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Influences of upwind emission sources and atmospheric processing on aerosol chemistry and properties at a rural location in the Northeastern U.S.

Continuous real‐time measurements of atmospheric aerosol with an Aerodyne high‐resolution time‐of‐flight aerosol mass spectrometer coupled with a fast temperature‐stepping thermodenuder were carried out in summer 2011 at Brookhaven National Laboratory (BNL, 40.871°N, 72.89°W) during the Department of Energy Aerosol Life Cycle Intensive Operational Period campaign. BNL was frequently downwind of emissions from the New York metropolitan area and was exposed to various combinations of anthropogenic, biogenic, and marine emissions based on air mass history. The average concentration of submicrometer aerosol (PM1) during this study was 12.6 µg m−3 with 64% of the mass being organic. Organic aerosol (OA) at BNL was found to be overwhelmingly secondary, consisting of (1) a fresher, semivolatile oxygenated organic aerosol (SV‐OOA; oxygen‐to‐carbon ratio (O/C) = 0.54; 63% of OA mass) that was strongly influenced by transported urban plumes; (2) a regional, more aged, low‐volatility OOA (LV‐OOA; O/C = 0.97; 29% of OA mass) influenced by aqueous‐phase processing; and (3) a nitrogen‐enriched OA (NOA; nitrogen‐to‐carbon ratio (N/C) = 0.185; 8% of OA mass) likely composed of amine salts formed from acid‐base reactions in industrial emissions. Urban emissions from the New York metropolitan areas to the W and SW in particular led to elevated PM1 mass concentration and altered aerosol composition at BNL. Transported urban plumes and local biogenic emissions likely interacted to enhance secondary organic aerosol production, primarily represented by SV‐OOA. These results suggest an important role that urban anthropogenic emissions play in affecting ambient PM concentration, composition, and physical‐chemical properties at rural areas in the Northeast U.S.