Chemical composition of free tropospheric aerosol for PM1 and coarse mode at the high alpine site Jungfraujoch
The chemical composition of submicron (fine\n\nmode) and supermicron (coarse mode) aerosol particles has\n\nbeen investigated at the Jungfraujoch high alpine research\n\nstation (3580ma.s.l., Switzerland) as part of the GAW\n\naerosol monitoring program since 1999. A clear seasonality\n\nwas observed for all major components throughout the period\n\nwith low concentrations in winter (predominantly free\n\ntropospheric aerosol) and higher concentrations in summer\n\n(enhanced vertical transport of boundary layer pollutants). In\n\naddition, mass closure was attempted during intensive campaigns\n\nin March 2004, February???March 2005 and August\n\n2005. Ionic, carbonaceous and non-refractory components\n\nof the aerosol were quantified as well as the PM1 and coarse\n\nmode total aerosol mass concentrations. A relatively low\n\nconversion factor of 1.8 for organic carbon (OC) to particulate\n\norganic matter (OM) was found in winter (February???\n\nMarch 2005). Organics, sulfate, ammonium, and nitrate\n\nwere the major components of the fine aerosol fraction that\n\nwere identified, while calcium and nitrate were the only\n\ntwo measured components contributing to the coarse mode.\n\nThe aerosol mass concentrations for fine and coarse mode\n\naerosol measured during the intensive campaigns were not\n\ntypical of the long-term seasonality due largely to dynamical\n\ndifferences. Average fine and coarse mode concentrations\n\nduring the intensive field campaigns were 1.7??gm???3\n\nand 2.4??gm???3 in winter and 2.5??gm???3 and 2.0??gm???3 in\n\nsummer, respectively. The mass balance of aerosols showed\n\nhigher contributions of calcium and nitrate in the coarse\n\nmode during Saharan dust events (SDE) than without SDE.