Urbanization and the Environment

Urbanization is the process in which green space (fields, trees, wetlands, etc) is converted into black space (concrete and asphalt).

There are a lot of local consequenses of this but nothing global (yet)

• Alters heat balance and heat exchange to environment
• Urban Heat Island:
• Stored heat in buildings, asphalt, etc.
• Increase nighttime convective circulation.
• Urban Wind Alleys but overall reduction in windspeed (10--30%)
• Pollutants in Atmosphere: Increase condensation nuclei!
• Case Study in Urban Heat Islands

ACID RAIN

Acid Rain and the Sulfur Cycle

Sources:
• Bacterial Emission --> 4.2 units per year (1.0 from land)
• Fossil Fuel Burning --> 2.5
• Blowing of Sea Salts --> 2.0
• Volcanoes --> 0.03

• Total = 8.73

  Removal Mechanisms:
  

• Precipitation; Land 4.0 (3.1 units runoff into ocean)
• Precipitation; Ocean 3.4
• Plant uptake (Land) --> 1.2

• total = 8.6

But although sources - removal is roughly zero notice the following:

1) The dominant removal mechanism is by precipitation (4.0 units). Together with plant uptake, 5.2 units are put back into essentially the top soil but 3.1 units of that runs off leaving 2.1 units in the top soil.

2) The only topsoil removal mechanism, however, is bacteria which process the sulfur at a rate of 1.0 units per year.

3) Hence the burning of fossil fuels and the subsequent rapid deposition of sulfur into the top soil via preciptiation means that lithospheric sulfur is being effectively mined and is deposited into the topsoil

4) Oceans are in even more non-equilibrium due to increased runoff from the land

Pie Chart Showing Sources of SO2 Emission

Emissions are going down

We measure acid rain in terms of the pH index. Water is neutral. The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. Each whole pH value below 7 is ten times more acidic than the next higher value.

New Brunswick Annual Data Trends

National PH Map

Effects on Hydrological Cycle:

Urbanization changes or eliminates many of the natural pathways in the Hydrological cycle. Some local examples include:

• Increased percentage of surface is rendered impervious to precipitation
• Storm sewers: Direct discharge to stream channels.
• Increased flooding in urban areas is now quite common. Midwest flood was enhanced because of this.
• accelerate soil erosion (mining!) more sediment in stream channels
  

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