Cities are increasingly pursuing more sustainable and resilient infrastructure. The increased use of Urban Ecological Infrastructure (UEI), including constructed treatment wetlands (CTW), may be particularly important for aridland cities with scarce water resources. In this paper we document eight years of nitrogen (N) dynamics in an aridland CTW in Phoenix, Arizona, USA, where N removal must be balanced by the trade-off of atmospheric water losses. We have documented a “biological tide”, wherein transpiration-driven water loss is actively replaced by a slow movement of surface water into the marsh from adjacent open water areas. Our analysis combined long-term water budget data with nitrogen budgets for the vegetated marsh and the entire CTW system. The objective was to demonstrate how the biological tide enhanced N uptake in this aridland CTW. We attributed roughly 50% of the annual N uptake by the vegetated marsh to new water entering via the biological tide. Thus, while it seems counter-intuitive to design aridland CTWs to optimize transpirational water losses, our data suggested that careful design of the plant community and spatial configuration of vegetated marsh versus open water may enhance both the biological tide and N removal efficiency.

城市越来越多地追求更可持续和更具弹性的基础设施。对于水资源稀缺的干旱城市，增加城市生态基础设施（UEI）的使用，包括人工处理湿地（CTW）的使用可能尤其重要。在本文中，我们记录了在美国亚利桑那州菲尼克斯的干旱地区CTW中八年的氮（N）动态，在该处必须通过平衡大气水损失来平衡氮的去除。我们已经记录了“生物潮”，其中蒸腾作用驱动的水损失被地表水从相邻的开阔水域缓慢进入沼泽的主动取代。我们的分析结合了植被沼泽和整个CTW系统的长期水预算数据和氮预算。目的是证明该干旱地区CTW中的生物潮如何增加氮的吸收。我们将植被沼泽每年吸收的大约50％的氮归因于通过生物潮汐进入的新水。因此，尽管设计干旱地区的CTW来优化蒸腾作用的水损失似乎是违反直觉的，但我们的数据表明，对植物群落进行精心设计以及植被沼泽相对于开放水域的空间配置可能会提高生物潮汐和氮的去除效率。