title: Contribution of Leaf Litter to Nutrient Export during Winter Months in an Urban Residential Watershed.
abstract: Identification of nonpoint sources of nitrogen (N) and phosphorus (P) in urban systems is imperative to improving water quality and better managing eutrophication. Winter contributions and sources of annual N and P loads from urban watersheds are poorly characterized in northern cities because monitoring is often limited to warm-weather periods. To determine the winter export of N and P, we monitored stormwater outflow in a residential watershed in Saint Paul, Minnesota during 2012-2014. Our data demonstrate that winter melt events contribute a high percentage of annual N and P export (50%). We hypothesized that overwintering leaf litter that is not removed by fall street sweeping could be an important source to winter loads of N and P. We estimated contributions of this source by studying decomposition in lawns, street gutters, and catch basins during two winters. Rates of mass and N loss were negligible during both winters. However, P was quickly solubilized from decomposing leaves. Using mass balances and estimates of P leaching losses, we estimated that leaf litter could contribute 80% of winter total dissolved phosphorus (TDP) loading in this watershed (∼40% of annual TDP loading). Our work indicates that urban trees adjacent to streets likely represent a major source of P pollution in northern cities. Management that targets important winter sources such as tree leaves could be highly effective for reducing P loading and may mitigate eutrophication in urban lakes and streams in developed cities.
authors.affiliation: Department of Ecology, Evolution and Behavior, University of Minnesota , Saint Paul, Minnesota 55108, United States.
authors.forename: Anika R
authors.identifier: 0000-0002-5640-0957
authors.initials: AR
authors.lastname: Bratt
authors.affiliation: Department of Ecology, Evolution and Behavior, University of Minnesota , Saint Paul, Minnesota 55108, United States.
authors.forename: Jacques C
authors.initials: JC
authors.lastname: Finlay
authors.affiliation: Department of Ecology, Evolution and Behavior, University of Minnesota , Saint Paul, Minnesota 55108, United States.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Hobbie
authors.affiliation: Department of Ecology, Evolution and Behavior, University of Minnesota , Saint Paul, Minnesota 55108, United States.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Janke
authors.affiliation: Department of Ecology, Evolution and Behavior, University of Minnesota , Saint Paul, Minnesota 55108, United States.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Worm
authors.affiliation: Department of Ecology, Evolution and Behavior, University of Minnesota , Saint Paul, Minnesota 55108, United States.
authors.forename: Kathrine L
authors.initials: KL
authors.lastname: Kemmitt
mesh_terms: D002947:Cities; D004784:Environmental Monitoring; D008910:Minnesota; D009584:Nitrogen; D010758:Phosphorus; D045483:Rivers
chemical_list: D010758:Phosphorus; D009584:Nitrogen