HR: 1400h
AN: A43A-18    [Abstracts]
TI: Physical Properties and Chemical Composition of Aerosols sampled in T1 site during MILAGRO Campaign
AU: * Castro, T
EM: telma@servidor.unam.mx
AF: Centro de Ciencias de la Atmosfera, Circuito Ext. de Ciudad Universitaria, Mexico, DF 04510, Mexico
AU: Mamani-Paco, R
EM: mmruben@atmosfera.unam.mx
AF: Centro de Ciencias de la Atmosfera, Circuito Ext. de Ciudad Universitaria, Mexico, DF 04510, Mexico
AU: Saavedra, M I
EM: sisabel@atmosfera.unam.mx
AF: Centro de Ciencias de la Atmosfera, Circuito Ext. de Ciudad Universitaria, Mexico, DF 04510, Mexico
AU: Garcia, J
EM: jyee180868@yahoo.com.mx
AF: Centro de Ciencias de la Atmosfera, Circuito Ext. de Ciudad Universitaria, Mexico, DF 04510, Mexico
AU: Amador, O
EM: oam@atmosfera.unam.mx
AF: Centro de Ciencias de la Atmosfera, Circuito Ext. de Ciudad Universitaria, Mexico, DF 04510, Mexico
AU: Carabali, G
EM: carabali81@hotmail.com
AF: Centro de Ciencias de la Atmosfera, Circuito Ext. de Ciudad Universitaria, Mexico, DF 04510, Mexico
AU: Salcido, A
EM: salcido@iie.org.mx
AF: Instituo de Investigaciones Electricas, Reforma 113, Col Palmira, Cuernavaca, MOR 62490, Mexico
AU: Herrera, E
EM: eduardo.herrera@cimav.edu.mx
AF: Centro de Investigacion en Materiales Avanzados, Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, CHI 31109, Mexico
AU: Baez, A
EM: barmando@atmosfer.unam.mx
AF: Centro de Ciencias de la Atmosfera, Circuito Ext. de Ciudad Universitaria, Mexico, DF 04510, Mexico
AB: Results from pollutant measurements and meteorological variables corresponding to the month of March of 2006 during the MILAGRO campaign at site T1 are presented (Tecamac, State of Mexico). Three 8-stage cascade impactors (MOUDI) were employed to obtain aerosol samples of different sizes. For organic species analysis, samples were collected with a PM_2.5 High Volume sampler. Mass and chemical composition (inorganic and organic species) were obtained with the use of analytical techniques. Particle morphology analysis was done with a TEM-EDAX System. Physical properties of aerosols were measured with a PSAP, a nephelometer and a CPC. According with area meteorology, days with Mexico City urban influence on T1 (March 9-12) and without influence (March 14 and 15) were analyzed. The particle average concentration during the whole campaign was 20,000 particles/cm³. For the days with and without urban influence the average concentrations were 17,500 and 8,000 particles/cm³ respectively. From the MOUDI data the highest particle concentration through the campaign was during the morning in the mode d₅₀=0.32 μm. On the other hand, the cumulative highest concentration of all the stages was observed for March 19 followed by March 9. Scattering and absorption coefficients average obtained on T1 were 5.1x10^-5 m^-1 and 2.54x10^-5 m^-1 respectively and single scattering albedo was 0.676. These values show T1 as a polluted atmosphere, just as happens with megacities. Morphology of particles captured in a MOUDI impactor was studied. Particles between d₅₀=0.18 μm and d₅₀=1.8 μm sampled in T1 associated with urban influence (March 9) tended to show less irregular shapes through different periods of that day. These findings suggest the presence of large numbers of secondary aerosols and aged agglomerated particles. Particles ranging from d₅₀=0.18 μm to d₅₀=1.8 μm sampled in T1 and associated mainly with surrounding areas influence, e.g. Tizayuca Industrial Park (March 15) showed variation in morphology with size. More irregular particles were found in the smallest size, and less irregular particles were present in the largest size. The highest concentrations of ions present in all 8 stages of the MOUDI were chlorine, sodium, calcium, and magnesium. For stages less than 1 μm, the dominant ions were sulfate, ammonium, and potassium. The nitrate ion showed an irregular behavior through the campaign. For the days with influence (March 10 to 12), the nitrate ion presented its higher concentration. During episodes without influence (March 14 and 15), potassium, chlorine, and ammonium ions showed high concentration. On average, polycyclic aromatic hydrocarbons present in PM_2.5 (from acenaphthylene to benzo[ghi]perylene) had concentrations between 0.2 to 0.5 ng/m³. In particular, naphthalene had a concentration of 2.5 ng/m³. Our results show that Tecamac population is certainly exposed to high levels of pollution from Mexico megacity.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 4801 Aerosols (0305, 4906)
DE: 4906 Aerosols (0305, 4801)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly