|M.Sc Student||Segal Rosenheimer Michal|
|Subject||Nitrogen Pollutants, Sources and Processes along the Lower|
|Department||Department of Agricultural Engineering||Supervisors||Professor Uri Shavit|
|Professor Emeritus Abraham Shaviv|
The Lower Jordan River is an important hydrological and ecological entity in the semi-arid area of the Jordan Valley, along the border between Israel and Jordan. Its source waters contain sewage, which contributes high ammonium loads to the river. We found that ammonium concentrations decreased from 20 to 0-5 mgN/ along the first 20 km of the Lower Jordan River, while nitrate concentrations increased from nearly zero to 10-15 mgN/. Mass balance calculations show that intensive nitrification occurs along the river flow, between kilometer 5 and 12, while further downstream nitrate increase is attributed mostly to an external subsurface water source that enters the river. Isotope analysis showed that nitrification of ammonium with high d15N(NH4) values (between 10 and 40) resulted in 15N-enriched nitrate. Consequently, d15N(NO3) values increased from less than 5 to 15-20. The external non-point water source is composed of several end members, one of which is agricultural return flow with high nitrate concentration and high d15N(NO3) values (10-17o/oo). The river system, although heavily polluted by sewage effluents, still showed some natural remediation ability, transforming sewage-derived ammonium into nitrate.