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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Distribution of CH4 and N2O in natural waters around Taiwan

Tseng, Hsiao-Chun 29 July 2005 (has links)
Abstract Methane (CH4) and nitrous oxide (N2O) are not only important but also long-lived greenhouse gases. Unfortunately, in Taiwan, although there are some data on CH4 emission from rivers and lakes there is no data about N2O emission from rivers, lakes and coasts. So this study investigated CH4 and N2O distribution in natural waters around Taiwan. In Taiwan, the average CH4 concentration in rivers is about 3082¡Ó12399nM (n=152). The average CH4 concentration in mountain lakes is about 2899¡Ó7291nM (n=51). The average CH4 concentration in lower elevation lakes and reservoirs is about 1825¡Ó2755nM ppmv (n=95). The average CH4 concentration in near-shore waters is about 36.7¡Ó285nM (n=476). The CH4 distribution is rivers> mountain lakes>low-elevation lakes and reservoirs >seawater. In southeastern China, the average CH4 concentration in rivers is about 1029¡Ó2487nM ppmv (n=36). The average CH4 concentration of samples taken from rivers in southeastern China is lower than Taiwan rivers. But the highest CH4 concentration of all samples is in Chih-Kan river of southeastern China (14914nM), due to uneven population distribution as well as different levels of development among cities and suburbs. In Taiwan, the average N2O concentration in rivers is about 32.8¡Ó69.1nM (n=58). In southeastern China, the average N2O concentration in rivers is about 29.7¡Ó9.05nM (n=36). The average N2O concentration in Taiwanese rivers is higher than found in southeastern China. This is likely because farmers in Taiwan use more synthetic fertilizers so the soil becomes full of N element, and then rivers and rains rinse the soil. This process has increased the concentration of N and N2O in rivers. In summer, the average CH4 and N2O concentrations in northern Taiwan Strait are about 3.27¡Ó2.42nM and 7.22¡Ó0.62nM (n=7), respectively; and the average CH4 and N2O fluxes are about 0.17¡Ó0.43£gmol/m2/h and 0.14¡Ó0.26 £gmol/m2/h, respectively. The average CH4 and N2O concentrations in southern Taiwan Strait are about 3.35¡Ó1.97nM and10.31¡Ó2.51nM (n=30), respectively; and the average CH4 and N2O fluxes are about 0.04¡Ó0.09£gmol/m2/h and 0.19¡Ó0.22 £gmol/m2/h, respectively. In winter, the average CH4 and N2O concentrations in northern Taiwan Strait are about 4.74¡Ó1.43nM and 8.41¡Ó0.46nM (n=9), respectively; and the average CH4 and N2O fluxes are about 0.10¡Ó0.14£gmol/m2/h and 0.008¡Ó0.033 £gmol/m2/h, respectively. The average CH4 and N2O concentrations in southern Taiwan Strait are about 4.70¡Ó2.42nM and 8.36¡Ó0.97nM (n=17), respectively; and the average CH4 and N2O fluxes are about 0.17¡Ó0.46£gmol/m2/h and 0.11¡Ó0.12 £gmol/m2/h, respectively. Taiwan Strait is a source of CH4 and N2O regardless of whether it is summer or winter. In summer, the average CH4 and N2O concentrations in the South China Sea are about 4.34¡Ó2.33nM and 8.23¡Ó1.5nM (n=55), respectively; and the average CH4 and N2O fluxes are about 0.33¡Ó0.35£gmol/m2/h and 0.20¡Ó0.24 £gmol/m2/h, respectively. It is a source of CH4 and N2O to the atmosphere. In summer, the average CH4 and N2O concentrations in the West Philippines Sea are about 3.18¡Ó1.57nM and 4.64¡Ó0.39nM (n=60), respectively; and the average CH4 and N2O fluxes are about 0.23¡Ó0.33£gmol/m2/h and -0.28¡Ó0.30 £gmol/m2/h, respectively. It is a source of CH4 but a sink of N2O to the atmosphere.
2

The Last 180 ka Benthic Foraminiferal Mg/Ca Record and the Implication on Intermediate Water Hydrology Variations of the Western Equatorial Pacific ( MD052922C )

Feng, Chun-Chin 29 August 2012 (has links)
The Antarctic Intermediate Water (AAIW) plays an important role on controlling globally climatic change. Numbers of researchers attempted to discuss whether AAIW across the equator or notduring glacial- interglacial transitions. In this study, we analyzed Mg/Ca and £UREE/Ca on benthic foraminiferal species, Cibicidoides wuellerstorfi, from core MD052922C, which retrieved from western equatorial Pacific region, for revealing the long-term variations of Paleohydrology in intermediate water depths of tropical Pacific. Our evaluated results reveal that the Mg/Ca ratios ranging from 1.27 to 2.04 mmol/mol, and ranging between 2.2 and 3.2¢J when calculating into paleotemoeratures.Highest Mg/Ca can be observed in MIS 6. This finding implies that the present AAIW mean temperature is colder than glacials, and the present AAIW is well-ventilated than that in glacials.Higher £UREEs/Ca values are usually well correlated with old and poor ventilated water masses. In our record, higher £UREEs/Ca values are observed at MIS 5 impling that the intermediate depth water mass of the western tropical Pacific is poor ventilated when comparing to glacials.

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