In general, atmospheric pollutants are dispersed by two mechanisms: wind speed and atmospheric turbulence.

FIG. 5.6.5 Effect of wind direction variability or pollutant concentration from constant source. (Continuous emission of 4 units per sec.)

FIG. 5.6.3 Wind rose showing direction and velocity frequencies.

Atmospheric turbulence usually includes those wind flow fluctuations that have a frequency of more than 2 cycles/hr. The more important fluctuations have frequencies in the 1-to-0.01-cycles/sec range. Turbulent fluctuations occur randomly in both vertical and horizontal directions. This air motion provides the most effective mechanism to disperse or dilute a cloud or plume of pollutants. Figure 5.6.5 shows the dispersive effect of fluctuations in horizontal wind direction.

Turbulence is induced in air flow in two ways: by thermal current from heating below (thermal turbulence) and by disturbances or eddies from the passage of air over irregular, rough ground surfaces (mechanical turbulence). These small eddies feed large ones.

Generally turbulent motion and, in turn, the dispersive ability of the atmosphere, are enhanced during solar heating over rough terrain. Conversely, turbulence is suppressed during clear nights over smooth terrain.

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Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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