Development and Application of Novel Isotope Techniques for Tracing Nutrient Cycling in Watersheds

在工业化农业中广泛施用氮(N)和磷(P)基肥料，以及在城市径流和城市及工业点源废水中广泛施用氮和磷，导致越来越多的养分释放到水生环境中。在包括加拿大在内的许多国家，这导致了含水层的硝酸盐负荷和地表水水体的富营养化，造成了诸如饮用水恶化和藻类繁殖等问题。这项为期5年的研究计划的目标是将新开发的同位素示踪剂与已建立的物理，化学和同位素方法相结合，以获得陆地和水生生态系统中N和P循环的新见解。将开发和应用新的同位素技术，以便更好地了解影响加拿大流域水质的氮和磷循环的来源和过程。这些包括：1)N2O的特定地点N同位素测量；2)分析硝酸盐和硫酸盐中的17-O，用于追踪大气中氮和硫的去向；3)测定磷酸盐的氧同位素比值，识别环境中影响磷酸盐的来源和过程；4)利用同位素标记测定土壤中氮的迁移时间；5)硼(B)同位素分析用于区分城市废水和农业回流。实验室实验、以不同土地利用方式为特征的农业土壤的土壤样块研究、人工溪流中控制的养分释放以及流域范围的研究将通过物理、化学和同位素技术的结合来测试这种新型的多示踪剂方法。预计研究小组将能够区分大气沉降、城市径流和废水、农业回流和工业点源的营养投入。这种新颖的多示踪方法的意义在于可以更好地量化自然和不同人为因素（包括城市、农业和工业活动）对地表水水体水质的影响。这些知识对于制定加拿大和其他地方的流域未来的水管理战略至关重要。

Widespread application of nitrogen (N)- and phosphorus (P)-based fertilizers in industrial agriculture, but also N and P in urban runoff and wastewater effluents from cities and from industrial point sources, cause increasing nutrient releases into aquatic environments. In many countries including Canada this has resulted in nitrate loading of aquifers and eutrophication of surface water bodies causing problems such as drinking water deterioration and algae blooms, among others. The objective of this 5-year research program is to combine newly developed isotope tracers with established physical, chemical and isotopic approaches to gain new insights into N and P cycling in terrestrial and aquatic ecosystems. Novel isotope techniques will be developed and applied in order to obtain a better understanding of sources and processes in the N and P cycles that affect water quality in Canadian watersheds. These include 1) site-specific N isotope measurements on N2O; 2) the analysis of 17-O in nitrate and sulfate for tracing the fate of atmospheric nitrogen and sulfur; 3) the determination of oxygen isotope ratios of phosphate to identify sources and processes affecting phosphate in the environment; 4) determining the transit time of N in soils with isotopic labels, and 5) boron (B) isotope analyses for differentiating urban waste water effluents from agricultural return flows. Laboratory experiments, soil plot studies with agricultural soils characterized by different land use, controlled nutrient releases in artificial streams, and watershed wide studies will be conducted to test this novel multi-tracer approach using a combination of physical, chemical and isotopic techniques. It is anticipated that the research team will be able to differentiate nutrient inputs from atmospheric deposition, urban runoff and wastewater effluents, agricultural return-flows, and industrial point sources. The significance of this novel multi-tracer approach is that the impact of natural and different anthropogenic factors, including urban, agricultural, and industrial activities, on water quality of surface water bodies will be better quantified. This knowledge will be essential for developing future water management strategies for watersheds in Canada and elsewhere.