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- ItemAtmospheric new particle formation at the research station Melpitz, Germany: Connection with gaseous precursors and meteorological parameters(Katlenburg-Lindau : EGU, 2018) Größ, Johannes; Hamed, Amar; Sonntag, André; Spindler, Gerald; Manninen, Hanna Elina; Nieminen, Tuomo; Kulmala, Markku; Hõrrak, Urmas; Plass-Dülmer, Christian; Wiedensohler, Alfred; Birmili, WolframThis paper revisits the atmospheric new particle formation (NPF) process in the polluted Central European troposphere, focusing on the connection with gas-phase precursors and meteorological parameters. Observations were made at the research station Melpitz (former East Germany) between 2008 and 2011 involving a neutral cluster and air ion spectrometer (NAIS). Particle formation events were classified by a new automated method based on the convolution integral of particle number concentration in the diameter interval 2-20 nm. To study the relevance of gaseous sulfuric acid as a precursor for nucleation, a proxy was derived on the basis of direct measurements during a 1-month campaign in May 2008. As a major result, the number concentration of freshly produced particles correlated significantly with the concentration of sulfur dioxide as the main precursor of sulfuric acid. The condensation sink, a factor potentially inhibiting NPF events, played a subordinate role only. The same held for experimentally determined ammonia concentrations. The analysis of meteorological parameters confirmed the absolute need for solar radiation to induce NPF events and demonstrated the presence of significant turbulence during those events. Due to its tight correlation with solar radiation, however, an independent effect of turbulence for NPF could not be established. Based on the diurnal evolution of aerosol, gas-phase, and meteorological parameters near the ground, we further conclude that the particle formation process is likely to start in elevated parts of the boundary layer rather than near ground level.
- ItemLong-term observations of tropospheric particle number size distributions and equivalent black carbon mass concentrations in the German Ultrafine Aerosol Network (GUAN)(München : European Geopyhsical Union, 2016) Birmili, Wolfram; Weinhold, Kay; Rasch, Fabian; Sonntag, André; Sun, Jia; Merkel, Maik; Wiedensohler, Alfred; Bastian, Susanne; Schladitz, Alexander; Löschau, Gunter; Cyrys, Josef; Pitz, Mike; Gu, Jianwei; Kusch, Thomas; Flentje, Harald; Quass, Ulrich; Kaminski, Heinz; Kuhlbusch, Thomas A.J.; Meinhardt, Frank; Schwerin, Andreas; Bath, Olaf; Ries, Ludwig; Gerwig, Holger; Wirtz, Klaus; Fiebig, MarkusThe German Ultrafine Aerosol Network (GUAN) is a cooperative atmospheric observation network, which aims at improving the scientific understanding of aerosol-related effects in the troposphere. The network addresses research questions dedicated to both climate- and health-related effects. GUAN's core activity has been the continuous collection of tropospheric particle number size distributions and black carbon mass concentrations at 17 observation sites in Germany. These sites cover various environmental settings including urban traffic, urban background, rural background, and Alpine mountains. In association with partner projects, GUAN has implemented a high degree of harmonisation of instrumentation, operating procedures, and data evaluation procedures. The quality of the measurement data is assured by laboratory intercomparisons as well as on-site comparisons with reference instruments. This paper describes the measurement sites, instrumentation, quality assurance, and data evaluation procedures in the network as well as the EBAS repository, where the data sets can be obtained (doi:10.5072/guan).
