Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. Title from title screen (viewed Mar. 21, 2007). Includes bibliographical references (leaves 97-101). Online version of the print original.

Inland lakes are important resources to humans, while the eutrophication effect caused by an overload of nutrients is a significant problem. This study focuses on utilizing the satellite remote sensing to monitor the water quality of Lake Simcoe, Ontario, Canada, which has been suffering from the overload of Total Phosphorus (TP) and therefore eutrophication for decades. The data employed in this study includes 22 cloud-free Landsat 5 TM images, as well as the nearly simultaneous in-situ data from 15 observation stations on the lake. Compared to the generally used model, an improved model is developed in this study to estimate the Secchi Disk Transparency (SDT), a parameter for water clarity measurements, using the TM images. Models based on different band combinations are compared to estimate the chlorophyll-a (chl-a) concentration. The results of these estimations are validated using the in-situ data by the linear regression analysis, and the accuracies are measured by the correlation coefficients R2. The results reveal that the improved SDT model provides higher prediction accuracies than the general model when applied to 68.2% (15 out of 22) of the images. The majority of the SDT predictions show high R2, whereas some of the estimated chl-a concentrations have weak relationships with the in-situ data. The possible reasons for this are the geo-location of stations, as well as the influences of chl-a and Dissolved Organic Carbon (DOC). The resultant concentration maps indicate that the eutrophic water is normally distributed at the near-shore areas and the northeastern part of Lake Simcoe. In addition, the southern Cook’s Bay has always been suffering from an extremely serious water quality problem even until now. Meanwhile, the water quality of the southwestern part of Lake Simcoe is much better than the other parts of this lake. The results also show that the water quality of Lake Simcoe was at its worst in August and September for the past 22 years while it was much better in the other sampling seasons. According to the trend of the monthly averaged SDT, on an overall scale, the SDT dropped from 1980 to 1982 and then kept relatively stable until the fall of 1992, followed by a gradual increase until 2000, and then stayed constant until the summer of 2008. The chl-a concentration reveals an inverse trend, i.e., the higher the chl-a concentration, the more turbid the water.

Inland lakes are important resources to humans, while the eutrophication effect caused by an overload of nutrients is a significant problem. This study focuses on utilizing the satellite remote sensing to monitor the water quality of Lake Simcoe, Ontario, Canada, which has been suffering from the overload of Total Phosphorus (TP) and therefore eutrophication for decades. The data employed in this study includes 22 cloud-free Landsat 5 TM images, as well as the nearly simultaneous in-situ data from 15 observation stations on the lake. Compared to the generally used model, an improved model is developed in this study to estimate the Secchi Disk Transparency (SDT), a parameter for water clarity measurements, using the TM images. Models based on different band combinations are compared to estimate the chlorophyll-a (chl-a) concentration. The results of these estimations are validated using the in-situ data by the linear regression analysis, and the accuracies are measured by the correlation coefficients R2. The results reveal that the improved SDT model provides higher prediction accuracies than the general model when applied to 68.2% (15 out of 22) of the images. The majority of the SDT predictions show high R2, whereas some of the estimated chl-a concentrations have weak relationships with the in-situ data. The possible reasons for this are the geo-location of stations, as well as the influences of chl-a and Dissolved Organic Carbon (DOC). The resultant concentration maps indicate that the eutrophic water is normally distributed at the near-shore areas and the northeastern part of Lake Simcoe. In addition, the southern Cook’s Bay has always been suffering from an extremely serious water quality problem even until now. Meanwhile, the water quality of the southwestern part of Lake Simcoe is much better than the other parts of this lake. The results also show that the water quality of Lake Simcoe was at its worst in August and September for the past 22 years while it was much better in the other sampling seasons. According to the trend of the monthly averaged SDT, on an overall scale, the SDT dropped from 1980 to 1982 and then kept relatively stable until the fall of 1992, followed by a gradual increase until 2000, and then stayed constant until the summer of 2008. The chl-a concentration reveals an inverse trend, i.e., the higher the chl-a concentration, the more turbid the water.

Thesis (M.S.) in Resource Economics and Policy--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaves 71-80).

Thesis (M.S.), Natural Resources (Water Science), University of Wisconsin--Stevens Point, 2002. / Includes bibliographical references (leaves 37-38).

Thesis (M.A.)--York University, 1997. Graduate Programme in Geography. / Typescript. Includes bibliographical references (leaves 182-185). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL:http://wwwlib.umi.com/cr/yorku/fullcit?pMQ27340.

