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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 to better understand their sources and fate. One particular study involves the impact of the Marshall Fire in Boulder County on indoor air in homes that were near the burnt area. Second, we are working on the emissions and chemistry of VOCs in urban air. One study that will be highlighted involved field measurements in Los Angeles in the Summer of 2022. Third, we are working on the indoor air chemistry induced by air cleaners such as germicidal UV lamps that are effective at inactivating airborne viruses. Finally, we are also using data from satellite remote sensing instruments to measure the pollutants from oil and natural gas production, in urban air and from wildfires.

 

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Understanding aerosols for indoor and outdoor air quality and climate
Jose-Luis Jimenez,
ANYL Faculty, CU Boulder

Our group’s research focuses on understanding the sources, properties, transformations, and sinks of aerosols (and of the gases that interact with them), which have major effects on human health and climate. In this talk I will briefly summarize ongoing projects in our group, with more emphasis on projects of interest to first year PhD students.

We frequently perform ambient aerosol composition measurements. We recently deployed an AMS in the NASA DC8 aircraft during the ASIA-AQ campaign in Spring 2024, investigating air pollution in South Korea, the Philippines, Taiwan, and Thailand; we also continue the analysis of data from previous aircraft campaigns. Since May 2023 we have been operating continuous measurements of aerosol composition in Denver with multiple instruments (ACSM, SMPS, Aethalometer, XAct) as part of the NSF ASCENT long-term monitoring program, which we are going to continue until at least 2030. We also collected data to characterize the precursors responsible for SOA formation in the Los Angeles area in Summer of 2020. I will summarize recent results from ongoing analyses of these projects.

Indoor air chemistry and airborne disease transmission has also been a focus over the last decade. Over the last 3 years we have been investigating the formation and/or removal of air pollutants by different “air cleaner” technologies, with a special focus on germicidal ultraviolet light (GUV). I will present results from recent experimental and modeling projects, including an analysis of GUV tradeoffs across all possible wavelengths, and the characterization of a catalyst to remove ozone from indoor air.

Dual frequency combs (DFC) are new light sources with unique properties for analytical spectroscopy. The mid-IR contains important chemical information about organic functional groups, but analysis of aerosols suspended in air in this region with FTIR was considered infeasible, due to interferences from narrow absorption lines of abundant gases such as CO2. As part of the collaborative IARPA SAURON project led by CU-Boulder Engineering, we are working to test the aerosol measurement capabilities of new DFC systems.

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