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理解流域氮的输出至关重要。硝酸盐（NO3 -）的截留，特别是反硝化作用，取决于多种因素：地球化学条件（主要是RedOx势）、基质（NO3 -和溶解有机碳（DOC）的大量可利用性）以及硝酸盐和DOC向可利用位置的迁移。我们将研究俄勒冈州和怀俄明州的河流的潜流带中硝酸盐保留的控制：4个森林河流河段，4个农业河流和4个城市河流。每个河段将与Lotic InterbiomeNitrogeneExperiment II（LINX II）项目合作进行15次NO3注入，该项目使用氮-15（15 N）技术研究吸收和保留。与LINX II合作可以对溪流和潜流氮循环进行协同和具有成本效益的检查。我们的研究目的是探讨控制小溪流潜流区硝酸盐截留和反硝化作用的因素，并定量分析这些溪流中由于潜流交换而截留的硝酸盐比例。我们将检验以下假设：（1）由于基质和速率的限制，水源、森林溪流中的潜流反硝化作用较低，但由于无机氮的限制，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是农业的中间网络位置将最大，然而，由于氮素的限制性较小，NO3 -的总损失将受到运输限制，生物同化作用将减少;（3）在城市河流河段，潜流带的潜在反硝化速率较高，但由于反硝化作用和生物同化作用都将被严重输送，河流河段纵剖面的高程测量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。我们已经成功地充分利用这种技术来模拟地下水流和计算潜流停留时间[例如，Kasahara和Wondzell，2003年; Wondzell等人，2003年]。我们将使用示踪剂测试，这是基于对它们用于测量低流区停留时间分布的新理解[Gooseff等人，2003; Haggerty等人，2000; Haggerty等人，我们将把我们的工作与LINX II NSF项目结合起来，在俄勒冈州和怀俄明州的12个LINX II实验河段的潜流区安装一个取样井和测压计网络。取样威尔斯井将提供进入潜流水的通道，从中我们将获得样品，用于测量15 NO3 -、15 N2（g）和15 N2 O（g）以及DO、DOC和其他物理和地球化学参数，这些参数将用于量化生物同化、反硝化和潜流带地下水流。我们将可以访问这些和其他内容的LINX II流数据（例如，15 NH 4+）N-物种。这项工作将建立在，并加强目前的LINX II项目。LINX II项目将受益于其12个站点的潜流区氮循环的量化，并将获得一种方法来完善氮动力学模型。三个实验河段在俄勒冈州立大学校园内，这使我们能够使用橡树溪作为动手，3门课程的主动学习实验室，每年招收300多名学生。通过这些课程，本科生和研究生的研究项目，并在我们的实地工作的本科生participationof，大量的学生将获得实地经验在水文学在经验适当的水平。USU研究团队将继续通过提顿科学学校与初中和高中学生互动，展示实地活动，并为这些学生提供实地实践经验。OSU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与项目相关的科学活动，并为K-12学生和教师传播结果，并将通过NSF赞助的地球仪计划促进当地学校对地表水水文学和水质的学习。