L12_Urban N (1)

Pollution Sources

• Point Source Pollution

  • Defined as any single identifiable source from which pollutants are discharged.

  • Examples include:

    • Pipe

    • Ditch

    • Ship

    • Factory smokestack (EPA)

• Non-point Source Pollution

  • Results from land runoff, precipitation, atmospheric deposition, drainage, seepage, or hydrologic modification (EPA).

Changes in Runoff

Key Factors

• Timing: Changes over seasonal cycles.

• Quantity: Total amount of runoff generated.

• Location: Geographic distribution of runoff sources.

• Quality: Contaminant levels in runoff water.(Adapted from Tague and Costello, 2008)

Runoff Differences

Urban vs. Non-Urban Systems

• Urban systems typically exhibit significant differences in:

  • Timing

  • Amount

  • Location

  • Quality of runoff.

• Potential pollutants in runoff can lead to environmental degradation.

Nitrogen Pollution

Significance in Aquatic Systems

• Nitrogen is a critical pollutant that affects aquatic ecosystems, particularly in the Chesapeake Bay.

Nitrogen Sources in Chesapeake Bay

• Fertilizer: 15%

• Air Emissions: 6% (including agricultural emissions)

• Manure: 17%

• Stormwater: 38%

• Sewage/Industry: 19%

• Septic systems: 4%

• Air pollution contributes to approximately 40% of total stormwater nitrogen. (Source: Chesapeake Bay Program)

Eutrophication

• Excess nitrogen promotes algal blooms, depleting oxygen and leading to dead zones.

• Impacts human health through contamination of drinking water and increased air pollutants affecting lung function.

Anthropogenic Changes to the Nitrogen Cycle

• Human activities now fix more nitrogen than natural sources (lightning and bacteria).

• Fossil fuel combustion returns stored nitrogen to the atmosphere.

Sources of Nitrogen in Urban Landscapes

• Fertilizer Use

• Pet Waste

• Atmospheric Deposition

  • Wet Deposition: 50%

  • Dry Deposition: 50%

• Sewage

Chesapeake Bay

• Declared impaired waters by USEPA.

• Requirement to reduce nitrate loadings by 40%.

• Need for strategies to decrease non-point source pollution.

Water Budget at Hubbard Brook

• Precipitation breakdown:

  • 100% Precipitation = 60% Streamflow + 40% Evapotranspiration

Research Methodology

Stream Flow Gaging Sites

• Varied landscapes:

  • Agricultural

  • Suburban

  • Urban

  • Forested reference sites.

Water Quality Variation

• Nitrate concentrations differ across landscapes.

  • Highest: Agricultural areas

  • Lower but significant in Suburban and Urban areas.

  • Forest areas showed the lowest levels of nitrate.

Predicting Nitrogen Sources

• Understanding the nitrogen cycle can help identify pollution sources for management.

Land Cover and Ecosystem Function

• Different land covers impact:

  • Water quality

  • Nutrient retention

  • Heat dissipation.

Monitoring Stations

• Represent landscapes impacts on nitrogen levels,

  • Monitoring includes fine analysis of landscape structure.

Effects of Herbaceous Vegetation

• Positive correlation with stream nitrate levels suggests vegetation may amplify nitrogen issues.

Urbanization Impacts

• Riparian zones affected differently across urban environments;

  • Changes include:

    • Water table levels

    • Species diversity

    • Plant health (Q. lobata) under varying incision conditions.

Denitrification Processes

Soil Conditions

• Increased moisture and organic matter favor denitrification, especially in flowing streams with low levels of incision.

Non-Nitrogen Concerns

• Other elements in runoff (pesticides, personal care products) also pose significant risks to water quality.

Final Review Questions

• Compare urban vs. non-urban water cycle differences.

• Explain point vs. non-point source pollution and implications for management.

• Describe nitrogen cycle pools and fluxes and anthropogenic impacts.

• Discuss watershed management and the riparian zone's role in mitigating nitrogen pollution.

• Analyze the differences in climatic impacts on nitrogen export in temperate vs. Mediterranean regions.