河口與近海環境懸浮顆粒物質之探討：顆粒性有機物之來源及懸浮顆粒之重量法測定

Suspended Particulate Matter in the estuarine and coastal environments: origin of organic matter determined from isotopic composition and gravimetric determination of suspended solid

吳栢兆(Po-chao Wu)

指導教授 ： 劉康克

國立中央大學/地球科學學院/水文與海洋科學研究所/碩士(2014年)

摘要

淡水河位於台灣北部，流域經過台北市與新北市，為台灣人口密度最高的地方。都市排放大量之廢水，對淡水河造成嚴重的污染，進而影響河中之懸浮顆粒物質等生地化過程。透過定性與定量分析顆粒物質，不僅可以了解淡水河口顆粒性有機物之來源以及生地化過程，也可以了解淡水河口懸浮顆粒物質之輸送過程。
過去之研究認為在淡水河口中之顆粒性有機物來源有汙水、土壤以及沉積物，然而本研究對前人2009年在重陽橋所測量之結果提出討論與推算。結果發現淡水河口中之汙水不是直接提供顆粒性有機物之來源，而是汙水所含營養鹽經由藻類吸收後，所產生之藻類以及其碎屑，才是主要的顆粒性有機物來源。本研究不僅找出藻類碎屑之特性，並且以此作為新的端成份重新考慮。經由推算後得到2009年2月之顆粒性有機物來源為藻類碎屑與沉積物各佔45.3%、51.3%，土壤佔3.5%。而2009年7月之顆粒性有機物主要來源為藻類碎屑，佔75.3%；沉積物為次要，佔17.3%，其餘則為土壤佔7.5%。
本研究也對河口與近岸海洋環境之懸浮顆粒濃度進行討論，結果顯示河口與海洋環境懸浮顆粒濃度會受到過濾之背景值影響(0.2 ~28 mg)。在這樣作用複雜的環境之下，進行少量體積過濾測量懸浮顆粒濃度時，就必須使用不同體積之樣水，進行重複過濾測定，再由迴歸分析，藉此修正背景值之影響，最後可以得到最可靠之懸浮顆粒濃度。換言之，進行一次之過濾測量結果是很不準確的。
未經背景值修正前，重量法測定結果與OBS資料兩者之相關性與顯著性皆不好(R2 = 0.151, p = 0.046)；迴歸修正之後再進行比較，兩者關係提升(R2 = 0.568, p < 0.001 )，顯示迴歸修正之重要。然而OBS資料較重量法結果高出很多，顯示OBS原先之設定可能有問題。在河口或近岸海洋環境這樣複雜的環境下，OBS之校正就必須更加嚴謹，才能得到最佳觀測結果。

關鍵字

顆粒性有機物 ； 懸浮顆粒濃度 ； 氮同位素組成 ； 淡水河 ； 碳氮比

並列摘要

The Danshuei River is located in Northern Taiwan and flows through the metropolitan are of the Taipei City and the New Taipei City, the most densely populated area in Taiwan. Large amount of waste is discharged into the Danshuei River and strongly affects the concentrations of suspended organic matter and nutrients. Qualitative and quantitative analyses of suspended particulate matter can not only give us information about the biogeochemical processes, but can also help us understand the transportation process of the suspended solid in the Danshuei River.
In the past, the particulate organic matter (POM) was assumed comprising of anthropogenic wastes, soils and river sediments. However, according to previous observations, it was found that anthropogenic waste not an important source of POM. Because of the high correlation between particulate organic carbon (POC) and chlorophyll-a, we considered that phytodetritus is an important source of particulate organic matter in the Danshuei River. Thus this study defined the properties of phytodetritus and used them to represent a new end-member to calculate the contributions from different sources of POM in the Danshuei estuary. Using a three end member mixing model based on δ15NPN values and C/N ratios, we calculated the fractions from the three major sources of POM,namely, phytodetritus, soils and bed-rock derived sediments, in the estuary. Their contributions were, respectively, 45.4%, 51.8% and 2.8% in February 2009, and 75.3%, 17.3% and 7.5% in July 2009.
This study also investigated the concentrations of suspended solid in the estuarine and coastal environments. The results show that the concentrations of suspended solid derived from the measurements were affected by blanks, which may be contributed by salt or dissolve organic matter retained by the filters. It is necessary to carry out replicated measurements for the concentration of suspended solid and use linear regression to obtain the most reliable results.
It was found that, without blank correction, the correlation between gravimetric results and OBS data (R2 = 0.151, p = 0.046) is insignificant. After correction for the blanks by regression analysis, they were significantly correlated (R2= 0.568, p < 0.001), indicating the importance of regression analysis for blank correction. However, most of the OBS data are overestimated relative to the gravimetric results, indicating problems with the original setting of the OBS. Therefore, calibration of the OBS should be carried out very carefully in order to obtain optimal results in such complicated environments.

並列關鍵字

particulate organic matter ； concentration of suspended solid ； nitrogen isotopic composition ； the Danshuei River ； C/N ratio

參考文獻

白書禎, 郭廷瑜, 鐘仕偉, 蘇宗德, 1998. 疊氮修正希巴辣光度測氧法及其在環境監測上應用. 化學(中國化學會) 56, 173-185.

彭宗仁, 劉滄棽, 林幸助, 2006. 穩定同位素在農業及生態環境上之應用. 台灣農業研究, 55-90.

Ahad, J.M.E., Ganeshram, R.S., Spencer, R.G.M., Uher, G., Upstill-Goddard, R.C., Cowie, G.L., 2006. Evaluating the sources and fate of anthropogenic dissolved inorganic nitrogen (DIN) in two contrasting North Sea estuaries. Science of the Total Environment, 372, 317-333.

Ashkenas, L.R., Johnson, S.L., Gregory, S.V., Tank, J.L., Wollhein, W.M., 2004. A stable isotope tracer study of nitrogen uptake and transformation in an old-growth forest stream. Ecology, 85, 1725-1739.

Barrie, A., Prosser, S.J., 1996. Automated analysis of light-element stable isotopes by isotope ratio mass spectrometer. Marcel Dekker, Inc, New York., 1-46.