海洋中的溶解態有機碳(Dissolved organic carbon, DOC)具有與大氣中二氧化碳相當的碳儲存量，而河口系統是碳循環中一個重要的組成因子，也是連接陸地與海洋之間的輸送帶，由於其特殊的化學、物理、地質及生物性質，使其成為最豐富之生態環境。DOC的研究對於化學海洋學和生物海洋學有重要的意義。本研究將對台灣海峽及台灣河川中DOC濃度分布及變化作探討，目的為了解DOC於不同季節輸出量對環境之影響。
台灣河川在乾、濕季時，DOC 濃度隨鹽度增加而遞減，而接近出海口測站DOC 濃度較低，是因受低濃度DOC的海水混合所導致。在河水流動的過程中，不斷會有陸源物質輸入，由DOC與Chl. a 、CH4及BOD皆呈現正相關來推論，生物作用與污染源輸入皆為DOC來源。台灣河川DOC(鹽度小於1)平均濃度分別為: 乾季245±254 μM, n=32 (42-1185 μM)；濕季:183±151 μM, n=24 (18-565 μM)。本研究所採集的25條河川總DOC Flux為87.8 Gg C/yr，推算台灣整體河川DOC Flux為101.9 Gg C/yr (濕季輸出通量66.7 Gg C/yr；乾季輸出通量35.2 Gg C/yr)。台灣河川DOC Flux雖然只占熱帶地區的0.07%，但DOC單位面積(3.92 gC/m2/yr)輸出量是熱帶區域(2.13 gC/m2/yr)的1.8倍，推測台灣人口密度高，國土開發狀況遠高於其他區域，因此人類活動對於DOC輸出有著相當大的影響。
台灣海峽冬季與夏季，DOC與Sigma-T皆有顯著的負相關，顯示海峽內海水中的DOC分佈主要受到物理混合作用。海峽西側的測站受大陸沿岸流影響，有較高的DOC濃度，且隨著深度增加，DOC濃度有遞減趨勢。底水因受到較多黑潮水的影響，而黑潮水本身DOC濃度較低，所以底水濃度會較低。冬季DOC的分解速率高於夏天，推測冬季時受到大陸沿岸流影響，帶來較多營養鹽且海水垂直混合良好，可提供細菌生長所需物質，因此冬天耗氧率較高。台灣海峽夏季DOC輸出量(北測線:3.85×1012 mol C/yr；南測線:3.75×1012 mol C/yr)較冬季輸出量(北測線:3.69×1012 mol C/yr；南測線:2.84×1012 mol C/yr)高。夏季因河川流量大，會輸送較多的陸源有機物質至海峽中，且西南季風盛行，會有較多的南海水流向海峽內，所以夏季的DOC輸出量較冬季高。

Dissolved organic carbon (DOC) is one of the largest pools of carbon in the ocean, and is of the same size as the carbon dioxide in the atmosphere. Estuaries connecting the land and the ocean are one of the most important DOC sources to the ocean, and play an important role in the global carbon cycle. Because of their complex chemical, physical, geological and biological properties, estuaries have become rich ecological environment. In this study, we investigated the seasonal distributions of DOC in the Taiwan Strait (TS) and Taiwanese rivers, aiming to understand the distributions and variations of DOC in different seasons.
The results show that DOC concentrations are generally the highest in the upper estuary, and then decrease downstream due to mixing with the low DOC seawater. The process of river flow constantly accumulates terrestrial material, and the DOC shows positive correlations with Chl. a, CH4 and BOD (Biochemical Oxygen Demand), suggesting that biological activities and pollutions could be sources of DOC in the estuary. The DOC concentrations (salinity<1) varied in dry (Nov.-Apr.) and wet (May-Oct.) seasons with ranges of 42-1185 μM (mean=245±254μM; n=32) and 18-565 μM (mean=183±151μM; n=24), respectively. The total DOC flux of 25 rivers is 87.8 Gg C/yr, which can be translated to the fluxes of all rivers in Taiwan to be 101.9 Gg C/yr. The amount of DOC flux in Taiwan is only about 0.07% of the tropical area, but the per unit area flux (3.92 gC /m2 /yr) is almost twice those of the tropical rivers (2.13 gC /m2 /yr). In Taiwan, the population density and land use are higher than the world average. Consequently, the impacts of the environment by human activities reveal the utmost export of DOC, and need further investigation.
Next, in the TS, the DOC shows significant negative correlations with Sigma-T, and the distributions of DOC are mainly controlled by physical mixing in both winter and summer. In the western TS, DOC concentration is relatively high, compared to the eastern part, and is because of low temperature and salinity, but high DOC coastal China current flowing from north to south. DOC concentration decreases with increasing depth owing to the intrusion at depth by the Kuroshio, which contains relatively low DOC.
In winter, the import of coastal China current brings more nutrients from north to south, and supports the growth of bacteria which depletes the DOC and oxygen. As the result, DOC decomposition rate is higher in winter than in summer. The TS’s DOC fluxes in summer (northern TS: 3.85×1012mol C/yr；southern TS: 3.75×1012mol C/yr) are higher than in winter (northern TS: 3.69×1012mol C/yr；southern TS: 2.84×1012mol C/yr). Main differences are due to the prevailing southwest monsoon winds in summer transporting more water from the South China Sea to the TS, and the river discharge brings more terrigenous organic matters into the TS. Therefore, the DOC export in summer is higher than in winter.

致謝.......................................................................................i
中文摘要...............................................................................ii
Abstract...............................................................................iv
目錄.....................................................................................vi
圖目錄................................................................................viii
表目錄..................................................................................x
第一章 前言..........................................................................1
第二章 研究材料與方法........................................................3
第三章 結果與討論-台灣河川部分........................................8
　　3.1台灣河川乾、濕季定義.............................................8
　　3.2 營養鹽(NO3-、NO2-、PO43-、SiO2)與鹽度關係..8
　　3.3 DOC(溶解態有機碳)與鹽度.....................................8
3.4 DOC與營養鹽、Chl. a、CH4關係...........................9
　　3.5 DOC與SS、POC、AOU關係.................................9
　　3.6 DOC與BOD (生化需氧量)關係..............................10
　　3.7台灣河川DOC濃度與DOC Flux..............................10
第四章 結果與討論-台灣海峽部分......................................21
4.1台灣海峽北部.........................................................21
4.2 台灣海峽南部........................................................23
　　4.3台灣海峽討論.........................................................26
　　4.4台灣海峽DOC Flux.................................................28
第五章 結論........................................................................30
參考文獻.............................................................................55
附錄一 台灣河川DOC濃度與DOC Flux表...........................60
附錄二 Huang, T.H., Fu, Y.H., Pan, P.Y., and Chen C.T.A., 2012. Fluvial carbon fluxes in tropical rivers. Current opinion in environmental sustainability, 4(2): 162-169.......60

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