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- ItemAerosol pollution maps and trends over Germany with hourly data at four rural background stations from 2009 to 2018(Katlenburg-Lindau : EGU, 2020) Heintzenberg, Jost; Birmili, Wolfram; Hellack, Bryan; Spindler, Gerald; Tuch, Thomas; Wiedensohler, AlfredA total of 10 years of hourly aerosol and gas data at four rural German stations have been combined with hourly back trajectories to the stations and inventories of the European Emissions Database for Global Atmospheric Research (EDGAR), yielding pollution maps over Germany of PM10, particle number concentrations, and equivalent black carbon (eBC). The maps reflect aerosol emissions modified with atmospheric processes during transport between sources and receptor sites. Compared to emission maps, strong western European emission centers do not dominate the downwind concentrations because their emissions are reduced by atmospheric processes on the way to the receptor area. PM10, eBC, and to some extent also particle number concentrations are rather controlled by emissions from southeastern Europe from which pollution transport often occurs under drier conditions. Newly formed particles are found in air masses from a broad sector reaching from southern Germany to western Europe, which we explain with gaseous particle precursors coming with little wet scavenging from this region. Annual emissions for 2009 of PM10, BC, SO2, and NOx were accumulated along each trajectory and compared with the corresponding measured time series. The agreement of each pair of time series was optimized by varying monthly factors and annual factors on the 2009 emissions. This approach yielded broader summer emission minima than published values that were partly displaced from the midsummer positions. The validity of connecting the ambient concentration and emission of particulate pollution was tested by calculating temporal changes in eBC for subsets of back trajectories passing over two separate prominent emission regions, region A to the northwest and B to the southeast of the measuring stations. Consistent with reported emission data the calculated emission decreases over region A are significantly stronger than over region B.
- ItemSignificant increase of aerosol number concentrations in air masses crossing a densely trafficked sea area(Amsterdam : Elsevier, 2015) Kecorius, Simonas; Kivekäs, Niku; Kristensson, Adam; Tuch, Thomas; Covert, David S.; Birmili, Wolfram; Lihavainen, Heikki; Hyvärinen, Antti-Pekka; Martinsson, Johan; Sporre, Moa K.; Swietlicki, Erik; Wiedensohler, Alfred; Ulevicius, VidmantasIn this study, we evaluated 10 months data (September 2009 to June 2010) of atmospheric aerosol particle number size distribution at three atmospheric observation stations along the Baltic Sea coast: Vavihill (upwind, Sweden), Utö (upwind, Finland), and Preila (downwind, Lithuania). Differences in aerosol particle number size distributions between the upwind and downwind stations during situations of connected atmospheric flow, when the air passed each station, were used to assess the contribution of ship emissions to the aerosol number concentration (diameter interval 50–400 nm) in the Lithuanian background coastal environment. A clear increase in particle number concentration could be noticed, by a factor of 1.9 from Utö to Preila (the average total number concentration at Utö was 791 cm−3), and by a factor of 1.6 from Vavihill to Preila (the average total number concentration at Vavihill was 998 cm−3). The simultaneous measurements of absorption Ångström exponents close to unity at Preila supported our conclusion that ship emissions in the Baltic Sea contributed to the increase in particle number concentration at Preila.
- ItemDecreasing trends of particle number and black carbon mass concentrations at 16 observational sites in Germany from 2009 to 2018(Katlenburg-Lindau : EGU, 2020) Sun, Jia; Birmili, Wolfram; Hermann, Markus; Tuch, Thomas; Weinhold, Kay; Merkel, Maik; Rasch, Fabian; Müller, Thomas; Schladitz, Alexander; Bastian, Susanne; Löschau, Gunter; Cyrys, Josef; Gu, Jianwei; Flentje, Harald; Briel, Björn; Asbach, Christoph; Kaminski, Heinz; Ries, Ludwig; Sohmer, Ralf; Gerwig, Holger; Wirtz, Klaus; Meinhardt, Frank; Schwerin, Andreas; Bath, Olaf; Ma, Nan; Wiedensohler, AlfredAnthropogenic emissions are dominant contributors to air pollution. Consequently, mitigation policies have been attempted since the 1990s in Europe to reduce pollution by anthropogenic emissions. To evaluate the effectiveness of these mitigation policies, the German Ultrafine Aerosol Network (GUAN) was established in 2008, focusing on black carbon (BC) and sub-micrometre aerosol particles. In this study, long-term trends of atmospheric particle number concentrations (PNCs) and equivalent BC (eBC) mass concentration over a 10-year period (2009-2018) were determined for 16 GUAN sites ranging from roadside to high Alpine environments. Overall, statistically significant decreasing trends are found for most of these parameters and environments in Germany. The annual relative slope of eBC mass concentration varies between-13.1% and-1.7% per year. The slopes of the PNCs vary from-17.2% to-1.7 %,-7.8% to-1.1 %, and-11.1% to-1.2% per year for 10-30, 30-200, and 200-800 nm size ranges, respectively. The reductions in various anthropogenic emissions are found to be the dominant factors responsible for the decreasing trends of eBC mass concentration and PNCs. The diurnal and seasonal variations in the trends clearly show the effects of the mitigation policies for road transport and residential emissions. The influences of other factors such as air masses, precipitation, and temperature were also examined and found to be less important or negligible. This study proves that a combination of emission mitigation policies can effectively improve the air quality on large spatial scales. It also suggests that a long-term aerosol measurement network at multi-type sites is an efficient and necessary tool for evaluating emission mitigation policies. © 2020 Author(s).
