Scott C. Herndon

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Manjula R. Canagaratna,1 John T. Jayne,1 David A. Ghertner,2 Scott Herndon,1 Quan Shi,1 Jose L. Jimenez,3 Philip J. Silva,1 Paul Williams,4 Thomas Lanni,5 Frank Drewnick,6 Kenneth L. Demerjian,6 Charles E. Kolb,1 and Douglas R. Worsnop1 1Center for Aerosol and Cloud Chemistry and Center for Atmospheric and Environmental Chemistry, Aerodyne Research Inc.,(More)
Organic aerosol (OA) particles affect climate forcing and human health, but their sources and evolution remain poorly characterized. We present a unifying model framework describing the atmospheric evolution of OA that is constrained by high-time-resolution measurements of its composition, volatility, and oxidation state. OA and OA precursor gases evolve by(More)
In August 2001, the Aerodyne Mobile Laboratory simultaneously measured NO, NO2, and CO2 within 350 m of a taxiway and 550 m of a runway at John F. Kennedy Airport. The meteorological conditions were such that taxi and takeoff plumes from individual aircraft were clearly resolved against background levels. NO and NO2 concentrations were measured with 1 s(More)
New diesel engine technologies and alternative fuel engines are being introduced into fleets of mass transit buses to try to meet stricter emission regulations of nitrogen oxides and particulates: Real-time instruments including an Aerodyne Research tunable infrared laser differential absorption spectrometer (TILDAS) were deployed in a mobile laboratory to(More)
Data from a recent field campaign in Mexico City are used to evaluate the performance of the EPA Federal Reference Method for monitoring the ambient concentrations of NO2. Measurements of NO2 from standard chemiluminescence monitors equipped with molybdenum oxide converters are compared with those from Tunable Infrared Laser Differential Absorption(More)
A compact, fast response, mid-infrared absorption spectrometer using thermoelectrically (TE) cooled pulsed quantum cascade (QC) lasers and TE detectors has been developed to demonstrate the applicability of QC lasers for high precision measurements of nitrous oxide and methane in the earth's atmosphere. Reduced pressure extractive sampling with a 56 m path(More)
A large and increasing fraction of the planet's population lives in megacities, especially in the developing world. These large metropolitan areas generally have very high levels of both gaseous and particulate air pollutants that have severe impacts on human health, ecosystem viability, and climate on local, regional, and even continental scales. Emissions(More)
Aerosol mass spectrometer (AMS) measurements are used to characterize the evolution of exhaust particulate matter (PM) properties near and downwind of vehicle sources. The AMS provides time-resolved chemically speciated mass loadings and mass-weighted size distributions of nonrefractory PM smaller than 1 microm (NRPM1). Source measurements of aircraft PM(More)
Engineering estimates of methane emissions from natural gas production have led to varied projections of national emissions. This work reports direct measurements of methane emissions at 190 onshore natural gas sites in the United States (150 production sites, 27 well completion flowbacks, 9 well unloadings, and 4 workovers). For well completion flowbacks,(More)
We present initial results obtained from an optical absorption sensor for the monitoring of ambient atmospheric nitrogen dioxide concentrations (0-200 ppb). This sensor utilizes cavity attenuated phase shift spectroscopy, a technology related to cavity ringdown spectroscopy. A modulated broadband incoherent light source (a 430-nm LED) is coupled to an(More)