Significance of Population Centers As Sources of Gaseous and Dissolved PAHs in the Lower Great Lakes

Abstract

Polyethylene passive samplers (PEs) were used to measure concentrations of gaseous and dissolved polycyclic aromatic hydrocarbons (PAHs) in the air and water throughout the lower Great Lakes during summer and fall of 2011. Atmospheric Σ 15PAH concentrations ranged from 2.1 ng/m 3 in Cape Vincent (NY) to 76.4 ng/m 3 in downtown Cleveland (OH). Aqueous Σ 18PAH concentrations ranged from 2.4 ng/L at an offshore Lake Erie site to 30.4 ng/L in Sheffield Lake (OH). Gaseous PAH concentrations correlated strongly with population within 3-40 km of the sampling site depending on the compound considered, suggesting that urban centers are a primary source of gaseous PAHs (except retene) in the lower Great Lakes region. The significance of distant population (within 20 km) versus local population (within 3 km) increased with sub-cooled liquid vapor pressure. Most dissolved aqueous PAHs did not correlate significantly with population, nor were they consistently related to river discharge, wastewater effluents, or precipitation. Air-water exchange calculations implied that diffusive exchange was a source of phenanthrene to surface waters, while acenaphthylene volatilized out of the lakes. Comparison of air-water fluxes with temperature suggested that the significance of urban centers as sources of dissolved PAHs via diffusive exchange may decrease in warmer months. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants that originate from oil spills as well as anthropogenic and natural combustion processes. Major sources include fossil fuel combustion, metal production, waste incineration, residential and commercial biomass burning, and vehicular emissions. 1-5 PAHs are often associated with densely populated areas, especially in industrialized countries. 3,4,6,7 PAHs and their transformation products are a primary 34 carcinogenic component of urban air pollution and health effects resulting from chronic exposure 35 are a serious concern. 8,9 36 Polyethylene passive samplers (PEs) are cost-effective, simple tools with lower detection 37 limits than traditional active sampling techniques. Instead of pumping air or water through a 38 filter, PEs accumulate hydrophobic organic contaminants (HOCs) over time via diffusion, 39 accumulating only truly dissolved or gas-phase molecules. 10 Concentrations of truly dissolved 40 HOCs are of interest because this fraction is available for direct diffusive exchange between 41 water and other reservoirs such as air, biota, or sediment. 42 The use of PEs facilitates simultaneous spatially resolved measurements and calculations of air-water diffusive exchange rates. For most HOCs, concentrations measured by PEs reflect a time-integrated concentration representative of the entire deployment period. For compounds that equilibrate during deployment, concentrations reflect the most recent concentration the sampler was exposed to. PEs have previously been used to measure HOCs in water and air 11-13 and to calculate air-water gradients of HOCs, but this method has not been applied to the l...

Atmospheric PAHs in North China: Spatial distribution and sources

“…For PAHs with high vapor pressure (N10 − 4 Pa at 25°C), such as ACY, ACE and FLU with lower molecular weight, highest R n occurs in larger radius. Similar results were also reported by McDonough et al (2014).…”

“…Further, the radius of highest R n decreases with the increased number of PAHs rings, i.e. 50 km for 2-ring PAHs, 40-50 km for 3-ring PAHs, 40 km for 4-ring PAHs, 30-40 km for 5.6-ring PAHs, suggesting that PAHs with higher ring number are more influenced by emissions of shorter distance (McDonough et al, 2014;Yang et al, 2013). For PAHs with high vapor pressure (N10 − 4 Pa at 25°C), such as ACY, ACE and FLU with lower molecular weight, highest R n occurs in larger radius.…”

“…In one previous study, to explore the influence of urbanization as sources of atmospheric PAHs in lower Great Lakes in the U.S., the concentration of PAHs was correlated with population within 1 km to 50 km radius from each site and strong correlation was found around 20 km radius (McDonough et al, 2014). Other than using an indirect indicator (population) for PAH emission data by McDonough et al (2014), emission inventory data of PAHs is used in this study to examine its correlation between emission and ambient concentration of PAHs. Emission within different radius weighted by trajectory probability (RTP effect for short), and the correlation between concentration and weighted emission from different radius are investigated based on the following steps, 1) Weighted emission.…”

Air-water exchange of PAHs and OPAHs at a superfund mega-site

“…Large bodies of water are often sinks for persistent organic pollutants (POP), especially PAHs (Baker and Eisenreich, 1990; Bamford et al, 1999a; Fang et al, 2012; McDonough et al, 2014; Nelson et al, 1998). Highly contaminated waters may also be sources of contaminants to air (Tidwell et al, 2016).…”

“…In each of these instances the direction of flux was calculated, but neither the rate of exchange nor the rate of mass transfer was determined (Lohmann et al, 2011; Morgan and Lohmann, 2008; Prest et al, 1995). Only two previous studies have used PSDs for quantitative assessment of diffusive flux of PAHs (McDonough et al, 2014; Tidwell et al, 2016). The limited number of quantitative studies assessing flux using PSDs shows that this application of an established technology is still in its infancy, and requires further demonstration and testing.…”