- ItemAerosol particle mixing state, refractory particle number size distributions and emission factors in a polluted urban environment: Case study of Metro Manila, Philippines(Oxford [u.a.] : Elsevier, 2017) Kecorius, Simonas; Madueño, Leizel; Vallar, Edgar; Alas, Honey; Betito, Grace; Birmili, Wolfram; Cambaliza, Maria Obiminda; Catipay, Grethyl; Gonzaga-Cayetano, Mylene; Galvez, Maria Cecilia; Lorenzo, Genie; Müller, Thomas; Simpas, James B.; Tamayo, Everlyn Gayle; Wiedensohler, AlfredUltrafine soot particles (black carbon, BC) in urban environments are related to adverse respiratory and cardiovascular effects, increased cases of asthma and premature deaths. These problems are especially pronounced in developing megacities in South-East Asia, Latin America, and Africa, where unsustainable urbanization ant outdated environmental protection legislation resulted in severe degradation of urban air quality in terms of black carbon emission. Since ultrafine soot particles do often not lead to enhanced PM10 and PM2.5 mass concentration, the risks related to ultrafine particle pollution may therefore be significantly underestimated compared to the contribution of secondary aerosol constituents. To increase the awareness of the potential toxicological relevant problems of ultrafine black carbon particles, we conducted a case study in Metro Manila, the capital of the Philippines. Here, we present a part of the results from a detailed field campaign, called Manila Aerosol Characterization Experiment (MACE, 2015). Measurements took place from May to June 2015 with the focus on the state of mixing of aerosol particles. The results were alarming, showing the abundance of externally mixed refractory particles (soot proxy) at street site with a maximum daily number concentration of approximately 15000 #/cm3. That is up to 10 times higher than in cities of Western countries. We also found that the soot particle mass contributed from 55 to 75% of total street site PM2.5. The retrieved refractory particle number size distribution appeared to be a superposition of 2 ultrafine modes at 20 and 80 nm with a corresponding contribution to the total refractory particle number of 45 and 55%, respectively. The particles in the 20 nm mode were most likely ash from metallic additives in lubricating oil, tiny carbonaceous particles and/or nucleated and oxidized organic polymers, while bigger ones (80 nm) were soot agglomerates. To the best of the authors’ knowledge, no other studies reported such high number concentration of ultrafine refractory particles under ambient conditions. Inverse modeling of emission factors of refractory particle number size distributions revealed that diesel-fed public utility Jeepneys, commonly used for public transportation, are responsible for 94% of total roadside emitted refractory particle mass. The observed results showed that the majority of urban pollution in Metro Manila is dominated by carbonaceous aerosol. This suggests that PM10 or PM2.5 metrics do not fully describe possible health related effects in this kind of urban environments. Extremely high concentrations of ultrafine particles have been and will continue to induce adverse health related effects, because of their potential toxicity. We imply that in megacities, where the major fraction of particulates originates from the transport sector, PM10 or PM2.5 mass concentration should be complemented by legislative measurements of equivalent black carbon mass concentration.
- ItemSeasonal variation of atmospheric particle number concentrations, new particle formation and atmospheric oxidation capacity at the high Arctic site Villum Research Station, Station Nord(München : European Geopyhsical Union, 2016) Nguyen, Quynh T.; Glasius, Marianne; Sørensen, Lise L.; Jensen, Bjarne; Skov, Henrik; Birmili, Wolfram; Wiedensohler, Alfred; Kristensson, Adam; Nøjgaard, Jacob K.; Massling, AndreasThis work presents an analysis of the physical properties of sub-micrometer aerosol particles measured at the high Arctic site Villum Research Station, Station Nord (VRS), northeast Greenland, between July 2010 and February 2013. The study focuses on particle number concentrations, particle number size distributions and the occurrence of new particle formation (NPF) events and their seasonality in the high Arctic, where observations and characterization of such aerosol particle properties and corresponding events are rare and understanding of related processes is lacking. A clear accumulation mode was observed during the darker months from October until mid-May, which became considerably more pronounced during the prominent Arctic haze months from March to mid-May. In contrast, nucleation- and Aitken-mode particles were predominantly observed during the summer months. Analysis of wind direction and wind speed indicated possible contributions of marine sources from the easterly side of the station to the observed summertime particle number concentrations, while southwesterly to westerly winds dominated during the darker months. NPF events lasting from hours to days were mostly observed from June until August, with fewer events observed during the months with less sunlight, i.e., March, April, September and October. The results tend to indicate that ozone (O3) might be weakly anti-correlated with particle number concentrations of the nucleation-mode range (10–30 nm) in almost half of the NPF events, while no positive correlation was observed. Calculations of air mass back trajectories using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model for the NPF event days suggested that the onset or interruption of events could possibly be explained by changes in air mass origin. A map of event occurrence probability was computed, indicating that southerly air masses from over the Greenland Sea were more likely linked to those events.
