Included in Issue: Spring 2023

Scientist Spotlight

By Dong Gao, Yale University
Lu Xu, incoming Assistant Professor
Energy, Environmental & Chemical Engineering
Washington University in St. Louis

How did you get involved in the aerosol science community?

The first time I heard the word “aerosol” was actually my first semester in grad school. I grew up in China and “aerosol” is not a common word that we learn at school. When I was admitted to the chemical engineering department at Georgia Tech, I originally planned to study catalysis. As part of the advisory selection process, I attended a 15-min research introductory presentation by Sally Ng, who just started as an assistant professor at Georgia Tech. She talked about aerosol, air quality, etc. What stroke me the most was a statement that Beijing has the worst air quality in the world. I was initially a bit “annoyed”, because despite the air quality in Beijing is notorious, it is not the worst. After a second, a contrary thought hit me that why I was “annoyed” by which city has the worst air quality. The goal should be improving the air quality in China as well as other places around the world. Her presentation also educated me the importance of air quality. After continual conversation with Sally and learning about the research area, I decided to study atmospheric chemistry.

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Which people or programs in our field have been the most influential to you and your path, or who have most influenced your ideas about aerosol research?

I am fortunate to work with several brilliant and exceptional scientists in our field. My PhD advisor Sally Ng really opened my door to atmospheric chemistry and broadly research. She taught me every aspect of research, like operating instrument, conducting chamber experiment, collaborating with others, writing papers, reviewing manuscripts, presenting at conferences, writing proposals, etc. I also enjoyed working with her in the lab to learn how to use Swageloks, leak check, and many other detailed skills. Basically, she shaped me as a researcher. At Caltech, I extremely enjoyed working with Paul Wennberg and John Crounse. They are truly insightful. It happened several times that a 5min conversation at lunch enlightened me to solve a question that had bothered me for weeks. I was also amazed and inspired by the tremendous efforts they spent over more than a decade to thoroughly investigate the chemistry of a single molecule, isoprene. For example, to study the hydrolysis of isoprene hydroxy nitrates, the Caltech group developed a novel instrument, synthesized standards, and conducted both laboratory and field measurements. Each component in this comprehensive project took years to accomplish. Ground-breaking findings are not discovered at one stroke. Finally, the NOAA chemical science laboratory is quite different from university labs. NOAA, as a national lab, has the resource to conduct large and collaborative campaigns. It is a quite valuable experience to learn from my advisor Carsten Warneke about how to organize and coordinate field campaigns.

What is the most interesting research contribution you’ve made so far?

I have worked on a number of research topics using different tools, to enrich my knowledge base. My PhD work on the interaction of biogenic and anthropogenic emissions on organic aerosol formation in the southeast U.S. is quite interesting. We did a lot of field measurements in the southeast U.S. and presented direct observational evidence on influence of sulfate and NOx on SOA formation from the oxidation of isoprene and monoterpenes. Later, I shifted focus from field measurements to laboratory studies at Caltech. Based on a set of well-designed experiments, I managed to experimentally quantify the isomerization rates of alpha-pinene peroxy radicals (RO2). Such kinetic data are rare in the literature, but they are critical to diagnose the VOC oxidation mechanism and to understand the oxidation products. In similar chamber experiments, I also investigate the chemical mechanism and quantify product yields in the oxidation of monoterpenes and aromatics. These fundamental laboratory studies provide essential parametrizations for use in atmospheric models. At NOAA, I devoted most of the time to developing Chemical Ionization Mass Spectrometry (CIMS) using a novel reagent ion NH4+. It is a highly versatile reagent ion for measurements of a wide range of oxygenated organic compounds. This method expands our capability to explore the unknown atmospheric composition.

What challenges were completely unexpected as you began and continue to grow your own research group?

I haven’t officially started my own group yet, but I anticipate a number of challenges based on conversations with my mentors and peers. Recruiting students could be challenging. Working with an early-career professor is like joining a start-up company. It could be riskier than joining a well-established group/company. But often high risk, high reward. Another expected challenge is time management. I expect to undertake a variety of tasks, including teaching, mentoring, writing, reading, department service, etc. It would take me some time to develop a system to compartmentalize my time and to conduct these activities efficiently. There are also many evident challenges, like work-life balance, team management, proposal writing, etc. I hope there are not too many unexpected challenges.

Are there new research directions that you see as particularly important or interesting?

I think instrument development is particularly important. Looking through the history of atmospheric chemistry, many ground-breaking discoveries in our field were enabled by the development of novel instrument that has advanced measurement capabilities. However, the instrument development is time-consuming and risky. Not many groups in universities work on instrument development. Using commercial instrument is more prevalent, because commercial instruments are robust and have speedy custom service. But to me, it is alarming if universities cultivate students who only know how to operate the instrument, instead of students who master instrument design, fabrication, and automation.

This Issue’s Newsletter Committee:

Editor | Krystal Pollitt, Yale UniversitySenior Assistant Editor | Justice Archer, University of BristolJunior Assistant Editor | Dong Gao, Yale UniversityGuest Contributor | Sarah Petters, Aarhus University