UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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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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    MOLECULAR DYNAMICS SIMULATION OF DICARBOXYLIC ACID COATED AQUEOUS AEROSOL: STRUCTURE AND PROCESSING OF WATER VAPOR
    (2010) Ma, Xiaofei; Zachariah, Michael R; Applied Mathematics and Scientific Computation; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Low molecular weight dicarboxylic acids constitute a significant fraction of water-soluble organic aerosols in the atmosphere. They have a potential contribution to the formation of cloud condensation nuclei (CCN) and are involved in a series of chemical reactions occurring in atmosphere. In this work, molecular dynamics simulation method was used to probe the structure and the interfacial properties of the dicarboxylic acid coated aqueous aerosol. Low molecular weight dicarboxylic acids of various chain lengths and water solubility were chosen to coat a water droplet consisting of 2440 water molecules. For malonic acid coated aerosol, the surface acid molecules dissolved into the water core and form an ordered structure due to the hydrophobic interactions. For other nanoaerosols coated with low solubility acids, phase separation between water and acid molecules was observed. To study the water processing of the coated aerosols, the water vapor accommodation factors were calculated.