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Supporting Evidences

Photolysis of Particulate Nitrate: a Daytime HONO Source and a Re-NOx-ification Pathway in the Troposphere ( TROPospheic HONO: TROPHONO ) A Component of NOMADSS (Nitrogen, Oxidants, Mercury, and Aerosol Distributions , Sources and Sinks) Field Campaign

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Supporting Evidences

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  1. Photolysis of Particulate Nitrate: a Daytime HONO Source and a Re-NOx-ification Pathway in the Troposphere (TROPospheic HONO: TROPHONO) A Component of NOMADSS (Nitrogen, Oxidants, Mercury, and Aerosol Distributions,Sources and Sinks) Field Campaign Xianliang Zhou (Wadsworth Center and SUNY Albany) Jochen Stutz (University of California, Los Angeles)

  2. Objective: To investigate the role of particulate nitrate photolysis in the cycling of reactive nitrogen species in the troposphere, focusing on HONO as an intermediate product. Hypothesis 1: Photolysis of particulate nitrate in aerosol particles, and, to a lesser extent, NO2 conversion on organic aerosol, are major sources of HONO in the low-NOx troposphere above the surface boundary layer. Hypothesis 2: Photolysis of particulate nitrate in aerosol particles represents an important pathway to recycle HNO3/nitrate back to photochemically reactive NOx (re-NOx-ification) in the troposphere.

  3. Supporting Evidences • Substantial daytime HONO exists in the upper atmospheric boundary layer and free troposphere  require a strong daytime HONO source in the air column. • Photolysis of particulate nitrate (pNO3) in aerosol is fast, with a lifetime of ~1.4 hr for pNO3, with HONO as a dominant product (HONO/NO2 = 3 - 9)

  4. Potential impact of p-NO3 photolysis on tropospheric photochemistry

  5. 1. Daytime horizontal transects and vertical profiling over land and ocean: To establish daytime distributions of HONO and its production rate, and their relationships with pNO3, NOx, pOrganics, aerosols, and O3 in different air masses. 2. Daytime HONO production in urban plumes: To study daytime HONO production in the urban plumes as a function of photochemical ages, and to establish the maximum HONO contribution from the NOx precursor. 3. Nighttime HONO accumulation/early morning decay: To study nighttime accumulation and morning hour decay of HONO . The HONO formation rates during the day and the night will be compared. 4. Bulk aerosol sampling: To collect aerosol samples for laboratory pNO3 photolysis experiments. Flight Strategy/Experimental Designs

  6. horizontal transects and vertical profiles *

  7. HONO system • Aqueous scrubbing • Azo dye derivatization • Long-Path Absorption Photometric (LPAP) detection of azo dye • Detection limit ~1 pptv • 90% response time ~1 min

  8. HONO system Ambient air Valve/sampler box MFC MFC Relays Relays SA/NED H2O SA/NED H2O

  9. HONO data from two HONO systems

  10. HNO3system • Aqueous scrubbing • NO3- to NO2- conversion on Cd-reductor • Azo dye derivatization • Long-Path Absorption Photometric (LPAP) detection of azo dye • Detection limit ~20 pptv • 90% response time ~1 min Ambient air Valve/sampler box MFC Relays Cdreductor NH4Cl buffer SA/NED

  11. PNO3system • Aqueous scrubbing • NO3- to NO2- conversion on Cd-reductor • Azo dye derivatization • Long-Path Absorption Photometric (LPAP) detection of azo dye • Detection limit ~20 pptv • 90% response time ~1 min Ambient air Valve/sampler box MFC Relays NH4Cl buffer Cdreductor SA/NED

  12. P-Organics system • Aqueous scrubbing • Long-Path Absorption measurement a 300 nm Valve/sampler box Ambient air MFC Relays H2O/AcN

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