Sources of particulate matter in the northeastern United States in summer: 2. Evolution of chemical and microphysical properties

摘要: [1] Measurements of aerosol particle size distributions and composition trace reactive gas mixing ratios were made on the NOAA WP-3D aircraft downwind mixed urban/industrial sources in northeastern United States (U.S.). These measurements noncloudy air during July August 2004, under conditions where cloud processing was not likely to play an important role oxidation chemistry. Under these conditions, particulate sulfate found be produced with exponential time constant ∼3.5 d from gas-phase SO2, which ubiquitous but inhomogeneously distributed pollution plumes. When submicron mass concentrations exceeded 15 μg m−3, associated ammonium dominated composition; at lower organic matter (OM) dominated. Since most urban plumes sampled contained substantial SO2 nearby industrial sources, apportionment between OM compounds governed largely by differences timescales those precursor volatile (VOCs) relative their transport time. may explain much variability previously published OM/sulfate for this region. observations indicate that even higher-than-expected secondary formation, U.S. potential inorganic emissions significantly exceeds anthropogenic VOC emissions.