Nitrogen transformation processes in the Elbe River: Distinguishing between assimilation and denitrification by means of stable isotope ratios in nitrate
(1) Leibniz Institute for Baltic Sea Research Warnemünde, Seestr. 15, 18119 Rostock, Germany;(2) Federal Institute of Hydrology, Am Mainzer Tor 1, 56068 Koblenz, Germany