Browsing by Subject "uptake"
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Item Laboratory investigation of chemical and physical properties of soot-containing aerosols(Texas A&M University, 2006-08-16) Zhang, DanSoot particles released from fossil fuel combustion and biomass burning have a large impact on the regional/global climate by altering the atmospheric radiative properties and by serving as cloud condensation nuclei (CCN). However, the exact forcing is affected by the mixing of soot with other aerosol constituents, such as sulfuric acid. In this work, experimental studies have been carried out focusing on three integral parts: (1) heterogeneous uptake of sulfuric acid on soot; (2) hygroscopic growth of H2SO4-coated soot aerosols; (3) effect of H2SO4 coating on scattering and extinction properties of soot particles. A low-pressure laminar-flow reactor, coupled to ion driftchemical ionization mass spectrometry (ID-CIMS) detection, is used to study uptake coefficients of H2SO4 on combustion soot. The results suggest that uptake of H2SO4 takes place efficiently on soot particles, representing an important route to convert hydrophobic soot to hydrophilic aerosols. A tandem differential mobility analyzing (TDMA) system is employed to determine the hygroscopicity of freshly generated soot in the presence of H2SO4 coating. It is found that fresh soot particles are highly hydrophobic, while coating of H2SO4 significantly facilitates water uptake on soot even at sub-saturation relative humidities. The results indicate that aged soot particles in the atmosphere can potentially be an efficient source of CCN. Scattering and extinction coefficient measurements of the soot-H2SO4 mixed particles are conducted using a threewavelength Nephelometer and a multi-path extinction cell. Coating of H2SO4 is found to increase the single scattering albedo (SSA) of soot particles which has impact on the aerosol direct radiative effect. Other laboratory techniques such as transmission electron microscopy (TEM) and Fourier transform infrared spectrometry (FTIR) are utilized to examine the morphology and chemical composition of the soot-H2SO4 particles. This work provides critical information concerning the heterogeneous interaction of soot and sulfuric acid, and how their mixing affects the hygroscopic and optical properties of soot. The results will improve our ability to model and assess the soot direct and indirect forcing and hence enhance our understanding of the impact of anthropogenic activities on the climate.Item Transports of Polymer Nanomedicine in the Environment(2013-11-14) Zhang, MingWith increasing production and commercial use of polymer nanomedicine and a lack of regulation to govern their disposal, polymer nanomedicine may enter into soils and ultimately into ground water system. In this dissertation, adsorption of polymeric nanoparticulate drug delivery system (PNDDS) in the environmental surface as well as uptake of nanomedicine into plants was investigated. Cellulose surface and silica surface were chosen as environmental surfaces and ryegrass was chosen as a plant. The adsorption of PNDDS onto cellulose and silica surface was studied by quartz crystal microbalance with dissipation (QCM) and atomic force microscopy (AFM). Uptake of PNDDS into ryegrass was investigated by spectrofluorometry (SFM), confocal microscopy, scanning electron microscopy (SEM) and cross sectional transmission electron microscopy (TEM). It is found that PNDDS can partially irreversibly adsorb on cellulose and silica surface. After adsorption, PNDDS may deform, disintegrate, or keep the same size depended on properties of PNDDS and PNDDS/surface interaction. Uptake of PNDDS into ryegrass was observed and PNDDS was found both in root cell and intercellular space. PNDDS could transport up to stem of ryegrass but not leaf. Adsorption onto root surface is the rate-determined step of the uptake process. This dissertation represents an important step in understanding environmental impact of polymer nanomedicine. This is very important considering that PNDDS on and in the plants may later be consumed by animals and bacteria and accumulate in their bodies, and can adversely influence environmental health. Also silica/cellulose surface and plants may also be used to treat waste water with PNDDS. Transport behavior and kinetics of PNDDS onto environmental surface studied in this dissertation also could guide to study transport behavior of the same type or other types of polymer nanomedicine in similar or other environmental systems.