Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
Displaying 1 - 2 of 2
Filtering by
- Creators: Johnson, Paul C
Description
Hydrocarbon spill site cleanup is challenging when contaminants are present in lower permeability layers. These are difficult to remediate and may result in long-term groundwater impacts. The research goal is to investigate strategies for long-term reduction of contaminant emissions from sources in low permeability layers through partial source treatment at higher/lower permeability interfaces. Conceptually, this provides a clean/reduced concentration zone near the interface, and consequently a reduced concentration gradient and flux from the lower permeability layer. Treatment by in-situ chemical oxidation (ISCO) was evaluated using hydrogen peroxide (H2O2) and sodium persulfate (Na2S2O8). H2O2 studies included lab and field-scale distribution studies and lab emission reduction experiments. The reaction rate of H2O2 in soils was so fast it did not travel far (<1 m) from delivery points under typical flow conditions. Oxygen gas generated and partially trapped in soil pores served as a dissolved oxygen (DO) source for >60 days in field and lab studies. During that period, the laboratory studies had reduced hydrocarbon impacts, presumably from aerobic biodegradation, which rebounded once the O2 source depleted. Therefore field monitoring should extend beyond the post-treatment elevated DO. Na2S2O8 use was studied in two-dimensional tanks (122-cm tall, 122-cm wide, and 5-cm thick) containing two contrasting permeability layers (three orders of magnitude difference). The lower permeability layer initially contained a dissolved-sorbed contaminant source throughout this layer, or a 10-cm thick non-aqueous phase liquid (NAPL)-impacted zone below the higher/lower permeability interface. The dissolved-sorbed source tank was actively treated for 14 d. Two hundred days after treatment, the emission reduction of benzene, toluene, ethylbenzene, and p-xylene (BTEX) were 95-99% and methyl tert-butyl ether (MTBE) was 63%. The LNAPL-source tank had three Na2S2O8 and two sodium hydroxide (NaOH) applications for S2O82- base activation. The resulting emission reductions for BTEX, n-propylbenzene, and 1,3,5 trymethylbenzene were 55-73%. While less effective at reducing emissions from LNAPL sources, the 14-d treatment delivered sufficient S2O82- though diffusion to remediate BTEX from the 60 cm dissolved-sorbed source. The overall S2O82- utilization in the dissolved source experiment was calculated by mass balance to be 108-125 g S2O82-/g hydrocarbon treated.
ContributorsCavanagh, Bridget (Author) / Johnson, Paul C (Thesis advisor) / Westerhoff, Paul (Committee member) / Kavazanjian, Edward (Committee member) / Bruce, Cristin (Committee member) / Arizona State University (Publisher)
Created2014
Description
Up to 25 percent of the operating budget for contaminated site restoration projects is spent on site characterization, including long-term monitoring of contaminant concentrations. The sensitivity, selectivity, and reproducibility of analytical methods have improved to the point where sampling techniques bear the primary responsibility for the accuracy and precision of the data. Most samples represent discrete concentrations in time and space; with sampling points frequently limited in both dimensions, sparse data sets are heavily extrapolated and the quality of data further limited.
Methods are presented for characterizing contaminants in water (groundwater and surface waters) and indoor air. These techniques are integrative, providing information averaged over time and/or space, as opposed to instantaneous point measurements. Contaminants are concentrated from the environment, making these methods applicable to trace contaminants. These methods have the potential to complement existing techniques, providing the practitioner with opportunities to reduce costs and improve the quality of the data used in decision making.
A conceptual model for integrative sampling of environmental waters is developed and a literature review establishes an advantage in precision for active samplers. A programmable sampler was employed to measure the concentration of chromate in a shallow aquifer exhibiting time-dependent contaminant concentrations, providing a unique data set and sustainability benefits. The analysis of heat exchanger condensate, a waste stream generated by air conditioning, is demonstrated in a non-intrusive method for indoor air quality assessment. In sum, these studies present new opportunities for effective, sustainable environmental characterization.
Methods are presented for characterizing contaminants in water (groundwater and surface waters) and indoor air. These techniques are integrative, providing information averaged over time and/or space, as opposed to instantaneous point measurements. Contaminants are concentrated from the environment, making these methods applicable to trace contaminants. These methods have the potential to complement existing techniques, providing the practitioner with opportunities to reduce costs and improve the quality of the data used in decision making.
A conceptual model for integrative sampling of environmental waters is developed and a literature review establishes an advantage in precision for active samplers. A programmable sampler was employed to measure the concentration of chromate in a shallow aquifer exhibiting time-dependent contaminant concentrations, providing a unique data set and sustainability benefits. The analysis of heat exchanger condensate, a waste stream generated by air conditioning, is demonstrated in a non-intrusive method for indoor air quality assessment. In sum, these studies present new opportunities for effective, sustainable environmental characterization.
ContributorsRoll, Isaac B (Author) / Halden, Rolf U. (Thesis advisor) / Johnson, Paul C (Committee member) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2015