Mass balance of nitrogen in constructed mangrove wetlands receiving ammonium-rich wastewater: Effects of tidal regime and carbon supply |
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| Authors: | NFY Tam AHY Wong MH Wong YS Wong |
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| Institution: | 1. Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361102, China;2. Department of Translational Medicine, Medical College of Xiamen University, Xiamen, Fujian 361102, China;3. Key Laboratory of Integrated Regulation and Resource Department on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, Jiangsu 210098, China;4. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, 71 East Beijing Road, Nanjing 210008, China;5. Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, Fujian 361102, China;1. University of New Caledonia, PPME, EA 3325, BP R4, 98851 Noumea, New Caledonia;2. Institut de Recherche pour le Développement (IRD), UMR 7590, UR 206 BP A5, 98848 Noumea, New Caledonia;3. Institut de Physique du Globe de Paris (IPGP), UMR 7154 CNRS, F-75238 Paris Sorbonne, France |
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| Abstract: | A series of computer-controlled mangrove tide-tanks planted with Kandelia candel was constructed to investigate the removal and transformation of ammonium–nitrogen under two tidal regimes: (i) 12-h wet/12-h dry (long tidal regime) and (ii) 6-h wet/6-h dry/6-h wet/6-h dry daily (short tidal regime). All tanks were irrigated with NH4Cl solution for nine water cycles (each cycle lasted for 5 weeks) at an amount of around 2.1 g NH4Cl (equivalent to 0.52 g N) per tank per cycle. During the experiment, total Kjeldahl nitrogen (TKN), inorganic nitrogen (N) (NH4+–, NO2?–, and NO3?–N) and carbon were completely removed by the mangrove system. The added NH4+–N was not detected in tidal water or accumulated in sediment. The mass balance of nitrogen showed that the discharge of ammonium-rich wastewater to mangrove wetlands enhanced microbial nitrogen transformation, particularly nitrification and denitrification processes, with 15–30% of the total nitrogen inputs returned to atmosphere as N2 gas. Growth of K. candel and macroalgae was stimulated by ammonium addition, and up to 3 and 7% of total N inputs were assimilated in plant and algal tissues, respectively. Constructed mangrove wetlands with short tidal regime had higher numbers of nitrifiers and significantly lower content of ammonium that those with long tidal regime. On the other hand, higher populations of denitrifiers and lower nitrate were found in mangroves with long tidal regime and with glucose addition. |
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