碩士 / 國立中央大學 / 水文與海洋科學研究所 / 98 / The Danshuei River watershed in northern Taiwan is heavily industrialized and commercially developed with more than five million inhabitants. Anthropogenic wastes discharged to the Danshuei River strongly affect the concentrations of suspended organic matter and nutrients. In this study, we use carbon and nitrogen isotopic compositions to trace the origin of organic matter. By analyzing nitrogen isotopic compositions of particulate nitrogen (PN) and dissolved inorganic nitrogen (DIN), we may determine isotope fractionation during algal uptake of nitrogen. From chemical and isotopic compositions we are able to better understand biogeochemical process in the Danshuei River System. We also established the relatively simple diffusion method to measure d15N-NH4+ in the Danshuei Estuary.
The results show that particulate nitrogen isotopic values (δ15NPN) in the Danshuei Estuary fall in the range from -17‰ to +4‰, which is lower than the values observed in other estuaries in the world. Since particulate organic matter (POM) and chlorophyll a (Chl-a) show good linear relationship, algae generated particulate organic matter (POM) should be important. The major source of nitrogen sustaining phytoplankton growth is ammonium (NH4+). The uptake process displays strong isotope fractionation with maximum δ15N shift reaching -19‰. Field observations of this study have corroborated the finding of Pennock et al., (1996) during culture of diatoms that ammonia uptake could be accompanied by large isotope fractionation.
In most studied estuaries in the world, the major nitrogen species is nitrate (NO3-), whereas ammonium (NH4+) is the major nitrogen species in the Danshuei Estuary. Because algal uptake of ammonium (NH4+) has strong isotope fractionation, particulate nitrogen isotopic values (δ15NPN) in the Danshuei Estuary are unusually low.
The distinctive biogeochemical features of the Danshuei Estuary warrant future studies on its nitrogen cycle and isotope fractionation processes.
| Identifer | oai:union.ndltd.org:TW/098NCU05761003 |
| Date | January 2010 |
| Creators | Chun-Shiang Cheng, 鄭峻翔 |
| Contributors | Kon-Kee Liu, Shuh-Ji Kao, 劉康克, 高樹基 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 187 |
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