An aerosol is a colloid of fine solid particles or liquid droplet, in air or another gas (Hinds, 1999).The total carbon (TC) in carbonaceous aerosols can be divided into Inorganic Carbon (IC), Organic Carbon (OC) and Elemental Carbon (EC).We measured carbonaceous aerosols at theSMEAR II (Station for measuring ecosystem atmosphere relations) in southern Finland based on division of Atmospheric Sciences of University of Helsinki. The measurements were carried out continuously from 2005 using different instruments. We used a thermal-optical method to analyze carbonaceous aerosols at Hyytiälä and examineddiurnal and seasonal variation in EC, OC, TC, OC/EC ratio, black carbon (BC) and organics. We found the mean concentrations of EC and OC estimated using Sunset Lab. OCEC analyzer and BC measured using Magee scientific Aethalometer were 0.22±0.19 µgC/m3, 1.53±0.92µgC/m3 and 0.35±0.30 µg/m3 respectively. Whereas the average concentration of BC measured using MAAP was 0.2±0.2 µg/m3. We also found concentrations of EC and BC to be low in summer and high in winter, whereas, the opposite was true for OC. EC, OC and BC showed no significant diurnal cycle, but clear seasonal cycle in all carbonaceous aerosols was evident. The aerosols mass measured by aerosolmass spectrometer (AMS) showed 58% organics, 28% sulfates, 5% nitrates, 9% ammonium and less than 1% chlorides at Hyytiälä.The primary organic carbon (POC) and secondary organic carbon (SOC) estimated by EC-tracer method contributed 5% and 95% respectively to the OC concentrations at Hyytiälä. The relations between different measurement instruments showed a good agreement.
