臺灣博碩士論文加值系統

過去對東海二氧化碳所進行過的研究，幾乎毫無例外地均指出，整個東海陸棚一年四季皆為大氣二氧化碳的「匯」。但近年來本實驗室在夏、冬兩季的觀測結果發現，在鄰近長江口的內陸棚海域，夏季時為大氣二氧化碳的強「匯」，冬季時則大致呈現海氣平衡的狀態。此種季節變化的特性，可由冬季時強烈的垂直混合作用，將夏季時累積在底水中的二氧化碳，帶至表水加以解釋。若此解釋為真，則當秋季水體開始發生垂直混合作用時，鄰近長江口的內陸棚海域應會呈現大氣二氧化碳「源」的狀態。為驗證上述假說，本研究利用海研一號 980 航次 ( 2011年10月22日~11月3日)，對秋季時整個東海陸棚碳化學參數及海氣二氧化碳交換通量的分布情形，進行了完整的調查。
研究結果顯示，表水 DIC 的變動範圍介於 1913 ~ 2058 μmol kg-1之間，呈現由內陸棚向外陸棚遞減的趨勢； TA 的變動範圍介於 2216 ~ 2267 μmol kg-1 之間， pH 介於 7.906 ~ 8.043 之間，兩者皆呈現由內陸棚向外陸棚遞增的趨勢。整體而言，上述碳化學參數之空間分布特徵皆與秋季時東海的環流形態相符。海–氣二氧化碳的分壓差 （ΔpCO2 = pCO2sw - pCO2air） 分佈範圍介於 -50 ~ 167 μatm 之間。深於等深線 60m 的中、外陸棚海域，ΔpCO2 皆小於 0 ，顯示此海域是大氣二氧化碳的「匯」；淺於等深線 60m 的內陸棚海域，ΔpCO2皆大於0，顯示此海域是大氣二氧化碳的「源」。整個東海陸棚 ΔpCO2 的平均值為 5 μatm，顯示就整體而言，秋季時東海陸棚扮演了大氣二氧化碳「源」的角色。海–氣二氧化碳交換通量的分佈範圍介於 -7.4 ~ 29.5 mmolC m-2 day-1 之間。「源」、「匯」區平均值分別為 7.0 ± 6.1和 -2.3 ± 1.5 mmolC m-2 day-1。將上述平均通量分別乘上面積後可求得：秋季時東海陸棚的「源」區，每天的二氧化碳釋放量約為 32440噸；「匯」區每天的吸收量約為 22200 噸。整體而言，東海陸棚秋季時扮演了大氣二氧化碳的「源」的角色，其淨釋放量約為每天 10240噸。
綜言之，本研究結果驗證了上述的假說：當秋季水體垂直混合作用開始發生時，的確可以將夏季時累積在底水中的二氧化碳重新釋放回大氣，使得此時東海陸棚轉變為大氣二氧化碳的「源」。然而，此結果明顯有別於1990年代秋季時的觀測數據。推測此差異可能與近二十年來，日益嚴重的優養化現象有關。

Previous studies in the 1990s have shown that the entire East China Sea (ECS) shelf was a sink for atmospheric CO2 all year round. However, more recent studies suggested that the inner shelf near the Changjiang Estuary may act as a CO2 source in autumn in response to the increased eutrophication over recent decades. In order to explore the ECS shelf currently acting as a sink or source of atmospheric CO2 in autumn, comprehensive carbon chemistry data (total alkalinity (TA), dissolved inorganic carbon (DIC), pH , and partial pressure of CO2 (pCO2) and other pertinent data (temperature, salinity, nitrate, and dissolved oxygen) were measured in the entire ECS shelf in October 2011.
Results show that the spatial variations of DIC, pH, and TA range from 1913 to 2025 μmol kg-1, 7.906 to 8.043, and 2216 to 2267 μmol kg-1, respectively, corresponding well to the seasonal circulation pattern. In addition, the inner shelf area (water depth ≤ 60m) was a source for atmospheric CO2 with an average sea-air exchange flux of 7.0±6.1 mmolC m-2 day-1, while the middle and outer shelf areas (water depth > 60 m) were a sink with an average flux of -2.3 ± 1.5 mmolC m-2 day-1. The average ΔpCO2 (ΔpCO2 = surface seawater pCO2 – atmospheric pCO2) and sea-air CO2 exchange flux in the entire study area were about 5 matm and 0.6 mmolC m-2 day-1, respectively, indicating that the ECS shelf acted as a source of atmospheric CO2 in autumn as a whole. Overall, the entire study area may release 10240 tons CO2 per day into the atmosphere in autumn. Moreover, the inner shelf near the Changjiang Estuary in autumn has changed from CO2 sink area in the early 1990s to source area in the late 2000s. This decadal change may be associated with the increased eutrophication over the past decades. This would increase both the photosynthetic removal of CO2 in surface waters and the respiratory release of CO2 in bottom waters during summertime, thereby returning more CO2 to the surface during the subsequent mixing season in autumn.

摘要 I
Abstract II
致謝 III
目錄 IV
表目錄 V
圖目錄 VI
一、緒論 1
1.1研究背景 1
1.2文獻回顧 2
1.3研究目的 2
二、材料與方法 5
2.1測站位置及採樣時間 5
2.2採樣方法 5
2.3分析方法 5
2.3.1海水酸鹼值(pH)之測定 5
2.3.2海水中溶解態無機碳(DIC)之測定 6
2.3.3海水中總滴定鹼度(TA)之測定 6
2.3.4海水中二氧化碳分壓(pCO2 )之計算 6
2.3.5走航式二氧化碳分壓分析系统(Underway pCO2 system )之連續測定 7
2.3.6海–氣界面二氧化碳通量之計算 7
2.4海水中表觀耗氧量(Apparent Oxygen Utilization，AOU) 8
三、結果 9
3.1表水溫鹽之空間分布 9
3.2表水碳化學參數之空間分布 9
3.3二氧化碳海–氣交換通量之空間分布 10
3.4溫度、鹽度、pH、DIC、TA和pCO2之垂直斷面分布 10
四、討論 13
4.1秋季時東海內陸棚海域大氣二氧化碳「源」區的成因 13
4.2與前人研究結果之比較 14
五、結論 17
參考文獻 19

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