Wednesday, July 29, 2015


Chinanu and I are working in the Gentner Lab for the summer, and we are studying Volatile Organic Compounds and their effect on the atmosphere.

Organic chemical compounds and carbon containing chemicals, and they make up an essential portion of the earth’s atmosphere.  Certain carbon containing atoms, such as oxides of carbon and cyanides, are considered inorganic, though the majority of carbon containing atoms are organic.  These compounds undergo various chemical reactions in the atmosphere, and our lab seeks to understand the reacted compounds, as well as the processes that take place.

Our lab is particularly interested in volatile organic compounds (VOCs), which are compounds that are emitted as gases from certain solids or liquids.  Understanding VOCs and how they play a vital part in atmospheric chemistry is important because many of them pose serious risks to not only the environment, but to human bodies as well.  VOCs degrade in the atmosphere to form free radicals (an uncharged molecule with an unpaired valence electron) and with oxygen in the troposphere to form ozone (O3).  Free radicals are then able to degrade further by an OH (hydroxide) reaction or photolysis into smaller and more oxidized particles.  Such processes not only have negative impacts on the environment, but on human health as well.  Ozone inhibits the ability of plants to open their microscopic pores, creates haze thereby decreasing visibility, and also decreases the amount of carbon dioxide they are able to use during photosynthesis.  In the human body, ozone causes inflammation in the lungs and can trigger chest pain, coughing, and throat irritation, even in healthy people. Free radicals can also accelerate aging in the human body and may lead to diseases.  Significant amounts of carbon can also be found in the particulate form, known as particulate matter (PM or PM2.5) and this as well can lead to health risk by irritating the lungs and building up in the body.  It is also the cause of haze, for the particles are able to scatter light.  In our samples, we collect both gases and aerosols, microscopically small particles suspended in air, that contain VOCs.  

Chinanu and I pack the tubes that are used in our data collection with different adsorbents of varying “strength”: quartz wool, glass beads, and Tenax.  After packing the tubes, we “condition” them by putting them by putting them in a system that pushes nitrogen gas (N2) through the tube at a high temperature to cleanse them of any organic material they may contain.  After conditioning, they are left to cool and then finally capped.  Sampling on field requires an air pump that is attached to the tubes to draw in air at a rate of approximately .115 L/min for 30 minutes.  After samples have been collected, they are taken back to the lab and placed in a freezer to ensure the gases do not diffuse out of the tube.  Finally they are analyzed in a Gas Chromatograph/ Mass Spectrometer (GCxMS) system to identify the compounds collected.  

Four different types of sources are taken into account when choosing a sampling site.  VOCs are released by anthropogenic (human made) and natural sources.  Sites were chosen at anthropogenic, biogenic, mixed emissions, and indoor sources.  A blank and three samples will be collected at the I-91 ramp entering into New Haven, East Rock Park, the Medical School, and inside the Yale Peabody Museum.  We expect to find quite a number of compounds from the all of the sources, but the types of compounds we find at each source will be a bit different because the emission source varies.  

Ground-level Ozone Effects. Retrieved July 29, 2015, from
Hamilton, J., Webb, P., Lewis, A., Hopkins, J., Smith, S., & Davy, P. (2004). Partially oxidised organic components in urban aerosol using GCXGC-TOF/MS. Atmospheric Chemistry And Physics Discussions Atmos. Chem. Phys. Discuss., 4(2), 1393–1423.

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