- ItemStructure, variability and persistence of the submicrometre marine aerosol(Milton Park : Taylor & Francis, 2017) Heintzenberg, Jost; Birmili, Wolfram; Wiedensohler, Alfred; Nowak, Andreas; Tuch, ThomasSubmicrometre dry number size distributions from four marine and one continental aerosol experiment were evaluatedjointly in the present study. In the marine experiments only data with back trajectories of at least 120 h without landcontact were used to minimize continental contamination. Log-normal functions were fitted to the size distributions.Basic statistics of the marine aerosol indicate a closed character of the size distribution at the lower size limit as opposedto an open character for corresponding continental data. Together with the infrequent occurrences of marine particlesbelow20 nmthis finding supports hypotheses and model results suggesting lowprobabilities of homogeneous nucleationin the marine boundary layer. The variability of submicrometre marine number concentrations was parametrized witha bimodal log-normal function that quantifies the probability of finding different number concentrations about a givenmedian value. Together with a four-modal log-normal approximation of the submicrometre marine size distributionitself, this model allows a statistical representation of the marine aerosol that facilitates comparison of experiments andvalidation of aerosol models. Autocorrelation at the one fixed marine site with a minimum of interruptions in timesseriesrevealed a strong size dependency of persistence in particle number concentration with the shortest persistenceat the smallest sizes. Interestingly, in the marine aerosol (at Cape Grim) persistence exhibits a size dependency thatlargely matches the modes in dg0, i.e. near the most frequent geometric mean diameters number concentrations aremost persistent. Over the continent, persistence of particle numbers is strongly constrained by diurnal meteorologicalprocesses and aerosol dynamics. Thus, no strong modal structure appears in the size-dependent persistence at Melpitz.As with the aerosol variability, marine aerosol processes in models of aerosol dynamics can be tested with these findings.
- ItemLong-term trends of black carbon and particle number concentration in the lower free troposphere in Central Europe(Berlin ; Heidelberg : Springer, 2021) Sun, Jia; Hermann, Markus; Yuan, Ye; Birmili, Wolfram; Collaud Coen, Martine; Weinhold, Kay; Madueño, Leizel; Poulain, Laurent; Tuch, Thomas; Ries, Ludwig; Sohmer, Ralf; Couret, Cedric; Frank, Gabriele; Brem, Benjamin Tobias; Gysel-Beer, Martin; Ma, Nan; Wiedensohler, AlfredBackground: The implementation of emission mitigation policies in Europe over the last two decades has generally improved the air quality, which resulted in lower aerosol particle mass, particle number, and black carbon mass concentration. However, little is known whether the decreasing particle concentrations at a lower-altitude level can be observed in the free troposphere (FT), an important layer of the atmosphere, where aerosol particles have a longer lifetime and may affect climate dynamics. In this study, we used data from two high-Alpine observatories, Zugspitze-Schneefernerhaus (ZSF) and Jungfraujoch (JFJ), to assess the long-term trends on size-resolved particle number concentrations (PNCs) and equivalent black carbon (eBC) mass concentration separated for undisturbed lower FT conditions and under the influence of air from the planetary boundary layer (PBL) from 2009 to 2018. Results: The FT and PBL-influenced conditions were segregated for both sites. We found that the FT conditions in cold months were more prevalent than in warm months, while the measured aerosol parameters showed different seasonal patterns for the FT and PBL-influenced conditions. The pollutants in the PBL-influenced condition have a higher chance to be transported to high-altitudes due to the mountainous topography, leading to a higher concentration and more distinct seasonal variation, and vice versa. The long-term trends of the measured aerosol parameters were evaluated and the decreased aerosol concentrations were observed for both FT and PBL-influenced conditions. The observed decreasing trends in eBC concentration in the PBL-influenced condition are well consistent with the reported trends in total BC emission in Germany and Switzerland. The decreased concentrations in the FT condition suggest that the background aerosol concentration in the lower FT over Central Europe has correspondingly decreased. The change of back trajectories in the FT condition at ZSF and JFJ was further evaluated to investigate the other possible drivers for the decreasing trends. Conclusions: The background aerosol concentration in the lower FT over Central Europe has significantly decreased during 2009–2018. The implementation of emission mitigation policies is the most decisive factor and the decrease of the regional airmass occurrence over Central Europe also has contributed to the decreasing trends. © 2021, The Author(s).