Factors affecting denitrification rates in experimental wetlands: Field and laboratory studies |
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| Institution: | 1. Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, People’s Republic of China;2. College of Environmental and Ecological Science, Xiamen University, Xiamen 361005, People’s Republic of China;1. Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, 46 Vanemuise Street, Tartu 51014, Estonia;2. Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, 46 Vanemuise Street, Tartu 51014, Estonia;3. Everglades Wetland Research Park, Florida Gulf Coast University, 4940 Bayshore Drive, Naples, FL 34112, USA;1. Fisheries College, Ocean University of China, Qingdao, 266001, China;2. School of Environment, Tsinghua University, Beijing, 100084, China;1. Shenzhen Key Laboratory of Marine Bioresource and Eco-Environmental Science, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, China;2. State Key Laboratory of Quality Research in Chinese Medicine, University of Macau, Macau 999078, China;3. Macau Landscape and Greening Association, Macau 999078, China;1. ECOLAB, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France;2. Grassland, Soil &Water Research Laboratory USDA-ARS, Temple, TX 76502, USA;3. Spatial Science Laboratory in the Department of Ecosystem Science and Management, Texas A&M University, College Station, TX 77845, USA;1. USGS California Water Science Center, 6000 J Street, Sacramento, CA 95819, United States;2. Bachand and Associates, Davis, CA, United States;3. University of California, Davis, United States |
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| Abstract: | To identify the conditions that promote high rates of denitrification we systematically investigated the interactions of wetland age, water temperature, organic carbon, macrophytic type and density, hydraulic conditions on denitrification rates in field and laboratory experiments. In the field, nitrate removal was consistently greater in a shallow, young, well-mixed constructed wetland, regardless of temperature and despite lower sediment denitrification potential (DNP), than in mature, more diverse, less well-mixed wetlands. We believe the presence of a benthic mesh, which supported a dense periphytic biofilm, to be partly responsible for the unexpectedly high observed rates. We measured the DNP of wetland sediments and periphyton in the laboratory with the acetylene block method under different temperatures, nitrate concentrations, and carbon sources. The overall DNP of periphyton was greater than the corresponding sediment samples on a per cell basis. We hypothesize that the organic carbon produced by the periphytic algae is readily degradable and promoted the higher denitrification rates. We found a positive relationship between DNP and biodegradable organic carbon concentration and identified chemical markers illustrating that biodegradability is promoted by a combination of polyhydroxyaromatic and polysaccharide parent structures. These findings highlight the importance of organic quality and the role of periphyton in accelerating the rates of denitrification in wetlands. |
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