In points of annual crop farming and close to residential the contribution of inorganic fertilizers to the total concentration of nitrate was estimated, based on the δ 15N-NO3 values, to be as high as more than 60% and the contribution of water waste was around 35-40%. This is the first time isotopic signature of nitrogen-15 in nitrate (δ15N-NO3) was applied as a tool to assess and identify sources of the nutrient in aquatic environment. Results of this study, although it was initial but it would be useful for the local environmental managers in developing suitable strategies to control over nitrogennutrient releases in order to keep the aesthetic appeal of Tuyen Lam Reservoir. |