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Volume 18, issue 8
Atmos. Chem. Phys., 18, 5879-5904, 2018
https://doi.org/10.5194/acp-18-5879-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Atmos. Chem. Phys., 18, 5879-5904, 2018
https://doi.org/10.5194/acp-18-5879-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 26 Apr 2018

Research article | 26 Apr 2018

Chemical characteristics of size-resolved atmospheric aerosols in Iasi, north-eastern Romania: nitrogen-containing inorganic compounds control aerosol chemistry in the area

Alina Giorgiana Galon-Negru1, Romeo Iulian Olariu1,2, and Cecilia Arsene1,2 Alina Giorgiana Galon-Negru et al.
  • 1“Alexandru Ioan Cuza” University of Iasi, Faculty of Chemistry, Department of Chemistry, 11 Carol I, 700506 Iasi, Romania
  • 2“Alexandru Ioan Cuza” University of Iasi, Integrated Centre of Environmental Science Studies in the North Eastern Region, 11 Carol I, Iasi 700506, Romania

Abstract. This study assesses the effects of particle size and season on the content of the major inorganic and organic aerosol ionic components in the Iasi urban area, north-eastern Romania. Continuous measurements were carried out over 2016 using a cascade Dekati low-pressure impactor (DLPI) performing aerosol size classification in 13 specific fractions over the 0.0276–9.94µm size range. Fine-particulate Cl, NO3, NH4+, and K+ exhibited clear minima during the warm season and clear maxima over the cold season, mainly due to trends in emission sources, changes in the mixing layer depth and specific meteorological conditions. Fine-particulate SO42− did not show much variation with respect to seasons. Particulate NH4+ and NO3 ions were identified as critical parameters controlling aerosol chemistry in the area, and their measured concentrations in fine-mode (PM2.5) aerosols were found to be in reasonable good agreement with modelled values for winter but not for summer. The likely reason is that NH4NO3 aerosols are lost due to volatility over the warm season. We found that NH4+ in PM2.5 is primarily associated with SO42− and NO3 but not with Cl. Actually, indirect ISORROPIA-II estimations showed that the atmosphere in the Iasi area might be ammonia rich during both the cold and warm seasons, enabling enough NH3 to be present to neutralize H2SO4, HNO3, and HCl acidic components and to generate fine-particulate ammonium salts, in the form of (NH4)2SO4, NH4NO3, and NH4Cl. ISORROPIA-II runs allowed us to estimate that over the warm season  ∼ 35% of the total analysed samples had very strongly acidic pH (0–3), a fraction that rose to  ∼ 43% over the cold season. Moreover, while in the cold season the acidity is mainly accounted for by inorganic acids, in the warm ones there is an important contribution by other compounds, possibly organic. Indeed, changes in aerosol acidity would most likely impact the gas–particle partitioning of semi-volatile organic acids. Overall, we estimate that within the aerosol mass concentration the ionic mass brings a contribution as high as 40.6%, with the rest still being unaccounted for.

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In north-eastern Romania, enhancement in emission sources, changes in the mixed layer depth, and specific meteorological conditions were identified as critical factors controlling the seasonal variation in particulate ionic species. Particulate NH4+ and NO3 ions were assigned as critical parameters controlling aerosol chemistry. Long-range transport phenomena play an important role. Exploring aerosols' chemical composition and chemical processes still involves many challenges.
In north-eastern Romania, enhancement in emission sources, changes in the mixed layer depth, and...
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