By Sarah Petters, Aarhus University
How did you get involved in aerosol science?
BB: It was luck of the draw! I was considering a PhD and knew I enjoyed analytical and environmental chemistry. The department head at my undergraduate institution, Bucknell, recommended Murray Johnston (also a Bucknell graduate, but he graduated more than a few years before me!) as a potential PhD supervisor because he had done great work in mass spectrometry, and I found mass spectrometry to be an exciting area with lots of different potential career trajectories. It just happened that Murray’s work was on mass spectrometry of aerosols.
What ideas and people have influenced you?
BB: I have been fortunate to have had many mentors and role models throughout my academic career. My undergraduate adviser, Molly McGuire, is the first person I conducted research with (on redox chemistry in clay minerals). She encouraged me to apply to graduate school, which I was unsure about pursuing at the time. I’m glad she was so supportive, as graduate school was a very good decision! Obviously, Murray Johnston has been a significant influence. The research conducted in his group was so varied and so creative that it provided me with many wonderful opportunities, from laboratory experiments to field studies. These experiences benefited me in the long term with respect to how I think about a scientific problem and what skill sets I can bring to bear on that challenge. I was fortunate to have other supportive mentors at Delaware, including Doug Ridge and Burnaby Munson, who provided additional grounding in the fundamentals of mass spectrometry. When I moved to Bristol for postdoctoral studies with Jonathan Reid, I was motivated by his research being the opposite of everything I had done up to that point while still remaining in the same field. Whereas during my graduate work I studied the chemical composition and reactivity of clusters and nanoparticles using mass spectrometry, for my postdoctoral work I studied the physical properties of supermicron droplets using optical and electrodynamic trapping approaches. The common theme was single particle measurements and doing basic science to answer important scientific questions. Along the way, Peter McMurry gave me some supportive and useful advice, and am fortunate I got to know him during a field campaign. Nowadays, I am thankful for the people I collaborate with, including Nonne Prisle, Cari Dutcher, Hallie Chelmo, Coty Jen, and Kevin Wilson, as they all have very different ways of thinking about problems, which has helped me to frame my current work in different contexts.
What are you known for?
BB: I have been fortunate to work in several exciting areas of aerosol research. The first scientific problem I addressed, as a graduate student, was to understand the chemical mechanism of atmospheric new particle formation. This process happens everywhere and contributes about 50% of cloud condensation nuclei. However, predicting when and where new particle formation will occur is challenging, as the chemical mechanism is not fully understood, though molecules like sulfuric acid, ammonia, amines, and organics are involved. My work showed that amines can play a central role in new particle formation. Essentially, atmospheric clusters are sponges for amines – they will rapidly replace any ammonia within them. Moreover, through field measurements, we were able to demonstrate closure in accounting for sulfuric acid’s contribution to this process. Along the way, we discovered some additional interesting pieces of information about atmospheric particles, such as silicon being present in a substantial fraction of atmospheric nanoparticles (probably due to siloxane emissions). During the pandemic, my research interests took a bit of a detour to study respiratory aerosols emission during breathing, speaking, exercise and the performing arts, and clinical procedures. This period was fast-paced and exhausting, but in the end the results altered government policy and led to changes in the National Health Service’s infection control manual. Now I am transitioning back to my regularly scheduled research, which right now is trying to better understand composition and chemistry at the surfaces of particles and droplets. Atmospheric particles have extremely high surface area to volume ratios, and we don’t yet fully appreciate how this impacts chemical reactions or even surface-bulk partitioning in these microscopic systems.
What is way harder than you thought it would be?
BB: Starting my group was much harder than I expected. The UK system is different from the US system in that in the UK you can get yourself funded, but you rarely will get a startup package to bring on people or purchase equipment. As a result, it took several years just to gain enough funding to bring on multiple graduate students and buy major equipment. Although the specifics are different for everybody, the general challenge is the same regardless of where you are. Eventually (hopefully!) it all works out.
What questions do you think will be interesting in the near future?
BB: Lately, I have been really interested in the role of pH and what pH really means when you get down to the level of a single particle. It just seems there are some really interesting and challenging fundamental chemical questions to explore in this area. I have not myself done any work on this, but I am enjoying following developments in the literature. In particular, I’ve found Andy Ault’s work particularly helpful in thinking about the problem.
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