Environmental Science & Technology Theses and Dissertations
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Item QUANTIFICATION OF IONOPHORE ANTIMICROBIALS ASSOCIATED WITH POULTRY LITTER AND THEIR DYNAMICS IN THE SOILS OF THE MID-ATLANTIC USA(2014) Biswas, Saptashati; McGrath, Joshua M; Sapkota, Amir; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Anticoccidants, biochemically known as ionophores are added to poultry feed for growth promotion, prophylactic and therapeutic purposes to better sorb nutrients and against coccidiosis caused by parasite Eimeria sp. Ionophores belong to the class of emerging contaminants, as they are not regularly monitored in the environment and not specifically treated in the effluents. Potentially, this can cause ionophores to enter into the environment freely. There is little information regarding the dynamics of ionophores in the environment. This has been related to the lack of reliable, sensitive and robust methods that can measure their trace levels from complex environmental matrices like soil, natural water and animal manure. Studies show ionophore toxicity exhibited in flora and fauna, even reported in humans above the dose of 1 mg kg-1. Hence accumulation of ionophores in the environmental can be detrimental. Our multi-scale investigation of ionophores involved, a) method development for trace analysis of ionophores in poultry manure using liquid chromatography triple quadrupole mass spectrometry (HPLC-–MS/MS), b) batch equilibrium studies of ionophores using soils from mid-Atlantic region of the USA and c) influence of soil physico-chemical parameters on dynamics of ionophores in soil-water systems. Our HPLC-–MS/MS method was successful in quantifying ionophores ranging from (19.19 ±± 6.6) µg kg-1 to (97.86 ±± 19.19) µg kg-1 with concentrations of monensin being the highest. This method was further used to investigate partitioning of monensin in soil-ndash;water systems relevant to the occurrence of ionophores in the natural environment. Sorption and desorption isotherms were developed and influence of soil physico-chemical parameters on the sorption-desorption processes were analyzed. C-–type linear isotherms were generated with partition coefficients ranging from (6.41±± 1.34) to (343.83 ±± 5.68) LKg-1. Soil parameters such as cation exchange capacities, pH, organic matter, sand and silt content were found to correlate with sorption in different conditions. A major focus of this dissertation was to develop novel methodologies and design experiments to execute our research objectives.Item HEXAVALENT CHROMIUM QUANTIFICATION AND REMEDIATION IN SOILS AND WASTE MATERIALS(2014) DeSarle, Catherine Rose; James, Bruce R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hexavalent chromium (Cr(VI)) is a carcinogen and a pollutant of soils and natural waters. The standard method to extract and quantify total Cr(VI) in soils and waste materials was modified to prevent method-induced reduction of Cr(VI) by not heating (95°C) but shaking (100 cycles/min) at 23°C, followed by quantification using the 1,5-diphenylcarbazide method or ion chromatography. Forms of carbon and Cr(VI) (mineralogical vs. soluble) significantly influenced method-induced reduction. The proposed method should be used with samples containing ≥ 10 g/kg organic C. The new method was used to study the reduction of Cr(VI) in soils with Fe(II), Fe(III), and organic carbon, and the Cr in remediated soils was fractionated. Fe(II) in combination with Fe(III) was the most effective at reducing Cr(VI) and immobilizing newly-reduced Cr(III). The extraction and quantification refinements are relevant to accurate and precise metrics for Cr(VI) and its remediation in soils.Item CHROMIUM OXIDATION-REDUCTION CHEMISTRY CONTROLLED BY IRON AND MANGANESE (HYDR)OXIDE SURFACES AND SOILS: COLUMN LEACHING AND SPECTROSCOPIC STUDIES(2014) Miller, Christina Langlois; James, Bruce R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Soil interfaces, including those defined by horizons and iron (Fe(III)) and manganese (Mn(III,IV)) (hydr)oxide mineral surfaces, are a largely unstudied area in soils research, especially in terms of their oxidation-reduction properties. This study attempted to address two questions related to this research deficiency. The first: how chromium (Cr) redox changes throughout mineralogically different soil horizons, and the second: how Cr redox structurally alters Fe(III) and Mn(III,IV) (hydr)oxides in synthetic, soil, and microbial systems. Both parts of the study used column leaching experiments along with Cr speciation techniques to study simulated soil horizon interfaces and Fe/Cr and Mn/Cr redox systems. X-ray absorption spectroscopic techniques were also utilized to analyze the mineral structure of Fe(III) and Mn(III,IV) (hydr)oxides. The results of the study indicate that there are significant interfacial properties affecting Cr(VI) reduction and that Cr(III) oxidation does change the mineral structures of synthetic, soil, and fungal Mn(III,IV)(hydr)oxides to varying degrees.