Cooperative Institute for Research in Environmental Sciences

Margaret Tolbert Group

Margaret Tolbert Group

We are a research group in the department of Chemistry and CIRES at the University of Colorado at Boulder. Our research is aimed at contributing to a better understanding of the Earth's complex atmosphere. Specifically, work in our group specializes in understanding atmospheric heterogeneous chemistry. For example, the importance of heterogeneous chemistry in catalyzing stratospheric ozone loss has been firmly established. In the case of the ozone hole, reactions on polar stratospheric clouds (PSCs) are responsible for repartitioning chlorine reservoir species into photochemically active species capable of catalytically destroying ozone. However, significant questions still remain as to the composition, phase, nucleation mechanisms, and surface chemistry of PSCs. Traditionally, work in our group has been aimed at answering these questions.

Today, the research in our group has expanded in an attempt to answer similar questions about cirrus clouds and other particulate matter that exist in the troposphere. Currently, our research explores the chemistry of tropospheric aerosols, and the impact of such aerosols on climate and visibility. Finally, we are also probing aerosols in other planetary atmospheres and studying the possible role of aerosols on early Earth as life was developing. Research in our group is funded primarily through NASA and NSF.

My interests are in the area of heterogeneous atmospheric chemistry, focusing on the chemical, physical, and optical properties of atmospheric aerosols.  In addition to fundamental studies of particles, we are also exploring how atmospheric aerosols impact current problems such as stratospheric ozone depletion, global climate change, urban smog, and visibility degradation.

Research in the Tolbert group is not limited to studies of atmospheric aerosols on the current-day Earth.  We are also probing the particles that might have been present at the earliest times in Earth’s history.  We are interested in how these particles might have impacted the climate of early Earth and the development of life on Earth.  As a parallel to early Earth, we are also studying aerosols and clouds on other planetary bodies such as Mars and Saturn’s moon Titan.

Our work is primarily laboratory based, but involves collaborations with theory teams and those involved in fieldwork.  Our primary support comes from the National Science Foundation and NASA.

Current Projects

Understanding oxygen incorporation into planetary atmospheric aerosols

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Optical Properties of Secondary Organic Aerosol

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Liquid water on Mars? The formation and stability of aqueous salt solutions on present day Mars

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Laboratory Studies of Titan and Early Earth Tholins

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Heterogeneous nucleation studied in a long working-distance optical trap

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NASA Mars Rover Team - Dr. Raina Gough has been selected to be part of a team of 28 scientists to work on NASA's Curiosity Rover in Mars.  Her laboratory studies on deliquescence, the process where a crystalline salt picks up atmoshperic water and turn into a solution, has shown that briney solutions can be stable and possibly exist for certain times on the surface of Mars.  If salty solutions exist on Mars, it would mean that liquid water, which is essential to life as we know it, is also present.  It is known that water exists on the surface of Mars, but currently only ice and water vapor (in the form of humidity) has been confirmed.  Liquid water has yet to be confirmed nor encounted by the Curiosity Rover.  Raina's work will provide more insight to the possibility of liquid water on Mars and potentially to life on Mars.  For more informatio check out these articles from CIRES and NASA about Raina and the science team for Curiosity.     

Recent Graduate - Raea Hicks.  A recent graduate of the Tolbert group, Raea's research focused on understanding the conversion of planetary atmospheric gases into aerosols.  To do this, she first made aerosol analogs by initiating photochemistry in gas mixtures relevant to the atmospheres of Titan and early Earth, then analyzed the products in situ with a specialized instrument called an aerosol mass spectrometer (AMS).  Specifically, she used isotopic labeling to determine the roles played by CH4 and CO2 in contributing carbon to early Earth aerosol analogs, and performed studies to deduce the role of pressure in nitrogen incorporation into Titan aerosol analogs.  As each study involved a different non-standard use of the AMS, Raea created new techniques to perform the experiments and analyze the data.  Now a post-doc at the Pacific Northwest National Laboratory, Raea leverages her expertise in non-standard AMS applications to address questions related to soil science.  In particular, she hopes to discover factors that control the conversion of carbon from soil organic matter to greenhouse gases.

Where are they now?  Dr. Danielle Nuding has taken a position as a Systems Engineer at the Jet Propulsion Laboratory in Pasadena, CA. Dr. Nuding will be working on mission development for assigned JPL flight projects, which will include developing systems and mission level architectures. Dr. Gregg Schill was awarded a National Science Foundation Postdoctoral Research Fellowship and will be working with Prof. Paul DeMott at Colorado State University in Fort Collins, CO. Dr. Schill will be continuing ice nucleation studies, but on ambient aerosol from biomass burning and fossil fuel combustion. Dr. Kyle Zarzana will join Dr. Steve Brown's group at the NOAA Earth System Research Laboratory in Boulder, CO. Dr. Zarzana will be using cavity enhanced spectroscopy to study glyoxal and other traces gases.

