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Urban rivers with a history of industrial use can exhibit spatial and temporal variations in contaminant concentrations that may significantly affect risk evaluations and assessment of remediation efforts. To more effectively estimate human and ecological health risks, we evaluated the spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) in an urban river using low-density polyethylene passive sampling devices (PSDs). PSDs simulate cell membranes and lipid tissue and accumulate only freely dissolved, and thus, bioavailable contamination. Using PSDs and high-pressure liquid chromatography we measured bioavailable concentrations of 15 priority pollutant PAHs over five years along 18.5 miles of the lower Willamette River including the Portland Harbor Superfund megasite. This area contains several PAH sources including coal tar and creosote sites, which underwent remediation during this study. Additional potential sources of PAHs include combined sewer overflows, urban runoff, atmospheric deposition and petroleum product leaks and spills. Results reveal increased urban bioaccessible PAH loading during wet seasons and high rain events, successful capping of the McCormick and Baxter Superfund site, increased bioavailable PAHs during dredging operations, and the potential for using PSDs for source apportionment. PAH concentrations, loads, and congener ratios changed significantly depending on location, river flow, precipitation, and contaminant removal activities. Our research demonstrates that human and ecological risk varies significantly by season and remediation technique. Additionally, our refined analytical method eliminated 80% of organic solvents and 100% of chlorinated solvents from the sampling method and also reduced labor and cost. Health professionals can apply the findings and refined technology to more effectively assess exposure to pollution.
Polycyclic aromatic hydrocarbons (PAHs) are a class of trace organic contaminants that can enter the environment from both natural and anthropogenic sources. Of these compounds, 16 are listed as high-priority contaminants by the EPA. PAHs are either petrogenic or pyrogenic. One potential anthropogenic source of PAHs is fuel seeps. The Tar River has been and is currently being affected by a legacy fuel seep from underground storage tanks in the area that have undergone remediation. Although research has been done on PAHs in fuel seeps and on PAH remediation, that research addressed sites soon after remediation. Research has generally not addressed how PAH contamination from a legacy seep historically remediated. This research aims to determine how a legacy seep affects PAH contamination in the Tar River as a function of river flow. To determine how the legacy seep is affecting the Tar River at different flow conditions, sites at and around the potential contamination site, Town Creek, were sampled over several months in 2022 and 2023. These samples were then filtered to separate particulates and dissolved PAHs. The identity and concentration of PAHs were determined using a gas chromatograph- mass spectrometer. The total PAHs and ratio of parent PAHs to the total PAHs were found to have no correlation with the gauge height of the river or the dissolved organic carbon (DOC) of the sites sampled. This suggests that the PAH contamination in the Tar River was not driven by river flow. Parent-to-total PAH ratio of less than 0.5 in the dissolved phase at the upstream (TC1) sampling site during 10-2-22 and 11-20-22 sampling events, and at a downstream site (D1) during a 11-20-22 sampling event, suggest that a petrogenic source affected these sites during these events. Individual PAH distributions at D1 had a petrogenic signature during a low flow period in the Tar River suggesting that it may have been affected by Town Creek during low flow events. This research adds to the knowledge base of contamination sites that have undergone remediation in the past and how they may still affect their environments.