Urban Sources

Urban areas include several sources of nitrogen that can eventually end up in Puget Sound via various pathways.

Urban sources include:

  • emissions from vehicles and other modes of transportation
  • emissions from industrial activities and building infrastructure
  • application of fertilizers on lawns
  • human wastewater (that goes to wastewater treatment plants)

Pathways of nitrogen delivery include:

  • Atmospheric deposition – air emissions from urban areas end up in the atmosphere and can be deposited again via wet or dry deposition.
  • Rivers and streams – urban sources can be discharged or delivered into the nearest water body to be carried into Puget Sound via a river or stream that then flows into Puget Sound.
  • Stormwater runoff – storm events carry nitrogen from land surfaces and into the nearest water body or storm drain, and eventually into Puget Sound.

Urbanization

This map shows the current (2011) and future (2020, 2040, and 2070) projected urban/developed areas in the Puget Sound region. As the population of Puget Sound grows, even more of this landscape will be developed to accommodate more people, wastewater, houses, cars, roads, and related industrial and commercial activities.

Future developed land was estimated by ENVISION, a tool developed by researchers from Oregon State University. ENVISION is a GIS-based tool for scenario-based community and regional integrated planning and environmental assessments. It allows for the representation of human decision-makers in landscape simulations. The tool actually has three different scenarios: 1) unconstrained growth, 2) status quo, and 3) managed growth. Each scenario represents different growth management decisions – the results on this map are from their ‘status quo’ scenario, which represents a continuation of current land-use trends in the region

When more land is developed, we have more impervious surfaces, which increase stormwater runoff. An increase in urbanization is also likely to increase nitrogen sources from urban areas.

Urban sources of nitrogen can be reduced by:

  • Using alternative means of transportation such as carpooling, using mass transit, riding the bus, vanpooling or ridesharing, and bike commuting.
  • Improving wastewater treatment technologies to remove nitrogen from wastewater.
  • Using low-impact development practices such as rain gardens.
  • Managing urban growth and protecting certain areas from development.
  • Landscaping with native plants and vegetation that do not need additional fertilizers.