In order to reconstruct a long-time tropical terrestrial record of Asian monsoon in South China, the organic carbon in a 120 m lacustrine sediments from Maar Lake Tianyang was analyzed. Results in TOC, C/N and δ13C value show two lines of variations: (1) from a deep lake environment below 42 m to a shallow lake environment of the upper 42 m, (2) environmental changes between glacial and interglacial conditions throughout the lacustrine sediment sequence. In the shallow lake stage, δ13C values change according to glacial and interglacial periods, comparable with other proxies such as pollen, TOC and magnetic susceptibility. However, variations of these proxies including δ13C values are suppressed in the deep lake sequence, a result of the exceptionally high in-situ aquatic (diatom) productivity within this tropical lake. To differentiate the internal productivity and terrigenous high plant input for the deep lake sequence, a three-end-member model (diatom, C3 and C4 land plants) was developed. The result helps extract further information from the deep lake sequence that reveals both the autochthonous productivity caused by lake-level and terrestrial changes by external forcing mechanisms. The n-alkanes indexes from 115 selected samples show distinctive distributions of various chain-length homologues. Most n-alkane indexes (e.g. Paq, CPI and ACL) show more frequent fluctuations than organic carbon records, implying other environmental alterations within the glacial and interglacial periods. Most n-alkanes indexes show a clear relationship with the palaeoclimate history, but further comparison of individual compound concentrations to other environmental indexes (pollen and δ13C values) suggests that n-C29 is a better index of tree concentration while n-C31 has alternative source from flowering trees instead of grasses. Unique appearance of hopanes in the deep lake sediments suggests high activity of methanotrophic bacteria in chemocline. The examination of GDGT concentration from 130 samples indicates pH, temperature and evolution of archaea and bacteria communities. Complications in the interpretation and correction of GDGT results are also discussed and several alternative corrections for palaeo-temperature reconstruction are provided for further investigations. According to both n-alkane and GDGT results, the sediment sequence contains mainly three different stages: the aquatic mixing community (Crenarchaeota and methanotrophic bacteria) from the bottom to 78m; the aquatic methanotrophic community (Euryarchaeota and methanotrophic bacteria); the terrestrial aerobic community (aerobic bacteria). / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

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L'eutrophisation antopogénétique et la baisse augmentant stimulent l'inéret sur l'avenir des lacs, leurs organismes et des rares plantes. L'objet de mon travail est le lac de Daugai et son territoire qui compte 38723 ha de surface, étant a l'élévation de Dzūkija. Dans mon travail, j'ai essayé d'évaluer l'influence de facteurs abiotiques et biotiques pour l'évolution du lac de Daugai et de son territoire. Le travai est fait sous le principe d'analyse cartographique et sous l'analyse de recherche botanique. J'ai utilisé les cartes topographiques: années 1890- 1: 21000, 1937 - 1:25000, 1957 - 1: 25 000, 1999 - 1: 10 000 (OTR10LT) pour faire l'analyse cartographique du lac Daugai. Cettes cartes sont liées au systeme de coordonnées de la Lituanie. (LKS - 94). La division de l'utilité du sol est faite sous le principe de vectorisation. Les aréales de l'utilité du sol dans ce territoire sont crées sous le format ArcView shape. Les surfaces des aréales sont utilisés pour l'analyse de données. Apres avoir comparé le matériel cartographique il est constaté que la surface du lac Daugai est changé de 1097, 58 a 915,81 ha pendant la periode de 1890 jusqu'a l'année 1999. Le niveau d'eau est changé de 131, 1 a 127,5 metres. La surface du lac et le niveau d'eau est changé a cause des travaux de méloration de 1928 et de 1966. Apres avoir asséché les prairies, les bois devenaient plus nombreux. On suppose que la superficie des bois va augmenter a cause du developpement du tourisme de la... [to full text]

Given the prominent role of nitrogen in the eutrophication of aquatic systems, recent increases in nitrogen loading to freshwaters are of concern. A comparison of nitrogen retention in freshwaters in North America and Europe shows that wetlands retain the greatest proportion of their nitrogen load, followed by lakes and then rivers. A comparison of the relative importance of nitrogen retention mechanisms found denitrification to be responsible for the greatest proportion followed by nitrogen sedimentation and then uptake by aquatic plants. A more in-depth examination of denitrification in the littoral sediments of Lake Memphremagog in Quebec, using the N2 flux technique, found an average denitrification rate of 111 mumol N m-2 h-1. Denitrification rates were positively related to the % organic matter of the sediment, temperature and macrophyte biomass density and negatively related to depth. These results, in combination with a review of the literature indicate that denitrification rates are higher in littoral than profundal sediments.