ALBERT

Description: The effect of anthropogenic and biogenic organic particles on atmospheric glaciation processes is poorly understood. We use an optical microscopy (OM) setup to identify the ice nuclei (IN) active in immersion freezing (IMF) and deposition ice nucleation (DIN) within a large population of particles collected on a substrate from an ambient environment in central California dominated by urban and marine aerosols. Multi-modal micro-spectroscopy methods are applied to characterize the physicochemical properties and mixing state of the individual IN and particle populations to identify particle-type classes. The temperature onsets of water uptake occurred between 235–257 K at subsaturated conditions and the onsets of IMF proceeded at subsaturated and saturated conditions for 235–247 K, relevant for ice nucleation in mixed-phase clouds. Particles also took up water and nucleated ice between 226–235 K and acted as deposition IN with onset temperatures below 226 K, a temperature range relevant to cirrus cloud formation. The identified IN belong to the most common particle-type classes observed in the field samples: organic coated sea salt, and Na-rich, secondary, and refractory carbonaceous particles. Based on these observations, we suggest that the IN are not always particles with unique chemical composition and exceptional ice nucleation propensity; rather, they are common particles in the ambient particle population. The results suggest that particle-type abundance and total particle surface area, is also a crucial factor, in addition to particle-type ice nucleation efficiency, in determining ice formation within the particle population.

Description: The modern chemical industry uses heterogeneous catalysts in almost every production process. They commonly consist of nanometre-size active components (typically metals or metal oxides) dispersed on a high-surface-area solid support, with performance depending on the catalysts' nanometre-size features and on interactions involving the active components, the support and the reactant and product molecules. To gain insight into the mechanisms of heterogeneous catalysts, which could guide the design of improved or novel catalysts, it is thus necessary to have a detailed characterization of the physicochemical composition of heterogeneous catalysts in their working state at the nanometre scale. Scanning probe microscopy methods have been used to study inorganic catalyst phases at subnanometre resolution, but detailed chemical information of the materials in their working state is often difficult to obtain. By contrast, optical microspectroscopic approaches offer much flexibility for in situ chemical characterization; however, this comes at the expense of limited spatial resolution. A recent development promising high spatial resolution and chemical characterization capabilities is scanning transmission X-ray microscopy, which has been used in a proof-of-principle study to characterize a solid catalyst. Here we show that when adapting a nanoreactor specially designed for high-resolution electron microscopy, scanning transmission X-ray microscopy can be used at atmospheric pressure and up to 350 degrees C to monitor in situ phase changes in a complex iron-based Fisher-Tropsch catalyst and the nature and location of carbon species produced. We expect that our system, which is capable of operating up to 500 degrees C, will open new opportunities for nanometre-resolution imaging of a range of important chemical processes taking place on solids in gaseous or liquid environments.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉de Smit, Emiel -- Swart, Ingmar -- Creemer, J Fredrik -- Hoveling, Gerard H -- Gilles, Mary K -- Tyliszczak, Tolek -- Kooyman, Patricia J -- Zandbergen, Henny W -- Morin, Cynthia -- Weckhuysen, Bert M -- de Groot, Frank M F -- England -- Nature. 2008 Nov 13;456(7219):222-5. doi: 10.1038/nature07516.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19005551" target="_blank"〉PubMed〈/a〉

