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

养分遗产和时间滞后：了解人类景观中的流域水文和生物地球化学反应

• 批准号: RGPIN-2014-03582
• 负责人: Basu, Nandita
• 金额: $ 2.19万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=565958
• 关键词: Nutrient; Legacies; Time; Lags; Understanding

Global population has seen a more than threefold increase over the last 100 years, accompanied by rapid changes in land use and a dramatic intensification of agriculture. Such changes have led to large increases in the inputs of nutrients, pesticides, and a variety of other contaminants to human-impacted landscapes. The majority of applied pollutants eventually find their way into both groundwater and surface water, leading to long-term problems of hypoxia, aquatic toxicity and drinking water contamination. Reductions in fertilizer application or other changes in management practices have been implemented to achieve improvements in water quality, but often they do not yield expected results. Such lack of response can be attributed to the buildup of legacy stores of contaminants within the landscape over decades of human impact that take years to deplete and can cause significant delays or time lags between best management practices implemented and water quality improvements observed. One of the essential themes of Dr Basu's research program is this landscape legacy created by histories of human impacts. Understanding the accumulation and depletion of such legacies will contribute to a fundamental knowledge of global nutrient budgets, while also answering practical questions regarding time lags that would be of interest to policy makers. The proposed Discovery research will build on Dr. Basu’s recent work, which provides intriguing new evidence of organic nitrogen (N) accumulation in the deeper soils of agricultural landscapes, specifically in the Mississippi River Basin. These findings raise important new questions regarding the role that such accumulations, or legacy, might play in catchment-scale N dynamics, and may help to explain the observed time lags. The proposed research will therefore seek to answer the following questions: (1) What mechanisms control the accumulation and depletion of N legacies within agricultural landscapes? (2) How do such legacies contribute to time lags between changes in management practices and improvements in water quality at the catchment scale? The work supported by this grant will take several interconnected paths toward addressing these questions. The study will focus on the Grand River Watershed (GRW) as an example of a large river basin heavily impacted by agriculture. First, available data regarding fertilizer use, crop and livestock production, and atmospheric deposition of N from the mid-20th century to the present will be synthesized. Such analysis will allow the quantification of the likely magnitude of legacy N stores within the basin. Field sampling will be carried out to determine current soil N levels as well as the age of soil organic carbon (C) and N via isotope dating techniques. Concurrently, a model will be developed to explore hypotheses regarding C-N dynamics throughout the soil profile and to clarify the major controls on N accumulation and depletion. As a complement to the above approaches, controlled laboratory experiments will be carried out to isolate and quantify the processes governing N transformations and transport. Research funded through the discovery grant will increase the fundamental understanding of N legacies in anthropogenic landscapes and their impacts on water quality. The project will leverage existing strengths in the university in the areas of water and ecohydrology, promote excellence in world class research, and contribute positively to Canada’s economy by retaining and training top HQP. The results of this research will contribute significantly to the field of watershed-scale nutrient transport and management choices related to Source Water Protection, thus allowing for the more effective management of Canadian Water Resources.

在过去100年中，全球人口增长了三倍多，同时土地使用发生了迅速变化，农业急剧集约化。这些变化导致营养素、杀虫剂和各种其他污染物大量增加，进入受人类影响的景观。大多数施用的污染物最终进入地下水和地表水，导致缺氧、水生毒性和饮用水污染等长期问题。为了改善水质，已经减少了化肥的使用或改变了其他管理做法，但这些做法往往没有产生预期的效果。这种缺乏响应的情况可归因于几十年来人类影响的景观中污染物的遗留储存的积累，这些储存需要数年时间才能耗尽，并可能导致实施最佳管理实践和观察到的水质改善之间的重大延迟或时间滞后。巴苏博士研究项目的一个重要主题是人类影响历史所创造的景观遗产。了解这些遗产的积累和消耗将有助于对全球养分预算的基本知识，同时也回答了决策者感兴趣的有关时间滞后的实际问题。拟议的发现研究将建立在巴苏博士最近的工作基础上，该工作提供了有趣的新证据，证明农业景观深层土壤中有机氮（N）的积累，特别是在密西西比河流域。这些研究结果提出了重要的新问题，这种积累，或遗产，可能发挥在流域尺度N动态的作用，并可能有助于解释观察到的时间滞后。因此，拟议的研究将试图回答以下问题：（1）是什么机制控制的积累和消耗的N遗产在农业景观？(2)这些遗留问题如何导致集水区管理实践变化和水质改善之间的时间滞后？这项资助支持的工作将采取几个相互关联的途径来解决这些问题。该研究将侧重于格兰德河流域（GRW）作为一个受农业严重影响的大型河流流域的例子。首先，将综合从世纪中期到现在有关肥料使用、作物和畜牧业生产以及大气氮沉降的可用数据。这种分析将允许量化流域内遗留N个商店的可能数量。将进行实地采样，以确定目前的土壤氮水平以及土壤有机碳（C）和氮的同位素测年技术的年龄。同时，将开发一个模型，探讨整个土壤剖面的碳氮动态的假设，并澄清氮积累和消耗的主要控制。作为上述方法的补充，控制实验室实验将进行隔离和量化的过程中，氮的转化和运输。通过发现补助金资助的研究将增加对人类景观中N遗产及其对水质影响的基本了解。该项目将利用该大学在水和生态水文学领域的现有优势，促进世界级研究的卓越，并通过保留和培训顶级HQP为加拿大经济做出积极贡献。这项研究的结果将大大有助于流域规模的营养盐运输和管理选择有关的水源保护领域，从而使加拿大水资源的更有效的管理。