Margaret Tolbert Named CU Distinguished Professor
The University of Colorado Board of Regents awarded Margaret Tolbert, Ph.D., a Fellow of the Cooperative Institute for Research in Environmental Sciences (CIRES), and two other CU professors the university’s highest faculty honor, designation as Distinguished Professor, Friday, Sept., 17, 2010.  Distinguished Professors are CU faculty members who are leaders in their fields and are recognized for their outstanding contributions in teaching, research and distinguished scholarship or creative work. To date, 56 professors across the CU system hold the title.

Rescent Publications

Primm K.M., R.V. Gough, and M.A. Tolbert, Freezing of perchlorate and chloride brines under Mars-relevant conditions, Geochimica et Cosmochimica Acta., Under Review.

Gough R.V., V.F. Chevrier, and M.A. Tolbert (2016), Formation of liquid water at low temperatures via the deliquescence of calcium chloride: Implications for Antarctica and Mars, Planetary and Space Science, 131, 79-87, doi: 10.1016/j.pss.2016.07.006

Hasenkopf C.A., D.P. Veghte, G.P. Schill, S. Lodoysamba, M.A. Freedman, and M.A. Tolbert (2016), Ice nucleation, shape, and composition of aerosol particles in one of the most polluted cities in the world: Ulaanbaatar, Mongolia, Atmos. Env., 139, 222-229, doi: 10.1016/j.atmosenv.2016.05.037

Davis R.D., S. Lance, J.A. Gordon, S.B. Ushijima, and M.A. Tolbert (2015), Contact efflorescence as a pathway for crystallization of atmospherically relevant particles, PNAS, 112, 15815-15820, doi: 10.1073/pnas.1522860113

Davis R.D., S. Lance, J.A. Gordon, and M.A. Tolbert (2015), Long Working-Distance Opticall Trap for in Situ Analysis of Contact-Induced Phase Transformations, Analytical Chemistry, 87, 6186-6194, doi:10.1021/acs.analchem.5b00809.

Hicks R.K., D.A. Day, J.L. Jimenez, and M.A. Tolbert (2015), Elemental Analysis of Complex Organic Aerosol Using Isotopic Labeling and Unit-Resolution Mass Spectrometry, Analytical Chemistry, 87, 2741-2747, doi:10.1021/ac504014g.

Nuding D.L. , R.D. Davis, R.V. Gough, and M.A. Tolbert (2015), The aqueous stability of Mars salt analog: Instant Mars, J. Geophys. Res-Planets, 120, 588-598, doi:10.1002/2014JE004722

Schill G.P., K. Genareau, and M.A. Tolbert (2015), Deposition and immersion-mode nucleation of ice by three distinct samples of volcanic ash, Atmos. Chem. Phys., 15, 7523-7536, doi:10.5194/acp-15-7523-2015

Hiranuma N., S. Augustin-Bauditz, H. Bingermer, C. Budke, J. Curtius, A. Danielczok, K. Diehl, K. Dreischmeier, M. Ebert, F. Frank, N. Hoffmann, K. Kandler, A. Kiselev, T. Koop, T. Leisner, O. Mohler, B. Nillius, A. Peckhaus, D. Rose, S. Weinbruch, H. Wex, Y. Boose, P.J. DeMott, J.D. Hader, T.C.J. Hill, Z.A. Kanji, G. Kulkarni, E.J.T. Levin, C.S. McCluskey, M. Murakami, B.J. Murray, D. Niedermeier, M.D. Petters, D. O’Sulllivan, A. Saito, G.P. Schill, T. Taijiri, M.A. Tolbert, A. Welti, T.F. Whale, T.P. Wright, and K. Yamashita (2015), A comprehensive laboratory study on the immersion freezing behavior of illite NX particles: a comparison of 17 ice nucleation measurement techniques, Atmos. Chem. Phys., 15 2589-2518, doi:10.5194/acp-15-2489-2015

Schill G.P. and M.A. Tolbert (2014), Heterogeneous Ice Nucleation on Simulated Sea-Spray Aerosol Using Raman Microscopy, J. Phys. Chem. C., 118, 29234-29241, doi:10.1021/jp505379j.