- ItemSea salt emission, transport and influence on size-segregated nitrate simulation: A case study in northwestern Europe by WRF-Chem(München : European Geopyhsical Union, 2016) Chen, Ying; Cheng, Yafang; Ma, Nan; Wolke, Ralf; Nordmann, Stephan; Schüttauf, Stephanie; Ran, Liang; Wehner, Birgit; Birmili, Wolfram; van der Gon, Hugo A.C. Denier; Mu, Qing; Barthel, Stefan; Spindler, Gerald; Stieger, Bastian; Müller, Konrad; Zheng, Guang-Jie; Pöschl, Ulrich; Su, Hang; Wiedensohler, AlfredSea salt aerosol (SSA) is one of the major components of primary aerosols and has significant impact on the formation of secondary inorganic particles mass on a global scale. In this study, the fully online coupled WRF-Chem model was utilized to evaluate the SSA emission scheme and its influence on the nitrate simulation in a case study in Europe during 10–20 September 2013. Meteorological conditions near the surface, wind pattern and thermal stratification structure were well reproduced by the model. Nonetheless, the coarse-mode (PM1 − 10) particle mass concentration was substantially overestimated due to the overestimation of SSA and nitrate. Compared to filter measurements at four EMEP stations (coastal stations: Bilthoven, Kollumerwaard and Vredepeel; inland station: Melpitz), the model overestimated SSA concentrations by a factor of 8–20. We found that this overestimation was mainly caused by overestimated SSA emissions over the North Sea during 16–20 September. Over the coastal regions, SSA was injected into the continental free troposphere through an “aloft bridge” (about 500 to 1000 m above the ground), a result of the different thermodynamic properties and planetary boundary layer (PBL) structure between continental and marine regions. The injected SSA was further transported inland and mixed downward to the surface through downdraft and PBL turbulence. This process extended the influence of SSA to a larger downwind region, leading, for example, to an overestimation of SSA at Melpitz, Germany, by a factor of ∼ 20. As a result, the nitrate partitioning fraction (ratio between particulate nitrate and the summation of particulate nitrate and gas-phase nitric acid) increased by about 20 % for the coarse-mode nitrate due to the overestimation of SSA at Melpitz. However, no significant difference in the partitioning fraction for the fine-mode nitrate was found. About 140 % overestimation of the coarse-mode nitrate resulted from the influence of SSA at Melpitz. In contrast, the overestimation of SSA inhibited the nitrate particle formation in the fine mode by about 20 % because of the increased consumption of precursor by coarse-mode nitrate formation.
- ItemEvaluation of the size segregation of elemental carbon (EC) emission in Europe: Influence on the simulation of EC long-range transportation(München : European Geopyhsical Union, 2016) Chen, Ying; Cheng, Ya-Fang; Nordmann, Stephan; Birmili, Wolfram; van der Gon, Hugo A.C. Denier; Ma, Nan; Wolke, Ralf; Wehner, Birgit; Sun, Jia; Spindler, Gerald; Mu, Qing; Pöschl, Ulrich; Su, Hang; Wiedensohler, AlfredElemental Carbon (EC) has a significant impact on human health and climate change. In order to evaluate the size segregation of EC emission in the EUCAARI inventory and investigate its influence on the simulation of EC long-range transportation in Europe, we used the fully coupled online Weather Research and Forecasting/Chemistry model (WRF-Chem) at a resolution of 2 km focusing on a region in Germany, in conjunction with a high-resolution EC emission inventory. The ground meteorology conditions, vertical structure and wind pattern were well reproduced by the model. The simulations of particle number and/or mass size distributions were evaluated with observations at the central European background site Melpitz. The fine mode particle concentration was reasonably well simulated, but the coarse mode was substantially overestimated by the model mainly due to the plume with high EC concentration in coarse mode emitted by a nearby point source. The comparisons between simulated EC and Multi-angle Absorption Photometers (MAAP) measurements at Melpitz, Leipzig-TROPOS and Bösel indicated that the coarse mode EC (ECc) emitted from the nearby point sources might be overestimated by a factor of 2–10. The fraction of ECc was overestimated in the emission inventory by about 10–30 % for Russia and 5–10 % for Eastern Europe (e.g., Poland and Belarus). This incorrect size-dependent EC emission results in a shorter atmospheric life time of EC particles and inhibits the long-range transport of EC. A case study showed that this effect caused an underestimation of 20–40 % in the EC mass concentration in Germany under eastern wind pattern.
