At the beginning of August, Vanessa and I were given a new objective to our research. Originally, we aimed mainly to just look at our four different sites and determine exactly which compounds are at each place. However, we eventually realized that we were getting a lot of data, but we wanted to figure out how to decipher it and figure out what is most important to all of us and residents/dwellers of New Haven. Dr. Gentner suggested then that we actually choose two of our sites to look at, the two of our sites that people visit/go to most often; the I-91 off-ramp and outside Yale Medical School. We also decided to zero in on key compounds (aromatics) which we knew were present at both sites; toluene, xylenes (p-,m-, and o-), ethylbenzene, trimethylbenzene, naphthalene, and methylnaphthalene. These are all potentially dangerous compounds, and we hoped that we could actually figure out the concentrations of them at the two sites, and thus, compare the air quality at each. However, this turned out to be a task that would be very complex and time-consuming: we would have to obtain calibration curves from chromatogram standards for these compounds. This is a task that we can hopefully take up in the near future (time-willing), but for now, we have figured out another way to compare the air at the two sites.
When a sample tube is put through the three-machine system in the lab (Thermal desorber-Gas Chromatograph-Mass Spectrometer), you eventually end up with a chromatogram, or a visual representation, of the compounds found in the sample. Along with this, you also get several factors that help in identifying/defining the specific compounds in the sample. The system can not immediately identify a compound in the sample; instead, you are given a “hit list”, or a list of possible matches to what is actually in the sample, along with what is called the retention time, retention indices, peak area, peak height, match, r-match, probability, and fragmentation factors. If we, for example, have a chromatogram from one I-91 and from one med school sample, and these two graphs are scaled the same way, we can single out a specific compound and compare the peak areas of that compound in each. If, for example, 1,2,4-trimethylbenzene has a higher peak area in the graphs of the samples from the med school than in those from the highway off-ramp, you can assume that there is more there than in the other location. This is the method we have decided to use in comparing the contents of the air in our two sites.
Final results are still pending, as Vanessa and I are still working on compiling our data and using the method described above to compare the air outside Yale Med School to that at the I-91 off-ramp. We are also hoping to find the specific sources of the compounds we find in the air samples at these places, whether they be from the food being cooked or from the fuel being used to cook it. For now, we CAN say that there are a number of similar compounds (specifically aromatics) at our two sites, and we hope to go further with our data so that eventually, we can make actual conclusions.