A global 3-D model to simulate long-range transport of PAHs: Effect of climate on transport to the Arctic

We simulate the long-range transport of polycyclic aromatic hydrocarbons (PAHs) to the Arctic under present and future climate using a global 3-D chemical transport model (GEOS-Chem). PAHs, toxic byproducts of combustion, reach the Arctic by long-range atmospheric transport. PAHs are semivolatile compounds that partition between the gas and particle phases. We implement temperature-dependent PAH partitioning into hydrophobic organic carbon (OC) and black carbon (BC) aerosols in the model to simulate this behavior. First, we test the validity of the model by comparing results to global measurements of the PAHs phenanthrene (PHE), pyrene (PYR), and benzo[a]pyrene (BaP) and find that for mean global and mean Arctic concentrations, measurements and model results are not statistically different and that the model captures 64 - 74% (r2s) of the concentration variability in non-urban locations. We then simulate daily transport of PHE, PYR, and BaP to the Arctic for the years 2005-2009. Preliminary results suggest the model captures up to 50% (r2s) of the variability in Arctic concentrations, and is able to capture episodic events. Source-receptor analyses indicate European and Russian sources account for approximately 80% of PAHs in the Arctic. The sensitivity of PAH transport to simulated future climate meteorology (GCAP) and to variable OC and BC concentrations is investigated, particularly with respect to transport to the Arctic and remote exposures. The implications for regional and global PAH regulatory policies are discussed.