Chemical and molecular characterization of free tropospheric aerosol sampled at the Pico Mountain Observatory

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Conference Proceeding

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Improved characterization of free tropospheric aerosol optical, chemical and morphological properties is essential to further our understanding of the aerosol lifecycle and the aerosol-climate implications. Free tropospheric aerosols were studied at the Pico Mountain Observatory, located on top of the Pico volcano in the Azores, Portugal (2225 m asl; 38.47°N, 28.40°W). The station is typically subjected to free tropospheric air masses that are long-range transported from North America. Recently, we deployed a set of four high-volume samplers for the chemical analysis of aerosol, a 3-wavelength nephelometer to measure aerosol light scattering and backscattering fraction, a two channels particle optical counter (for particles larger than 300 nm), and a sequential sampler to collect aerosols on nucleopore membranes and lacy carbon grids for electron microscopy analysis. Black carbon mass equivalent concentrations have been measured at the station since 2001 with a 7-wavelength aethalometer. Summertime daily concentrations of free tropospheric organic carbon, elemental carbon, water-soluble organic carbon (WSOC), anions and cations were measured from high-volume filter samples. Selected WSOC samples were further analysed using ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Molecular formulas were assigned to accurate masses as described in Mazzoleni et al., 2012. Thousands of monoisotopic compounds containing C, H, O, N, and S were identified from the negative and positive ion ultrahigh resolution FT-ICR mass spectra. The comprehensive composition of free tropospheric WSOC was compared to non-urban aerosol samples collected at the Storm Peak Laboratory in the Rocky Mountains of northwestern Colorado (3220 m asl; 40.455°N, -106.744°W). Considerable differences in the elemental ratios and molecular unsaturation were observed. This presentation will discuss those differences and their relationship to aerosol ageing with respect to long-range transport.

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© 2013 by the American Association for Aerosol Research (AAAR). AAAR grants contributing authors full rights to the use of their own abstracts.

Publication Title

2013 American Association for Aerosol Research Annual Conference