Nuding D.L., E.G. Rivera-Valentin, R.D. Davis, R.V. Gough, V.F. Chevrier, and M.A. Tolbert (2014), Deliquescence and efflorescence of calcium perchlorate: An investigation of stable aqueous solutions relevant to Mars, Icarus, 243, 420-428, doi:10.1016/j.icarus.2014.08.036

Zarzana K.J., C.D. Cappa, and M.A. Tolbert (2014), Sensitivity of Aerosol Refractive Index Retrievals Using Optical Spectroscopy, Aerosol Sci. Tech., 48, 1133-1144, doi:10.1080/02786826.2014.963498

Thalman R., K.J. Zarzana, M.A. Tolbert, and R. Volkamer (2014), Rayleigh scattering cross-section measurements of nitrogen, argon, oxygen and air, Journal of Quantitative Spectroscopy and Radiative Transfer, 147, 171-177, doi:10.1016/j.jqsrt.2014.05.030. 

Cable M.L., S.M. Hörst, C. He, A.M. Stockton, M.F. Mora, M.A. Tolbert, M.A. Smith, and P.A. Willis (2014), Identification of primary amines in Titan tholins using microchip nonaqueous capillary electrophoresis, Earth Planet. Sci. Lett., 403, 99-107, doi:10.1016/j.epsl.2014.06.028

Sihvonen S.K., G.P. Schill, N.A. Lyktey, D.P. Veghte, M.A. Tolbert, and M.A. Freedman (2014), Chemical and Physical Transformations of Aluminosilicate Clay Minerals Due to Acid Treatment and consequences for Heterogeneous Ice Nucleation, J. Phys. Chem. A., 118, 8787-8796, doi:10.1021/jp504846g.

Robinson C.B., G.P. Schill, and M.A. Tolbert (2014), Optical growth of highly viscous organic/sulfate particles, J. Atmos. Chem., 71, 145-156, doi:10.1007/s10874-014-9287-8

Gough R.V., V.F. Chevrier, and M.A. Tolbert (2014), Formation of aqueous solutions on Mars via deliquescence of chloride-perchlorate binary mixtures, Earth and Planetary Science Letters, 393, 73-82, doi:10.1016/j.epsl.2014.02.002. 

Yoon Y.H., S.M. Hörst, R.K. Hicks, R. Li, J.A. de Gouw, and M.A. Tolbert (2014), The role of benzene photolysis in Titan haze formation, Icarus, 233, 233-241, doi:10.1016/j.icarus.2014.02.006. 

Hawkins L.N., M.J. Baril, N. Sedhi, M.G. Galloway, D.O. De Haan, G.P. Schill, and M.A. Tolbert (2014), Formation of semisolid, oligomerized aqueous SOA: Lab simulations of cloud processing, Environmental Science and Technology, 48, 2273-2280, doi:10.1021/es4049626. 

Schill G.P., D.O. De Haan, and M.A. Tolbert (2014), Heterogeneous ice nucleation on simulated secondary organic aerosol, Environmental Science and Technology, 48, 1675-1682, doi:10.1021/es4046428. 

Hörst S.M. and M.A. Tolbert (2014), The effect of carbon monoxide on planetary haze formation, Astrophysical Journal, 781, 53, doi:10.1088/0004-637X/781/1/53.

Robinson C.B., G.P. Schill, K.J. Zarzana, and M.A. Tolbert (2014), Impact of organic coatings on optical growth of ammonium sulfate particles, Environmental Science and Technology, 47, 13339-13346, doi:10.1021/es4023128.  

Updated 20 Dec 2016

Qualified students interested in becoming a member of the Tolbert group should apply to the University of Colorado Boulder through the Department of Chemistry and Biochemistry. Details can be found on the Department's web site on Graduate Programs.

For more information about the Analytical, Environmental, and Atmospheric Division, please see the division webpage


If you’re already a CU student and interested in our group, feel free to contact anyone in the group for more information about us or to attend our weekly meetings on Tuesday 1 - 3pm in Ekley S274!



University of Colorado
CIRES Building - Room 318
Campus Box 216
University of Colorado
Boulder, CO  80309-0216

Phone Numbers

Student Office: 303-492-1433
Student Lab: 303-492-1199
Maggie's Office: 303-492-3179
CIRES FAX: 303-492-1149

Campus Location
The Tolbert lab and offices are located on the first floor of the CIRES building. Enter the atrium in the Ekeley Building from the south and turn right (east) at the top of the stairs. For directions to the CIRES building, go to Directions to CIRES.

Student Offices: CIRES 146, 149, 152
Student Lab: CIRES 137, 138