Hydrological Control of Particle Entrainment and Nitrogen Cycling in Beach Aquifer Mixing and Reaction Zones

桑迪是沿海地区宝贵的娱乐和经济资源，也提供重要但往往未得到重视的生物地球化学和生态服务。海滩含水层是陆地和海洋之间重要的水文界面，溶解在地下水中的陆地污染物在到达海洋之前会通过这些含水层。在这些含水层内有反应区，可以缓和化学通量;了解控制这种反应的过程对于预测促进生态地球化学和生态效益的条件至关重要。这项工作的目标是获得新的认识的作用，物理过程的流体流动和有机颗粒运输在保持海滩含水层的反应性，并评估人为和自然变化对污染物负荷的海洋的潜在影响。该现场、实验室和模拟研究将（1）评估由于潮汐和波浪作用导致的流体流动和相关有机颗粒并入桑迪的驱动机制、模式和速率，（2）表征海滩沉积物和孔隙水中有机物质的量、性质和反应性，以及（3）确定由于颗粒和溶解有机基质的流动、混合和呼吸作用而导致的营养物进入和通过海滩的浓度和通量的时空变化。拟议的工作将填补知识的空白，这将允许从海滩含水层系统的物理特性推断潜在的反应性。从科学结果中开发的预测能力可以转移到其他系统和过程（例如漏油修复），并将能够预测人类影响以及海平面和气候的长期变化对海滩生态服务的潜在影响含水层反应堆。这项研究将有助于海滩管理人员评估桑迪的生态价值和管理活动的必要性，以维持生态系统服务。这项工作还可以帮助管理人员关心沿海富营养化作出更准确的估计营养负荷的河口和沿海沃茨的基础上容易评估的物理特性的海岸线。该研究将产生教育影响，为对日益跨学科和多学科环境问题感兴趣的研究生和本科生提供跨学科培训。现场将发展成为特拉华州大学（UD）水文地质学课程和高中学生UD潮汐营的实践培训场所。

Sandy beaches are valuable recreational and economic resources in coastal regions, and also provide important but often underappreciated biogeochemical and ecological services. Beach aquifers are important hydrological interfaces between land and sea through which terrestrial contaminants dissolved in groundwater pass prior to reaching the ocean. Within these aquifers are reactive zones that can moderate chemical fluxes; understanding of the processes that control such reactivity is essential for predicting the conditions that promote biogeochemical and ecological benefits. The objectives of this work are to gain new understanding of the role that physical processes of fluid flow and organic particle transport have in maintaining the reactivity of beach aquifers and to assess the potential impact of anthropogenic and natural changes on contaminant loads to the ocean. This field, laboratory, and modeling study will (1) assess the driving mechanisms, patterns, and rates of fluid flow and associated organic particle incorporation into sandy beaches as a result of tide and wave action, (2) characterize the amount, nature, and reactivity of organic matter in beach sediments and porewater, and (3) determine spatial and temporal variations in the concentrations and fluxes of nutrients to and through the beach resulting from flow, mixing, and respiration of particulate and dissolved organic substrates. The proposed work will fill a gap in knowledge that will allow inference of potential reactivity from the physical characteristics of beach aquifer systems. The predictive capacity developed from the scientific results can be transferred to other systems and processes (such as oil spill remediation) and will enable prediction of potential effects of human influences and longer-term changes in sea level and climate on the ecological services of beach aquifer reactors. The research will aid beach managers in assessing the ecological value of sandy beaches and the need for management activities to maintain ecosystem services. The work may also help managers concerned with coastal eutrophication make more accurate estimates of the nutrient loads to estuarine and coastal waters based on easily assessed physical characteristics of shorelines. The research will have educational impacts, providing interdisciplinary training for graduate and undergraduate students interested in increasingly inter- and multi-disciplinary environmental issues. The field sites will be developed into hands-on training sites for hydrogeology courses at the University of Delaware (UD) and for the UD TIDE Camp for high school students.