【摘要】：東江是廣東省及香港特別行政區(qū)重要的飲用水源,其水質的好壞直接關系到廣州、深圳、香港等城市的人民生活和經濟發(fā)展。近年來,隨著經濟的快速發(fā)展和城市化進程的加快,大量富含氮的生活和工農業(yè)污水排放進入東江,已影響到東江干流的水質。氮的超標排放會造成水環(huán)境質量的下降,導致水體發(fā)生富營養(yǎng)化。同時,大量進入河流的氮蓄積在沉積物中,引發(fā)的內源性污染問題也日益突出,引起了國內外學者的廣泛關注。因此了解流域內氮各形態(tài)的含量及分布狀況,探討沉積物中氮的釋放特征及遷移轉化規(guī)律,研究了沉積物-水界面氮的交換通量和影響因素,對控制東江干流的污染狀況,合理保護東江優(yōu)質水源具有重要意義。以東江干流(惠州段)為研究對象,在自然環(huán)境調查的基礎上,于2013年6月~2014年3月在東江干流(惠州段)選取6個采樣點進行采樣,研究了東江干流(惠州段)水體氮的含量,進行水質評價,測定沉積物-水界面氮的交換通量,并進行了不同影響因素下的實驗室模擬試驗,分析了沉積物-水界面氮遷移轉化的影響因素,主要得出以下結論:(1)東江干流(惠州段)水質大部分時間狀況良好,其中TN水質較差,基本滿足Ⅳ~Ⅴ類(湖、庫,以N計),有些點位為劣Ⅴ類;氨氮濃度普遍不高,大部分時間采樣點的值均小于0.5mg/L,水質基本滿足Ⅱ類要求;硝氮濃度的變化范圍為1.28~2.22 mg/L,水體中亞硝氮含量較低,濃度變化范圍為0.001~0.071mg/L。采用內梅羅綜合指數(shù)法對水體氮進行評價,結果表明:硝氮是水體的主要污染物,屬于輕度污染;氨氮和亞硝氮屬于清潔狀態(tài),其中亞硝氮清潔度較高。(2)東江干流(惠州段)沉積物-水界面氨氮全年交換通量均為正值,表明東江干流(惠州段)沉積物作為氨氮的源。硝氮、亞硝氮表現(xiàn)為各點位交換通量均較小。在交換通量模擬試驗中,初始階段沉積物中的氨氮迅速向上覆水釋放。隨著實驗時間的延長,氨氮在沉積物與上覆水之間的交換減慢,氨氮的交換通量逐漸減小。硝氮在沉積物與水界面的交換通量與氨氮變化不同,硝氮的交換通量較小,且沉積物并不是一直作為硝氮的源或匯,而是多次出現(xiàn)匯源轉換。(3)沉積物-水系統(tǒng)交換通量模擬試驗表明:隨著溫度的升高,水體礦化產生的氨氮增多,同時消耗了溶解氧,阻止了硝化反應的進行。厭氧條件氨氮的釋放速率高于有氧條件下的速率,有利于沉積物中氨氮的釋放。硝化和反硝化作用作為沉積物-水系統(tǒng)氮素遷移和交換的主要過程,其發(fā)生同時受到溶解氧的限制。pH值越低,水體中氫離子的濃度越大,交換作用增強,沉積物中釋放的氨氮就越多,加重上覆水中的氮素負荷,相反氨氮交換量減少;在堿性條件下,水體中氨氮減少,氨氮在沉積物和水體之間的濃度梯度增大,加速了氨氮從沉積物中的釋放速率。綜上結果表明,硝氮是上覆水主要的污染物,沉積物是氨氮重要的內在污染源。在沉積物中溶解氧不足條件下,硝氮被還原造成沉積物中氨氮濃度升高,沉積物成為氨氮的源。溫度升高、溶解氧降低以及過酸、過堿條件均有利于沉積物中氨氮的釋放。
[Abstract]:Dongjiang River is an important drinking water source in Guangdong Province and Hong Kong Special Administrative Region. Its quality of water is directly related to the people's lives and economic development of Guangzhou, Shenzhen and Hong Kong. In recent years, with the rapid economic development and the acceleration of urbanization, a large number of nitrogen-rich domestic and industrial and agricultural wastewater discharged into Dongjiang River has affected the East. Water quality in the main stream of the river. Excessive discharge of nitrogen will lead to the decline of water environmental quality and eutrophication. At the same time, the endogenous pollution caused by the accumulation of large amounts of nitrogen into the river sediments has become increasingly prominent, which has aroused widespread concern of scholars at home and abroad. The characteristics of nitrogen release, transport and transformation in sediments were discussed. The nitrogen exchange flux and influencing factors at the sediment-water interface were studied. It is of great significance to control the pollution of the main stream of the Dongjiang River and protect the high quality water sources of the Dongjiang River. In March 14, six sampling sites were selected to study the nitrogen content, water quality assessment, nitrogen exchange flux at the sediment-water interface, and laboratory simulation tests were carried out to analyze the influencing factors of nitrogen migration and transformation at the sediment-water interface. The main conclusions are as follows: (1) The water quality of the main stream of Dongjiang River (Huizhou Section) is in good condition for most of the time, and TN water quality is poor, which basically meets Class IV-V (lake, reservoir, N count), and some points are inferior Class V; the concentration of ammonia nitrogen is generally not high, the value of sampling points is less than 0.5mg/L in most of the time, and the water quality basically meets Class II requirements; The concentration range of nitrite nitrogen was 0.001-0.071 mg/L. The results showed that nitrate nitrogen was the main pollutant in the water body and belonged to light pollution. Ammonia nitrogen and nitrite nitrogen were clean state, and the nitrite nitrogen was clean. The annual ammonia-nitrogen exchange fluxes at the sediment-water interface in the prefecture section are all positive, indicating that the sediments in the main stream of the Dongjiang River (Huizhou section) are the source of ammonia-nitrogen. The exchange flux between sediment and overlying water slows down and ammonia-nitrogen exchange flux decreases gradually. The exchange flux of nitrate-nitrogen at the sediment-water interface is different from that of ammonia-nitrogen, and the exchange flux of nitrate-nitrogen is small. The sediment is not always used as the source or sink of nitrate-nitrogen, but often occurs sink-source conversion. (3) Simulation of exchange flux in sediment-water system. The results show that with the increase of temperature, the ammonia nitrogen produced by water mineralization increases, and the dissolved oxygen is consumed, which prevents nitrification. The release rate of ammonia nitrogen under anaerobic conditions is higher than that under aerobic conditions, which is beneficial to the release of ammonia nitrogen from sediments. The lower the pH value, the greater the concentration of hydrogen ion in the water, the stronger the exchange effect, the more ammonia nitrogen released from the sediment, which aggravates the nitrogen load in the overlying water and decreases the ammonia-nitrogen exchange capacity in the opposite direction. Under alkaline conditions, the ammonia-nitrogen in the water body decreases, and the ammonia-nitrogen concentration between the sediment and the water body increases. The results show that nitrate is the main pollutant in overlying water and sediment is an important internal source of ammonia nitrogen. Under the condition of insufficient dissolved oxygen in sediment, nitrate is reduced to increase the concentration of ammonia nitrogen in sediment and sediment becomes the source of ammonia nitrogen. The reduction of ammonia and the release of ammonia nitrogen from sediments are beneficial to the reduction of oxygen and the over acid conditions.
【學位授予單位】：吉首大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：X52

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