Drivers of Biogenic Reactive Nitrogen Oxide Emissions in Southern Indiana Deciduous Forests
Clara Lietzke,
CU ANYL 1st year

In the troposphere, reactive nitrogen oxides (NO_y = NO, NO₂, HONO) are harmful pollutants. Conversion of NO to NO₂ propagates the radical reactions that oxidize volatile organic compounds (VOCs) and generate hydroxyl radical (OH). NO₂ is directly photolyzed to produce ozone (O₃), a harmful air pollutant and main component of smog. Anthropogenic emissions of nitrogen oxide and nitrogen dioxide (NO_x = NO + NO₂) have declined with the enactment of air pollution control policy, increasing the importance of biogenic NO_y emissions. Previous work characterizing sources and sinks of NO_y has been focused on soil microbial emissions, although emissions of NO_x from plant matter have also been directly observed. To determine the short-term impact of leaf senescence on local NO_y levels, we conducted the Fall Forest Exchange of Reactive Nitrogen (FFERN) field campaign, where we observed substantial NO emissions from American Sycamore leaf litter, particularly under specific stressors like dew and freezing events. Here, we investigate the mechanism of NO_y emissions from American Sycamore and other tree species leaves in addition to their response to different stressors, such as drying, rehydration, freezing, and cutting.

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Base-mediated depolymerization of amine-cured epoxy resins
Katherine Stevenson,
CU ANYL 1st year

Carbon fiber-reinforced epoxy composites are used in multiple industries, including for aerospace, automotive, and wind energy applications, due to their excellent strength-to-weight ratios and tunable material properties. Fortunately, recycling strategies for carbon fiber-based composites are emerging, with the primary focus on recovery of fibers due to the cost and energy intensity in their production. In addition to fiber recovery, there is an opportunity to recycle the epoxy components, such that ideal recycling strategies would yield both post-consumer fibers and epoxy monomers for reuse. Here, we examine potassium tert-butoxide-mediated cleavage of C–O and C–N bonds in amine-cured epoxy resins. We accomplish this via developing model compounds that reflect both C–O and C–N linkages in amine-cured epoxy composites, before expanding to both model linear thermoplastics and thermosets. We obtain excellent yields of both phenol (up to 97% molar yield) and amine products (up to 99 mol%) from aromatic and/or aliphatic amine-based model compounds. This system enables up to quantitative yield of bisphenol-A and up to 58% molar yield of aniline from model thermoplastic epoxy amines and 71% molar yield of BPA from a reaction with a thermoset substrate. These data correspond to 15% mass recovery of BPA from a commercial epoxy thermoset.