Abstract
Abstract. An increase in the sulfate aerosols observed in the period 1–6 April 2014 over Austria is analyzed using in situ measurements at an Austrian air quality background station, lidar measurements at the closest EARLINET stations around Austria, CAMS near-real-time data, and particle dispersion modeling using FLEXPART, a Lagrangian transport model. In situ measurements of SO2, PM2.5, PM10, and O3 were performed at the air quality background station Pillersdorf, Austria (EMEP station AT30, 48∘43′ N, 15∘55′ E). A CAMS aerosol mixing ratio analysis for Pillersdorf and the lidar stations Leipzig, Munich, Garmisch, and Bucharest indicates the presence of an event of aerosol transport, with sulfate and dust as principal components. For the sulfate layers identified at Pillersdorf from the CAMS analysis, backward- and forward-trajectory analyses were performed, associating lidar stations with the trajectories. The lidar measurements for the period corresponding to trajectory overpass of associated stations were analyzed, obtaining the aerosol layers, the optical properties, and the aerosol types. The potential sources of transported aerosols were determined for Pillersdorf and the lidar stations using the source–receptor sensitivity computed with FLEXPART, combined with the MACCity source inventory. A comparative analysis for Pillersdorf and the trajectory-associated lidar stations showed consistent aerosol layers, optical properties and types, and potential sources. A complex pattern of contributions to sulfate over Austria was found in this paper. For the lower layers (below 2000 m) of sulfate, it was found that central Europe was the main source of sulfate. Medium to smaller contributions come from sources in eastern Europe, northwest Africa, and the eastern US. For the middle-altitude layers (between 2000 and 5000 m), sources from central Europe (northern Italy, Serbia, Hungary) contribute with similar emissions. Northwest Africa and the eastern US also have important contributions. For the high-altitude layers (above 5000 m), the main contributions come from northwest Africa, but sources from the southern and eastern US also contribute significantly. No contributions from Europe are seen for these layers. The methodology used in this paper can be used as a general tool to correlate measurements at in situ stations and EARLINET lidar stations around these in situ stations.
Highlights
Sulfate is one of the major aerosol components for particles with a diameter smaller than 2.5 μm (PM2.5) and for particles with a diameter smaller than 10 μm (PM10)
The in situ measurements of SO2, O3, PM2.5, and PM10 concentrations recorded at Pillersdorf for the period 15 March– 14 April 2014 (Umweltbundesamt Austria, 2014) are shown in Fig. 1, together with the averaged values for this period
The time series of aerosol mixing ratios from Copernicus Atmosphere Monitoring Service (CAMS) nearreal-time data for Pillersdorf are shown for the same period in Fig. 2 for “total aerosols”, for sulfate, and for dust
Summary
Sulfate is one of the major aerosol components for particles with a diameter smaller than 2.5 μm (PM2.5) and for particles with a diameter smaller than 10 μm (PM10). More details about the mass concentration of these aerosol components from various rural and urban sites in Europe are given in the IPCC AR5 report (Stocker et al, 2013). The anthropogenic sulfate is produced mainly by oxidation of sulfur dioxide (SO2), or produced by aqueous phase reactions, where O3 and hydrogen peroxide act as important oxidants (Seinfeld and Pandis, 2006), or by adsorption of SO2 on solid particles and subsequent reaction with adsorbed oxygen; the exact mechanism depends on several atmospheric factors (solar radiation, presence of catalysts, NOx, temperature, relative humidity, etc.). The adsorption is an important mechanism of sulfate production in the urban atmosphere.
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