PRELIMINARY ANALYSIS OF NITRATE LOADING IN THE UPPER ELBE RIVER BASIN, CZECH REPUBLIC

Nitrate contamination of water is a worldwide issue. Nitrate is especially dangerous for young children, and may result in potentially fatal methemoglobinemia (blue baby syndrome) when > 10 mg/L N-NO₃ (~50 mg/L NO₃^-). Nitrate in surface water may also lead to eutrophication, which can result in low dissolved oxygen in lakes and estuaries. Sources of NO₃^- contamination include nitrate fertilizers, wastewater treatment plants and industries, individual domestic septic systems, runoff from animal feedlots, and natural soil nitrogen. Nitrate concentrations in the Elbe River drainage, covering 148,270 km² in Germany and the Czech Republic, has been a long-time issue. The upper one-third of the basin, located almost entirely in the Czech Republic. Although concentrations of other pollutants have decreased significantly since monitoring began in the late 1960’s, NO₃^- concentrations, which in some river reaches exceed the European Union (EU) standard of 50 mg/L, have decreased only slightly or remained constant.

At the German border the calculated average 2000-2008 Elbe discharge is 9.4 x 10⁹ m³/yr and annual NO₃^- loading is 37.4 x 10⁶ kg/yr. The upper Elbe has four major tributaries the Labe (Elbe), Berounka, Ohre, and Vltava whose percentages of total discharge and NO₃^- loading are 10.3/10.4, 28.0/33.3, 12.6/8.9, and 49.1/47.4 percent, respectively. Flow and NO₃^- concentrations for 138 locations were obtained from the Czech Hydrometerolical Institute. δ¹⁵N was used to identify NO₃^- sources. The δ¹⁵N of commercial fertilizers, mineralized soil nitrate and animal and human wastes are commonly -4‰ to 4‰, 3‰ to 8‰, >10‰, respectively. δ¹⁵N contents, determined for 57 locations, were plotted against NO₃^- concentration to determine the relationship between concentration and isotope composition. Nitrate loading for each sample site was calculated using historical concentration, δ¹⁵N contents, and flow data for 2000-2008. Preliminary calculations suggest that ~ 75% of the nitrate load is from human and animal waste, likely wastewater treatment plants and septic systems. Approximately 25% is mineralized soil nitrogen, and < 1% is from fertilizer. These results are unanticipated because agriculture is a major part of land use in the Czech Republic. Fifty-four percent of the land is used for agriculture and 34% is forested