Acknowledgements

1. MCP TOF Mass Spectrometer PreAmp W mode V mode Signal to ADC Generation Chopper Thermal Vaporization & 70 ev EI Ionization PTOF Region Aerodynamic Lens (2 Torr) Turbo Pump Turbo Pump Turbo Pump Particle Inlet (1 atm) 2 1 Base Case Fig. 6 Fast airborne aerosol size and composition measurements from the NCAR C-130 during the MIRAGE-Mex 2006 field campaign Peter DeCarlo1,2, Ed Dunlea1, Joel Kimmel1, and Jose-Luis Jimenez1 1Cooperative Institute for Research in Environmental Science, University of Colorado 2Department of Atmospheric Science, University of Colorado PRELIMINARY DATA • Instrument Description • The HR-ToF-AMS1 follows the successful Quadrupole-Aerosol Mass Spectrometer,2 and the compact Time-of-Flight-Aerosol Mass Spectrometer.3 The instrument samples aerosol through an aerodynamic lens and can size particle based on Particle Time-of-Flight. Particles are impacted on a heated conical surface typically at 600 C. The resulting vapor plume is ionized by Electron Ionization and mass spectra are taken by a High Resolution TOFMS. • This new version of the instrument is capable of: • High Time Resolution • High Mass Resolution (See Fig 11) • High Sensitivity (low detection limits) • For a full description of the HR-ToF AMS See Talk 8D4 (Wednesday at 12:20) • For information on Integration and example high resolution data see Dunlea et al. Paper 14H46 Introduction The Mega City Initiative: Local and Global Research Observations (MILAGRO) field campaign was conducted during the March 2006. MILAGRO was designed as a pseudo-Lagrangian experiment, with ground sites and mobile laboratories sampling emissions and early aging. Aircraft platforms followed the emissions as they aged further. For a listing of contributing science partners (see Fig 1). Research Flight 3 This flight covered a wide geographical area. The flight path included various ages of pollution, including aged pollution over the Gulf of Mexico, fresh outflow from Mexico City, and pollution sampled on trasects through the Mexico City basin. Fig. 7a Fig. 4a Fig. 4b Figures 4a,b show a high correlation with 550 nm submicron light scattering. The data reported here are 15 second data points, clearly demonstrating the quantitative and high time resolution capabilities of the HR-ToF-AMS. Fig. 7b • In Figures 7a. And 7b. the organic portion of the mass spectrum was normalized so that total organic signal was equal to 1. Figures were then generated by the percent change of each m/z from a base case mass spectrum (See Fig 6). • Base case was a low level transect of Mexico City • Leg 1 was fresh outflow from the basin • Leg 2 was more aged pollution down wind of Mexico City. • Figure 7a and b show that nearly all nominal m/z peaks decrease in relative contribution to the organic mass. • A handful of peaks increase in contribution all of which fall into the organic ion series corresponding to oxygenated organic fragments. High resolution analysis should provide more insight. As these results are preliminary more analysis with more case studies are needed to confirm this result. Fig. 1 Contributing Science partners and geographic extent of the different sampling platforms. Fig. 5 Mexico City Basin The Megacities Impact on Regional and Global Environment (MIRAGE) campaign was part of MILAGRO and involved the deployment of the NCAR C-130 aircraft (see Fig 2), on which we deployed the High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). This was the first aircraft deployment of this instrument. Figure 5 shows the time trace of the different AMS species with plane altitude in black. The Mexico City Basin is easily distinguished from other airmasses due to the high level of Nitrate. Figure 6 shows the flight track of the C-130 colored by organic aerosol mass. Pollution appears to follow a trajectory from the city to the North East. a b PRELIMINARY DATA Spiral 1 Spiral 2 Spiral 3 Fig. 11 Fig. 12 Schematic of the HR-ToF-AMS Research Flight 12 This flight began with a late morning vertical profile west of Mexico City. Then proceeded into the basin to sample. Nitrate was very elevated compared to outside of the basin. A few passes by Tula and some volcanic plumes can be seen by elevated sulfate. A second spiral in the same location as the first, but 4 hours later showed some change in the vertical profile. The flight ended with a spiral down, south of Veracruz where models had predicted pollution to be. • Future Work • Preliminary results are very promising but a full exploration of the many facets of the data set are still required. Future analysis will seek to address the following: • Incorporation of high resolution mass spectral data into the analysis • Secondary organic aerosol formation: chemical composition and aging. • Analysis of size distributions and comparison to other sizing measurements onboard the C-130 • O/C ratios of different aerosol plumes sampled • Examination of role of Aerosol Nitrate in the reactive Nitrogen budget. • Role of high molecular mass compounds in aging of aerosol. Fig. 2 NCAR C-130 Fig. 3 HR-ToF-AMS • Flight Descriptions • 12 research flights were conducted during the course of March 2006 (~90 hours of flight time). During the course of the campaign intercomparisons were made with: • Ground sites • Satellites • Other Aircraft (DOE G-1, NASA DC-8, NASA B-200) • Many types of aerosols and emissions were sampled on the flights including: • “Fresh” Mexico City aerosols • Various aged plumes from Mexico City • Volcanic emissions • Biomass burning fires Mexico City Basin Fig. 8 Spiral 1 Spiral 2 Spiral 3 Acknowledgements We wish to thank A. Clarke, J. Zhou, Y. Shinozuka, and S. Howell from the University of Hawaii for the use of their OPC and Nephelometer data. Roya Baherini, C. Simmons and A. Middlebrook were instrumental in our integration onto the C-130. In addition thanks are due to the coordinators of the MILAGRO/MIRAGE field project. This research is supported by the US National Science Foundation (grants ATM-0449815, ATM 0513116, and S05-39607 (HIAPER) and NASA (grant NNG04GA67G) P. DeCarlo is grateful for funding from the EPA STAR Fellowship Program (FP-91650801) Fig. 9a Fig. 9b Fig. 10a Fig. 10b Spiral 3 was performed south of Veracruz and was coordinated with the NASA B-200. Many chemically distinct layers can be seen in the AMS data. These features are reproduced with the vertical profile of relative humidity and also with submicron 550 nm scattering. Differences in the AMS total mass and scattering at the 15-18k ft level are likely due to particles which were smaller in size and hence less efficient at scattering light, and AMS CE differences with acidic sulfate. Size distributions (not shown) indicate a bimodal sulfate distribution in this layer. Spirals 1 and 2 were performed in the same location approximately 4 hours apart. In both cases 2 distinct sulfate layers can be seem at high altitude. In the second spiral changes it appears that there is a layer of pollution which pushes in between the 2 sulfate layers, and right on top of the lower layer. This could be pollution from the basin flowing out of the city and over the ridge between Popocatepetl and Pico de Orizaba. The high signal to noise of these measurements demonstrate the benefits of the HR-ToF-AMS. • References • DeCarlo P.F. et al. Analytical Chemistry, submitted (2006) • Jayne, J. T., et al., Aerosol Science and Technology2000, 33, 49-70. • Drewnick, F.et al., Aerosol Science and Technology2005, 39, 637-658.\