Collaborative Research: Evolution of Dissolved Organic Nitrogen (DON) from the Headwaters to the Catchment Outlet: Sources, Variation with Scale, and Differences with DOC.

合作研究：溶解有机氮 (DON) 从源头到流域出口的演变：来源、规模变化以及与 DOC 的差异。

• 批准号: 0809231
• 负责人: Myron Mitchell
• 金额: $ 7.03万
• 依托单位: SUNY College of Environmental Science and Forestry
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-10-01 至 2012-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0809231&HistoricalAwards=false
• 关键词: Collaborative; Research; Evolution; Dissolved; Organic

This proposal seeks to advance our understanding of the transport and fate of dissolved organic nitrogen (DON) in watersheds. We address three novel questions which have not been studied previously: (a) what is the relative influence of terrestrial versus aquatic (in-stream) sources/sinks on DON and bioavailable (BDON) dynamics at various points along the drainage path? (b) how do DON and BDON exports vary with catchment scale? and (c) how do DON dynamics differ from DOC and what mechanisms are responsible for these differences? We address these questions across varying temporal scales from baseflow to storm events and across seasons. Contributions of DON from various catchment sources are expected to change dramatically between baseflow and storm-event conditions while seasonal changes can especially influence BDON. Catchment sources investigated include ? precipitation, throughfall, stemflow, forest floor, hillslope soil water, wetland soil and ground water, groundwater seeps, hyporheic zone, and streamflow. We will not only investigate how the amounts of DON in various catchment sources influence DON export, but also investigate how the mobility (adsorption-desorption kinetics) and lability of various dissolved organic matter (DOM) constituents (e.g., hydrophobic and hydrophilic fractions) regulate DON export. Special attention is given to differences in DON and DOC responses in light of hydrologic flow paths, storm event magnitude and seasonal timing, antecedent catchment wetness, and redox conditions. We address these questions across zero- to third-order forested catchments of the Big Elk Creek in NE Maryland, which are representative of Piedmont catchments in the mid-Atlantic region. The catchments have already been intensively instrumented, and preliminary data from the site is available since March 2007. We will implement end member mixing analysis (EMMA) at multiple points in the catchments to characterize the spatial pattern of runoff sources and DON contributions. Innovative, new, spectrofluorometric tools such as specific UV absorbance (SUVA) and excitation-emission matrices (EEMs) are used to characterize DOM composition including an in-situ logging fluorometer. A strong interdisciplinary team of scientists with diverse strengths but complimentary interests will evaluate the questions. We anticipate that this study will result in the first conceptual model of DON that characterizes the relative influences of terrestrial and instream processes across various catchment scales.Results from this study will have direct practical implications for: (a) drinking water research since DON contributes to the formation of toxic disinfection by-products; and (b) nutrient enrichment of coastal estuaries (e.g., Chesapeake bay) since DON is bioavailable. An on-line data archive will be created to disseminate the data and results from this study. This data archive will be linked through the web site of the Center for Critical Zone (CCZ) at the University of Delaware and the Delaware Water Resources Center (DWRC). Dissemination of fact sheets to practitioners in regional offices of the US Natural Resources Conservation Service, US Forest Service, US EPA, and Maryland?s Forest Service should broaden the impact of the proposed research. The instrumented watershed will be (is being) used as a ?demonstration? and educational watershed laboratory. This will enable us to develop new interdisciplinary partnerships with other scientists and students within and outside UD. This project will provide valuable interdisciplinary research experiences for undergraduate and graduate students from the Bioresources Engineering, Geology, Plant and Soil Sciences, and Geography Departments. Under-represented groups will be actively recruited by the PI and Co-PI?s with the intention of filling two or more undergraduate and graduate assistantships. A female graduate student will be the PhD student on this project. The final outreach component of this project will involve the Fair Hill Nature Center and its experienced staff of environmental and experiential education teachers. The Fair Hill Nature Center is a non-profit entity, educating k-8 students about responsible environmental stewardship. The Fair Hill Nature Center educates over 8,000 school children annually. PIs on this project will be actively involved with the teachers and staff of the Fair Hill Nature Center staff to provide educational seminars on watersheds, soils, and forests and will participate in student field trips to the instrumented watershed.

这一建议旨在促进我们对溶解有机氮(DON)在流域中的运移和归宿的理解。我们解决了三个以前没有研究过的新问题：(A)陆地和水生(溪流中)源/汇对排水路径沿线不同点处DON和生物有效性(BDON)动态的相对影响是什么？(B)DON和BDON出口如何随集水规模变化？以及(C)DON Dynamic与DOC有何不同，这些差异是由什么机制造成的？我们在不同的时间尺度上解决这些问题，从基流到风暴事件，再到季节。不同来源的DON在基流和风暴事件条件下的贡献预计将发生显着变化，而季节变化对BDON的影响尤为明显。调查的集水区来源包括？降水、穿透雨、树干径流、森林地面、山坡土壤水、湿地土壤和地下水、地下水渗漏、湿润带和溪流。我们不仅将研究不同来源的DON对DON输出的影响，还将研究不同溶解有机物(DOM)组分(如疏水和亲水部分)的流动性(吸附-解吸动力学)和稳定性如何调节DON输出。特别注意了DON和DOC响应的差异，根据水文流动路径、风暴事件的大小和季节时间、之前的集水区湿度和氧化还原条件。我们在马里兰州东北部的大麋鹿溪零级到三级森林集水区解决这些问题，这些集水区是大西洋中部地区皮埃蒙特集水区的代表。集水区已经进行了密集的测量，自2007年3月以来，已有来自该站点的初步数据。我们将在流域的多个点进行端元混合分析(EMMA)，以表征径流来源和DON贡献的空间格局。创新的新的荧光光谱工具，如比紫外线吸收(SUVA)和激发-发射矩阵(EMM)被用来表征DOM的组成，包括现场测井荧光仪。一个由不同优势但兴趣互补的科学家组成的强大的跨学科团队将对这些问题进行评估。我们预计，这项研究将产生第一个DON概念模型，描述不同流域尺度上陆地和河流过程的相对影响。本研究的结果将对：(A)饮用水研究，因为DON有助于有毒消毒副产品的形成；(B)沿海河口(例如切萨皮克湾)的营养物质丰富，因为DON是可生物利用的。将建立一个在线数据档案，以传播这项研究的数据和结果。该数据档案将通过特拉华大学关键区中心(CCZ)和特拉华州水资源中心(DWRC)的网站连接起来。向美国自然资源保护局、美国林务局、美国环保局和马里兰州S林务局的地区办事处的从业人员分发情况说明书应该会扩大拟议研究的影响。仪表化的分水岭将被用作示范吗？和教育分水岭实验室。这将使我们能够与密歇根大学内外的其他科学家和学生发展新的跨学科伙伴关系。该项目将为生物资源工程、地质学、植物和土壤科学以及地理系的本科生和研究生提供宝贵的跨学科研究经验。代表不足的群体将由主计长和S副主任委员积极招聘，以填补两个或两个以上的本科生和研究生助教职位。一名女研究生将成为这个项目的博士生。该项目的最后外展部分将涉及费尔希尔自然中心及其经验丰富的环境和体验式教育教师工作人员。费尔希尔自然中心是一个非营利性实体，教育K-8学生负责任的环境管理知识。费尔希尔自然中心每年为8000多名学童提供教育。该项目的PIS将积极参与公平山自然中心的教师和工作人员的工作，提供关于流域、土壤和森林的教育研讨会，并将参加学生对仪器分水岭的实地考察。