Volatile organic compounds (VOCs) emitted by trees in response to abiotic stress evoke high levels of secondary organic aerosol (SOA) compounds. Few techniques exist to provide chemically-resolved submicron (PM1) particle mass concentrations and source apportionment of stress-induced emissions from trees and SOA formation. The chemical composition of atmospheric aerosol particles was characterized using an aerosol chemical speciation monitor (ACSM) at a mixed-mature forest site – the Aukštaitija Integrated Monitoring Station in the eastern part of Lithuania. The organic fraction of PM1 consisted of SOA (76%) and of anthropogenic combustion related primary organic aerosol (POA) (24%). The analysis of tree trunk circumference revealed three shrinkage and three normal increase episodes. During the episodes of tree trunk circumference shrinkage, several m/z signal (m/z 42, 43, 45, 48, 50) intensities were found to be magnified together with the daily SOA concentration. The stress response analysis confirm that tree trunk circumference shrinkage may be observed through the enhancement of selected m/z signals and result in increased SOA levels.

The chemical composition of submicron aerosol particles was characterized using an aerosol chemical speciation monitor (ACSM) at a mixed-mature forest site at the Aukštaitija Integrated Monitoring Station in the eastern part of Lithuania. Four organic aerosol (OA) factors were determined by positive matrix factorization (PMF) analysis applied for the ACSM data: semi-volatile oxygenated OA (SVOOA, the contribution to the total OA mass concentration was 33%), low-volatile oxygenated OA (LVOOA, 39%), cooking related OA (COA, 15%) and biomass burning OA (BBOA, 13%). In our study secondary organic aerosol (SOA) has been identified as one of the most important contributors to the submicron particle (PM1) mass concentration. A comparison between SVOOA and submicron forest organic aerosol mass (SFOM) was performed, and a good correlation of 0.75 between them was found. In our study the SOA concentration dependence on temperature was explored in 3 means: firstly, by investigating aerosol mass spectra measured during hot and cold days. It has been found that during hot days events signal intensities of m/z 42, 43, 45, 53 and 59 were about 2.1–2.7 times higher compared to those during cold days. Secondly, by investigating the temperature dependence of SVOOA and estimated SFOM. It has been found that SFOM and SVOOA concentrations increase with temperature. Thirdly, by assessing the influence of temperature related stomatal conduction on SVOOA concentration: no direct influence on SVOOA concentration was observed.