Description: The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brownlee, Don -- Tsou, Peter -- Aleon, Jerome -- Alexander, Conel M O'd -- Araki, Tohru -- Bajt, Sasa -- Baratta, Giuseppe A -- Bastien, Ron -- Bland, Phil -- Bleuet, Pierre -- Borg, Janet -- Bradley, John P -- Brearley, Adrian -- Brenker, F -- Brennan, Sean -- Bridges, John C -- Browning, Nigel D -- Brucato, John R -- Bullock, E -- Burchell, Mark J -- Busemann, Henner -- Butterworth, Anna -- Chaussidon, Marc -- Cheuvront, Allan -- Chi, Miaofang -- Cintala, Mark J -- Clark, B C -- Clemett, Simon J -- Cody, George -- Colangeli, Luigi -- Cooper, George -- Cordier, Patrick -- Daghlian, C -- Dai, Zurong -- D'Hendecourt, Louis -- Djouadi, Zahia -- Dominguez, Gerardo -- Duxbury, Tom -- Dworkin, Jason P -- Ebel, Denton S -- Economou, Thanasis E -- Fakra, Sirine -- Fairey, Sam A J -- Fallon, Stewart -- Ferrini, Gianluca -- Ferroir, T -- Fleckenstein, Holger -- Floss, Christine -- Flynn, George -- Franchi, Ian A -- Fries, Marc -- Gainsforth, Z -- Gallien, J-P -- Genge, Matt -- Gilles, Mary K -- Gillet, Philipe -- Gilmour, Jamie -- Glavin, Daniel P -- Gounelle, Matthieu -- Grady, Monica M -- Graham, Giles A -- Grant, P G -- Green, Simon F -- Grossemy, Faustine -- Grossman, Lawrence -- Grossman, Jeffrey N -- Guan, Yunbin -- Hagiya, Kenji -- Harvey, Ralph -- Heck, Philipp -- Herzog, Gregory F -- Hoppe, Peter -- Horz, Friedrich -- Huth, Joachim -- Hutcheon, Ian D -- Ignatyev, Konstantin -- Ishii, Hope -- Ito, Motoo -- Jacob, Damien -- Jacobsen, Chris -- Jacobsen, Stein -- Jones, Steven -- Joswiak, David -- Jurewicz, Amy -- Kearsley, Anton T -- Keller, Lindsay P -- Khodja, H -- Kilcoyne, A L David -- Kissel, Jochen -- Krot, Alexander -- Langenhorst, Falko -- Lanzirotti, Antonio -- Le, Loan -- Leshin, Laurie A -- Leitner, J -- Lemelle, L -- Leroux, Hugues -- Liu, Ming-Chang -- Luening, K -- Lyon, Ian -- Macpherson, Glen -- Marcus, Matthew A -- Marhas, Kuljeet -- Marty, Bernard -- Matrajt, Graciela -- McKeegan, Kevin -- Meibom, Anders -- Mennella, Vito -- Messenger, Keiko -- Messenger, Scott -- Mikouchi, Takashi -- Mostefaoui, Smail -- Nakamura, Tomoki -- Nakano, T -- Newville, M -- Nittler, Larry R -- Ohnishi, Ichiro -- Ohsumi, Kazumasa -- Okudaira, Kyoko -- Papanastassiou, Dimitri A -- Palma, Russ -- Palumbo, Maria E -- Pepin, Robert O -- Perkins, David -- Perronnet, Murielle -- Pianetta, P -- Rao, William -- Rietmeijer, Frans J M -- Robert, Francois -- Rost, D -- Rotundi, Alessandra -- Ryan, Robert -- Sandford, Scott A -- Schwandt, Craig S -- See, Thomas H -- Schlutter, Dennis -- Sheffield-Parker, J -- Simionovici, Alexandre -- Simon, Steven -- Sitnitsky, I -- Snead, Christopher J -- Spencer, Maegan K -- Stadermann, Frank J -- Steele, Andrew -- Stephan, Thomas -- Stroud, Rhonda -- Susini, Jean -- Sutton, S R -- Suzuki, Y -- Taheri, Mitra -- Taylor, Susan -- Teslich, Nick -- Tomeoka, Kazu -- Tomioka, Naotaka -- Toppani, Alice -- Trigo-Rodriguez, Josep M -- Troadec, David -- Tsuchiyama, Akira -- Tuzzolino, Anthony J -- Tyliszczak, Tolek -- Uesugi, K -- Velbel, Michael -- Vellenga, Joe -- Vicenzi, E -- Vincze, L -- Warren, Jack -- Weber, Iris -- Weisberg, Mike -- Westphal, Andrew J -- Wirick, Sue -- Wooden, Diane -- Wopenka, Brigitte -- Wozniakiewicz, Penelope -- Wright, Ian -- Yabuta, Hikaru -- Yano, Hajime -- Young, Edward D -- Zare, Richard N -- Zega, Thomas -- Ziegler, Karen -- Zimmerman, Laurent -- Zinner, Ernst -- Zolensky, Michael -- New York, N.Y. -- Science. 2006 Dec 15;314(5806):1711-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, University of Washington, Seattle, WA 98195, USA. brownlee@astro.washington.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17170289" target="_blank"〉PubMed〈/a〉

