HR: 0800h
AN: A41A-0022    [Abstracts]
TI: Scanning Electron Microscope Evaluation of Aerosol Speciation in New York City: Metal Content in Sulfate Aerosols Relative to Total Suspended Particulates
AU: * Steiner, J
EM: steiner@sci.ccny.cuny.edu
AF: Department of Earth and Atmospheric Sciences of The City College of New York, CUNY, Room J106 138th and Convent Avenue, New York, NY 10031 United States
AU: * Steiner, J
EM: steiner@sci.ccny.cuny.edu
AF: PhD Program in Earth and Environmental Sciences, City University of New York, 365 fifth Avenue, New York, NY 10016 United States
AU: Rudolph, E
EM: lizrud@sci.ccny.cuny.edu
AF: Department of Earth and Atmospheric Sciences of The City College of New York, CUNY, Room J106 138th and Convent Avenue, New York, NY 10031 United States
AU: Rudolph, E
EM: lizrud@sci.ccny.cuny.edu
AF: PhD Program in Earth and Environmental Sciences, City University of New York, 365 fifth Avenue, New York, NY 10016 United States
AU: Cesaire, M
EM: MCesaire@sci.ccny.cuny.edu
AF: Department of Earth and Atmospheric Sciences of The City College of New York, CUNY, Room J106 138th and Convent Avenue, New York, NY 10031 United States
AU: Lakhankar, A
EM: tarendra@ce.ccny.cuny.edu
AF: Department of Earth and Atmospheric Sciences of The City College of New York, CUNY, Room J106 138th and Convent Avenue, New York, NY 10031 United States
AB: Total suspended PM2.5 particulates measured in northern New York City using a METONE beta-attenuation mass monitor exhibit a local maximum in April 2004 of 29 micrograms per cubic meter. This increase accompanies an April-to-July decrease in trace metals, Ti, Fe, Cu, Zn, Ba, measured for the total suspended particulates by x-ray fluorescence and atomic absorption (AA) spectroscopy (representative May values: 10 mg/m3 Ba, 8.9 mg/m3 Zn, and 0.7 mg/m3 Cu). Scanning electron microscopy and energy dispersive microanalyses (SEM/EDS) of trace-metal-enriched filters reveals that metals are present as both major element and trace element components of aerosols. The dominant major element species include metals, metal sulfides and metal oxides, whereas the trace metals occur principally in sulfates, carbonates and organo-sulfates. Mass balance calculations for the principle species, sulfate-rich aerosols (ca. 50-80% of the population), indicate that the approximately 5% total trace metals in sulfate crystals by SEM/EDS agrees closely with the measured total suspended particulate values obtained by AA for the same samples. Sulfate aerosols comprise a complex class that varies chemically from a nitrogen (ammonium)-based to calcic composition (approximately CaSO4-2.5H2O by SEM/EDS). Compositions include minor classes of alkali-enriched sulfates and iron sulfates. Sulfate accumulation also occurs during impaction resulting occasionally in 20 micron aggregates that vary systematically from a 10 micron calcic sulfate core to an ammonium-carbonate rim. A thermo-gravimetric study of the sulfate aerosols shows that approximately 50 to 80 percent of the sulfate is decomposed by igniting the quartz filters to 500øC; degassing points at 250øC and 320øC are indicative of the destruction of relatively amorphous alkali-nitrogen and related sulfates whereas temperatures in excess of 600øC are required to decompose the crystalline metal sulfates. Residual metals accumulate oxygen during post-320øC firing resulting in a weight recovery of approximately 30%. Preliminary analysis of the back-trajectories of metal-sulfate-enriched air masses is consistent with enrichment from industrial sources.
DE: 4801 Aerosols (0305)
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting