons are in direct contact with the
aquatic environment. Here, we used electrophysiological techniques to record odor-evoked responses from the sensory epithelium and the olfactory bulb as direct
measures of olfactory function in juvenile coho salmon. In fish exposed to copper,
chlorpyrifos, or esfenvalerate for 7 days, field potentials recorded from the sensory
epithelium and the olfactory bulb showed reduced or obscured olfactory responses to
two classes of odorants, which activate non-overlapping populations of receptor
neurons. To determine if this reduced sensory input can subsequently alter or diminish
olfactory-mediated predator avoidance behaviors, paired physiological and behavioral
tests were conducted on juvenile coho exposed to copper. In fish exposed to 2-20
��g/L copper for 3 hours, olfactory sensitivity was reduced by ~50-9O%. When these
fish were presented with a predatory alarm cue (conspecific skin extract), fish with
reduced olfactory function increasingly failed to exhibit antipredator behavior. In the
following experiments, we show that chlorpyrifos and copper can impair the
biochemical and physiological biology of salmonids at environmentally-relevant
concentrations, and that these sublethal effects can alter potentially important
behavioral patterns. / Graduation date: 2004
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Exposure and health risk assessment for farmers occupationally exposed to chlorpyrifos in Sri Lanka and drinking water and house dust analysis for chlorpyrifosAponso, G. Lalith M. 30 July 2001 (has links)
Graduation date: 2002
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A solid phase microextraction/gas chromatography method for estimating the concentrations of chlorpyrifos, endosulphan-alpha, edosulphan-beta and endosulphan sulphate in waterAdam, Hassan Ali January 2003 (has links)
Thesis (MTech (Chemical Engineering))--Peninsula Technikon, Cape Town, 2003 / The monitoring of pesticide contamination in surface and groundwater is an essential
aspect of an assessment of the potential environmental and health impacts of
widespread pesticide use. Previous research in three Western Cape farming areas found
consistent (37% to 69% of samples) pesticide contamination of rural water sources.
However, despite the need, monitoring of pesticides in water is not done due to lack of
analytical capacity and the cost of analysis in South Africa. The Solid Phase
Microextraction (SPME) sampling method has been developed over the last decade as
a replacement for solvent-based analyte extraction procedures. The method utilizes a
short, thin, solid rod of fused silica coated with an absorbent polymer. The fibre is
exposed to the pesticide contaminated water sample under vigorous agitation. The
pesticide is absorbed into the polymer coating; the mass absorbed depends on the
partition coefficient of the pesticide between the sample phase and the polymeric
coating, the exposure time and factors such as agitation rate, the diffusivity of the
analyte in water and the polymeric coating, and the volume and thickness of the
coating. After absorption, the fibre is directly inserted into the Gas Chromatograph
(GC) injection port for analysis.
For extraction from a stirred solution a fibre will have a boundary region where the
solution moves slowly near the fibre surface and faster further away until the analyte is
practically perfectly mixed in the bulk solution by convection. The boundary region
may be modelled as a layer of stationary solution surrounded by perfectly mixed
solution.
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