Résumé confidentiel / Confidential abstract

This dissertation investigates unexplained vapor intrusion field data sets that have been observed at hazardous waste sites, including: 1) non-linear soil gas concentration trends between the VOC source (i.e. contaminated groundwater plume) and the ground surface; and, 2) alternative pathways that serve as entry points for vapors to infiltrate into buildings and serve to increase VOC exposure risks as compared to the classic vapor intrusion model, which primarily considered foundation cracks as the route for vapor entry. The overall hypothesis of this research is that theoretical knowledge of fate and transport processes can be systematically applied to vapor intrusion field data using a multiple lines of evidence approach to improve the science-based understanding of how and when vapor intrusion exposure risks will pose increased exposure risk; and, ultimately this knowledge can be used to develop policies that reduce exposure risks. The first objective of this research involved numerical modeling, field sampling and laboratory tests to investigate which factors influence soil gas transport within the subsurface. Combining results of all of these studies provide improved understanding of which factors influence VOC fate and transport within the subsurface. Importantly, the results demonstrate a non-linear trend between the VOC source concentration in the subsurface and the ground surface concentration at the study site, which disagrees with many vapor intrusion conceptual models. Ultimately, the source concentration may not be a good predictor of shallow soil gas concentrations. Laboratory tests described the effect of soil characteristics such as the soil water content on VOC vapor diffusion. The numerical model was able to explain specific conditions that could not be described by the field and laboratory data alone. A paper was published that summarizes the major outcomes from this objective (Pennell et al, 2016). The second objective of this research investigated preferential pathways for VOC vapor migration into buildings. Sewer systems can act as important pathways for vapor intrusion. The research objective is to evaluate conditions that increase the potential for inhalation exposure risks via vapor intrusion thorough sewer systems into indoor spaces. A field study was conducted in California over a 4-year period to investigate the spatial and temporal variability of alternative pathways (e.g. aging infrastructure piping systems) within the context of vapor intrusion exposure risks. A paper was published that summarizes the major outcomes from the field study (Roghani et al. 2018). The final research objective involved the development of a numerical model to describe VOC fate and transport within a sewer system. The numerical model predicts VOC mass transport. The model results were compared to the field data and provides insight about the role preferential pathways play in increasing VOC exposure risks.

xiii, 153 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / The purpose of this study was to learn more about the transition experiences of one group of high school students ( N = 75) as they began attending one alternative pathway: an Early College High School program on a community college campus. A four-part conceptual framework of college readiness provided a structure from which to explore the experiences of students in the college environment. One of the four framework areas--academic behaviors (self-management)--was the focus of this study. Data were collected by means of a pre-post survey, student interviews, and staff interviews in order to understand better the college readiness perceptions of the students, principally as evidenced by changes in their academic self-management behaviors. The survey data were organized into pre-post group comparisons and were reported in terms of descriptive statistics. The data from semi-structured interviews with participants provided additional insight into changes in the academic and social behaviors of the students. Results indicate that students' academic behaviors changed during the first term of college. Over the eight survey domains measured, mean scores generally increased moderately between the pre and post surveys in several domains associated with academic behaviors, with two key domains--self-awareness and learning habits (i.e., learning strategies/study habits)--showing the most growth. Additionally, student interview comments demonstrated changes at the end of their first term of ECHS in their study habits and in their ownership of their school efforts. The overall changes in students' academic behaviors imply that they learned new skills as a result of participation in the ECHS program. / Committee in charge: David Conley, Chairperson, Educational Methodology, Policy, and Leadership; Philip McCullum, Member, Educational Methodology, Policy, and Leadership; Christopher Murray, Member, Special Education and Clinical Sciences; Jean Stockard, Outside Member, Planning Public Policy & Mgmt