ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
Filtering by
- All Subjects: Environmental engineering
- Creators: Fraser, Matthew
Alternative VI pathways, involving vapor transport along sewer lines and other subsurface infrastructure, have recently been found to be significant contributors to VI impacts at some sites. This study evaluated approaches for identifying and characterizing the significance of alternative VI pathways and assessed the effectiveness of conventional mitigation at a site with an alternative VI pathway that can be manipulated to be on or off. The alternative pathway could not be identified using conventional pathway assessment procedures and can only be discovered under controlled pressure method (CPM) conditions. Measured emission rates were two orders of magnitude greater than screening model estimates and sub-foundation vertical soil gas profiles changed and were no longer consistent with the conventional VI conceptual model when the CPM test was conducted. The pipe flow VI pathway reduced the vacuum performance of the sub-slab depressurization (SSD) VI mitigation system, but the SSD system still provided sufficient protection to the house.
The relationship between groundwater table fluctuations and subsurface vapor emissions and transport is examined using multi-year data from the field site, and is studied in the laboratory. In addition, a broader range of conditions is examined through use of modeling validated with the experimental data. The results indicate that fluctuating groundwater tables will lead to amplified volatile organic chemical (VOC) emissions from groundwater to soil surface relative to steady water table elevation, however, the magnitude of this amplification is less concerned when long-term water fluctuation present. No clear correlations were found between VOC emissions and water table changes at the study site where annual water table fluctuations of about 0.3 m existed. Significant VOC emission amplifications by water table fluctuation would be expected under shallow groundwater conditions according to model analysis results.
Novel, sensitive methods of measuring NDMA in air were developed based on Solid Phase Extraction (SPE) and Solid Phase Microextraction (SPME) coupled to Gas Chromatography-Mass Spectrometry (GC-MS). The two measuring techniques were evaluated in laboratory experiments. SPE-GC-MS was applicable in ambient air sampling and NDMA in ambient air was found in the 0.1-13.0 ng/m3 range.
NDMA photolysis, the main degradation atmospheric pathway, was studied in the atmospheric aqueous phase. Water soluble organic carbon (WSOC) was found to have more impact than inorganic species on NDMA photolysis by competing with NDMA for photons and therefore could substantially increase the NDMA lifetime in the atmosphere. The optical properties of atmospheric WSOC were investigated in aerosol, fog and cloud samples and showed WSOC from atmospheric aerosols has a higher mass absorption efficiency (MAE) than organic matter in fog and cloud water, resulting from a different composition, especially in regards of volatile species, that are not very absorbing but abundant in fogs and clouds.
NDMA formation kinetics during chloramination were studied in aqueous samples including wastewater, surface water and ground water, at two monochloramine concentrations. A simple second order NDMA formation model was developed using measured NDMA and monochloramine concentrations at select reaction times. The model fitted the NDMA formation well (R2 >0.88) in all water matrices. The proposed model was then optimized and applied to fit the data of NDMA formation from natural organic matter (NOM) and model precursors in previously studies. By determining the rate constants, the model was able to describe the effect of water conditions such as DOC and pH on NDMA formation.