AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Optical Characterization of Aerosols at a Rural Site in Southeast England During the Winter ClearfLo Campaign
Paola Massoli, Allison Aiken, Kyle Gorkowski, Scott Herndon, Edward Fortner, John Jayne, William Brooks, LEAH WILLIAMS, Puneet Chhabra, Nga Lee Ng, Timothy Onasch, Jonathan Franklin, Mavendra Dubey, Douglas Worsnop, Andrew Freedman, Aerodyne Research, Inc
Abstract Number: 169 Working Group: Urban Aerosols
Abstract We present results on the optical characterization of aerosols during the ClearfLo (Clean Air for London) Intensive Operating Period that took place from mid-January to mid-February, 2012 at a rural site southeast of London, England. The site, situated at the Kent Showground in Detling, is located approximately 50 km southeast of central London. Over the course of the campaign, the sampled air masses were of local (from a motorway proximate to the site), regional (Thames Estuary) or distant (continental European) origin. Data were collected from two separate inlets that were outfitted with 2.5 micron cutoff impactors. The first inlet was routed to a CAPS PMex (Aerodyne Research, ARI) particle optical extinction monitor and a Multi-Angle Absorption Photometer (MAAP) (ThermoFisher), both operated a nominal wavelength of 630 nm. The second inlet was routed to a CAPS PMex monitor operated at 450 nm and a Photo-Acoustic Soot Spectrometer (PASS-3) (Droplet Measurement Technologies) which provided particle absorption at three wavelengths (780 nm, 532 nm and 405 nm). The second inlet also contained a provision for alternately routing the air sample flow through a ARI particle denuder operated at temperatures up to 250 ºC. Optical extinction, absorption and the calculated single scattering albedo (SSA) were measured at multiple wavelengths over a period of approximately three weeks. Extinction levels varied from 7 to 230 Mm-1; the absorption varied between 1 and 32 Mm-1. The SSA averaged ~ 0.85 over the study. Periods of relatively low aerosol loadings and low SSA (0.6) corresponded to air masses dominated by emissions from local sources (e.g., traffic). Instead, high extinction and absorption levels corresponded to outflow from continental Europe. The optical data presented here are discussed in a broader context and combined with results from the chemical composition information obtained from co-located ARI SP-AMS and HR-ToF aerosol mass spectrometers (AMSs).