HR: 1340h
AN: A43C-1420    [Abstracts]
TI: Evidence for Biomass Burning from 14C and 13C/12C Measurements at T-0 and T-1 during MILAGRO.
AU: * Gaffney, J S
EM: jsgaffney@ualr.edu
AF: University of Arkansas at Little Rock, 2801 S. University Ave., Little Rock, AR 72204, United States
AU: Marley, N A
EM: namarley@ualr.edu
AF: University of Arkansas at Little Rock, 2801 S. University Ave., Little Rock, AR 72204, United States
AU: Tackett, M J
EM: mjtackett@ualr.edu
AF: University of Arkansas at Little Rock, 2801 S. University Ave., Little Rock, AR 72204, United States
AU: Sturchio, N C
EM: sturchio@uic.edu
AF: University of Illinois at Chicago, 845 W. Taylor St., Chicago, IL 60607, United States
AU: Heraty, L J
EM: lheraty@uic.edu
AF: University of Illinois at Chicago, 845 W. Taylor St., Chicago, IL 60607, United States
AU: Martinez, N
EM: namartin@nsf.gov
AF: University of Illinois at Chicago, 845 W. Taylor St., Chicago, IL 60607, United States
AU: Hardy, K
EM: kavita.hardy@gmail.com
AF: Swarthmore College, 500 College Ave., Swarthmore, PA 19081, United States
AU: Guilderson, T
EM: tguilderson@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, United States
AB: Both stable carbon isotopic and radiocarbon characterizations of aerosols can yield important information regarding the sources of carbonaceous aerosols in urban and regional environments. Biomass derived materials are labeled due to their recent photochemical activity in radiocarbon and vary depending upon the photochemical pathway (either C-4 or C-3) in stable carbon-13 content. C-4 being enriched over C-3. During the MILAGRO campaign, quartz filter samples were taken at 12 hour intervals from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. These samples were taken at the two super-sites, T-0 (Instituto Mexicano de Petroleo in Mexico City) and T-1 (Universidad Technologica de Tecamac, State of Mexico). The total carbon content was analyzed for stable carbon isotopic composition as well as for radiocarbon. Stable isotope mass spectroscopy was used to determine the carbon-13 to carbon-12 isotopic ratios on carbon dioxide. The carbon dioxide was then converted to graphite for analysis by accelerator mass spectrometry at the Center for Accelerator Mass Spectrometry at Lawrence Livermore National Laboratory. Results are presented for the carbon-13 content relative to the PDB standard and radiocarbon is given relative to recent carbon. The results for total radiocarbon content show that the carbonaceous aerosol content in Mexico City has more than half of the carbon coming from biomass derived sources. These can include inflow of biomass burning aerosols into the T-0 site as well as the input from local burning of biofuels and trash containing biomass derived materials (paper, boxes, etc.). Data also indicate that at the T-1 site biomass burning of C-4 grasses appears to be significant in that the carbon-13 values observed are enriched. Also at T-1 the radiocarbon levels are also found to be slightly higher indicating regional biomass burning as a significant contributor to aerosol carbon in the 0.1 to 1.0 micron size fraction. Some day and night differences were observed that indicate secondary organic aerosols are contributing and that a significant fraction of these aerosols are biomass derived. Further analyses of organic carbon and elemental carbon fractions are underway. This work was performed as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX- Mex) under the support of the Atmospheric Science Program. This research was supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-07ER64328.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0368 Troposphere: constituent transport and chemistry
DE: 0454 Isotopic composition and chemistry (1041, 4870)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting