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    請使用永久網址來引用或連結此文件: http://ir.lib.ncu.edu.tw/handle/987654321/44401


    題名: 淡水河口之顆粒性有機碳、氮同位素及溶解性無機氮同位素之研究;A Study of Particulate Organic Carbon and Nitrogen and Dissolved Inorganic Nitrogen and Their Isotopic compositions in the Danshuei Estuary
    作者: 鄭峻翔;Chun-Shiang Cheng
    貢獻者: 水文與海洋科學研究所
    關鍵詞: 同位素分化效應;顆粒性有機物質;氮循環;Particulate organic matter;Isotope fractionation;Nitrogen cycle
    日期: 2010-07-21
    上傳時間: 2010-12-09 10:50:56 (UTC+8)
    出版者: 國立中央大學
    摘要: 淡水河位於臺灣北部,流域內工商業發達,人口聚居達五百萬以上。都市的廢水排入淡水河中,對河中懸浮物質與營養鹽有很大的影響。本研究乃利用碳、氮同位素作為示蹤劑,去探討有機物的來源。藉由分析顆粒性氮及溶解性無機氮之同位素組成,從兩者之關係,進而了解藻類吸收無機氮營養鹽之同位素分化作用。透過這些化學及同位素組成之分析,可以讓我們更了解淡水河系統中,有機物來源及生地化過程。本研究建立一個氨氮同位素標本製備方法:擴散法(Diffusion Method),來量測淡水河的銨(d15N-NH4+)之氮同位素組成,對本研究極有助益。 本研究進行了三次淡水河口採樣,在重陽橋利用兩個潮汐週期採得鹽度(0~16 psu)之水樣,可代表河口中段之狀況。主要目的是了解水體中營養鹽濃度的變化,以及與其它水文因子的關係,藉以探討影響淡水河顆粒性有機物的主要因子與生地化過程。 淡水河之顆粒性氮同位素值在-17‰~+4‰之間,比世界其他河川的顆粒性氮之同位素值(-2‰~+20‰)來的輕很多。研究結果顯示,淡水河口之顆粒性有機物與葉綠素大多有良好之線性關係,顯示河口中藻類所產生之顆粒性有機物十分重要,推斷是藻類吸收污水中之營養鹽後生長出來,而藻類生長所需氮的主要來源是污水中的銨離子,在吸收過程中有強烈的同位素分化作用,顆粒性有機氮與銨離子之同位素差異可達-19‰。本研究首次證實Pennock等人(1996)在實驗室中培養矽藻所觀察到的受銨濃度影響之強烈同位素分化作用,在淡水河口的水體中的確會發生。 在世界上許多研究過的河川中主要的氮物種是硝酸根,而淡水河口是以銨離子為主要的氮物種,由於藻類吸收銨離子之強烈分化作用,使得淡水河口中所量測到的顆粒性氮之同位素值,比世界其他河川所量測出之顆粒性氮之同位素值來的輕很多。 由於淡水河河口之特殊環境,未來可對其氮循環及同位素分化作用作進一步之探討。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.
    顯示於類別:[水文與海洋科學研究所] 博碩士論文

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