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Interest in halocarbons has been sparked by experimental evidence suggesting that these compounds are potential carcinogens and teratogens. The U.S. EPA started a nationwide program in 1970 to identify and quantify trace organic compounds in public water supplies and sewage effluents. To date no detailed large-scale areal ground-water surveys delineating concentrations of these halocarbons have been reported in the literature at the part per trillion level and below. The objectives of this dissertation are twofold: (1) identification, quantification, and detailed areal mapping of several halocarbon species in ground water near the Santa Cruz River northwest of Tucson, Arizona; and (2) development of halocarbon techniques for age dating recently recharged (0-40 years old) ground water. The halocarbon compounds considered are: trichlorofluoromethane (CC1₃F), dichlorodifluoromethane (CC1₂F₂), carbon tetrachloride (CC1₄), chloroform (CHC1₃), trichloroethylene (C₂HC1₃), methyl chloroform (CH₃CC1₃), and tetrachloroethylene (C₂C1₄). Objective (1) includes discussions of the areal halocarbon distributions detected in the ground water, their sources, and a qualitative comparison of the distributions to ground-water quality and land use patterns adjacent to the Santa Cruz River. Objective (2) utilizes the exponential atmospheric concentration buildup of CCl₂F₂, CC1₃F, and CCl₄, and the ratios of CCl₂F₂ to CCl₃F and CCl₄ to CCl₃F. Water samples from wells and the Santa Cruz River were collected in glass syringes and brought to the laboratory for analysis. An electron-capture gas chromatograph coupled to a gas stripping/concentration unit was used to quantify the halocarbons. Four high concentration areas were delineated, each probably associated with a different source: the CWUA area which was irrigated with sewage effluent during the 1960's; Rillito Creek (near its confluence with the Santa Cruz) which is a major ground-water recharge source; the Ina Road treatment plant/landfill/oxidation ponds area; and the Roger Road treatment plant "sewer farm" which is irrigated with sewage effluent. The CCl₂F₂ to CCl₃F ratio distribution indicates that most ground water in the study area is at least partially mixed with recharge less than 30 years old. The ground water adjacent to the Rillito has an apparent age of less than 10 years, in agreement with the CCl₃F distribution. Ground water in the Cortaro area has an apparent age of about 25 years, correlating with the start of irrigation in the area.

Ground water has traditionally been considered safe for human consumption without treatment. However, it is an increasingly significant cause of human disease. Although ground water accounts for only approximately 20% of the nation's water supply, over 50% of the waterborne disease outbreaks in the United States are due to the consumption of contaminated ground water. It has been estimated that 65% of the cases of illness in these outbreaks are caused by enteric viruses. Little, however, is known about the persistence of viruses in ground water. The purpose of this study was to try to determine the chemical, physical, and biological factors influencing virus survival in ground water. This information will be helpful in developing criteria for determining safe distances between drinking water wells and sources of potential contamination such as septic tanks and waste application sites. Ground water samples were obtained from eleven sites throughout the United States. In addition, twenty samples were collected from the Tucson basin. The water temperature was measured at the time of collection. Several physical and chemical characteristics (including pH, nitrates, turbidity, and hardness) were determined for each sample. Separate polypropylene tubes containing 50 ml of water were inoculated with each of three viruses: poliovirus-1, echovirus-1 and MS-2 coliphage. Duplicate tubes containing water which had been filtered to remove the indigenous bacteria were also inoculated with viruses. The tubes were incubated at the in situ ground water temperature; selected samples were incubated at two additional temperatures. One-ml subsamples were withdrawn at predetermined intervals over a 30-day period and assayed to determine the number of microorganisms remaining. Multiple regression analysis revealed that temperature was the only water characteristic significantly correlated with the decay rates of all three viruses. Bacteria did not have a consistent effect on the decay rate of the viruses. In addition, no significant differences were found among the decay rates of the three viruses, suggesting that MS-2 coliphage may be able to be used as a model of animal virus behavior in the environment.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

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