During the NASA Student Airborne Program (SARP) mission, high frequency whole air sampling during a missed-approach to Los Angeles International airport (LAX) provided air mass signatures collected in close proximity to their urban and oceanic sources. Each whole air sample was analyzed for 80 speciated halocarbons, hydrocarbons and organic nitrates. Unlike other airborne missions, high frequency whole air sampling of about 70 samples collected over a 20 minute period (15 second fill per sample) during a 150 km flight path at low altitude (< 2 km) provided a more detailed profile of the Los Angeles air shed than has been previously possible. Correlations between CH3I, CHBr3, and MeONO2 (marine tracers) versus C2Cl4 and HCFC-22 (anthropogenic tracers) were used to distinguish between purely marine air and air influenced by emissions from Los   Angeles.  Of the 80 speciated C1-C10 volatile organic compounds that were measured, 60 were elevated in air from the Los   Angeles air shed. These included C1-C10 alkanes, C6-C8 aromatics, C2-C3 alkenes, halons, HCFCs, HFCs, CH3CCl3, chlorinated solvents (e.g., C2Cl4, CHCl3, CH2Cl2), and organic nitrates. Marine species emitted in this region of the Pacific were found to include MeONO2, EtONO2, CH2Br2, CHBr3, CH3I and DMS. Note that the C3 organic nitrates were not enhanced in the marine wing, and instead they are attributed to urban photochemistry. Overall, high-frequency and low-altitude whole air sampling during the LAX missed-approach clearly distinguished urban and oceanic sources and allowed a detailed chemical signature for Los   Angeles air to be determined.

Characterizing air mass collected at lower troposphere(< 2km) during the 2011 student airborne mission (SARP): Focused on the high frequency sampling during the missed-approach to LAX

244th National Meeting (2012)

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