Particle-Phase PAH AMS Measurements in Mexico City During the MCMA-2003 Field Campaign

Particle-phase PAH AMS Measurements in Mexico City during the MCMA-2003 Field Campaign

AMS Users Meeting Institut für Chemie und Dynamik der Geosphäre Jülich, Germany August 26th, 2005

Katja Dzepina Jimenez Group University of Colorado at Boulder

Mexico City - Population: ~ 20 millions -Geo. Loc.:19ºN, 99ºW - Elevation: 2240m - ¾ of the city surrounded by

www.gesource.ac.uk/worldguide/ mountains - MCMA-2003 -> Mexico City Metropolitan Area 2003 field campaign Orizaba - March 29-May 4, 2003 Tonantzintla - CENICA Supersite CENICA - Organized by Luisa and IMP Merced UNAM/CCA Mario Molina of MIT N Ajusco

1 Aerosol Pollution in Mexico City

On a good day …

On a good day … and on the bad one!

AMS mass spectra (MS) of PAHs generated in a laboratory propane flame study

With the courtesy of J. Slowik

2 Possible PAH Assignments in an AMS MS 202 Fluoranthene

Pyrene 276 226 252 Indeno[1,2,3-cd]fluoranthene ) 400 Cyclopenta[cd]pyrene -3 216 Benzo[a]pyrene

1- o-Phenylenepyrene methylp 240 Benzo[k]fluoranthene yrene Benzo[ghi]fl 300 uoranthene 178 Napthalene- nums Phenanthrene Benzo[b]fluoranthene Dibenzo[ghi,mno]chrysene 2,3-Benzofluorene

Nums- 200 Diphenylethyne dodecahyd Perylene 1,2-Benzofluorene rochrysene 152 166 190 Benzo[ghi]perylene 300 Anthracene Biphenylene Fluorene 4H- 1-methylpyrene Benzo[e]pyrene Cyclopenta[def Coronene 100 ]phenanthrene Acenaphthylene 1H-Phenalene Nitrate Equivalent Mass Concentration (µg m

140 160 180 200 220 240 260 280 300 m/z (Daltons) With the courtesy of J. Slowik and Y. Rudich

Ambient Spectra

AMS Measures following PAHs (noted are their MW): -202 -216 -226 -228 -240 -242 -252 -276 -300

3 PAH Fragmentation Table

PAH Fragmentation Table – cont. Fragmentation tables used with the AMS data analysis software [Allan et al., 2004] to encode the subtraction procedure for the organics and PAHs at the m/z’s relevant to AMS.

4 PAH Fragmentation Table – cont. Example of m/z 202 m/z frag_org frag_PAH 199 199 200 frag_organic[202] 200,-frag_organic[200] 201 0.167*frag_organic[195],0.167*frag_organic[197],0.167*fr 201,-frag_organic[201] ag_organic[199],0.167*frag_organic[205],0.167*frag_orga nic[207],0.167*frag_organic[209] 202 0.167*frag_organic[194],0.167*frag_organic[196],0.167*fr 202,-frag_organic[202] ag_organic[198],0.167*frag_organic[204],0.167*frag_orga nic[206],0.167*frag_organic[208] 203 203,-frag_PAH[203] 16*0.011*frag_PAH[202] 204 204 m/z 201 frag_org: 0.167*frag_organic[195],0.167*frag_organic[197],0.167*frag_organic[199], 0.167*frag_organic[205],0.167*frag_organic[207],0.167*frag_organic[209] m/z 202 frag_org: 0.167*frag_organic[194],0.167*frag_organic[196],0.167*frag_organic[198], 0.167*frag_organic[204],0.167*frag_organic[206],0.167*frag_organic[208]

PAH Fragmentation Table – cont. Example of m/z 202

5 Comparison of MCMA-2003 (ambient) and propane flame (laboratory) AMS PAH MS

Comparison of MCMA-2003 (ambient) and NIST PAH MS

6 APAH, SPAH and FPAH MCMA-2003 Time Series

Conclusions

-Ambient AMS PAH measurement are reported for the first time.

-Aerosol-phase PAHs are present at high conc. in Mexico City, and seem to be generated by traffic emissions and are being coated and/or react away in the intense photochemistry in the city.

-An approximate background subtraction method that allows us to remove the interferences from non-PAH organics on m/z’s of the PAH molecular ions has been developed.

- Comparison with flame and NIST PAH spectra shows that the AMS is capable of measuring particulate PAH in ambient air within the limitations of the subtraction procedure. APAHs with the same MW (MW = 202, 216, 226, 228, 240, 242, 252, 276, and 300), as well as well as total APAH loadings can be obtained.

7 Questions?