- ItemA parameterization of the heterogeneous hydrolysis of N2O5 for mass-based aerosol models: Improvement of particulate nitrate prediction(Katlenburg-Lindau : EGU, 2018) Chen, Ying; Wolke, Ralf; Ran, Liang; Birmili, Wolfram; Spindler, Gerald; Schröder, Wolfram; Su, Hang; Cheng, Yafang; Tegen, Ina; Wiedensohler, AlfredThe heterogeneous hydrolysis of N2O5 on the surface of deliquescent aerosol leads to HNO3 formation and acts as a major sink of NOx in the atmosphere during night-time. The reaction constant of this heterogeneous hydrolysis is determined by temperature (T), relative humidity (RH), aerosol particle composition, and the surface area concentration (S). However, these parameters were not comprehensively considered in the parameterization of the heterogeneous hydrolysis of N2O5 in previous mass-based 3-D aerosol modelling studies. In this investigation, we propose a sophisticated parameterization (NewN2O5) of N2O5 heterogeneous hydrolysis with respect to T, RH, aerosol particle compositions, and S based on laboratory experiments. We evaluated closure between NewN2O5 and a state-of-the-art parameterization based on a sectional aerosol treatment. The comparison showed a good linear relationship (R Combining double low line 0.91) between these two parameterizations. NewN2O5 was incorporated into a 3-D fully online coupled model, COSMO-Muscat, with the mass-based aerosol treatment. As a case study, we used the data from the HOPE Melpitz campaign (10-25 September 2013) to validate model performance. Here, we investigated the improvement of nitrate prediction over western and central Europe. The modelled particulate nitrate mass concentrations ([NO3-]) were validated by filter measurements over Germany (Neuglobsow, Schmücke, Zingst, and Melpitz). The modelled [NO3-] was significantly overestimated for this period by a factor of 5-19, with the corrected NH3 emissions (reduced by 50 %) and the original parameterization of N2O5 heterogeneous hydrolysis. The NewN2O5 significantly reduces the overestimation of [NO3-] by ∼ 35 %. Particularly, the overestimation factor was reduced to approximately 1.4 in our case study (12, 17-18 and 25 September 2013) when [NO3-] was dominated by local chemical formations. In our case, the suppression of organic coating was negligible over western and central Europe, with an influence on [NO3-] of less than 2 % on average and 20 % at the most significant moment. To obtain a significant impact of the organic coating effect, N2O5, SOA, and NH3 need to be present when RH is high and T is low. However, those conditions were rarely fulfilled simultaneously over western and central Europe. Hence, the organic coating effect on the reaction probability of N2O5 may not be as significant as expected over western and central Europe.
- 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.
- 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.
- ItemAerosol number-size distributions during clear and fog periods in the summer high Arctic: 1991, 1996 and 2001(Milton Park : Taylor & Francis, 2017) Heintzenberg, Jost; Leck, Caroline; Birmili, Wolfram; Wehner, Birgit; Tjernström, Michael; Wiedensohler, AlfredThe present study covers submicrometer aerosol size distribution data taken during three Arctic icebreaker expeditions in the summers of 1991, 1996 and 2001. The size distributions of all expeditions were compared in log-normally fitted form to the statistics of the marine number size distribution provided by Heintzenberg et al. (2004) yielding rather similar log-normal parameters of the modes. Statistics of the modal concentrations revealed strong concentration decreases of large accumulation mode particles with increasing length of time spent over the pack ice. The travel-time dependencies of both Aitken and ultrafine modes strongly indicate, as other studies did before, the occurrence of fine-particle sources in the inner Arctic. With two approaches evidence of fog-related aerosol source processeswas sought for in the data sets of 1996 and 2001 because they included fog drop size distributions. With increasing fog intensity modes in interstitial particle number concentrations appeared in particular in the size range around 80 nm that was nearly mode free in clear air. A second, dynamic approach revealed that Aitken mode concentrations increased strongly above their respective fog-period medians in both years before maximum drop numbers were reached in both years. We interpret the results of both approaches as strong indications of fog-related aerosol source processes as discussed in Leck and Bigg (1999) that need to be elucidated with further data from dedicated fog experiments in future Arctic expeditions in order to understand the life cycle of the aerosol over the high Arctic pack ice area.