HR: 0800h
AN: H41D-0325    [Abstracts]
TI: Identification and Quantification of Diffuse Nitrogen Inputs Into a River System Using Stable Isotopes of Nitrogen and Oxygen in Nitrate
AU: * Deutsch, B
EM: Barbara.Deutsch@io-warnemuende.de
AF: Baltic Sea Research Institute, Seestr. 15, Rostock, 18119 Germany
AU: Liskow, I
EM: Iris.Liskow@io-warnemuende.de
AF: Baltic Sea Research Institute, Seestr. 15, Rostock, 18119 Germany
AU: Voss, M
EM: Maren.Voss@io-warnemuende.de
AF: Baltic Sea Research Institute, Seestr. 15, Rostock, 18119 Germany
AB: A dual-isotope approach with $\delta^{15}$N and $\delta^{18}$O in nitrate was carried out to identify and quantify the diffuse nitrate inputs into a river system in Mecklenburg-Vorpommern (Germany). The three main nitrate sources (drainage water from agricultural soils, groundwater and atmospheric deposition) and the river were sampled monthly from November 2002 to April 2003. To determine the contribution of each sampled nitrate source to the total river nitrate a standard dual isotope, three source linear mixing-model was used. Drainage water nitrate had a mean $\delta^{15}$N value of 10.1 $\permil$ and a $\delta^{18}$O of 5.5 $\permil$, and was significantly different to groundwater nitrate (mean $\delta^{15}$N = 1.1 $\permil$, $\delta^{18}$O = 1.5 $\permil$) and nitrate from atmospheric deposition (mean $\delta^{15}$N = 1.9 $\permil$, $\delta^{18}$O = 50.9 $\permil$). The low $\delta^{18}$O values of groundwater and drainage water nitrate indicated that it was mainly formed during the nitrification process. Isotope values of the river nitrate were close to the values of drainage water nitrate with a mean $\delta^{15}$N of 9.0 $\permil$ and a $\delta^{18}$O of 6.1 $\permil$. The mixing-model revealed that the nitrate from the drainage water contributed 88 % of the river nitrate. Contribution of nitrate from groundwater and atmospheric deposition was 10 % and 2 %, respectively. These results agree with estimations of nitrate input data for this study area given by a nutrient emissions model.
DE: 4845 Nutrients and nutrient cycling
DE: 4870 Stable isotopes
DE: 1800 HYDROLOGY
DE: 1803 Anthropogenic effects
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting