Abstract
Abstract. The Puijo aerosol–cloud observation station is a unique measurement site for its location in the mixed region between the boreal forestland and the municipality of Kuopio, Finland. A measurement campaign was carried out at the station during fall 2010. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-Tof-AMS) was deployed to characterize the atmospheric submicron aerosols. Positive matrix factorization (PMF) was applied to the unified high-resolution mass spectra organic species with NO+ and NO2+ ions to discover the intrinsic relationships between the organic and inorganic species and their daily cycles. On average, the submicron aerosols in this study were dominated by organic and sulfate species, composing 48.2 and 28.7% of total observed aerosol mass, respectively, with smaller contributions from ammonium (9.3%), nitrate (4.9%), chloride (0.8%) and BC (8.1%). The sources of these species included the primary emissions originating from the city area, secondary formation from both natural and anthropogenic emissions and regional transport. The PMF analysis succeeded in separating the mixed organic and inorganic spectra into three distinct organic and one inorganic factors. For organic factors, the semi-volatile oxygenated organic aerosol (SVOOA) and low-volatility oxygenated OA (LVOOA) accounted for 54.8 and 36.3% of total organic masses, respectively, while the hydrocarbon-like organic aerosol (HOA) accounted for 8.9% of total organics, with its main source from urban emissions. The inorganic factor is identified as NH4NO3, comprising 6.9% of the fitted aerosol mass by PMF. Based on the PMF results, the nitrate species were separated into organic and inorganic components, with the organic nitrates contributing one-third of the total nitrate mass. The results highlight both anthropogenic and biogenic emissions as important atmospheric aerosol sources in a forest–urban mixed region.
Highlights
Atmospheric aerosols are acknowledged for the important roles they play in climate via the direct and indirect effects (e.g., IPCC, 2013)
The oxidants due to anthropogenic activities such as NO3 radical, ozone (O3) and hydroxyl radical (OH) c3a2n react with biogenic volatile organic carbon (VOC) to enhance ponents in a boreal forestland–urban mixed region in this study identified one more factor, which was an hydrocarbon-like organic aerosol (HOA) factor, than that observed in the boreal forest at Hyytiälä (Raatikainen et al, 2010), where the aerosols are identified by Positive matrix factorization (PMF) as containing semi-volatile oxygenated organic aerosol (SVOOA) and low-volatility oxygenated OA (LVOOA)
The uinnocregrataniinctyni3itnr2at3de3etaeerrmosino-l possible formation of organic nitrate from nocturnal oxidation (NO3-initiated) of anthropogenic and biogenic VOCs, in this study shows (Fig. 10b), which is high concentrations believed to be due to tfhroemem3thi3sesinoonrsthfreoamst which has already been obs3e2rved in the boreal forest in Hyytiälä
Summary
Atmospheric aerosols are acknowledged for the important roles they play in climate via the direct and indirect effects (e.g., IPCC, 2013). Atmospheric aerosols originate from a wide variety of natural and anthropogenic sources and processes, either from primary emissions or secondary formation Their chemical properties can be studied both by online and offline techniques, each allowing for different insights into molecular composition. Most of the AMS data sets analyzed by PMF are from measurements in urban, urban-downwind and rural/remote sites These sites are usually separately dominated by anthropogenic or biogenic aerosol sources alone (Ng et al, 2010). A particular focus of this study is particulate nitrate since nitrate is an important constituent of atmospheric aerosols, and the determination and quantification of particulate organic nitrate remains a challenge (Fry et al, 2009, 2013; Liu et al, 2012; Rollins et al, 2012; Farmer et al, 2010). This is the first study to report the particulate organic nitrate distinguished by PMF
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