Sources of Selected Chemical Components in Atmospheric Components in Finland
Authors:   , Vestenius Mika 
Published: October 2021

Air pollution is an important environmental risk to human health and ecosystems around the world. Particulate matter (PM), especially fine particulate matter, is an important part of this air pollution problem. Particle composition varies greatly and depends on the emission source. In addition to inorganic components, organic particulate fraction can contain several hundred organic compounds from anthropogenic and natural sources. The health risk of particulate is related to the particle size and the compounds inside or on the surface of the aerosol particles. The overall aim of this thesis was to study the selected chemical substances of atmospheric aerosol from both anthropogenic and natural sources. Concentrations of polycyclic aromatic hydrocarbons (PAH) and biogenic organic acids in aerosol were measured, and their effect on the local air quality was estimated. The sources of PAHs, trace elements, biogenic volatile organic compounds (BVOCs), and persistent organic compounds (POPs) in air were studied using positive matrix factorization (PMF), which was used as the main source apportionment tool in three of five papers and for the unpublished data in this thesis. Particles from burning emissions, e.g., diesel particles and particles from biomass burning, are the most toxic in our daily environment. Because of intensive wood use for heating and in sauna stoves, residential biomass burning is the major PAH air pollution source in Finland. Sources of atmospheric PAH pollution and its influence on local air quality were estimated at Virolahti background air quality station and in the Helsinki Metropolitan Area (HMA). The main source of PAHs at Virolahti were found to be combustion- and traffic-related source from the direction of St. Petersburg. Instead, local traffic appeared to have a very small influence on PAH levels in HMA, as local residential wood burning was found to be the main b(a)p source in Helsinki Metropolitan Area. Biogenic VOCs like monoterpenes and sesquiterpenes are highly reactive and oxidize rapidly in the atmosphere, producing secondary organic aerosol (SOA). We showed that positive matrix factorization (PMF) is a useful tool in estimating separate sources in a quasistationary dynamic system like ambient VOC concentrations in the boreal forest. Selected biogenic organic acids were measured from fine particles in the boreal forest in order to estimate their influence on aerosol production. Results indicated that sesquiterpene emissions from boreal forest are probably underestimated and their oxidation products probably have more important role in the SOA production that previously estimated. The Kola Peninsula area was found to be the major source of heavy metal pollution at Pallas. However, as Norilsk Nickel has now partly shut down its metallurgical operations, the trace element and SO2 emissions from the Kola Peninsula should be declining in the future. The ambient concentrations of POP compounds are globally declining but, in the Arctic, for some compounds this is not the case. In the source apportionment study for Pallas 1996–2018 POPs data, relatively big portion of measured POPs at Pallas came within the marine source from clean areas from the north. These long-lived compounds, which have migrated into the Arctic from the southern areas along the air and sea currents for many decades, are now released back into the atmosphere from the melting Arctic ice cover due to global warming. For these compounds, the Arctic has turned from the sink to the source.