Collaborative Research: Controls on hyporheic nitrate retention - discriminating among transport, reaction-rate, and substrate limitation

合作研究：控制次流硝酸盐保留 - 区分运输、反应速率和底物限制

• 批准号: 0409534
• 负责人: Roy Haggerty
• 金额: $ 25.82万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-15 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409534&HistoricalAwards=false
• 关键词: Collaborative; Research; Controls; hyporheic; nitrate

0409534The transport and fate of nitrogen in stream networks is critical to understanding watershed exportsof nitrogen. Nitrate (NO3 - ) retention, and denitrification in particular, is known to be dependent upona variety of factors: geochemical conditions (chiefly RedOx potential), substrate (largely availabilityof NO3 - and dissolved organic carbon (DOC)), and transport of nitrate and DOC to favorablelocations for denitrification. We will examine the controls of nitrate retention in the hyporheic zonesof streams in Oregon and Wyoming: 4 forested stream reaches, 4 agricultural streams, and 4 urbanstreams. Each reach will be the subject of 15 NO3 - injections in partnership with the Lotic InterbiomeNitrogen eXperiment II (LINX II) project which is using nitrogen-15 ( 15 N) techniques to studyuptake and retention. Collaborating with LINX II allows synergistic and cost-effective examinationof stream and hyporheic nitrogen cycling. The objectives of our research are to examine the factorscontrolling nitrate retention and denitrification in hyporheic zones of small streams and to quantifythe fraction of nitrate retention in these streams due to hyporheic exchange. We will test thefollowing hypotheses: (1) hyporheic denitrification in headwater, forested streams will be lowbecause of substrate and rate limitations, yet biotic assimilation will be high, relative to agriculturaland urban streams, because of inorganic N-limitation; (2) hyporheic denitrification will be greatestin mid-network locations where surrounding land use is predominantly agricultural, however, totalloss of NO3 - will be transport-limited and biotic assimilation will be reduced because nitrogen is lesslimiting; and (3) potential rate of denitrification in the hyporheic zone will be high in the urbanstream reaches, but total nitrate retention in the hyporheic zone will be low because bothdenitrification and biotic assimilation will be severely transport-limited.Elevation surveys of the longitudinal profiles of the stream reaches will be used to quantify channelmorphology and provide a base for groundwater flow and reactive transport simulations. We havesuccessfully used this technique to model groundwater flow and calculate hyporheic residence timedistributions [e.g., Kasahara and Wondzell, 2003; Wondzell et al., 2003]. We will use tracer testsbased on new understanding of their use for measuring residence time distributions in the hyporheiczone [Gooseff et al., 2003; Haggerty et al., 2000; Haggerty et al., 2002].We will couple our work to the LINX II NSF project by installing a sampling well andpiezometer network in the hyporheic zone of 12 LINX II experimental reaches in Oregon andWyoming. The sampling wells will provide access to hyporheic water, from which we will obtainsamples for measurement of 15 NO3 - , 15 N2(g), and 15 N2O(g) as well as DO, DOC and other physical andgeochemical parameters, which will be used to quantify biotic assimilation, denitrification, andgroundwater flow in the hyporheic zone. We will have access to LINX II stream data on these andother (e.g., 15 NH4 + ) N-species. The work will build upon, and enhance the current LINX II project.The LINX II project will benefit from quantification of nitrogen cycling in the hyporheic zone of 12of its sites and will gain a method to refine models of nitrogen dynamics.Three of the experimental reaches are on OSU campus, which allows us to use Oak Creek as a hands-on, active-learning laboratory in 3 courses with a combined annual enrollment of more than 300students. Through these courses, undergraduate and graduate research projects, and the participationof undergraduates in our field work, a large number of students will gain field experience inhydrology at experience-appropriate levels. The USU research team will continue to interact withmiddle school and high school students through the Teton Science School, demonstrating fieldactivities and facilitating hands-on field experience for these students. Together, the OSU and USUresearch teams will develop a web site with our data and project-related science activities anddissemination of results for K-12 students and teachers, and will promote learning about surfacewater hydrology and water quality in local schools through the NSF-sponsored GLOBE program.

0409534河流网络中氮的运输和归宿对于了解流域氮的输出至关重要。已知硝酸盐 (NO3 - ) 保留，特别是反硝化取决于多种因素：地球化学条件（主要是氧化还原电位）、底物（主要是 NO3 - 和溶解有机碳 (DOC) 的可用性）以及硝酸盐和DOC 到反硝化的有利位置。我们将研究俄勒冈州和怀俄明州溪流潜流区硝酸盐滞留的控制：4 条森林溪流、4 条农业溪流和 4 条城市溪流。每个区域都将与 Lotic InterbiomeNitrogen eXperiment II (LINX II) 项目合作进行 15 NO3 注射，该项目使用氮 15 ( 15 N) 技术来研究吸收和保留。与 LINX II 合作可以对流和潜流氮循环进行协同且经济有效的检查。我们研究的目的是研究控制小溪流潜流区硝酸盐滞留和反硝化的因素，并量化这些溪流中由于潜流交换而滞留的硝酸盐比例。我们将检验以下假设：（1）由于底物和速率限制，森林溪流源头的潜流反硝化作用较低，但由于无机氮限制，相对于农业和城市溪流，生物同化作用较高； (2) 潜流反硝化作用在周围土地利用主要为农业的网络中部位置最为明显，然而，NO3 的总损失将受到运输限制，并且生物同化将减少，因为氮的限制较小； (3)城市河流河段中潜流区反硝化的潜在速率较高，但由于反硝化和生物同化都受到严重的运输限制，潜流区总硝酸盐滞留率较低。河流河段将用于量化河道形态，并为地下水流和反应性输运模拟提供基础。我们已经成功地使用这种技术来模拟地下水流并计算潜流停留时间分布[例如，Kasahara 和 Wondzell，2003 年； Wondzell 等人，2003]。我们将基于对示踪剂测试用于测量潜流区停留时间分布的新理解而使用示踪剂测试[Gooseff et al., 2003;哈格蒂等人，2000； Haggerty et al., 2002]。我们将通过在俄勒冈州和怀俄明州 12 个 LINX II 实验河段的潜流带安装采样井和渗压计网络，将我们的工作与 LINX II NSF 项目结合起来。采样井将提供地下水的入口，我们将从中获取样品，用于测量 15 NO3 - 、 15 N2(g) 和 15 N2O(g) 以及 DO、DOC 和其他物理和地球化学参数，这些参数将用于测量量化潜流带的生物同化、反硝化和地下水流量。我们将能够访问这些和其他（例如 15 NH4 + ）N 物种的 LINX II 流数据。这项工作将建立在当前 LINX II 项目的基础上，并对其进行增强。LINX II 项目将受益于其 12 个地点的潜流区氮循环的量化，并将获得一种改进氮动力学模型的方法。其中三个实验达到了位于 OSU 校园内，这使我们能够将 Oak Creek 作为 3 门课程的实践、主动学习实验室，每年招收的学生总数超过 300 名。通过这些课程、本科生和研究生研究项目以及本科生参与我们的实地工作，大量学生将获得适合经验水平的水文学实地经验。 USU 研究团队将继续通过提顿科学学院与初中和高中学生互动，展示现场活动并促进这些学生的实践现场经验。俄勒冈州立大学和 USU 研究团队将共同开发一个网站，其中包含我们的数据和项目相关的科学活动以及 K-12 学生和教师的成果传播，并将通过 NSF 资助的项目促进当地学校了解地表水水文学和水质。全球计划。