10.13

Aerosol Chemical Characterization on Board the DOE G1 Aircraft using a Particle-into-Liquid-Sampler during the TexAQS 2000 experiment

Yin-Nan Lee, Brookhaven National Laboratory, Upton, NY; and Z. Song, Y. Liu, P. Daum, R. Weber, D. Orsini, N. Laulainen, J. Hubbe, and V. Morris

A particle-into-liquid-sampler (PILS) coupled to ion chromatography (IC) analysis was deployed on board the DOE-G1 aircraft during the 2000 Texas Air Quality Study to determine the ionic components of aerosol particles with aerodynamic size smaller than 2.5 µm (PM2.5). The sampling frequency was 3 minutes with a sample integration time of ~120 seconds. Six ions, namely, NH₄⁺, SO₄^2-, NO₃^-, Na⁺, K⁺, and Ca²⁺, were quantified with a limit of detection of ~0.1 µg m^-3. While NH₄⁺ and SO₄^2- (median and maximum concentrations of 1.6 and 5.0, and 1.8 and 9.4 µg m^-3, respectively) dominated the ionic components, NO₃^- was typically very low, less than 0.2 µg m^-3, with occasional excursions reaching nearly half that of SO₄^2-. Na⁺ was nearly always present but at low concentration levels, i.e., < 0.3 µg m^-3. Although K⁺ and Ca²⁺ were observed in only ~15% of the samples, K⁺ reached as high as 6 µg m^-3. NH₄⁺ to SO₄^2- molar ratios were typically greater than 2 and frequently exceeded 4, suggesting the presence of additional anions. The total ion mass concentration correlated strongly with the PM2.5 mass estimated from the size/number distributions of accumulation mode particles. The mass fraction of the ions varied between ~40% and ~90%. The mass difference between the PM2.5 and total ions showed a good correlation with black carbon. Since organic carbon and black carbon are typically strongly correlated, this observation suggests that organic compounds dominated this mass difference.

  Extended Abstract (604K)

Session 10, TEXAQS air quality study: Part II
Thursday, 17 January 2002, 8:30 AM-5:00 PM

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