金門水庫水質變化及高有機性污染形態成因分析

Analyses of the change of water quality and the high organic pollution formation in Kinmen reservoirs

林其鋒(Chi-Feng Lin)

指導教授 ： 吳先琪

國立臺灣大學/工學院/環境工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.02123

摘要

金門湖庫多屬於淺層的在槽湖庫且多處於優養化狀態。水庫提供金門區域約42%公共給水之水源，但因水質不佳，處理困難，故其比例逐年下降。溶解性有機質濃度高與優養化是湖庫水質的主要問題。高濃度的溶解性有機碳(DOC)，在淨水程序中生成消毒副產物(如三鹵甲烷)而使飲水人暴露在致癌的風險中，並且增加淨水成本。因此本研究以金門榮湖與金沙水庫為對象，探討水庫水質變化與高有機物污染之成因及改善方法。
自動溫度記錄計連續監測垂直水溫之結果顯示夏季水體會形成分層，使底層成為厭氧狀態而增加內部營養鹽釋出量。但分層現象易受到強風，大雨及氣溫下降而破壞。在九月份即發生水體翻轉情況使得水體完全混合。水質調查分析顯示榮湖與金沙水庫受高濃度營養鹽的入流影響，產生優養情況。除了七月份兩水庫受颱風影響造成綠藻優勢，以及金沙水庫二月份矽藻大量生長外，其餘時期榮湖與金沙水庫皆以藍綠藻為主要優勢藻種，其中更以柱孢藻(Cylindrospermopsis rociborskii)為優勢種。而柱孢藻形成優勢的原因為水中氮磷比低，混合良好，且其可分泌胞外物質抑制其他藻類。
水庫溶解性有機碳來自集水區與內部自生的產物(底泥釋出與藻類分泌與排泄物)所影響。穩定碳同位素結果顯示庫內溶解性有機碳來源多為藻體分泌物。在冬季至春季，藻類競爭激烈，產生大量藻類分泌物而增加水中溶解性有機碳濃度。

關鍵字

水庫 ； 溶解性有機碳 ； 金門 ； 底泥釋出 ； 藻類消長 ； 穩定碳同位素

並列摘要

Reservoirs in Kinmen are shallow and in-channel reservoirs, and most of them are under eutrophic condition. Reservoirs provide 42 % of the water sources for water treatment plants in Kinmen. The fraction of raw water drawn from reservoirs has been reduced in recent years due to the deterioration of water quality, which lowered the production rate of water treatment plants. Particularly, the high dissolved organic carbon (DOC) in most of the reservoirs is high potential of disinfection byproducts in drinking water, which pose risk of cancer to public and increase the cost for water treatment. Therefore, it is the aim of this study to investigate the change of water quality, the formation of high organic matter, and the possible improving approaches. Rong-hu reservoir and Jin-sha reservoir are the two studied reservoirs.
The results of continuous monitoring of temperature profiles in these two reservoirs indicate that stratification was formed in summer, which led to an anaerobic condition at the bottom of the water column and increased the amount of internal nutrient loading. The stratification was easily broken by strong wind, heavy rainfall and low air temperature. And the turnover occurred quite early in September, which well mixed the water body. The results of water quality investigation showed that the nutrients in reservoirs were imported by run-offs containing high concentration of nutrient. Blue-green algae dominated in the two reservoirs for the whole year, except in July 2013 in the two reservoirs and February 2014 in Jin-sha reservoir. Cylindrospermopsis rociborskii, one of the blue-green algae, outgrew all other algal species in most of time by taking the advantages of low N/P, well-mixing water body, and suppressing other algae by secreting extracellular polymeric substances.
DOCs in the reservoirs were from watersheds and internal sources, sediment and algal exudates. The results of stable isotope carbon ratio analyses showed that DOC in reservoir was mainly produced by algae. In winter and spring, vigorous competition among phytoplanktons induced large amount of algal secretion which formed DOC in water.

並列關鍵字

Reservoir ； DOC ； Kinmen ； sediment release ； algal speciation ； isotope carbon ratio

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