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

沙质海滩是沿海地区宝贵的娱乐和经济资源，也提供重要但往往被低估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通过它。在这些含水层内有可调节化学通量的反应区；了解控制这种反应的过程对于预测促进生物、地球化学和生态效益的条件至关重要。这项工作的目的是对流体流动和有机颗粒运输的物理过程在维持海滩含水层的反应性方面所起的作用有新的了解，并评估人为和自然变化对海洋污染物负荷的潜在影响。这项现场、实验室和模拟研究将(1)评估由于潮汐和波浪作用而进入沙滩的流体和相关有机颗粒的驱动机制、模式和速率，(2)表征海滩沉积物和孔隙水中有机物的数量、性质和活性，以及(3)确定由于颗粒和溶解的有机底物的流动、混合和呼吸而进入和通过海滩的营养物质浓度和通量的时空变化。拟议的工作将填补知识空白，使人们能够根据海滩含水层系统的物理特征推断潜在的反应性。根据科学成果开发的预测能力可以转移到其他系统和进程(如溢油补救)，并将能够预测人类影响的潜在影响以及海平面和气候的较长期变化对海滩含水层反应堆生态服务的影响。这项研究将帮助海滩管理人员评估沙滩的生态价值以及维持生态系统服务的管理活动的必要性。这项工作还可帮助关心沿海富营养化问题的管理人员根据易于评估的海岸线物理特征，更准确地估计河口和沿海水域的营养物质负荷。这项研究将产生教育影响，为对日益跨学科和多学科的环境问题感兴趣的研究生和本科生提供跨学科培训。这些现场将被开发为特拉华大学(UD)水文地质学课程的实践培训场地，以及为高中生开设的UD潮汐营地。

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.