Graduate Thesis Or Dissertation
 

Local scale spatial and temporal variation in wet deposition of persistent organic pollutants by snow

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/xk81jn90x

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  • The objective of this research was to assess the variability of POP deposition by snow on a 10 km spatial scale by measuring the POP concentrations in fresh-fallen snow from remote alpine sites. Samples of pre-metamorphic snow were concurrently collected from three remote alpine sites, of matched altitude and exposure, along a 10 km transect of the HJ Andrews Research Forest in the Cascade Mountains of Oregon. During ten snow events, eighty-seven samples of pre-metamorphic snow were collected between January 2013 and February 2014. Samples were collected within 12 hours of a snow deposition event, with air temperatures below 0˚C and low solar irradiance for the period between deposition and collection. Samples were extracted using solid phase extraction (SPE) and analyzed by gas chromatography-mass spectroscopy (GC-MS) for 57 persistent organic pollutants, including PAHs and a variety of current and historic-use pesticides and pesticide degradation products. Sixteen of the seventeen PAHs analyzed for were detected in over 35% of the samples collected. Total PAH concentrations in individual samples ranged from below quantifiable limits to 53.5 ng per liter of snow water equivalents (SWE). The most frequently detected PAH was fluoranthene, which was detected in 69% of all samples, with a maximum measured concentration of 22.2 ng/L[subscript SWE]. The pesticide degradation products, endosulfan sulfate and heptachlor epoxide, were detected at quantifiable concentrations in all samples, and were the most frequent chlorinated compound detected, with concentration ranges of 0.070 - 1.430 ng/L[subscript SWE] and 0.983 - 5.83 ng/L[subscript SWE], respectively. Dieldrin and chlorpyrifos were detected with maximum measured concentrations of 3.14 ng/L[subscript SWE] and 3.11 ng/L[subscript SWE], respectively. However, detection of each was limited to a single snow event. Of the hexachlorocyclohexanes, α-HCH was detected in 7 of 87 samples, but β-HCH and ϒ-HCH (Lindane) were not detected at quantifiable concentrations in any sample. Detections of chlorodiphenylmethane pesticides and degradation products (isomers of DDT, DDD and DDE) were largely limited to two individual snow events. No statistically significant evidence of between-site differences in POP concentration in fresh-fallen, pre-metamorphic snow was found at the 95% confidence level. Analysis of between-event variance found significant between-event differences in total PAH, total gas-phase PAH, total particulate-phase PAH and total pesticide concentration for all events. Source region impact factors (SRIFs) were used to assess regional contributions to POP deposition at HJ Andrews Experimental Forest. No SRIF positive correlations of total gas-phase PAH or total particulate-phase PAH concentration with any source region were found to be statistically significant at the 95% level. Retene and pyrene concentrations were positively correlated with air mass time in Oregon. A similar analysis showed a statistically significant correlation at the 95% level between pesticide concentrations and air mass time in Washington and Oregon. No statistically significant correlation was found between total pesticide concentration and the Willamette Valley or Eastern Washington/Oregon source regions. Statistically significant correlations (p<0.05) were found between solar irradiance and total gas-phase PAH, total particulate-phase PAH, fluorene, pyrene and endosulfan sulfate concentrations, and between reciprocal snow temperature and phenanthrene concentration.
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