Date of Award
Doctor of Philosophy in Oceanography
Thousands of hydrophobic organic contaminants (HOCs) are present in air and water worldwide, yet we know little about how these chemicals’ concentrations vary spatially and temporally, or what biological effects they have in concert. The first four studies described in this dissertation present data from a sampling campaign in which passive polyethylene samplers (PEs) deployed throughout the lower Great Lakes region (Lake Erie and Lake Ontario) from 2011 to 2014. Results were used to deduce air-water fluxes and analyze spatial trends of the truly gaseous and dissolved fraction of three distinct groups of HOCs: polycyclic aromatic hydrocarbons (PAHs), polycyclic musks (PCMs), and organic flame retardants (OFRs), with the goal of better understanding how sources and physico-chemical properties determine the environmental transport and spatial distribution of these HOCs. The specific objectives of these studies were to determine whether gaseous and dissolved HOCs exhibited positive correlation with regional population density within 25 km of each site in the lower Great Lakes region, investigate whether diffusive air-water exchange of HOCs was primarily leading to volatilization from, or absorption into, the lakes’ surface waters, and investigate health risks of ambient urban air by measuring aromatic hydrocarbon receptor (AhR)-mediated potency of the truly gaseous mixture of HOCs accumulated in PEs deployed in air on the Lake Erie shoreline near Cleveland (OH). Results showed that the radius at which strongest correlation between gaseous HOC concentration and human population was observed depended on vapor pressure, and a relationship between the maximum distance where significant correlation occurred and compound vapor pressure is presented for amassed PAH, PBDE, and PCM data. Air-water exchange calculations based on simultaneously deployed air and water PEs indicated that diffusive exchange of PAHs was variable based on compound and season. PCMs were found to be volatilizing from the lakes’ surface waters, suggesting that Lake Erie and Lake Ontario were acting as secondary sources of PCMs, while PBDEs were absorbed into surface waters. Bioassay experiments performed on PE extracts showed that <30% of AhR-mediated potency for gaseous air extracts was explained by target compounds measured via chemical analysis, suggesting that targeted analysis may underestimate health risks posed by gas-phase ambient air.
The fifth and sixth studies described in this dissertation focused on measuring uptake of emerging and legacy HOCs into PEs to inform future calculation of ambient air and water concentrations from PE measurements. PE uptake profiles over 21-day deployments were used to determine whether target compounds reached equilibrium during deployment, and PE-water and PE-air partitioning coefficients (KPEW and KPEA) were calculated. KPEW values for PAHs agreed fairly well with empirical values from literature in most cases, while values for PCMs and OPEs were generally lower than predicted based on chemical properties, suggesting that PE-derived concentrations for these compounds may be underestimated when using this approach.
The seventh and final study included in this dissertation presents concentrations of dissolved organophosphate esters (OPEs), a group of emerging OFRs with atypical physico-chemical properties, derived from PEs deployed in the North Atlantic deep ocean from 2014-2015 and in Canadian Arctic surface waters during the summers of 2015 and 2016 to investigate long-range transport of OPEs to remote aquatic environments. For the first time, estimated concentrations of OPEs in polar ocean surface water and remote ocean deep water are reported. The greatest concentrations of OPEs were measured in Canadian Arctic surface waters, with the chlorinated OPE species most abundant. OPEs exhibited unexpectedly flat vertical profiles in the North Atlantic Fram Strait, possibly due to a high degree of mixing and/or release of dissolved-phase OPEs from sinking particles. This study demonstrated that OPEs are widespread, even in remote environments, and that concentrations are much greater than those of other OFRs in the Arctic, suggesting that OPEs should be a priority for further study.
McDonough, Carrie A., "Spatial Distribution, Air-Water Exchange, and Toxicity of Organic Pollutants Using Passive Samplers" (2017). Open Access Dissertations. Paper 586.
Available for download on Saturday, April 21, 2018