Denitrification and nitrous oxide in the North Sea |
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| Institution: | 1. Department of Mathematics, Karnatak University, Pavate Nagar, Dharwad, 580003, India;2. Department of Computer Science (MCA), KLE Technological University, BVB Campus, Hubli, 580031, India;3. Department of Mathematics, IIT Madras, Chennai, 600036, India;1. Boston Children''s Hospital, Department of Otolaryngology and Communication Enhancement, 333 Longwood Avenue, 3rd floor, Boston, MA 02115, USA;2. Harvard Medical School, Department of Otology and Laryngology, 25 Shattuck Street, Boston, MA 02115, USA;1. Department of Vascular and Endovascular Surgery, Wake Forest University School of Medicine, Winston-Salem, NC;2. Department of Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, NC;3. Hypertension & Vascular Disease Research Center, Wake Forest University School of Medicine, Winston-Salem, NC;4. Department of Biostatistical Sciences, Wake Forest University School of Medicine, Winston-Salem, NC;1. Universidad Nacional Autónoma de México (UNAM), Instituto de Ciencias del Mar y Limnología, Ciudad Universitaria, 04510 Coyoacán, Mexico;2. School of the Earth, Ocean and Environment, University of South Carolina, Columbia, SC 29208, USA;3. Universidad Nacional Autónoma de México (UNAM), Instituto de Ciencias del Mar y Limnología, Calz. Joel Montes Camarena s/n, 82040 Mazatlán, Mexico |
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| Abstract: | In situ sediment denitrification rates were determined in the major areas of deposition of the North Sea, using the acetylene block technique. In addition, nitrous oxide profiles of the water column were determined. Nitrous oxide production generally occurred in the photic zone possibly due to nitrification; and throughout the water column in the German Bight region. Consumption at depth was possibly due to reduction in the anoxic microzones of faecal pellets, concentrated at the thermocline. Saturation of surface waters was 102.2% compared to 130.3% in the German Bight region. Calculated flux of nitrous oxide to the atmosphere was 9.5 × 106 kg yr−1, over half of which was produced in the German Bight.Sediment denitrification rates varied through three orders of magnitude; the highest value of 150 μmol m−2 d−1 was recorded in the Norwegian Trench. Nitrous oxide production by the sediments was low (1.1 μmol m−2 d−1 max.), and was undetectable at half of the sites. Sediment nutrient profiles exhibited porewater nitrate concentrations exceeding that of the overlying water suggesting that denitrification was fuelled by nitrification, which, in turn was related to other environmental variables. A significant positive relationship existed between in situ denitrification rate and the nitrate content of the upper sediment. Extrapolation of the rate to the total area of deposition in the North Sea suggests that denitrification is responsible for a minimum loss of 7.5–12% of the total annual nitrogen contaminant input. |
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