Atmospheric Chemistry Program Seminar
Ozone Production in Los Angeles: Investigating Spatial Differences in the Impacts of NOx Emission Control by Margarita Reza,
ANYL 1st year, CU Boulder
Los Angeles has historically experienced the highest ozone in the U.S. Strategies to reduce high ozone have included reduction of emissions of both nitrogen oxides (NOx) and volatile organic compounds (VOC), the two main precursors to ozone. Observations of ozone on weekdays and weekends, as well as from many intensive atmospheric experiments in LA, have indicated that for decades ozone production chemistry in LA has remained sensitive to VOC rather than NOx. However, very recent literature has suggested that LA ozone chemistry may be transitioning to a chemical regime that is sensitive to NOx, which would mean that LA air quality is positioned to benefit from NOx emission control on diesel truck traffic that are currently in the implementation phase. This study investigates this possible chemical- regime transition by first looking at the temporal trends in NOx concentrations at nine monitoring stations throughout LA. Spatial variability is found in the observed rate of decrease of NOx, suggesting that ozone has been affected differently throughout the LA basin. To investigate this potential spatial variability in the impacts of NOx changes, and, potentially, the change in ozone chemistry sensitivity to NOx, data gathered from the Geostationary Trace Gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument on board the NASA UC12-B King Air on June 26th and 27th , 2017 was used. An analytical model was used to simulate ozone production in LA to identify the sensitivity of ozone production to NOx. Understanding the dependence of ozone production on NOx is critical for developing effective control strategies in this area.
Nanopore Sensing for Single-Molecule Glycomics by Melissa Morris,
ANYL 1st year, CU Boulder
Single-molecule sensing represents the ultimate in chemical sensitivity, but is tremendously challenging to achieve. Because imaging at the nanoscale is difficult and expensive, developing techniques to measure single molecules requires ingenuity, and often relies on the interpretation of electrical signals. So how do nanopores help us measure at the single-molecule level? A nanopore is simply a nano-sized hole in a membrane or material. In the early stages of nanopore science, biological nanopores were isolated from nature, and now the field has turned to solid state nanopores. The Dwyer research group uses an electric field to create solid state nanopores in silicon nitride (SiNx) membranes, using a technique adopted from Vincent Tabard-Cossa. Once the SiNx membrane has a hole, we mount it in a holder, so that it sits between two wells of electrolyte. We then monitor the electrical current to detect single molecules as they pass through the nanopore. In this study, we explored how solid state nanopores can be used to detect and characterize sugar molecules. Sugars have complex branching structures, and significant molecule to molecule variability. However, sugars are easily absorbed by the body, and their potential to be used as a new drug delivery system depends on their characterization.
 Kwok, H., Briggs, K., Tabard-Cossa, V. Nanopore Fabrication by Controlled Dielectric Breakdown. PLOS ONE. 2014, 9, e92880.
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