A. James Clark School of Engineering
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item ENVIRONMENTAL FATE OF POLYBROMINATED DIPHENYL ETHERS IN AGRICULTURAL SOILS WHICH HAVE RECEIVED BIOSOLIDS APPLICATION(2008) Andrade, Natasha Almeida; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Polybrominated diphenyl ethers (PBDEs) are used as additives in consumer products for their fire-retardant properties. While scientists observe PBDEs in various environmental media, little is known of their fate in soils. This study examines the potential fate of PBDEs in soils treated with biosolids. Surface soil samples were collected from commercial farms in the Mid-Atlantic region. Biosolids samples from the source wastewater treatment plant were collected to evaluate PBDE levels and trends. Results show that mean concentration of PBDEs in biosolids from this plant is 1496±158µg/kgd.w., mean concentration in soil from fields that had not received biosolids was 6.8µg/kgd.w., fields with a single application had a mean of 18µg/kgd.w., and fields with multiple applications had a mean of 52µg/kgd.w. Statistical analysis revealed that concentrations in the multiple application group were significantly higher than those in the single application group. This work suggests that PBDEs are relatively persistent in agricultural soils.Item Contaminants in the atmosphere of the Delmarva Peninsula: impact of local activities and atmospheric transport(2007-04-10) Goel, Anubha; Torrents, Alba; McConnell, Laura L; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Anubha Goel, Doctor of Philosophy, 2007 Upper Delmarva Peninsula (within the Chesapeake Bay watershed), where the land use is predominantly agricultural, may be a significant source of pesticides (contributors in the declining water quality and bio-diversity of associated wetlands of the Chesapeake Bay) to the region. Although the Peninsula is predicted to be receiving significant inputs of herbicides through atmospheric deposition, the extent of local or regional atmospheric transport and deposition of pesticides to this area is poorly understood. The goal of this research was to determine the atmospheric levels and estimate deposition flux of pesticides in the Upper Delmarva Peninsula. This was accomplished by collecting weekly air samples (n=271) and event based rain samples (n=489) from three locations in the region (Dover and Lewes, DE; Cambridge, MD) for the period 2000-2003. The samples were analyzed for the presence of 34 pesticides (19 current use (CUPs), 15 historical (HUPs)) and 4 congeners of penta-BDE (PBDEs) using gas chromatograph-mass spectrometry (GC-MS). Statistically analyzed data was used to evaluate factors impacting phase distribution and the contribution of wet deposition to the levels in Chesapeake Bay. The more persistent insecticides and fungicides occur ubiquitously while application on corn influences herbicide occurrence and levels. Atmospheric CUP levels are driven by regional agricultural activity. CUPs do not exist in equilibrium and local meteorological conditions (like high relative humidity) influence phase distribution. The wet deposition flux of insecticide and fungicide is dependent on the total rainfall amount during the sampling period while timing and frequency relative to application on corn impacts herbicide flux. Levels in rainwater of some pesticides (endosulfans, chlorothalonil, diazinon etc.) were high enough to be of concern for the biota associated with the region's water bodies and associated wetlands and reveals that atmospheric deposition arising out of short range atmospheric transport can result in significant pesticide input to non-target areas. HUP atmospheric levels are lower than in the Great Lakes and are decreasing at a faster rate. This study reveals that spray irrigation of treated wastewater is an unknown source of toxic PBDEs to the atmosphere and can result in elevated levels at locations downwind of the irrigation fieldItem Functionalization of Nanoparticles for Biological Applications(2005-12-09) Koh, Isaac; Ehrman, Sheryl H.; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Functionalization of metal oxide nanoparticles enables their use in biological applications via hybridization of biological molecules and modification of surface properties. This Ph. D research is aimed at increasing knowledge of the process of metal oxide nanoparticle functionalization for biological applications. The achievements presented in this dissertation can be divided into three categories: i) a fluorescence-based quantitative evaluation of surface coverage and bio-activity of antibodies immobilized on magnetic nanoparticles (MNPs), ii) differential functionalization of SiO2/TiO2 mixed nanoparticles via preferential binding of phosphonic acids to TiO2 and subsequent trimethyl silyl group binding to the remaining surface, and iii) X-ray scattering (XRS)-mediated detection of peak shifts of a biological substrate, Escherichia coli (E. coli), as a function of applied magnetic field strength and magnetic nanoparticle concentration in a cell growth medium. In a study of MNP surface modification, quantitative evaluation of anti-mouse IgG binding on MNPs and bioactivity on MNPs was conducted via fluorescence assays. Nanosize -Fe2O3 particles were hybridized with anti-mouse IgG via silane chemistry with 3-aminopropyltriethoxy silane and glutaraldehyde activation. A chemisorption isotherm via fluorescence assays demonstrated that immobilization of anti-mouse IgG can be stoichiometrically controlled with the surface coverage at saturation corresponding to 36% of the theoretical limit. The immobilized anti-IgG retains ~50% of its bioactivity at saturation. Differential functionalization of SiO2/TiO2 mixed nanoparticles was demonstrated via aqueous-phase preferential binding of phosphonic acids to TiO2 and subsequent binding of trimethyl silyl group to the remaining surface. SiO2/TiO2 mixed nanoparticles with three different mole ratios of Si/Ti together with pure SiO2 and TiO2 nanoparticles were used in comparative XPS study of differential functionalization. Differential functionalization of metal oxide-metal oxide mixed nanoparticles demonstrated herein adds a route to multifunctional nanoparticles. An In situ XRS study of E. coli in applied magnetic fields up to 423 mT was performed. Two peaks, a sharp peak at q = 0.528 Å-1 (1.189 nm) and a diffuse peak at q = 0.612 Å-1 (1.027 nm), were detected in XRS of MNP-absent E. coli culture. The presence of SiO2/-Fe2O3 MNPs at 40 mg/L in E. coli growth medium changes the sharp peak to the lower side of q as a function of applied magnetic field strength, while the position of the diffuse peak is invariable. 362 mT was found to be a critical magnetic field strength, at which the sharp peak disappears. This study demonstrates magnetic field-assisted interactions between E. coli cell membranes and MNPs.