Mean chemical composition in winter an summer and typical morphology for each size fraction. Pies present the complete chemical composition of each size fraction (averaged for winter and summer experiments separately). EC: elemental carbon, WIOM: water-insoluble organic matter, WSOM: water-soluble organic matter, NO3
-: nitrate, NH4
+: ammonium, nssSO4
2-: non-sea-salt sulphate, sea salt (calculated from sodium concentration), dust (mineral dust particles calculated from calcium concentration). Unaccounted is the difference between the aerosol fraction mass (gravimetric measurement) and sum of the major components EC, WIOM, WSOM, NO3
2-, sea salt and dust. Morphology pictures (right side) present typical particles of size fractions and observed using TEM analysis.