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Environmental Pollution 152 (2008) 351e360 www.elsevier.com/locate/envpol
Nitrous oxide emission from polyculture constructed wetlands: Effect of plant species Yanhua Wang a, Ryuhei Inamori b, Hainan Kong a,*, Kaiqin Xu c,d, Yuhei Inamori b, Takashi Kondo c, Jixiang Zhang e a
School of Environmental Science and Engineering, Shanghai Jiaotong University, 800 Dong Chuan Road, Min Hang, Shanghai 200240, P.R. China b Faculty of Symbiotic Systems Science, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan c National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan d State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan Unviversity, Wuhan 430072, P.R. China e School of Economics and Management, Southeast University, Nanjing, Jiangsu 210096, P.R. China Received 6 March 2007; received in revised form 7 June 2007; accepted 10 June 2007
Zizania latifolia has a large contribution to global warming. Abstract Loss of nitrogen from the soil-plant system has raised environmental concern. This study assessed the fluxes of nitrous oxide (N2O) in the subsurface flow constructed wetlands (CWs). To better understand the mechanism of N2O emission, spatial distribution of ammonia-oxidizing bacteria (AOB) in four kinds of wetlands soil were compared. N2O emission data showed large temporal and spatial variation ranging from 5.5 to 32.7 mg N2O m2 d1. The highest N2O emission occurred in the cell planted with Phragmites australis and Zizania latifolia. Whereas, the lower emission rate were obtained in the cell planted with P. australis and Typha latifolia. These revealed that Z. latifolia stimulated the N2O emission. Transportation of more organic matter and oxygen for AOB growth may be the reason. The study of AOB also supported this result, indicating that the root structure of Z. latifolia was favored by AOB for N2O formation. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Polyculture constructed wetlands; Ammonia-oxidizing bacteria; Nitrous oxide; Fluorescence in situ hybridization
1. Introduction Increase of nitrous oxide (N2O) emission causes concern due to its contribution to global warming and destruction of the ozone layer (Dyominov and Zadorozhny, 2005). The contribution per molecule of N2O to the absorption of infrared radiation was 200e300 times more than that of carbon dioxide (Tanikawa et al., 1995; Kimochi et al., 1998) and it was increasing at a rate of 0.2e0.3% per year (IPCC, 2001). More than 65% of atmospheric N2O comes from soil as a result of nitrification and denitrification (Bouwman, 1990). Flux of * Corresponding author. Tel.: þ862 1 3420 3735; fax: þ862 1 5474 0825. E-mail address:
[email protected] (H. Kong). 0269-7491/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2007.06.017
N2O has been measured in the wastewater (Bernet et al., 1996) and various types of wastewater treatment processes such as municipal wastewater treatment plants (Czepiel et al., 1995; Su¨mer et al., 1995), land application of wastewater (Itokawa et al., 1996; Kong et al., 2002) and marshes (Augustin et al., 1998). Natural wetlands are characterized by anaerobic conditions and low turnover rates for organic matter, and are thus important terrestrial sinks for carbon and nitrogen (Augustin et al., 1998). Constructed wetlands (CWs) systems are combinations of natural wetlands and wastewater treatment plants, which apply various technological designs, using natural wetland processes, associated with wetland hydrology, soils, microbes and plants. The sustainable operation of the systems depends on high-rate conversion of
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characteristics of N2O emission from treatment processes need further analytical evaluation. The objectives of this study were: (1) to investigate the effect of seasonal change on spatial distribution of AOB in the polyculture CWs without previous cultivation; and (2) to seek to establish the relationship between N2O emission and some physicochemical parameters. 2. Materials and methods 2.1. Description of site and operation The study was conducted in the 3-year CWs systems located in the National Institute for Environmental Studies of Tsukuba, Japan (36 420 N, 140 180 E). Four CWs systems were established using a subsurface flow design for treating artificial domestic wastewater. The treatment cells are 88 cm deep and 56 cm in diameter with a substrate of an 18 cm gravel layer as the supporting medium and 43 cm sand (particle size