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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)
EPA, it has not been subjected to the Agency's required peer and policy review and therefore does not necessary reflect the views of the Agency, and no official endorsement should be inferred. The authors thank the MTA for their cooperation, including Chris Bush for providing bus fleet information and Dana Lowell for help in organizing the logistics of the(More)
Atmospheric Chemistry and Physics Discussions This discussion paper is/has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP if available. Abstract Simulated primary organic aerosols (POA), as well as other particulates and trace gases, in the vicinity of Mexico City are evaluated(More)
Recent technological advances have allowed the development of robust, relatively compact, low power, rapid response (approximately 1 s) instruments with sufficient sensitivity and specificity to quantify many trace gases and aerosol particle components in the ambient atmosphere. Suites of such instruments can be deployed on mobile platforms to study(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 NO 2. Measurements of NO 2 from standard chemilumines-cence 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)
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)
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)
A mobile laboratory was used to measure on-road vehicle emission ratios during the MCMA-2003 field campaign held during the spring of 2003 in the Mexico City Metropolitan Area (MCMA). The measured emission ratios represent a sample of emissions of in-use vehicles under real world driving conditions for the MCMA. From the relative amounts of NO x and(More)
The Aerodyne Mobile Laboratory "chased" in-use curbside passenger buses operated by various operators in New York City. With the cooperation of New York State's Metropolitan Transit Authority, the relationships between the emissions of the several gas-phase species and particulate loadings were investigated across several bus technologies, bus types, and(More)