Thesis (Ph. D.)--University of Florida, 1988. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 149-153).

Sediments excavated from dredging operations are known as dredged materials. Beneficial reuse of dredged materials in confined utilization facilities (CUFs) is a new approach that has the potential to productively utilize large quantities of dredged materials. However, several factors can inhibit the use of dredged materials in CUFs. In this study, high levels of salts and polycyclic aromatic hydrocarbons (PAHs) were investigated. In the first part of this study, 176,000 m3 of saline dredged materials was placed into a CUF. In less than 4 years, most of the dredged materials had developed horizonation and converted to Inceptisols. The formation of pedogenic Bg horizons in these soils occurred after a polygonal prism network had developed which partially disintegrated into a blocky structured, oxidized horizon with an abundance of redoximorphic features. During the study period, the soil chemistry of the weathering dredged materials shifted from Na-dominated to Ca and Mg-dominated system, allowing plant invasion. In the second part of the study, a bench-scale greenhouse bioremediation experiment was conducted to test the effectiveness of biosolids, compost, and straw at enhancing PAH degradation. Initial concentrations of PAHs decreased significantly after 150 days using standard methods of extraction. However, at 327 days the concentrations of many PAHs, especially those with higher molecular weights, had rebounded close to initial levels. This indicates that PAH bioremediation studies using organic matter additions and conducted using standard methods of extraction need to be carried out longer periods of time or that extraction methods need to be improved. / Master of Science

Thesis (Ph. D.)--Ohio state University, 1924. / Autobiography. "Reprinted from the Ohio journal of science, vol. XXVIII, no. 1, January, 1928." Bibliography: p. 38.

Thesis (Ph. D.)--Cornell University, 1930. / Cover title. Published also as Bulletin 356 of the Maine Agricultural experiment station. "Literature cited": p. 219-221.

When considering how insecticides impact beneficial insects, in addition to direct mortality, we need to assess sublethal effects on population numbers which reduce the efficacy of the predators and parasitoids in reducing pest insects. The physiological sublethal effects can result in reduced longevity and reproduction. Understanding the sublethal effects of insecticides on beneficial insects is important in agroecosystems, especially in the context of natural biological control which aims to augment endemic natural enemies. The objective of this research study was to evaluate the environmental effects of insecticides on non target predator and parasitoid insects, combining the review of the literature and the synthesis of both a laboratory and a field research study. The lab study considered the effects of chlorpyrifos and deltamethrin on three natural enemies of Russian wheat aphid; the field study considered the effects of chlorpyrifos, deltamethrin, cyhalothrin-lambda and imidacloprid on ground dwelling arthropods in a Canola field.

As the world’s increasing human population demands greater agricultural intensity, concerns regarding environmental nutrient loading are also rising. Landowners in the Tobacco Creek Model Watershed (TCMW) in southern Manitoba, Canada, have implemented beneficial management practices to reduce nutrient loading to surface waters. Among these practices is a network of small reservoirs that have been shown to reduce nutrient concentrations downstream. It is unclear what is contributing to this ecosystem service, but bacterial denitrification is thought to be important. To understand the role of these reservoirs in excess nitrate removal and assess how this ecosystem service can be optimized, denitrification activity in reservoirs and stream pools of the watershed was measured via the chloramphenicol-amended acetylene block technique. Results indicated that denitrification activity was positively correlated with measured nitrate concentrations and sediment organic carbon (SOC), and negatively correlated with sediment particle size and pH. Regression trees typically identified nitrate as the primary node in partitioning denitrification activity. Importantly, reservoirs exhibited higher denitrification activity and were at times less likely to be nitrate-saturated than stream pools. This finding was attributed mainly to higher levels of SOC, and lower concentrations of dissolved oxygen found in reservoirs. Nitrate was added to a set of samples to test for nitrate saturation, which is an indicator of poor ecological status, as nitrate concentrations exceed the denitrification capacity of microbes. Almost half of measurements (49%) demonstrated nitrate saturation, indicative of the need for additional remediation activity in the watershed. Classification trees suggested a threshold for nitrate saturation across sites at 0.68 mg L-1 NO3 + NO2. Findings from this research reveal that reservoirs not only improve nitrate removal capacity, but could inform the proposed construction of additional reservoirs in the TCMW. Understanding nutrient retention in this system could also have implications for downstream ecosystems such as Lake Winnipeg; an intensely eutrophic lake that has become a high priority area for remediation.

Thesis (M.S.)--Oregon State College, 1960. / Typescript. Includes bibliographical references (leaves 67-69). Also available on the World Wide Web.

Thesis (Ph. D.)--Ohio state University, 1924. / Autobiography. "Reprinted from the Ohio journal of science, vol. XXVIII, no. 1, January, 1928." Bibliography: p. 38.

Thesis (M.S.)--Virginia Polytechnic Institute and State University. / Vita. Abstract. Includes bibliographical references (leaves 46-51). Also available via the Internet.

Thesis (M.S.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.