Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry ? Part I: quantification, shape-related collection efficiency, and comparison with collocated instruments

D. Salcedo (1, 2) , K. Dzepina (2, 3) , T. B. Onasch (4) , M. R. Canagaratna (4) , Q. Zhang (2) , A. Rr. Huffman (2, 3) , P. F. Decarlo (2, 5) , J. T. Jayne (4) , P. Mortimer (4) , D. R. Worsnop (4) , C. E. Kolb (4) , K. S. Johnson (6) , B. Zuberi (6) , L. C. Marr (6) , L. T. Molina (6) , M. J. Molina (6) , R. M. Bernabé (7) , B. Cardenas (7) , C. Márquez (7) , J. S. Gaffney (8) , N. A. Marley (8) , A. Laskin (9) , V. Shutthanandan (9) , J. L. Jimenez (2, 3)

1 Centro de Investigaciones Quimicas
2 CIRES - Cooperative Institute for Research in Environmental Sciences
3 Department of Chemistry and Biochemistry [Boulder]
4 Center for Aerosol and Cloud Chemistry
5 AOS Program - Atmospheric and Oceanic Sciences Program [Princeton]
6 EAPS - Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge]
7 Centro Nacional de Investigacion Capacitacion Ambiental
8 ANL - Argonne National Laboratory [Lemont]
9 EMSL - William R. Wiley Environmental Molecular Sciences Laboratory

An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite, while another was deployed in the Aerodyne Mobile Laboratory (AML) during the Mexico City Metropolitan Area field study (MCMA-2003) from 31 March?4 May 2003 to investigate particle concentrations, sources, and processes. This is the first of a series of papers reporting the AMS results from this campaign. The AMS provides real time information on mass concentration and composition of the non-refractory species in particulate matter less than 1 µm (NR-PM₁) with high time and size-resolution. For the first time, we report field results from a beam width probe, which was used to study the shape and mixing state of the particles and to quantify potential losses of irregular particles due to beam broadening inside the AMS. Data from this probe show that no significant amount of irregular particles was lost due to excessive beam broadening. A comparison of the CENICA and AML AMSs measurements is presented, being the first published intercomparison between two quadrupole AMSs. The speciation, and mass concentrations reported by the two AMSs compared relatively well. The differences found are likely due to the different inlets used in both instruments. In order to account for the refractory material in the aerosol, we also present measurements of Black Carbon (BC) using an aethalometer and an estimate of the aerosol soil component obtained from Proton-Induced X-ray Emission Spectrometry (PIXE) analysis of impactor substrates. Comparisons of AMS + BC + soil mass concentration with other collocated particle instruments (a LASAIR Optical Particle Counter, a Tapered Element Oscillating Microbalance (TEOM) and a DustTrak Aerosol Monitor) are also presented. The comparisons show that the AMS + BC + soil mass concentration during MCMA-2003 is a good approximation to the total PM_2.5 mass concentration.

Domaines: Océan, Atmosphère

D. Salcedo, K. Dzepina, T. B. Onasch, M. R. Canagaratna, Q. Zhang, et al.. Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry ? Part I: quantification, shape-related collection efficiency, and comparison with collocated instruments. Atmospheric Chemistry and Physics Discussions, 2005, 5 (3), pp.4143-4182. ⟨hal-00303924⟩