First Month: Method Development

Before we got the photolysis lamp (a xenon arc lamp), we did some preliminary trials by exposing the brown carbon to sunlight the old fashioned way.

Before we got the photolysis lamp (a xenon arc lamp), we did some preliminary trials by exposing the brown carbon to sunlight the old-fashioned way.

The first month of my research with Prof. O’Brien was focused primarily on method development. Our goal was to develop procedures that would produce reliable and reproducible data. This meant running different versions of our main experiment and tweaking variables to address sources of error and contamination.

Our experiment in its most basic form involved creating a solution of 4-Nitrophenol, a type of brown carbon, and photolyzing it using a lamp that mimicked the light of the sun. The goal of this experiment is to model a species of brown carbon at the same concentrations and conditions it would be exposed to in clouds, and to measure the rate of its degradation under exposure to sunlight. Using published literature and trial and error, we determined the optimal pH and concentrations of our solution to maximize its rate of photolysis (pH=3.5, concentration of 15 micromolar). We also developed protocols to keep glassware and solutions clean and free of contaminants. During this time we also made sure that the UV-vis spectrometer (the primary instrument we used to collect data) was producing consistent measurements that could be recreated from day to day. This troubleshooting included stabilizing the sample in the instrument and taking repeated measurements to account for instrumental error.

Much of this time was also spent familiarizing myself with the project and with reading the output from the UV-vis. I did not have any experience with these techniques prior to this summer, and so it took some time to get the hang of everything and to have enough experience for me to know what good data looked like.

By the end of the first month of research, we were able to produce data that matched the literature on 4-Nitrophenol photolysis. From here, we would continue on to our experiment measuring the effect of secondary organic aerosols (SOAs) on the system.


  1. Hi Lydia, your research topic is absolutely interesting! I always wonder about the dynamics of climate and ecosystem, and carbon definitely plays an important role in atmosphere. Though I am not chemistry major, your topic is easily accessible and intriguing. For your second post, it makes sense to me that your focus is on producing both valid and reliable data. When I conduct psychology experiment, that was also my goal. I am curious how could you control different variables, such as using different types of brown carbon, and in what way could you show the changes corresponding each condition?