CAREER: Nitrogen Sources, Pathways, and Fluxes in Chesapeake Bay Watershed Wetlands

由于城市人口的增长、商业肥料的大规模使用以及高密度畜牧生产的径流，美国各地的河流、湖泊和沿海地区的水质正处于危险之中。在切萨皮克湾流域内，流域管理者和土地所有者继续努力减少养分流失，尽管几十年来一直在努力改善海湾的健康状况。近年来，随着利益相关者努力实施更好的流域管理实践，人们越来越关注湿地恢复，将其作为改善水质的工具，同时还提供水生栖息地和增加生物多样性。不幸的是，我们对如何优化恢复湿地的位置和功能以改善水质的理解仍然有限。在本项目中，研究者将采用集约化湿地监测和大规模数据分析相结合的方法，更好地了解在气候和土地利用条件变化的情况下，如何减少农业养分径流到下游水道。该项目还有一个外联部分，将涉及开发一个试点的切萨皮克夏季水研究所计划。该项目将研究生研究人员与以切萨皮克湾为重点的机构工作人员和其他利益相关者聚集在一起，促进信息交流，发展“以问题为重点”的研究团队，并使用基于过程和数据驱动的建模方法来回答有关改善切萨皮克湾水质的问题。本研究的主要目的是更好地了解景观氮(N)对现有和可恢复湿地的通量的控制，从而更好地预测湿地对切萨皮克湾流域水质的贡献。为了实现这一目标，PI将使用mesa -一种广泛使用的除草剂异丙甲氯的代谢物-作为农业硝酸盐的新型示踪剂，以确定不同土地利用类型和位置的湿地交叉N通量途径的程度，并量化由此产生的湿地N去除量。PI将利用来自国家湿地状况评估的数百个现有水质样本，以及对个别湿地站点的MESA进行更深入的监测，以更好地了解湿地与地下水N通量的空间变化连通性，从而完善湿地N去除量和相关N2O通量的估计。此外，MESA手性分析将用于估算遗留N到现有湿地的通量，从而更好地了解遗留N对当前水质的贡献。该奖项由地球科学部的水文科学项目和环境生物学部的生态系统科学项目共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The water quality of rivers, lakes, and coastal regions across the U.S. is at risk due to growing urban populations, large-scale use of commercial fertilizers, and runoff from high-density livestock production. Within the Chesapeake Bay Watershed, watershed managers and landowners continue to struggle with reducing nutrient runoff, despite decades of initiatives to improve the health of the Bay. In recent years, as stakeholders have worked to implement better watershed management practices, there has been increased interest in wetland restoration as a tool to improve water quality, while also providing aquatic habitat and increasing biodiversity. Unfortunately, our understanding of how to optimize the placement and function of restored wetlands to improve water quality remains limited. In this project, the investigator will use a combination of intensive wetland monitoring and large-scale data analysis to better understand how to reduce agricultural nutrient runoff to downstream waterways under changing climate and land-use conditions. The project also has an outreach component that will involve development of a pilot Chesapeake Summer Water Institute program. The program will bring graduate student researchers together with Chesapeake Bay-focused agency staff and other stakeholders to facilitate exchange of information, the development of ‘problem-focused’ research teams, and the use of process-based and data-driven modeling approaches to answer questions regarding improvement of Chesapeake Bay water quality.The primary objective of the proposed research is to better understand controls on fluxes of landscape nitrogen (N) to current and restorable wetland sites and, thus, to better predict the contributions of wetlands to water quality in the Chesapeake Bay Watershed. To meet this objective, the PI will use MESA–a metabolite of the widely used herbicide metolachlor–as a novel tracer of agricultural nitrate to identify the extent to which wetlands across a range of land-use types and positions intersect N flux pathways, and to quantify the resulting magnitudes of wetland N removal. The PI will leverage hundreds of existing water-quality samples from the National Wetland Condition Assessment together with more intensive monitoring of MESA at individual wetland sites to better our understanding of the spatially varying connectivity of wetlands with both groundwater N fluxes, and thus to refine estimates of wetland N removal magnitudes and associated N2O fluxes. In addition, analysis of MESA chirality will be used to estimate fluxes of legacy N to existing wetlands, thus bettering our understanding of the contribution of legacy N to current water quality.This award is co-funded by the Division of Earth Science's Hydrologic Sciences program and the Division of Environmental Biology's Ecosystems Sciences program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.