Biogenic Organic Aerosol as an indicator of the forest abiotic stress

Abstract

Volatile organic compounds (VOCs) have a substantial impact on the oxidant balance of the lower layers of the atmosphere. As result, they affect tree growth and ecosystem performance. Also, VOCs play significant role in new particle formation process and they change physicochemical properties of the existing particles. Wherein, such ecosystem like forest are the main source of the biogenic VOCs and in the global scale their emissions higher than anthropogenic VOCs. Thus, we investigated the changes of the physicochemical properties of the aerosol particles in forest environment. The measurements were performed applying a Scanning Mobility Particle Sizer, an Aerodynamic Particle Spectrometer and an Aerosol Chemical Speciation Monitor. During measurement campaign, it was observed new particle formation phenomena. Fresh nucleated particles were characterized by low oxidation level and high particle number concentration of the nucleation mode. Wherein, the polydisperse coagulation process was much higher than the condensation growth of the nucleated particles. Also, we determined that the nucleation process of the aerosol particle was related with the trees abiotic stress, which was observed by temperature increase. The analyse of the aerosol mass spectra showed that the methanol (CH3OH, m/z 33), acetone (C3H6O2, m/z 59), methyl-ethyle-ketone (C4H8O, m/z 73) and salicyl-aldehyde (C7H8O2, m/z 123) emissions were identified as heat related. Meanwhile, methanol, acetone and methyl emissions showed great dependency of heat and light. They showed high correlation (>0.9) with one another. However, the salicyl-aldehyde could be assigned to heat stress marker. Thus, we can conclude that biogenic organic aerosol particles can be an indicator of the abiotic stress of the forest and that could to expand understanding of the forest ecosystem. The study is based on the results from national project supported by Lithuanian Council of Research "FOREstRESS"(SIT - 3/2015).