Description: Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sandford, Scott A -- Aleon, Jerome -- Alexander, Conel M O'd -- Araki, Tohru -- Bajt, Sasa -- Baratta, Giuseppe A -- Borg, Janet -- Bradley, John P -- Brownlee, Donald E -- Brucato, John R -- Burchell, Mark J -- Busemann, Henner -- Butterworth, Anna -- Clemett, Simon J -- Cody, George -- Colangeli, Luigi -- Cooper, George -- D'Hendecourt, Louis -- Djouadi, Zahia -- Dworkin, Jason P -- Ferrini, Gianluca -- Fleckenstein, Holger -- Flynn, George J -- Franchi, Ian A -- Fries, Marc -- Gilles, Mary K -- Glavin, Daniel P -- Gounelle, Matthieu -- Grossemy, Faustine -- Jacobsen, Chris -- Keller, Lindsay P -- Kilcoyne, A L David -- Leitner, Jan -- Matrajt, Graciela -- Meibom, Anders -- Mennella, Vito -- Mostefaoui, Smail -- Nittler, Larry R -- Palumbo, Maria E -- Papanastassiou, Dimitri A -- Robert, Francois -- Rotundi, Alessandra -- Snead, Christopher J -- Spencer, Maegan K -- Stadermann, Frank J -- Steele, Andrew -- Stephan, Thomas -- Tsou, Peter -- Tyliszczak, Tolek -- Westphal, Andrew J -- Wirick, Sue -- Wopenka, Brigitte -- Yabuta, Hikaru -- Zare, Richard N -- Zolensky, Michael E -- New York, N.Y. -- Science. 2006 Dec 15;314(5806):1720-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astrophysics Branch, NASA-Ames Research Center, Moffett Field, CA 94035, USA. ssandford@mail.arc.nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17170291" target="_blank"〉PubMed〈/a〉

Description: The fine particles serving as cloud condensation nuclei in pristine Amazonian rainforest air consist mostly of secondary organic aerosol. Their origin is enigmatic, however, because new particle formation in the atmosphere is not observed. Here, we show that the growth of organic aerosol particles can be initiated by potassium-salt-rich particles emitted by biota in the rainforest. These particles act as seeds for the condensation of low- or semi-volatile organic compounds from the atmospheric gas phase or multiphase oxidation of isoprene and terpenes. Our findings suggest that the primary emission of biogenic salt particles directly influences the number concentration of cloud condensation nuclei and affects the microphysics of cloud formation and precipitation over the rainforest.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pohlker, Christopher -- Wiedemann, Kenia T -- Sinha, Barbel -- Shiraiwa, Manabu -- Gunthe, Sachin S -- Smith, Mackenzie -- Su, Hang -- Artaxo, Paulo -- Chen, Qi -- Cheng, Yafang -- Elbert, Wolfgang -- Gilles, Mary K -- Kilcoyne, Arthur L D -- Moffet, Ryan C -- Weigand, Markus -- Martin, Scot T -- Poschl, Ulrich -- Andreae, Meinrat O -- New York, N.Y. -- Science. 2012 Aug 31;337(6098):1075-8. doi: 10.1126/science.1223264.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biogeochemistry Department, Max Planck Institute for Chemistry, Mainz 55020, Germany. c.pohlker@mpic.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22936773" target="_blank"〉PubMed〈/a〉

