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An Aerodyne quadruple aerosol mass spectrometer (Q-AMS) has been used to provide on-line measurements of size dependent chemical composition of fine aerosol particles (PM 1 ) at the Air Pollution Research Station in Preila, Lithuania, representing the east Baltic region. The size dependent chemical composition measurements by AMS have revealed that in marine air masses 118 nm mode organics-containing particles were fresher compared to sulfate-containing particles (295 nm), likely originated as secondary aerosol from forest emissions or produced by primary sea spray over the Baltic Sea. In polluted continental air masses sulfate and organics were highly internally mixed and aged. The mass spectral results indicated that the major components of organic compounds were oxygenated organic species with strong signals at m/z 18, 43, 44 with several specific features. Positive matrix factorization (PMF) of AMS organic mass spectral data has identified three factors: aged oxygenated low-volatility organic aerosol (LV-OOA), less oxygenated semi-volatile organic aerosol (SV-OOA), and biogenic organic aerosol (BGOA) of either terrestrial or marine origin. The measurements were compared with a real-time particulate matter Beta Absorption Monitor (Thermo ESM Andersen) and Micro Orifice Uniform Deposit Impactor (MOUDI) data. The intercomparison showed a good correlation and a stable ratio between PM 1 and PM 2.5 concentrations. A comparison of the on-line Q-AMS data and the off-line MOUDI fine particle (<1 μm) data yielded a reasonable agreement in size distributions but not the absolute mass concentrations due to sampling conditions, evaporation of acidic species from sampling substrates and bounce of the particles in the MOUDI.

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We applied stable carbon isotope ratio ( 13 C/ 12 C) and radiocarbon ( 14 C) analysis for the quantification of three main aerosol sources (coal, biomass and liquid fossil fuel derived aerosol emissions). Submicron aerosol samples (PM 1 ) were collected from 27 th October, 2014 to 19 th January, 2015 at a suburban site of Vilnius city (Lithuania). To determine fossil and non-fossil contributions to submicron carbonaceous aerosol particles, 14 C measurements of total carbon (TC) were performed using single stage accelerator mass spectrometer (SSAMS, NEC, USA). The concentrations of TC and δ 13 C in PM 1 fraction were measured using elemental analyzer interfaced to isotope ratio mass spectrometer (EA-IRMS).The TC concentration during measurement period ranged from 1.3 to 9.6 µg m -3. The variation of TC concentrations can be explained by the influence of long-range transport and dispersion properties of the boundary layer (mixed layer depth).We found that biomass-derived aerosol sources are prevailing in Vilnius during wintertime and ranged from 57% to 84% of total carbonaceous aerosol fraction. Applying isotope mass balance calculations the traffic emissions were estimated to be 15 ± 7% and coal combustion made up 14 ± 9% in PM 1 . To provide better information about the pollution sources, the carbon isotope analysis along air mass transport pattern was performed. Our results demonstrated that the high contribution to PM 1 from coal burning (up to 40%) was observed for air masses transported from highly industrialized Western Europe regions. Combination of stable carbon isotope ratio with the radiocarbon data allow to distinguish coal from liquid fossil fuel in the aerosol particle emissions.

In the present study, a combination of the stable carbon isotope ratio (C/C) with radiocarbon data (C) allowed us to perform the aerosol source apportionment. Filter samples of PM were collected during the warm and cold periods in rural and urban sites in Lithuania. The C/C ratio of total carbon (TC) was measured using the single stage accelerator mass spectrometer quantifying of fossil and non-fossil derived aerosol emissions. The δC value was measured using an elemental analyser interfaced with an isotope ratio mass spectrometer. We have found that the highest fraction of contemporary carbon (f = 0.82) was measured during a warm period in a rural location. A higher fraction of fossil fuel-derived carbon was observed for air masses transported from highly industrialized Western European regions during both seasons. Isotope mass balance calculations revealed that the traffic emissions composed 15 and 25 % in rural and urban sites, respectively, and did not change during either season. Input from coal-derived aerosol particles was estimated to be 15 % at an urban site during the cold period. The combination of the stable carbon isotope ratio with the radiocarbon data allowed us to distinguish coal, liquid fossil fuel combustion, and non-fossil derived aerosol particle emissions.

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