Atmospheric Chemistry Program Seminar
Chemistry of Volatile Organic Compounds in the Atmosphere
Joost de Gouw, ANYL faculty, CU Boulder
"Volatile organic compounds (VOCs) are released from many different natural and man-made sources to the atmosphere. VOCs are removed by different oxidants on time scales of minutes to months with oxidized VOCs, ozone and fine particles as a result. These processes affect air quality and climate and are a challenge to understand due to the large number of different VOCs that are released to the atmosphere and the analytical difficulties in measuring all of these compounds as well as their oxidation products.
In our laboratory, we make measurements of VOCs by proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF) and gas chromatography mass spectrometry (GC-MS). PTR-TOF allows measurements of many different VOCs with high time resolution and without the need for pre-separation or sample treatment. GC-MS allows higher chemical detail, but at the cost of time resolution. We also combine these methods to better understand the compounds that are detected by PTR-TOF in different environments.
Several different ongoing and future projects will be presented in this seminar. First, we use PTR-TOF for measurements of VOCs in indoor environments. From the results we learn about the sources of VOCs from people, chemical products and building materials, the chemical transformations of these VOCs and other loss process such as surface uptake and ventilation to the atmosphere. Second, we are working on the emissions and chemistry of VOCs released from volatile chemical product (VCP) use to the atmosphere, which was recently discovered to be the dominant source of VOCs in urban air. In this research we make measurements of VOCs in urban air, separate the different emission sources and describe the chemical transformations of VOCs after emission. Finally, we are working on a chamber study to better understand the formation of secondary organic aerosol from biogenic VOCs."
Laboratory Studies of Contact Efflorescence in a Long Working Distance Optical Trap
Maggie Tolbert, ANYL faculty, CU Boulder
"Because homogeneous salt efflorescence typically requires low relative humidity (RH), atmospheric salt particles are often assumed to be aqueous throughout much of their atmospheric lifetime. Here we use a long working distance optical trap to examine heterogeneous efflorescence that occurs when a supersaturated salt droplet comes into contact with a solid particle. We compare our findings for pure salt droplets with those obtained for salt/organic droplets where the organic may be found either in a core shell structure or as an amorphous/glassy solid. We find that in many cases, single collisions with a range of nuclei promote efflorescence at relatively high RH, causing salt particles to be solid for more of their atmospheric lifetime. Similar experiments are proposed in the future to examine the role of contact in ice cloud nucleation."
This seminar is remote only. Please contact Anne for the link to access the session. Note that this seminar begins at 12:40 PM.