PAH concentrations simulated with the AURAMS-PAH chemical transport model over Canada and the USA

Abstract

The off-line Eulerian AURAMS chemical transport model was adapted to simulate the atmospheric fate of seven PAHs: phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene + triphenylene, and benzo[a]pyrene. The model was then run for the year 2002 with hourly output on a~grid covering southern Canada and the continental USA with 42 km horizontal grid spacing. Model predictions were compared to ~ 5000 24 h average PAH measurements from 45 sites, eight of which also provided data on particle/gas partitioning which had been modelled using two alternative schemes. This is the first known regional modelling study for PAHs over a North American domain and the first modelling study at any scale to compare alternative particle/gas partitioning schemes against paired field measurements. <br><br> Annual average modelled total (gas + particle) concentrations were statistically indistinguishable from measured values for fluoranthene, pyrene and benz[a]anthracene whereas the model underestimated concentrations of phenanthrene, anthracene and chrysene + triphenylene. Significance for benzo[a]pyrene performance was close to the statistical threshold and depended on the particle/gas partitioning scheme employed. <br><br> On a day-to-day basis, the model simulated total PAH concentrations to the correct order of magnitude the majority of the time. Model performance differed substantially between measurement locations and the limited available evidence suggests that the model spatial resolution was too coarse to capture the distribution of concentrations in densely populated areas. A more detailed analysis of the factors influencing modelled particle/gas partitioning is warranted based on the findings in this study

Air and seawater pollution and air–sea gas exchange of persistent toxic substances in the Aegean Sea: spatial trends of PAHs, PCBs, OCPs and PBDEs

“…PTS include organochlorine pesticides (OCPs), such as hexachlorobenzene (HCB), hexachlorocyclohexane (HCH), and dichlorodiphenyltrichloroethane (DDT), and banned industrial chemicals such as polychlorinated biphenyls (PCBs), banned in Europe since the 1970s, only recently restricted industrial chemicals, such as polybrominated diphenylethers (PBDEs), and combustion by-products, such as polycyclic aromatic hydrocarbons (PAHs, all combustion types) and also HCB (waste burning), which primary emissions are ongoing. LRT of chlorinated PTS (Semeena et al 2006;UNECE 2010) and also of PAHs Galarneau et al 2014) is enhanced by re-volatilisation from surfaces (multihopping; significance of secondary sources in air). The same can be expected for most other PTS, as they resist to degradation in the soil and surface water and are semivolatile (vapour pressures between 10 −6 and 10 −2 Pa at 298 K).…”

Toxic volatile organic air pollutants across Canada: multi-year concentration trends, regional air quality modelling and source apportionment

“…Previous modelling studies for toxic VOCs, performed by the U.S. EPA, have used the Community Multiscale Air Quality (CMAQ) chemical transport model (Luecken et al 2006;Luecken et al 2012). Environment Canada has also used AURAMS to model toxic PAHs across North America (Galarneau et al 2014). Benzo-[a]-pyrene (BaP) predictions are of particular interest; however, more model development is needed, as the Galarneau et al evaluation shows that AURAMS significantly over-predicts BaP.…”