Beginning in the mid-1960's synthetic nucleoside derivatives of polyazaindolizines and polyazaindenes were studied for their anticancer activities. The most promising nucleosides for anticancer activity were pyrrolo-, imidazo-, and s-triazolo- pyrimidines and triazines. Syntheses of 1,2,4-triazolo 3,4c -1,2,4-triazine-7-oxide, 1,2,4-triazolo 3,4c pyrazine-7-oxide and 1,2,4-triazolo 2,3c pyrazine-7-oxide were achieved by the cyclization of the appropriate 3-hydrazinoazine N-oxide with diethoxymethyl acetate. When different one carbon cyclization agents react with the 3-hydrazinoazine-1-oxides they did not produce the expected polyazaindene-7-oxides. The reaction of formic acid with 3-hydrazino-1,2,4-triazine-1-oxide or 3-hydrazinopyrazine-1-oxide produced the 3-formylhydrazino derivatives. Similarly, the reactions of the 3-hydrazino -pyrazine-1-oxide and -triazine-1-oxide with benzaldehyde, acetic anhydride, or phenylisothiocyanate produced the 3-benzylideno, 3-acetyl, and 3-(4-phenylthiosemicarbizide) derivatives, respectively. The direct N-oxidation of imidazo 1,2a pyrazine with meta-chloroperbenzoic acid produced the imidazo 3,4c pyrazine-7-oxide. Proton nuclear magnetic resonance analyses of the polyazaindenes N-oxides has produced a set of shielding and deshielding parameters for ring protons. The mass spectral information obtained for the polyazaindene N-oxides suggests that the five membered ring of polyazaindene N-oxide has a decreased reactivity to electrophilic reagents when compared to the parent compound. The nitrogen-15 nuclear magnetic resonance spectra obtained for selected polyazaindenes were used to predict the percentage of contribution between two ground state resonance contributing structures. The nitrogen-15 nuclear magnetic resonance spectra of several substituted pyridine, pyrazine, pyrimidine and 1,2,4-triazine derivatives and their N-oxides were correlated with substituent contributions and ground state contributing structures. From this data, correlations between the nitrogen-15 chemical shifts and aromatic electron deficiency have been established.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

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I investigated the use of nitrogen isotopes as a tracer of sewage contamination on coral reefs. Sewage is isotopically distinct from marine nitrogen, allowing its use as a tracer in this environment. Emphasis was placed on sampling modem coral tissues, as modern coral reefs are in a rapid state of decline, possibly as a result of sewage contamination. Samples were collected in Zanzibar for two separate studies. The first study involved sampling over a depth/light gradient on large coral heads. These data, when combined with data from Jamaica, show light is a controlling factor on the nitrogen isotopic composition of coral tissue. Regression of delta15N of coral tissue with depth/light attenuation explains 75-90% of the variance. Results indicate increased fractionation with depth, which is related to the symbiotic nature of corals. Light-sufficient, nitrogen-limited zooxanthellae ( in the coral tissue ) must diffusl! all available nitrogen, and there is little fractionation. At depth, light-limited, nitrogen-sufficient zooxanthellae fractionate nitrogen during assimilation processes. These results have important implications for the use of nitrogen isotopes as a sewage tracer on reefs. In general, increased nutrients to the reef environment result in decreased water clarity, or lowered available light to the coral. This could lower the zooxanthellae's nitrogen requirements and allow fractionation (isotopic depletion). Corals have been shown to become reliant on heterotrophy in non-limiting nutrient conditions, related to loss of control over their zooxanthellae. This suggests the delta15N of their tissues would reflect their diet (and therefore the source of contamination). The counteractive effects of these two factors suggests it may not be possible to resolve the source of eutrophication to corals using the isotopic signatures of their tissue. That is, if the contamination gradient is coincident with a gradient in the symbiotic relationship (i.e. from nutrient limited to nutrient non-limited) or trophic status, there is little possibility of resolution of sewage effects. Results from the second sample suite from Zanzibar and a sample suite from Jepara Bay, Indonesia confirm this hypothesis. Zanzibar samples were collected at a eutrophied and non-eutrophied reef, and show no significant difference between isotopic data. This may be a result of distance from source, or the counter-effects of light. At Jepara Bay, samples were collected along a contamination gradient, from 2 point source discharges. Isotopic data show significant change along the gradient, with the entire bay eutrophied. Without delta15N from all potential nitrogen sources it is impossible to adequately conclude whether sewage was the contaminant using isotopes. Other data collected from these reefs do support the interpretation of anthropogenic contamination. These data include decline in coral and fish communities (determined using biological assays, Zanzibar), and increased heavy metal and chlorophyll-a concentrations (Jepara). One control on nitrogen isotope composition of modern corals was identified, and others suggested. Results will remain enigmatic until sample suites including complete water chemistry, source chemistry, and light regime are interpreted. / Thesis / Master of Science (MSc)

