Collaborative Research: Impacts of urbanization on nitrogen biogeochemistry in xeric ecosystems

城市化极大地改变了半干旱生态系统中氮(N)化合物的运动和转化。特别是在城市地区，特别是在干旱和半干旱环境中，饮用水的硝酸盐污染是一个日益令人关切的问题，在这些地区，城市径流得到积极管理，以补充地下水和增加供水。然而，水资源管理人员和城市规划者缺乏关于哪些生态系统特征在控制这种补给水的质量，特别是其硝酸盐浓度方面最重要的信息。本研究将量化亚利桑那州图森和凤凰城流域（CAP LTER）的降雨径流中硝酸盐的来源、运输和命运如何随城市土地利用的密度和类型而变化。硝酸盐出口的季节模式将被表征，新的同位素示踪技术将用于了解硝酸盐来源和控制氮在半干旱城市化梯度中的转化机制。这些机制将被建模并集成到交互式可视化产品中，这些产品将有助于有关城市发展模式和雨水管理方法的决策。这项研究将有助于确定干旱和半干旱沙漠地表水和地下水硝酸盐污染的来源。在这些地区，水是宝贵的，但不断增加的地下水和地表水污染事件威胁着这一重要资源。这项研究协调了当地（图森、凤凰城）、州（亚利桑那州）和联邦（国家大气沉积计划/环境保护局）的资源，以关注一个具有当地、区域和全球影响的问题。该项目将招募公民科学家志愿者，培训研究生和本科生进行政策相关研究，促进科学家和决策者之间的互动，并开发可转移的可视化工具。

Urbanization dramatically modifies the movement and transformations of nitrogen (N) compounds in semi-arid ecosystems. In particular, nitrate contamination of drinking water is a growing concern in urban areas, especially in arid and semi-arid environments, where urban runoff is actively-managed to recharge groundwater and augment water supplies. Water managers and urban planners, however, lack information on what ecosystem characteristics are most important in controlling the quality of this recharged water, especially its nitrate concentrations. This research will quantify how sources, transport, and fate of nitrate in storm runoff vary with the density and type of urban land use in Tucson and Phoenix (CAP LTER), Arizona watersheds. Seasonal patterns of nitrate export will be characterized, and new isotopic tracer techniques will be used to understand nitrate sources and mechanisms controlling nitrogen transformations along semi-arid urbanization gradients. These mechanisms will be modeled and integrated into interactive visualization products that will aid in decision-making regarding urban development patterns and storm water management approaches.This research will help identify sources of surface water and groundwater nitrate contamination in arid and semi-arid deserts. Water is precious in these regions, yet increasing incidences of contamination of ground and surface waters threaten this vital resource. This research coordinates local (Tucson, Phoenix), state (Arizona), and federal (National Atmospheric Deposition Program/Environmental Protection Agency) resources to focus on a problem that has local, regional and global implications. The project will engage citizen-scientist volunteers, train graduate and undergraduate students in policy-relevant research, foster interactions between scientists and decision makers, and develop transferable visualization tools.