The Influence of Planting of Fast-growing Eucalyptus on Hydrochemical Characteristics and Nitrogen Pollution Sources of Reservoirs Water

Since 2001, the planting of fast-growing eucalyptus in Guangxi Province, China have had a fast development and formed the local ecological and economic features. However, large area of the planting of fast-growing eucalyptus also brought many prominent environmental problems. Lots of fast-growing eucalyptus are planted because of their economic value in Guangxi Province, China. Based on the growing characteristics of fast-growing eucalyptus and Guangxi soil nutrient status planting eucalyptus must pay attention to the application of fertilizer. Therefore, nitrogen and phosphorus substances inclueded in a lot of fertilizer which go into the soil would be discharged into the surrounding reservoir through surface runoff, infiltration, water and soil loss, which would cause the reservoir eutrophication. Typical reservoirs which there are a large number of planting eucalyptus around are chosen as the research object. On the basis of sample collection and the analysis of the conventional water chemical characteristics, the research analyzes typical reservoirs nitrogen pollution sources and the influence of eucalyptus planting on reservoir water quality based on Nitrogen Stable Isotope Tracer Technology. The NO₃^--N, NH₄^＋-N concentration and the δ¹⁵N value of the soil indicate that the nitrogen sources of the soil around the reservoir mainly come from atmospheric precipitation and fertilizer. The δ¹⁵N of reservoir water indicates that the main nitrogen source is chemical fertilizer. This research applies the Nitrogen Stable Isotope Tracer Technology to indicate nitrogen pollution sources of typical reservoirs and analyzes the influence of planting of fast-growing eucalyptus on reservoir water quality. Through the analysis, the results of the research are consistent with the actual situation. Therefore, the method of applying Nitrogen Stable Isotope Tracer Technology to indicate the nitrogen pollution source is feasible and credible.