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摘要
Purpose Sediments are significant methane (CH4) sources of the atmosphere. However, the mechanisms of CH4 generation remain unclear in sediments of shallow urban lakes. The aims of this investigation were to study the characterization of environmental parameters, CH4 generation, and methanogen populations in Wulongtan Lake, China, which is affected solely by nonpoint pollution. @@@ Materials and methods The concentrations of CH4 in the atmosphere and of vertical sediment profiles and the methane flux at the air-water interface were monitored in the summer of 2012. Environmental parameters in the water column and in the vertical sediment profiles were assayed. The activities of cellulose, saccharase, polyphenol oxidase, and urease enzyme and 16S rRNA gene copy numbers of Archaea (ARC), Methanobacteriales (MBT), Methanococcales (MCC), Methanomicrobiales (MMB), Methanosarcinales (MSL), Methanosarcinaceae (MSC), and Methanosaetaceae (MST) were determined in the vertical sediment profiles. The abundance of methyl-coenzyme A reductase (ME) gene was also determined to evaluate the total activities of methanogens. @@@ Results and discussion High CH4 concentrations were detected in the atmosphere above the lake, and the mean CH4 flux at the air-water interface was 6.21 mM m(-2) h(-1). Dissolved oxygen decreased with an increase of water depth. Eh values and CH4 contents increased, but total nitrogen, water content, and total organic carbon (TOC) decreased with an increase of sediment depth. Cellulose, saccharase, polyphenol oxidase, and urease activities were detected in all sedimentary layers. The copy number of 16S rRNA gene (wet weight) for Archaea reached the highest value in the surface sediment. Copy numbers of ME were higher at 12-33 cm than at 0-6 cm. In general, abundances of MMB, MBT, and MSL were higher than that of MCC in the same sedimentary layer. 16S rRNA gene copy numbers of MST decreased with increasing depth, while MSC was higher at 18-27 cm than that at other sections. These indicate that hydrogenotrophic, aceticlastic, and methylotrophic pathways coexisted in these sediments. Principal component analysis revealed that in the sediments, the level of CH4 was closely related with several parameters including saccharase, urease, ME, and MBT, while TOC content was related to CEL, MST, ARC, water content, and Eh. @@@ Conclusions High CH4 release potential was detected in this shallow urban lake and can be ascribed to the anaerobic aquatic environment, bacterial enzyme activities, and methanogens. The orders MMB, MBT, and MSL were dominant in sediments for CH4 production. The presence of orders or families of methanogens might be determined by the types of available substrates in lake sediments.
- 出版日期2014-5
- 单位河海大学
