Chemistry & Biochemistry Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2752

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    MEASUREMENTS OF AEROSOL PHYSICOCHEMICAL PROPERTIES
    (2022) Razafindrambinina, Patricia Nirina; Asa-Awuku, Akua A; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Tiny liquid or solid particles suspended in the air with sizes ranging between several nanometers to several microns, collectively referred to as aerosol particles, are ubiquitous in the atmosphere and have been shown to affect a planet’s radiative budget. Aerosol particles have the ability to directly reflect and absorb solar radiation leading to a cooling or heating the planet’s surface, respectively (aerosol direct effect). Aerosol particles can also indirectly affect the net radiative forcing through water uptake and cloud formation prior to reflecting and absorbing solar radiation (aerosol indirect effect). In my dissertation, I utilize lab-based measurements to measure the optical properties of mineral dust and Martian dust simulants, and quantify the water uptake and cloud condensation nuclei activity of secondary organic aerosols (SOA), and water-soluble organic compounds in various mixing states and relative humidities. This body of work provides directly-measured values that may reduce uncertainties in climate prediction when used as inputs in future climate and air quality models.
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    PROBING ATMOSPHERIC AEROSOL AND GAS PROPERTIES WITH PHOTOACOUSTIC SPECTROSCOPY
    (2011) Bueno, Pedro Antonio; Zachariah, Michael R; Dickerson, Russell R; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Absorption by atmospheric aerosols is the wild card for global climate change. Issues regarding atmospheric gases and aerosols have been at the forefront and the work presented within is directed at those issues. Specifically, work has been performed in order to help understand the issue of absorption in the atmosphere and whether this contributes towards positive forcing or warming of the atmosphere. In the process of conducting this research a custom, first-principles photoacoustic spectrometer was improved, calibrated and used extensively in order to obtain knowledge of the interaction of light with atmospherically relevant gases and make the first measurements of absorbing aerosols. The absorption cross-section of uncoated and coated soot was measured and quantified and found to be consistent with other work where amplifications on the order of nearly 100% were observed with uncertainty levels much lower than previously reported. Soot was also found to be optically thin where the total mass of the soot contributes to the absorption. Consequential to the soot work, the photoacoustic spectrometer developed to measure the absorption was utilized as a high precision greenhouse gas sensor. The photoacoustic spectrometer was found to produce results on the absorption of CO2 to within 3% of the theoretically predicted line profile Moreover, the photoacoustic spectrometer was used to determine measurable coating thicknesses of less than 10 nanometers on 100 nm soot particles.