Description: Surface- and volume-limited chemical reactions on and in atmospheric aerosol particles cause growth while changing organic composition by 13 to 24% per day. Many of these particles contain carbonaceous components from mineral dust and combustion emissions in Africa, Asia, and North America and reveal reaction rates that are three times slower than those typically used in climate models. These slower rates for converting from volatile or hydrophobic to condensed and hygroscopic organic compounds increase carbonaceous particle burdens in climate models by 70%, producing organic aerosol climate forcings of as much as -0.8 watt per square meter cooling and +0.3 watt per square meter warming.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maria, Steven F -- Russell, Lynn M -- Gilles, Mary K -- Myneni, Satish C B -- New York, N.Y. -- Science. 2004 Dec 10;306(5703):1921-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemical Engineering, Princeton University, Princeton, NJ 08544, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15591199" target="_blank"〉PubMed〈/a〉

Description: [1]  Ambient particles and the dry residuals of mixed-phase cloud droplets and ice crystals were collected during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) near Barrow, Alaska, in spring of 2008. The collected particles were analyzed using Computer Controlled Scanning Electron Microscopy with Energy Dispersive X-ray analysis (CCSEM/EDX) and Scanning Transmission X-ray Microscopy coupled with Near Edge X-ray Absorption Fine Structure spectroscopy (STXM/NEXAFS) to identify physico-chemical properties that differentiate cloud-nucleating particles from the total aerosol population. A wide range of individually mixed components was identified in the ambient particles and residuals including organic carbon compounds, inorganics, carbonates, and black carbon. Our results show that cloud droplet residuals differ from the ambient particles in both size and composition, suggesting that both properties may impact the cloud-nucleating ability of aerosols in mixed-phase clouds. The percentage of residual particles which contained carbonates (47%) was almost four times higher than in ambient samples. Residual populations were also enhanced in sea salt and black carbon and reduced in organic compounds relative to the ambient particles. Further, our measurements suggest that chemical processing of aerosols may improve their cloud-nucleating ability. Comparison of results for various time periods within ISDAC suggests that the number and composition of cloud-nucleating particles over Alaska can be influenced by episodic events bringing aerosols from both the local vicinity and as far away as Siberia.

Description: The energy flows in Earth’s natural and modified climate systems are strongly influenced by the concentrations of atmospheric particulate matter (PM). For predictions of concentration, equilibrium partitioning of semivolatile organic compounds (SVOCs) between organic PM and the surrounding vapor has widely been assumed, yet recent observations show that organic PM...

Description: We use a Lagrangian dispersion model driven by a mesoscale model with four-dimensional data assimilation to simulate the dispersion of elemental carbon (EC) over a region encompassing Mexico City and its surroundings. The region was the study domain for the 2006 MAX-MEX experiment, which was a component of the MILAGRO campaign. The results are used to identify periods when biomass burning was likely to have had a significant impact on the concentrations of elemental carbon at two sites, T1 and T2, downwind of the city, and when emissions from the Mexico City Metropolitan Area (MCMA) were likely to have been more important. They are also used to estimate the median ages of EC affecting the specific absorption of light, αABS, at 870 nm as well as to identify periods when the urban plume from the MCMA was likely to have been advected over T1 and T2. Median EC ages at T1 and T2 are substantially larger during the day than at night. Values of αABS at T1, the nearer of the two sites to Mexico City, were smaller at night and increased rapidly after mid-morning, peaking in the mid-afternoon. The behavior is attributed to the coating of aerosols with substances such as sulfate or organic carbon during daylight hours, but such coating appears to be limited or absent at night. Evidence for this is provided by scanning electron microscopy images of aerosols collected at the sampling sites. During daylight hours the values of αABS did not increase with aerosol age for median ages in the range of 1–4 h. There is some evidence for absorption increasing as aerosols were advected from T1 to T2 but the statistical significance of that result is not strong.