Long-Range Atmospheric Transport of Polycyclic Aromatic Hydrocarbons: A Global 3‑D Model Analysis Including Evaluation of Arctic Sources

2015-12-16T21:48:17Z (GMT) by Carey L. Friedman Noelle E. Selin
We use the global 3-D chemical transport model GEOS-Chem to simulate long-range atmospheric transport of polycyclic aromatic hydrocarbons (PAHs). To evaluate the model’s ability to simulate PAHs with different volatilities, we conduct analyses for phenanthrene (PHE), pyrene (PYR), and benzo­[a]­pyrene (BaP). GEOS-Chem captures observed seasonal trends with no statistically significant difference between simulated and measured mean annual concentrations. GEOS-Chem also captures variability in observed concentrations at nonurban sites (<i>r</i> = 0.64, 0.72, and 0.74, for PHE, PYR, and BaP). Sensitivity simulations suggest snow/ice scavenging is important for gas-phase PAHs, and on-particle oxidation and temperature-dependency of gas-particle partitioning have greater effects on transport than irreversible partitioning or increased particle concentrations. GEOS-Chem estimates mean atmospheric lifetimes of <1 day for all three PAHs. Though corresponding half-lives are lower than the 2-day screening criterion for international policy action, we simulate concentrations at the high-Arctic station of Spitsbergen within four times observed concentrations with strong correlation (<i>r</i> = 0.70, 0.68, and 0.70 for PHE, PYR, and BaP). European and Russian emissions combined account for ∼80% of episodic high-concentration events at Spitsbergen.