Source identification of short-lived air pollutants in the Arctic using statistical analysis of measurement data and particle dispersion model output

Abstract

Abstract. As a part of the IPY project POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate Chemistry, Aerosols and Transport), this paper studies the sources of equivalent black carbon (EBC), sulphate, light-scattering aerosols and ozone measured at the Arctic stations Zeppelin, Alert, Barrow and Summit during the years 2000-2007. These species are important pollutants and climate forcing agents, and sulphate and EBC are main components of Arctic haze. To determine where these substances originate, the measurement data were combined with calculations using FLEXPART, a Lagrangian particle dispersion model. The climatology of atmospheric transport from surrounding regions on a twenty-day time scale modelled by FLEXPART shows that the stations Zeppelin, Alert and Barrow are highly sensitive to surface emissions in the Arctic and to emissions in high-latitude Eurasia in winter. Emission sensitivities over southern Asia and southern North America are small throughout the year. The high-altitude station Summit is an order of magnitude less sensitive to surface emissions in the Arctic whereas emissions in the southern parts of the Northern Hemisphere continents are more influential relative to the other stations. Our results show that for EBC and sulphate measured at Zeppelin, Alert and Barrow, northern Eurasia is the dominant Correspondence to: D. Hirdman (dhi@nilu.no) source region. For sulphate, Eastern Europe and the metal smelting industry in Norilsk are particularly important. For EBC, boreal forest fires also contribute in summer. No evidence for any substantial contribution to EBC from sources in southern Asia is found. European air masses are associated with low ozone concentrations in winter due to titration by nitric oxides, but are associated with high ozone concentrations in summer due to photochemical ozone formation. There is also a strong influence of ozone depletion events in the Arctic boundary layer on measured ozone concentrations in spring and summer. These results will be useful for developing emission reduction strategies for the Arctic.

Black carbon in the Arctic: the underestimated role of gas flaring and residential combustion emissions

“…The high-latitude flaring emissions occur mainly in the North Sea, the Norwegian Sea, the northeastern part of European Russia and western Siberia. The Russian flaring emissions specifically are located along the main low-level pathway of air masses entering the Arctic (Stohl, 2006), in an area that was also identified as the source region of the highest measured BC concentrations at the Arctic measurement stations Alert, Barrow and Zeppelin (Hirdman et al, 2010). Thus, if the GAINS estimates for the Russian flaring emissions are correct, we might expect this source to be responsible for a large fraction of the BC loadings in the Arctic lower troposphere -something that has not yet received attention in the literature.…”

“…For all stations except for Summit and Station Nord we had data available for the years 2008-2010, corresponding to the modeling period. For Summit, we used the data set produced by Hirdman et al (2010), where influence from local pollution sources (mainly a diesel generator) was removed by filtering the data according to wind direction. These data were, however, only available until fall 2008, so we used the years [2005][2006][2007][2008].…”

“…However, there are many other episodes, for which the model-measurement comparison and the BC / CO enhancement ratios indicate large flaring contributions. In fact, using a statistical method, the flaring region in Russia was identified already by Hirdman et al (2010) as the key source region for the highest measured EBC concentrations at Zeppelin, Barrow and Alert. However, Hirdman et al (2010) could not attribute the EBC to flaring as a source type because at the time of their study information on flaring emissions was not available.…”

“…In fact, using a statistical method, the flaring region in Russia was identified already by Hirdman et al (2010) as the key source region for the highest measured EBC concentrations at Zeppelin, Barrow and Alert. However, Hirdman et al (2010) could not attribute the EBC to flaring as a source type because at the time of their study information on flaring emissions was not available. Similarly, Eleftheriadis et al (2009) for EBC (using a different instrument) and Tunved et al (2013) for sub-micrometer aerosol mass concentration identified the same source region for the Zeppelin observatory.…”

Source identification and airborne chemical characterisation of aerosol pollution from long-range transport over Greenland during POLARCAT summer campaign 2008

“…Air masses over central Greenland especially follow the second and third pathways (Hirdman et al, 2010), due to the elevation of the ice sheet (>3.2 km). However, it must be taken into consideration that low-level transport to the Arctic is nearly absent during summer and that the Arctic front retreats far North during this time of year so that the sampled air masses were not always of true Arctic character.…”