Nutrient Legacies and Time Lags: Understanding Catchment Biogeochemical Responses in Anthropogenic Landscapes

与高水平施肥和集中畜牧活动有关的过量营养物质进入地下水和地表水，导致缺氧、水生毒性和饮用水污染等问题。减少肥料施用或实施其他最佳管理做法（BMPs）已用于改善水质，但往往没有产生预期的结果。这种缺乏响应的原因是遗留存储的积累，可能导致BMP的实施和水质改善之间存在明显的时间滞后。了解人为遗产的积累和消耗如何改变水质是我研究计划的重点。这项研究不仅解决了全球营养预算的一个关键缺口，而且还有助于建立一个实用的框架，为水质管理设定现实的、特定时间的目标。“发现”号的研究将建立在我最近工作的基础上，该工作提供了有机氮(N)在农业土壤中积累的新证据，并提出了关于N遗产在流域尺度N动态中的作用的重要问题：(1)农业景观中控制遗留N积累和消耗的机制是什么？(2)这些遗产如何导致管理实践变化与水质改善之间的时间滞后？***在拟议的工作中，将建立一个模型来探索有关土壤碳氮动力学的假设，并阐明对氮积累和消耗的控制。该模型将使用现有数据集和特定项目的实地工作进行验证。在哈罗农业研究站的合作工作中，将在一系列肥料处理下确定遗留氮的深度依赖积累，并将使用同位素分析来检测排水中硝酸盐的来源。此外，将在确定的时间序列上进行实地研究，以确定农业用地退役后的氮浓度轨迹。由此开发的渗透带遗留模型将在空间明确的框架中使用，以量化从地块到田野到集水区的一系列尺度的时间滞后，适用于加拿大国内外的流域。这将为在全球范围内分析与遗产有关的时间滞后对沿海水域养分负荷的作用奠定基础。***通过“发现”资助的研究将增加对人为景观中N遗产及其对水质影响的基本认识。该项目将利用大学在水和生态水文学方面的现有优势，通过培养水和环境领域的顶尖HQP，为加拿大经济做出积极贡献。研究结果将对流域尺度养分运输领域作出重大贡献，从而允许更有效地管理加拿大水资源。***********

Excess nutrients associated with high levels of fertilizer application and concentrated livestock operations find their way into both ground and surface waters, leading to problems of hypoxia, aquatic toxicity and drinking water contamination. Reductions in fertilizer application or implementation of other best management practices (BMPs) have been carried out to improve water quality, but often they do not yield expected results. Such lack of response is attributed to buildups of legacy stores that can cause significant time lags between BMP implementation and water quality improvements. Understanding how the accumulation and depletion of anthropogenic legacies alter water quality is the focus of my research program. The research not only addresses a critical gap in global nutrient budgets, but also helps to create a practical framework for setting realistic, time-specific goals for water quality management. ***The Discovery research will build on my recent work, which provides new evidence of organic nitrogen (N) accumulation in agricultural soils and raises important questions regarding the role of N legacy in catchment-scale N dynamics: (1) What mechanisms control legacy N accumulation and depletion within agricultural landscapes? (2) How do such legacies contribute to time lags between changes in management practices and improvements in water quality? ***In the proposed work, a model will be developed to explore hypotheses regarding soil carbon-nitrogen dynamics and to clarify controls on N accumulation and depletion. The model will be validated using both existing datasets and project-specific fieldwork. In collaborative work at the Harrow Agricultural Research Station, depth-dependent accumulation of legacy N will be determined under a range of fertilizer treatments, and isotope analysis will be used for source detection of nitrate in drainage water. In addition, field studies will be carried out across an identified chronosequence to determine N concentration trajectories after agricultural land retirement. The vadose zone legacy model thus developed will be used in a spatially explicit framework to quantify time lags at a range of scales, from plot to field to catchment, for watersheds both within and outside Canada. This will lay the groundwork for a more global-scale analysis of the role of legacy-related time lags in nutrient loading to coastal waters. *** Research funded through the Discovery will increase fundamental understanding of N legacies in anthropogenic landscapes and their impacts on water quality. The project will leverage existing university strengths in water and ecohydrology and contribute positively to Canada's economy by training of top HQP in the water and environmental sector. Research results will contribute significantly to the field of watershed-scale nutrient transport, thus allowing for more effective management of Canadian Water Resources.***********