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.
Available at: http://works.bepress.com/l-mazzoleni/74/