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North Canal Oxidation Process Of Ammonia Nitrogen And Microbial Response Characteristics

Posted on:2013-02-14Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y YuFull Text:PDF
GTID:1111330371474797Subject:Physical geography
Abstract/Summary:PDF Full Text Request
Many rivers in urban have been seriously polluted by industrialization and urbanization. Excess influx of nitrogen from anthropogenic source into rivers can alter the nutrient pool in an aquatic system. Ammonia nitrogen was degraded through nitrification and denitrification processes and aquatic bio-assimilation. There are microorganisms participate in both kinds of mechanism. Therefore, it is very important to understand the role of microorganisms in the process of nitrogen transformation in order to address nitrogen pollution. Ammonia-oxidizing process is rate-limiting in which chemoautotrophic ammonia-oxidizing bacteria transfers ammonia to nitrite uses ammonia and carbon dioxide as a carbon and nitrogen, combined with oxygen molecules. In this process, organic carbon is not directly involved in, but plays an important role in the nitrification process. Analyzing on each form of nitrogen, transformation, environmental factors and microorganisms in degradation process helps to know much better about ammonia pollution of river water. To study the ammonia-oxidizing process and ammonia-oxidizing bacterial by molecular biology techniques redound to understanding dynamic process nitrogen transport mechanism and make a foundation to govern of the river ammonia pollution.Beiyun River is the important urban river in Beijing that ammonia pollutes seriously and dissolved oxygen concentration lowly. The main purpose of this study was:(1) Understand water pollutants concentration in Beiyun River and Nitrogen pollute distribution feature;(2) Assess the spatial pattern of bacterial community in Beiyun River and the relationship with nutrients and other environmental factors in water;(3) Establish a credible scientific method to determine the quantity of ammonia oxidizing bacteria in water and observe the relation of AOB growth trend response to nitrogen and organic carbon;(4) assess the nitrification activity in water of Beiyun River and its influence factors;(5) explore the impact of human factors and environmental factors on the nitrification process of Beiyun River. The main conclusions be summarized as following:1) Water quality and pollutants' spatial-temporal distribution characteristic was monitored during2010-2011spring, summer, autumn and winter seasons. TN, TP and COD in water were higher than Environmental quality standards for surface water level Ⅲ and Ammonia nitrogen and COD were the main pollute factors by factor analyze. Ammonia concentration was maintained at a high level on temporal and spatial scales. The distributaries, Qinghe River, Bahe River and Liangshuihe River, were influent large number of nutrient concentrations into Beiyun River. Ammonia concentration was showed decreasing trend within a short distance of Beiyun river where was without pollution resources. Dissolved oxygen was showed fluctuating which was affected by influent of distributary and intercept of flood gate and other human activities.2) The bacterial community composition in Beiyun River was examined by terminal restriction fragment length polymorphism (T-RFLP) with PCR amplified16S rDNA fragment during spring, summer and winter2011. The richness, diversity, and evenness in water samples were low that indicated the ecological status of Beiyun River was fragile.The bacterial communities in summer was significantly higher than spring and winter and the218bp fragment was the dominant bacterial in Beiyun river. The bacterial communities in closed water area like reservoir and floodgate have large differences with flux in Beiyun River. Canonical Correspondence Analysis (CCA) through CANOCO software represented the bacterial community in Beiyun River was influenced by nutrients and environmental variables, such as DOC, TP and temperature.3)491bp16S rDNA fragment was amplified targeting the ammonia-monooxygenase gene analyzed Blast homology in GenBank showed that amplification products had high homology with culture-independent ammonia-oxidizing bacteria. AOB population in water was quantified by qRT-PCR targeting amoA, the application curve and melting curve showed that the results were reliable that arrange from6.9×107to1.7x109copies/L. Compared with the results in other research showed that AOB population in Beiyun River was considerable quantity and more than which was in Dong River, Minjiang River and Seine River.Degradation process of inorganic nitrogen and DOC simultaneous with AOB growth in water of Beiyun River was observed through simulation experiments in laboratory. The nitrification process required19days capable of ammonia degradation to a lower level in high ammonia pollution water with no exogenous input. In this process there may have heterotrophic microorganisms involved in the degradation of ammonia beside AOB. AOB and heterotrophic microbes went to death and release organic nitrogen and organic carbon after Ammonia-oxidizing process completely due to lack of nitrogen.4) Carbon degradation process and ammonia degradation process was conducted into two phases. Ammonia-oxidizing process using CO2as carbon source rather than organic carbon that are competed oxygen with carbon degradation process. In order to assess the amount of oxygen consumed during nitrification, an allylthiourea in-hibitor (ATU) was used within ten days of the carbonization process and the oxygen consumption of the nitrification process were observed. And nitrifying activity calculated by the difference between the sum of nitrite and nitrate ions in the samples incubated without and with ATU inhibitor. The result showed that oxygen consumption for microbiological decomposition of nitrogen compounds account for a larger proportion of total biological oxygen demand. Compared with other rivers, potential nitrification activity in water of Beiyun River was high which was provided a sufficient organic carbon and ammonia nitrogen to ammonia-oxidizing bacteria and other microorganisms. But the nitrifying activity in Beiyun River was unable to depredate such high concentrations of ammonia. Nutritional factors and nitrification activity were regressed that result of DTN and DOC concentration was negatively correlated with nitrification activity.5) The space distribution of ammonia, DOC, nitrification activity and the population of ammonia-oxidizing bacteria in two study areas was monitored in situ experiment. The result was showed that ammonia concentration and nitrification activity in water of Shahe Reservoir and Yangwa floodgate were similar. Nitrifying activity and population of AOB in downstream of Shahe floodgate was decreasing due to pollution sources import. But the high nitrification capacity just maintained at a short distance of downstream, ammonia was increasing while nitrifying activity and population of AOB in downstream decreased. Dissolved oxygen increasing and particulate matter resuspension in downstream because Yangwa floodgate had been open frequently lead to flow rate proliferation instantaneous which beneficial to the growth of nitrifying activity and ammonia-oxidizing bacteria. At the same time, removal of particulate matter could be an internal pollution result in ammonia increasing in downstream.
Keywords/Search Tags:Urban river, Ammonia, Ammonia-oxidizing process, Ammonia oxidizingbacteria, Molecular Biolog
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