Graduate Thesis Or Dissertation
 

Semi-volatile organic compounds and developing organisms : accumulation in California mountain tadpoles in the field and fish embryo exposures in the laboratory

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/hm50tv00k

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  • The atmospheric transport and deposition of semi-volatile organic compounds (SOCs), including current and historic use pesticides, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), to mountain ecosystems may result in the exposure of tadpoles to these SOCs. This exposure has been implicated in amphibian population declines in California. Tadpoles encounter sediment during burrowing and feeding, making sediment a potential route of SOC exposure. Little is known about the potential adverse effects of SOCs on developing tadpoles at the relatively low concentrations measured in mountain ecosystems. A matrix solid phase dispersion (MSPD) method was developed and validated to measure over 70 SOCs in tadpole tissue. The MSPD method was used to analyze tadpole samples collected from 81 sites throughout the Cascade and Sierra Nevada Mountains in California. Sediment samples from these sites were also analyzed and the tadpole and sediment SOC concentrations were investigated with respect to regional pesticide use. The tadpole and sediment concentrations of current use pesticides, including dacthal, endosulfan II, endosulfan sulfate, and total endosulfans, were significantly negatively correlated with site distance from pesticide use areas. Tadpole and sediment concentrations were not significantly positively correlated within regions indicating possible differences in food web exposure and tadpole metabolism of the SOCs between ecosystems. However, tadpole and sediment concentrations of several SOCs were significantly correlated on a statewide basis, indicating regional differences, i.e. low SOC concentrations in the Cascades and high concentrations in the SEKI tadpoles and sediment. Endosulfan sulfate was the most frequently detected SOC and its developmental toxicity, along with endosulfan I was investigated using the zebrafish model. An abnormal response of embryos and larvae to touch, indicating neurotoxicity, was the most sensitive endpoint for endosulfan I and the sulfate, with EC₅₀s of 2.2 μg/L and 23 μg/L, corresponding to tissue EC₅₀s of 367 ng/g and 4552 ng/g wet weight, respectively. However, NOAEC and tissue EC₅₀s were above those measured in the tadpoles collected from mountain ecosystems for which the maximum measurement of total endosulfans was 1.62 ng/g wet weight. Finally, endosulfan I was approximately ten times more toxic than endosulfan sulfate in developing zebrafish.
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