Long-term sub-micrometer aerosol chemical composition in the boreal forest: inter- and intra-annual variability

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http://hdl.handle.net/10138/314107

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Heikkinen , L , Äijälä , M , Riva , M , Luoma , K H , Dällenbach , K , Aalto , J , Aalto , P , Aliaga Badani , D A , Aurela , M , Keskinen , H-M , Makkonen , U , Rantala , P , Kulmala , M , Petäjä , T , Worsnop , D & Ehn , M 2020 , ' Long-term sub-micrometer aerosol chemical composition in the boreal forest: inter- and intra-annual variability ' , Atmospheric Chemistry and Physics , vol. 20 , no. 5 , pp. 3151-3180 . https://doi.org/10.5194/acp-20-3151-2020

Title: Long-term sub-micrometer aerosol chemical composition in the boreal forest: inter- and intra-annual variability
Author: Heikkinen, Liine; Äijälä, Mikko; Riva, Matthieu; Luoma, Krista Hannele; Dällenbach, Kaspar; Aalto, Juho; Aalto, Pasi; Aliaga Badani, Diego Alonso; Aurela, Minna; Keskinen, Helmi-Marja; Makkonen, Ulla; Rantala, Pekka; Kulmala, Markku; Petäjä, Tuukka; Worsnop, Douglas; Ehn, Mikael
Contributor: University of Helsinki, INAR Physics
University of Helsinki, INAR Physics
University of Helsinki, INAR Physics
University of Helsinki, INAR Physics
University of Helsinki, Air quality research group
University of Helsinki, Ecosystem processes (INAR Forest Sciences)
University of Helsinki, INAR Physics
University of Helsinki, INAR Physics
University of Helsinki, INAR Physics
University of Helsinki, Institute for Atmospheric and Earth System Research (INAR)
University of Helsinki, Institute for Atmospheric and Earth System Research (INAR)
University of Helsinki, INAR Physics
University of Helsinki, INAR Physics
Date: 2020-03-16
Language: eng
Number of pages: 30
Belongs to series: Atmospheric Chemistry and Physics
ISSN: 1680-7316
URI: http://hdl.handle.net/10138/314107
Abstract: The Station for Measuring Ecosystem Atmosphere Relations (SMEAR) II is well known among atmospheric scientists due to the immense amount of observational data it provides of the Earth atmosphere interface. Moreover, SMEAR II plays an important role for the large European research infrastructure, enabling the large scientific community to tackle climate- and air-pollution-related questions, utilizing the high-quality long-term data sets recorded at the site. So far, this well-documented site was missing the description of the seasonal variation in aerosol chemical composition, which helps understanding the complex biogeochemical and physical processes governing the forest ecosystem. Here, we report the sub-micrometer aerosol chemical composition and its variability, employing data measured between 2012 and 2018 using an Aerosol Chemical Speciation Monitor (ACSM). We observed a bimodal seasonal trend in the sub-micrometer aerosol concentration culminating in February (2.7, 1.6, and 5.1 mu g m(-3) for the median, 25th, and 75th percentiles, respectively) and July (4.2, 2.2, and 5.7 mu g m(-3) for the median, 25th, and 75th percentiles, respectively). The wintertime maximum was linked to an enhanced presence of inorganic aerosol species (ca. 50 %), whereas the summertime maximum (ca. 80 % organics) was linked to biogenic secondary organic aerosol (SOA) formation. During the exceptionally hot months of July of 2014 and 2018, the organic aerosol concentrations were up to 70 % higher than the 7-year July mean. The projected increase in heat wave frequency over Finland will most likely influence the loading and chemical composition of aerosol particles in the future. Our findings suggest strong influence of meteorological conditions such as radiation, ambient temperature, and wind speed and direction on aerosol chemical composition. To our understanding, this is the longest time series reported describing the aerosol chemical composition measured online in the boreal region, but the continuous monitoring will also be maintained in the future.
Subject: ATMOSPHERIC AEROSOL
DATA SETS
HYYTIALA
INORGANIC AEROSOL
MASS-SPECTROMETER
PARTICLE
PTR-MS
SEMICONTINUOUS GAS
SOURCE APPORTIONMENT
VOLATILE ORGANIC-COMPOUNDS
114 Physical sciences
4112 Forestry
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