Aircraft observations of aerosol composition and ageing in New England and Mid‐Atlantic States during the summer 2002 New England Air Quality Study field campaign

Abstract

[1] Aerosol chemical composition, size distribution, and optical properties were measured during 17 aircraft flights in New England and Middle Atlantic States as part of the summer 2002 New England Air Quality Study field campaign. An Aerodyne aerosol mass spectrometer (AMS) was operated with a measurement cycle of 30 s, about an order of magnitude faster than used for ground-based measurements. Noise levels within a single measurement period were sub mg m À3 . Volume data derived from the AMS were compared with volume measurements from a Passive Cavity Aerosol Spectrometer (PCASP) optical particle detector and a Twin Scanning Electrical Mobility Spectrometer (TSEMS); calculated light scattering was compared with measured values from an integrating nephelometer. The median ratio for AMS/TSEMS volume was 1.25 (1.33 with an estimated refractory component); the median ratio for AMS/nephelometer scattering was 1.18. A dependence of the AMS collection efficiency on aerosol acidity was quantified by a comparison between AMS and PCASP volumes in two high sulfate plumes. For the entire field campaign, the average aerosol concentration was 11 mg m À3 . Compared with monitoring data from the IMPROVE network, the organic component made up a large fraction of total mass, varying from 70% in clean air to 40% in high concentration sulfate plumes. In combination with other optical and chemical measurements, the AMS gave information on secondary organic aerosol (SOA) production and the time evolution of aerosol light absorption. CO is taken as a conservative tracer of urban emissions and the ratios of organic aerosol and aerosol light absorption to CO examined as a function of photochemical age. Comparisons were made to ratios determined from surface measurements under conditions of minimal atmospheric processing. In air masses in which the NO x to NO y ratio has decreased to 10%, the ratio of organic aerosol to CO has quadrupled indicating that 75% of the organic aerosol is secondary. Also, the ratio of light absorption to CO has more than doubled, which is interpreted as an equivalent increase in the light absorption efficiency of black carbon due to aerosol ageing.

Performance of an Aerodyne Aerosol Mass Spectrometer (AMS) during Intensive Campaigns in China in the Summer of 2006

“…E S can be approximated as unity for submicron particles following the results of Huffman et al (2005) and Salcedo et al (2006). On the other hand, laboratory experiments by Matthew et al (2008) 4 ratio) could be used for empirically estimating CE for ambient particles (Crosier et al 2007;Kleinman et al 2007) and for laboratory-generated particles (Matthew et al 2008). In our cases, however, no systematic dependence of CE (ratio of AMS-SO 4 ratio has been found in the PRD and CAREBEIJING data (not shown).…”

Organic aerosol composition and sources in Pasadena, California, during the 2010 CalNex campaign

“…The Pasadena OA/ΔCO versus photochemical age plot follows the upper limit of the range of previously reported values, although the differences should not be over interpreted given the uncertainties associated with the background CO determination (indicated by the error bars) and the photochemical age calculations. The photochemical age uncertainty has been discussed extensively in previous papers and is due to, in part, the presence of mixed sources with different emission profiles and spatial distributions [e.g., Kleinman et al, 2007;Parrish et al, 2007]. We evaluate this potential source of error in section E of the supporting information, and use sensitivity studies to determine that photochemical age may be underestimated by approximately 10% in our analysis.…”

Biogenic carbon and anthropogenic pollutants combine to form a cooling haze over the southeastern United States

“…This is consistent with in situ aircraft data (42)(43)(44), where the organic fraction of the total aerosol has been shown to increase with height, even though surface sulfate concentrations were much larger than surface organic concentrations. Similarly, Kleinman et al (45) show that aloft outside of urban regions throughout the eastern U.S., the organic fraction dominates the total aerosol mass with average concentrations of 6.5 and 11 g m Ϫ3 , respectively. Consistent with photochemical production after convective transport of BVOC precursors are vertical profile observations of peroxides in this region, with maxima between 1 and 4 km (21).…”