Seasonal observation and source apportionment of carbonaceous aerosol from forested rural site (Lithuania). (1st March 2022) - Masalaite, A.
Abstract: In this work, we conducted a study of the stable carbon isotope ratios of total carbon (δ 13 CTC ) for submicron aerosol particles (<1 μm) that were collected year round (2014) at a hemiboreal forest site in Lithuania. Higher δ 13 CTC values characterised the seasonal variation in δ 13 CTC during the cold season (average −26.9 ± 0.7‰) with lower values observed during the warm season (−27.6 ± 0.6‰). The total carbon (TC) concentration was below 8 μg/m 3 during the one-year measurement period. There was one pollution event in autumn when concentrations reached up to 14.8 μg/m 3 . In addition to the offline analysis of the filter samples, the online measurements of aerosol physical and chemical properties were conducted from 15 May to September 27, 2014 by operating the Aethalometer AE-31 and a quadrupole-type Aerosol Chemical Speciation Monitor (ACSM). Source apportionment was conducted by analysing the ACSM mass spectra using Positive Matrix Factorisation (PMF). Three main factors were derived, pointing to primary emissions from biomass burning along with the secondary formation of less and more oxygenated organic aerosol of biogenic origin. A comparative analysis of δ 13 CTC with organic carbon (OC), elemental carbon (EC), and organic markers justified two dominant sources (biomass burning and fossil fuel combustion) of aerosol particles at the hemiboreal forest site during the cold season. Highlights: δ 13 C seasonal variation at the hemiboreal forest site was observed. Biogenic origin emissions dominated during the warm season. PMF analysis yielded a three-factor solution: MOOA, LOOA, and BBOA. BB and FF emissions dominated during the cold season.