Until recently it has been widely believed that significant anthropogenic influences on the environment began in Canada following the onset of European colonization. However, our paleolimnological data indicate that centuries prior to European settlement, ponds on Ellesmere and Bathurst Island were impacted by Thule Inuit whalers, whose activities altered nutrient levels in nearby ponds. Two Thule Inuit whaling sites were selected based on input from several archaeologists, to ensure good coverage of the Thule geographic range and proximity to freshwater ponds. Multiple independent paleolimnological proxies have been used to analyze a pond from Ellesmere Island, showing taxonomic shifts in diatoms assemblages coinciding with 1.5 - 2‰ shifts in d15N, during the period of Thule occupation (ca. 1000 – 1670 AD). Increases in the relative abundance of Amphora ovalis, indicate nutrient concentrations above average for the High Arctic. Elevated levels of nitrogen and phosphorus were observed in the pond indicating the continuing influence of nutrient inputs centuries after the abandonment of the camp. Meanwhile, on Bathurst Island, the orientation of the Deblicquy site, such that the large majority of the Thule nutrient inputs are focused towards one of our two study ponds, provided us with the opportunity to compare two ponds that are essentially identical with the exception of the degree of Thule influence. In our “impacted” site, a marked increase in Stephanodiscus minutulus, coincides with a 2‰ shift in d15N. While our a priori determined control site shows no major changes in geochemistry or algal composition. Previous research on Bathurst Island used water chemistry and surface sediment diatoms to construct a diatom-inferred total nitrogen model for Bathurst Island. However, this study was limited by excluding unbuffered, low pH sites which characterize the western half of Bathurst Island. By expanding the previous Bathurst Island dataset to include western sites, we have been able to construct a diatom-inferred pH model which will prove invaluable in future climate research in this region. Together, these three studies serve to highlight the sensitivity of freshwater ecosystems to relatively minor anthropogenic disturbances and represent some of the earliest known anthropogenic impacts on North American aquatic ecosystems. / Thesis (Master, Biology) -- Queen's University, 2007-12-20 15:20:46.342

I examined the distribution of stable isotope ratios of nitrogen $( delta sp{15}$N) and carbon $( delta sp{13}$C) in fish and aquatic invertebrates. Animals are enriched in $ delta sp{15}$N compared to their diet and I hypothesized that among-lake variation in the $ delta sp{15}$N of a top predator should reflect variation in the length of the food chain leading to it. A comparative study of a biomagnifying contaminant, mercury, confirmed that the presence or absence of certain key organisms such as pelagic forage fish and the crustacean Mysis relicta determined among-lake variation in mercury in lake trout, a top predator in the lakes. Mercury levels from the longest food chains where pelagic forage fish and Mysis were present were higher than those from the shortest food chains where these last two components were missing. This biogeographic variation in food chain length was correlated with variation in the $ delta sp{15}$N of trout. The use of $ delta sp{15}$N as a continuous, integrative measure of trophic position was further supported by its correlation to mercury in lake trout. However, such cross-system comparisons in $ delta sp{15}$N can be complicated by differences in $ delta sp{15}$N at the base of the food chain. Using large primary consumers (unionid mussels) as bio-indicators, I showed that $ delta sp{15}$N increases markedly with the human population in the lake watershed, an effect of the high $ delta sp{15}$N of human sewage. Correcting for this baseline variation in $ delta sp{15}$N, I reported that food chains leading up to nearshore fish species varied by about only one trophic level among the 35 lakes studied. A study of the $ delta sp{15}$N of coral reef and intertidal organisms collected along the coast of the the Carribean island of Barbados extended these patterns observed in lakes to coastal systems: baseline variation in $ delta sp{15}$N was related to human density on the adjacent watershed and within-site variation $ delta sp{15}$N

Thesis (Ph. D.)--Lehigh University, 2006. / Includes vita. Includes bibliographical references (leaves 187-192).

Understanding the redistribution and fate of N is essential for justification of Best Management Practices (BMP). This project was conducted on a Hecla fine sandy loam (sandy, mixed, Aquic Haploboroll) soil at the BMP field site near Oakes, North Dakota. One objective of this investigation was to evaluate the residence times of N03- -N in 20 undisturbed lysimeters and its infiltration time through the soil profile to tile drains. Corn (Zea mays L.) was fertilized with 135 kg N ha -1 as ¹⁵N-enriched urea plus 13.5 and 48.1 kg N ha -1 preplant for 1993 and 1994, respectively. Urea-N was band applied to 20 and 10 undisturbed lysimeters at 2.0 and 5.93 atom percent (at %) ¹⁵N in 1993 and 1994, respectively. Average resident times of N03- -N in the lysimeters was 11.7 months. Lysimeter and tile drainage indicate the presence of preferential pathways. Residence times of N03- -N depend on frequency and intensity of precipitation events. Another objective was to determine what portion of the total N in the crop was from applied urea-N and what portion was from the native soil-N. Nitrogen plots received ¹⁵N enrichments of 4.25 and 5.93 at % ¹⁵N in 1993 and 1994, respectively. At the end of the 1993 and 1994 growing season, 41.5% and 35.7% of the labeled fertilizer N remained in the soil profile, while the total recovery of applied ¹⁵N in the soil-plant system was 86.2% and 75.4%, respectively. Low recoveries of applied N may have been the result of soil or aboveground plant biomass volatilization, or denitrification or preferential flow processes. Further research needs to be conducted with strict accountability of gaseous loss and the mechanism(s) responsible. / U.S. Bureau of Reclamation

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