10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Trend of Elemental and Organic Carbon (EC/OC) Concentrations at the National Atmospheric Observatory Košetice (Czech Republic) in 2009-2016
MILAN VANA, Adéla Holubová Šmejkalová, Czech Hydrometeorological Institute
Abstract Number: 176 Working Group: Carbonaceous Aerosol
Abstract Carbonaceous aerosol particles in the atmosphere are formed mainly of elemental carbon and organic compounds (Seinfeld, Pandis 2006). Elemental (EC) and organic carbon (OC) are the products of imperfect combustion of organic materials (coal, oil, petrol, wood and biomass); sources of OC also include the resuspension of dust, which is related to transport, and biogenic particles. While EC is emitted into the atmosphere only directly, OC can be formed by the reactions of gaseous organic precursors. The large number of toxicological studies collected in the WHO document of 2012 are related to the negative effects of carbonaceous aerosols on human health. Regular EC/OC measurement has been implementing at the National Atmospheric Observatory Košetice (NAOK) since 2009 within the framework of EU-projects EUSAAR (European Supersites for Atmospheric Aerosol Research) and later ACTRIS (Aerosols, Clouds, and Trace gases Research Infrastructure Network) and ACTRIS-2. Sampling frequency is every 6th day on 2 quartz-fibre filters. The samples are analyzed using EC-OC Sunset Lab Dual Analyzer. In 2013, a parallel measurement using a field semi-online OC/EC analyzer from Sunset Instrument started. Both instruments sampled an aerosol fraction PM2.5 and denuders were used to remove volatile organic compounds. Automatic optical corrections (based on a laser transmission monitoring) for charring were made during each thermal-optical analysis. The presented trend study is based on manual data, the data from the analyzer were used only for completing the data series when the manual data is missing. Kosetice Observatory, operated by the Czech Hydrometeorological Institute (CHMI), was established in 1988. The observatory is located in free area outside of settlement (49°35´ N, 15°05´E, 534 m above sea level) and represents the Czech Republic in several international long-term monitoring programmes (EMEP, GAW). Detailed information is available at (Vana et al., 2013).The used statistical method for trend analysis in this study is based on the nonparametric Mann-Kendall test for trend and the nonparametric Sen’s method for the magnitude of the trend. The EC emissions in the Czech Republic display continuously decreasing trend from 4,8 (kt) in 2009 to 3,2 kt in 2015. This tendency is reflected in the statistically significant downward trend of EC concentrations at NAOK from 0,6 µg.m-3 in 2009 to 0,3 µg.m-3 in 2016. Slightly decreasing trend was found both in cold (October-March) and warm (April-September) period. The difference between the seasons in not visible. OC concentrations shows decreasing tendency, which is not statistically significant. In the period 2009-2013 the mean annual concentrations stagnated round 3,5 µg.m-3 and then dropped under 3 µg.m-3. The similar tendency is visible also in the cold period. On the other hand, in the warm period, no trend was found. The mean annual ratio of EC on total carbon (TC) was 13%. No visible tendency was found during the period under review. In the warm period, the ratio was lower (11%) with decreasing tendency. On contrary, significant upward trend of the ratio was found in the cold period (mean annual ratio 15%).
The research leading to these results has received funding from the project for support of national research infrastructure ACTRIS – participation of the Czech Republic (ACTRIS-CZ - LM2015037) – Ministry of Education, Youth and Sports of the Czech Republic.