Abstract
In situ investigation results of aerosol optical properties (absorption and scattering) and chemical composition at an urban background site in Lithuania (Vilnius) are presented. Investigation was performed in May-June 2017 using an aerosol chemical speciation monitor (ACSM), a 7-wavelength Aethalometer and a 3-wavelength integrating Nephelometer. A positive matrix factorisation (PMF) was used for the organic aerosol mass spectra analysis to characterise the sources of ambient organic aerosol (OA). Five OA factors were identified: hydrocarbon-like OA (HOA), biomass-burning OA (BBOA), more and less oxygenated OA (LVOOA and SVOOA, respectively), and local hydrocarbon-like OA (LOA). The average absorption (at 470 nm) and scattering (at 450 nm) coefficients during the entire measurement campaign were 16.59 Mm−1 (standard deviation (SD) = 17.23 Mm−1) and 29.83 Mm−1 (SD = 20.45 Mm−1), respectively. Furthermore, the absorption and scattering Angström exponents (AAE and SAE, respectively) and single-scattering albedo (SSA) were calculated. The average AAE value at 470/660 nm was 0.97 (SD = 0.16) indicating traffic-related black carbon (BCtr) dominance. The average value of SAE (at 450/700 nm) was 1.93 (SD = 0.32) and could be determined by the submicron particle (PM1) dominance versus the supermicron ones (PM > 1 µm). The average value of SSA was 0.62 (SD = 0.13). Several aerosol types showed specific segregation in the SAE versus SSA plot, which underlines different optical properties due to various chemical compositions.
Highlights
Atmospheric aerosols significantly influence both global and local climate, and their loadings have substantially increased since preindustrial times. e impact of particles depends on their chemical composition and physical properties. e light absorption and light scattering are two main processes of interaction between aerosol particles and solar radiation in the atmosphere
Continuous measurements of aerosol mass concentration, size distribution, and optical properties were performed from 11 May to 14 June, 2017. e sampling site is located in Vilnius (Lithuania) (54°38′36′′N, 25°10′58′′E) 12 m above the ground level
Vilnius is the capital of Lithuania with 0.5 million habitants. e sampling site is 8 km away from the city centre and can be described as an urban background
Summary
Julija Pauraite , Kristina Plauskaite, Vadimas Dudoitis, and Vidmantas Ulevicius. SRI Center for Physical Sciences and Technology, Savanoriu Avenue 231, LT-02300 Vilnius, Lithuania. Received 31 May 2018; Revised 8 August 2018; Accepted 12 August 2018; Published 17 September 2018
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