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Timothy Bertram: Then and Now / 2011 Early Career Award Winner


Atmospheric chemistry plays a central role in regulating concentrations of air pollutants, greenhouse gases, and aerosol particles. However, it is not often clear how detailed chemical mechanisms explored in the laboratory translate to real-world scenarios, or how best to represent complex chemical processes in chemistry and climate models.

This challenge is particularly difficult when dealing with chemical reactions that occur at the surface of complex environmental interfaces such as aerosol particles, cloud droplets, or the ocean surface. The support that I received from DOE's Office of Science permitted me to explore a line of research that merged traditional laboratory techniques with field analyses to directly probe heterogeneous and multiphase reactions occurring on atmospheric aerosol particles in the field.

Personally, this award led to new connections within the atmospheric science community that provided critical perspectives on my research ideas and how they connect to the broader objectives of the community of researchers.

This award also gave me the latitude to think broadly and creatively about questions of importance that I wanted to steer my research program towards. Now, as a professor of chemistry and atmospheric and oceanic sciences, I have research projects that span from detailed chemical mechanisms explored in the laboratory to large-scale field projects.

The support that I received as a DOE Early Career awardee gave me the perspective to connect these two subfields and has shaped my perspective on the field of atmospheric chemistry.


Timothy Bertram is a professor in the Department of Chemistry and an affiliate professor in the Department of Atmospheric and Oceanic Sciences and the Environmental Chemistry and Technology graduate program at the University of Wisconsin – Madison.


The Early Career Research Program provides financial support that is foundational to early career investigators, enabling them to define and direct independent research in areas important to DOE missions. The development of outstanding scientists and research leaders is of paramount importance to the Department of Energy Office of Science. By investing in the next generation of researchers, the Office of Science champions lifelong careers in discovery science.

For more information, please go to the Early Career Research Program.


In situ Measurements of Heterogeneous Reactions on Ambient Aerosol Particles: Impacts on Atmospheric Chemistry and Climate

Heterogeneous reactions, occurring between gases and aerosol particles, alter the climate‐relevant properties of aerosols and catalyze reaction processes that are energetically unfavorable in the gas phase. The objective of this project is to identify the mechanistic drivers that control the variability in heterogeneous aerosol processes through direct in situ measurement of reaction kinetics on ambient aerosol particles.

The heterogeneous reactivity of complex, ambient aerosol particles will be investigated to determine: (1) how laboratory investigations of heterogeneous processes conducted on model, simple systems represent the real atmosphere, (2) the impact of heterogeneous processes on ambient particle hygroscopicity and optical properties, and (3) the uptake kinetics for a host of atmospheric trace gases as a function of particle composition and phase.

The results of these investigations will be used to directly improve the representation of heterogeneous processes in global climate models.


O.S. Ryder, A.P. Ault, J.F. Cahill, T.L. Guasco, T.P. Riedel, L.A. Cuadra-Rodriguez, C.J. Gaston, E. Fitzgerald, C. Lee, K.A. Prather, T.H. Bertram, “On the role of particle inorganic mixing state in the reactive uptake of N2O5 to ambient aerosol particles.” Environ. Sci. Technol 48 (3), 1618 (2014). [DOI: 10.1021/es4042622:10.1021/es4042622]


Additional profiles of the Early Career Research Program award recipients can be found at

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Sandra Allen McLean is a Communications Specialist in the Office of Science, Office of Communications and Public Affairs