Changes in background aerosol composition in Finland during polluted and clean periods studied by TEM/EDX individual particle analysis

• Main Authors: Niemi, J. V., Saarikoski, S., Tervahattu, H., Mäkelä, T., Hillamo, R., Vehkamäki, H., Sogacheva, L., Kulmala, M.
• Other Authors: Division of Population Biology, Finnish Meteorological Institute (FMI), Nordic Envicon Ltd., Department of Physics Helsinki, Falculty of Science Helsinki, Helsingin yliopisto = Helsingfors universitet = University of Helsinki-Helsingin yliopisto = Helsingfors universitet = University of Helsinki
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2006
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Arctic; Arctic Ocean
• Online Access: https://hal.science/hal-00296072; https://hal.science/hal-00296072/document; https://hal.science/hal-00296072/file/acp-6-5049-2006.pdf

International audience Aerosol samples were collected at a rural background site in southern Finland in May 2004 during pollution episode (PM 1 ~16 µg m ?3 , backward air mass trajectories from south-east), intermediate period (PM 1 ~5 µg m ?3 , backtrajectories from north-east) and clean period (PM 1 ~2 µg m ?3 , backtrajectories from north-west/north). The elemental composition, morphology and mixing state of individual aerosol particles in three size fractions were studied using transmission electron microscopy (TEM) coupled with energy dispersive X-ray (EDX) microanalyses. The TEM/EDX results were complemented with the size-segregated bulk chemical measurements of selected ions and organic and elemental carbon. Many of the particles in PM 0.2?1 and PM 1?3.3 size fractions were strongly internally mixed with S, C and/or N. The major particle types in PM 0.2?1 samples were 1) soot and 2) (ammonium)sulphates and their mixtures with variable amounts of C, K, soot and/or other inclusions. Number proportions of those two particle groups in PM 0.2?1 samples were 0?12% and 83?97%, respectively. During the pollution episode, the proportion of Ca-rich particles was very high (26?48%) in the PM 1?3.3 and PM 3.3?11 samples, while the PM 0.2?1 and PM 1?3.3 samples contained elevated proportions of silicates (22?33%), metal oxides/hydroxides (1?9%) and tar balls (1?4%). These aerosols originated mainly from polluted areas of Eastern Europe, and some open biomass burning smoke was also brought by long-range transport. During the clean period, when air masses arrived from the Arctic Ocean, PM 1?3.3 samples contained mainly sea salt particles (67?89%) with a variable rate of Cl substitution (mainly by NO 3 ? ). During the intermediate period, the PM 1?3.3 sample contained porous (sponge-like) Na-rich particles (35%) with abundant S, K and O. They might originate from the burning of wood pulp wastes of paper industry. The proportion of biological particles and C-rich fragments (probably also biological origin) were highest ...