HR: 0830h
AN: H51C-03    [Abstracts]
TI: Nitrogen Isotopes - Tracers for Nitrogen Transformations in Small Constructed Wetlands
AU: * Reinhardt, M
EM: miriam.reinhardt@eawag.ch
AF: Swiss Federal Institute for Environmental Science and Technology (EAWAG), Limnological Research Center, Seestr. 79, Kastanienbaum, 6047 Switzerland
AU: Gaechter, R
EM:
AF: Swiss Federal Institute for Environmental Science and Technology (EAWAG), Limnological Research Center, Seestr. 79, Kastanienbaum, 6047 Switzerland
AU: Mueller, B
EM:
AF: Swiss Federal Institute for Environmental Science and Technology (EAWAG), Limnological Research Center, Seestr. 79, Kastanienbaum, 6047 Switzerland
AU: Wehrli, B
EM:
AF: Swiss Federal Institute for Environmental Science and Technology (EAWAG), Limnological Research Center, Seestr. 79, Kastanienbaum, 6047 Switzerland
AB: Small artificial wetlands are increasingly applied to reduce non-point source pollution and to contribute to the restoration of eutrophicated freshwaters and coastal marine ecosystems. In the agricultural catchment area of Lake Sempach in Central Switzerland, several wetlands were constructed at the interface between subsurface drainage system and receiving waters. In order to evaluate nitrogen retention efficiency of the systems and to identify major processes controlling their performance, nitrate, ammonium, particulate and dissolved organic nitrogen in the inflowing and outflowing water as well as δ¹⁵N of nitrate, ammonium and sediment were analyzed in a three pond system. During the studied 26 months the wetland retained 27% of the nitrogen load corresponding to a surface related retention of 51g N m^-2 yr^-1. Nitrate in the inlet contributed 48% to the total nitrogen load and was characterized by high δ¹⁵N-NO₃(>13‰) typical for intensively manured grassland soils. Increasing δ¹⁵N-NO₃ in the wetland compared to the inlet was attributed to denitrification whereas decreasing δ¹⁵N-NO₃ during stagnant periods was due to anoxic mineralization of particulate organic matter and subsequent nitrification.
DE: 1040 Isotopic composition/chemistry
DE: 1615 Biogeochemical processes (4805)
DE: 1871 Surface water quality
DE: 1890 Wetlands
SC: Hydrology [H]
MN: 2005 Joint Assembly