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Title:Detection of particle-phase polycyclic aromatic hydrocarbons in Mexico City using an aerosol mass spectrometer
Authors:Džepina, Katja (Author)
Arey, Janet (Author)
Marr, Linsey C. (Author)
Worsnop, D. (Author)
Salcedo, Dara (Author)
Zhang, Q. (Author)
Onasch, Timothy B. (Author)
Molina, Luisa T. (Author)
Molina, Mario J. (Author)
Jimenez, Jose L. (Author)
Files:This document has no files. This document may have a phisical copy in the library of the organization, check the status via COBISS. Link is opened in a new window
Language:English
Work type:Unknown ()
Tipology:1.01 - Original Scientific Article
Organization:UNG - University of Nova Gorica
Abstract:We report the quantification of ambient particle-bound polycyclic aromatic hydrocarbons (PAHs) for the first time using a real-time aerosol mass spectrometer. These measurements were carried out during the Mexico City Metropolitan Area field study (MCMA-2003) that took place from March 29 to May 4, 2003. This was the first time that two different fast, real-time methods have been used to quantify PAHs alongside traditional filter-based measurements in an extended field campaign. This paper focuses on the technical aspects of PAH detection in ambient air with the Aerodyne AMS equipped with a quadrupole mass analyzer (Q-AMS), on the comparison of PAHs measured by the Q-AMS to those measured with the other two techniques, and on some features of the ambient results. PAHs are very resistant to fragmentation after ionization. Based on laboratory experiments with eight PAH standards, we show that their molecular ions, which for most particulate PAHs in ambient particles are larger than 200 amu, are often the largest peak in their Q-AMS spectra. Q-AMS spectra of PAH are similar to those in the NIST database, albeit with more fragmentation. We have developed a subtraction method that allows the removal of the contribution from non-PAH organics to the ion signals of the PAHs in ambient data. We report the mass concentrations of all individual groups of PAHs with molecular weights of 202, 216, 226 + 228, 240 + 242, 250 + 252, 264 + 266, 276 + 278, 288 + 290, 300 + 302, 316 and 326 + 328, as well as their sum as the total PAH mass concentration. The time series of the Photoelectric Aerosol Sensor (PAS) and Q-AMS PAH measurements during MCMA-2003 are well correlated, with the smallest difference between measured PAH concentrations observed in the mornings when ambient aerosols loadings are dominated by fresh traffic emissions. The Q-AMS PAH measurements are also compared to those from GC–MS analysis of filter samples. Several groups of PAHs show agreement within the uncertainties, while the Q-AMS measurements are larger than the GC–MS ones for several others. In the ambient Q-AMS measurements the presence of ions tentatively attributed to cyclopenta[cd]pyrene and dicyclopentapyrenes causes signals at m/z 226 and 250, which are significantly stronger than the signals in GC–MS analysis of filter samples. This suggests that very labile, but likely toxic, PAHs were present in the MCMA atmosphere that decayed rapidly due to reaction during filter sampling, and this may explain at least some of the differences between the Q-AMS and GC–MS measurements.
Keywords:AMS, PAH, Mexico City
Year of publishing:2007
Number of pages:str. 152-170
Numbering:iss. 2/3, Vol. 263
COBISS_ID:59052803 Link is opened in a new window
UDC:54
ISSN on article:1387-3806
URN:URN:SI:UNG:REP:ZICOQI2F
DOI:10.1016/j.ijms.2007.01.010 Link is opened in a new window
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Record is a part of a journal

Title:International Journal of Mass Spectrometry
Shortened title:Int. j. mass spectrom.
Publisher:Elsevier
ISSN:1387-3806
COBISS.SI-ID:80283136 New window

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