In urban watersheds, street tree leaf litter is a critical biogenic source of phosphorus (P) in stormwater runoff. Stormwater extracts P from leaf litter and transports it, through the storm sewer network, to a receiving waterbody potentially causing downstream eutrophication. The goal of this study is to understand P leaching dynamics of two prevalent tree species (Norway maple (Acer platanoides) and green ash (Fraxinus pennsylvanica)) in three urban residential watersheds in Madison, Wisconsin, USA. Leaf litter was collected from the three basins during Fall 2017 and 2018. Laboratory experiments showed an initial rapid total dissolved phosphorus (TDP) release that gradually plateaued over a 48-hour period. The total TDP released from Norway maple (2.10 mg g⁻¹) was greater than from green ash (1.60 mg g⁻¹). Within the same species, increased fragmentation of leaves led to more rapid initial TDP release, but not greater total TDP release. Increased aging of senescent leaves decreased total TDP release. Incubation temperature and volume of water in contact with leaves may not be critical factors affecting TDP leaching dynamics. Predictive equations were derived to characterize time-variable TDP release of both Norway maple and green ash leaves. Potential TDP release from leaf litter estimated using these equations was compared with field-measured end-of-pipe TDP loads in one of the study watersheds. Our results indicate that preventing leaf litter from accumulating in streets is an important stormwater quality control measure.

在城市流域中，街头落叶是雨水径流中磷的重要生物来源。雨水从枯枝落叶中提取磷，然后通过雨水排放管网将其运输到接收水体，这可能导致下游富营养化。这项研究的目的是了解美国威斯康星州麦迪逊市的三个城市居民流域中两种流行的树种（挪威枫（Acer platanoides）和绿灰（Frazinus pennsylvanica））的磷淋溶动力学。在2017年秋季和2018年秋季从三个流域收集了落叶凋落物。实验室实验表明，最初的快速总溶解磷（TDP）迅速释放，并在48小时内逐渐趋于平稳。从挪威枫树释放的总TDP（2.10 mg g ^-1）大于绿灰（1.60 mg g ^-1）。在同一物种内，叶片碎片增加导致初始TDP释放更快，但总TDP释放却不大。衰老叶片衰老增加会降低总TDP释放。与叶片接触的温育温度和水量可能不是影响TDP淋洗动力学的关键因素。推导了预测方程式，以表征挪威枫树和绿灰叶随时间变化的TDP释放。在这些研究流域之一中，将使用这些方程式估算的潜在凋落物释放的TDP与现场测量的管道末端TDP负载进行了比较。我们的结果表明，防止垃圾在街道上堆积是一项重要的雨水质量控制措施。