• Author / Uploaded
• gayne

Citation preview

Air Pollution Air pollution may be defined as the presence of substances in concentrations that make the air harmful or dangerous to breathe or to cause damage to plants, animals and property.

3.1 TYPES OF POLLUTANTS

In general, there are only two types of pollutants: particulates and gaseous. Particulates are finely divided solids and liquids, such as dust, fumes, smoke, fly ash, mist and spray. Gaseous pollutants are, by definition, pollutants in gaseous form. Gaseous pollutants have the property of filling any available space until their concentrations fall to equilibrium by diffusion. CLASSIFICATION OF POLLUTANTS Major Class Particulates

Subclass  Solid  Liquid

Examples Dust, smoke, fumes, fly ash Mist, spray

Gases  Organic

 Hydrocarbons

 Hexane, benzene, ethylene, methane, butane, butadiene.

 Aldehydes and

 Formaldehyde, acetone

ketones  Other organics

 Chlorinated hydrocarbons, alcohols

Oxides of carbon  Inorganic

Oxides of sulphur

 CO, CO2

Oxides of nitrogen

 SO2, SO3

Other inorganics

 NO2, NO  H2S, HF, NH3

When carbon monoxide and oxygen are introduced to the blood through the alveolar sacs of the lungs, the former is absorbed 210 times more than the latter in terms of the equilibrium absorption coefficient of oxygen. Thus, if [HbCO] is the concentration of carboxyhaemoglobin and [HbO2] is the concentration of oxyhaemoglobin, their equilibrium concentration ratio is:

p [ HbCO ] =210 CO HbO 2 pO 2

( )

where pCO and pO2 are the partial pressures of carbon monoxide and oxygen in the lungs respectively. The concentration of carbon monoxide in the blood is expressed empirically in terms of the percentage saturation: %HbCO = 0.005[CO]0.85(t)0.63 where [CO] is the concentration of CO in ppm,  represents the physical activity level (1 for sedentary activity up to 3 for heavy work), t represents the duration of activity in minutes. HEALTH EFFECTS OF HbCO AT VARIOUS LEVELS IN THE BLOOD HbCO Level < 1.0 1.0 – 1.5

Demonstrated Effect No apparent effect Some evidence of effect on behaviour is

1.5 – 4.5

noticeable Time interval discrimination, visual acuity, brightness determination, and certain other

> 4.5 4.5 - 80

psychomotor functions are impaired. Cardiac and pulmonary functional changes Headache, fatigue, drowsiness, coma, respiratory failure, and death.

Example 3.1

The concentration of CO in a street intersection reaches the national ambient standard of 35 ppm. Technicians from the Department of Public Works are repairing a break in the water line. Estimate the CO concentration in their blood after 1 hour of work and make conclusions as to their work performance. Solution %HbCO = 0.005[CO]0.85(t)0.63 Let  = 2 %HbCO = 0.005[35]0.85(2*60)0.63 = 2.1 %  Their work performance is impaired. Private Study: 

Indoor air pollution



Acid rain



Ozone depletion



Global warming



The greenhouse effect



Climate change



End-of-pipe solutions



Green chemistry