碩士 / 國立臺灣大學 / 海洋研究所 / 93 / The marine nitrogen cycle plays a major role in controlling the biological pump and the environmental conditions of South China Sea (SCS) that are conducive to the study on nitrogen cycle and possible importance on nitrogen fixation. Using nitrate anomaly as precursor, Wong et al., (2002) had indicated that significant contribution of the re-mineralization of nitrogen-rich organic matter were formed by nitrogen fixation. In this study, a series of in-situ and ln-house analysis were performed to demonstrate the seasonal variations of dissolved nitrogenous species and its diurnal variations. Which observed as the first time in South China Sea, completed vertical distributions of various dissolved nitrogen, including nitrite, nitrate, ammonium and dissolved organic nitrogen (DON). In hope to better understand the nitrogen cycle and gain direct evidence of nitrogen fixation. As part of the supporting works for SEATS (South East Asia Time-series Study) program of NCOR, researches were conducted during November 2002 to March 2004.
In this work, nitrite was measured by standard pink azo dye method and ammonium was measured by improved indophenol blue spectrophotometric method. Nitrate was measured by cadmium reduction flow injection analysis method. Total dissolved nitrogen (TDN) was first converted to nitrate by UV photo-oxidation method with addition of persulfate. It is found that, In the euphotic zone (0-200m) DON were the dominate species in the TDN pool. Ammonium, nitrite and DON have highest concentrations in depth 60-80m, correspondent to the chlorophyll-a maximum layer. In addition, during different time, a secondary ammonium concentration maximum can also be found at shallower depth (~ 40m) may be caused by the occurrence of nitrogen fixation. In this study, highest nitrite concentration was found in summer, and lowest appeared in winter. However, the thickness of nitrite distribution in winter is greater than in summer. Result also indicated that the nitrate nutricline in SCS varied seasonally possibly caused by water column structure.
| Identifer | oai:union.ndltd.org:TW/093NTU05274005 |
| Date | January 2005 |
| Creators | Yu-Han Tsai, 蔡宇涵 |
| Contributors | Liang-Saw Wen, 溫良碩 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 96 |
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