Environmental Impacts:

Acid Deposition

Environmental Impacts:

Acid Deposition

 

Unfortunately, the effects of pollution do not end when they are released into the atmosphere.  Many of the pollutants, especially Nitrogen oxides (NOx) and Sulfur oxides (SOx), chemically interact with sunlight and other atmospheric substances such as water vapor to produce acidic compounds such as Nitric acid (HNO3) and Sulfuric acid (H2SO4).  For example Sulfuric acid is created when sulfur dioxide reacts with water in the atmosphere(1):

 

 

 

 

Once these secondary pollutants have been created, they can then be re-deposited back on earth through a process called acid deposition.  This can take place either through wet deposition or dry deposition.

 

 

 Wet Deposition

 

 Wet deposition, in the form of acid rain, snow, fog, or cloud vapor, usually occurs within 2-14 days from when the acidic secondary pollutant has been formed (2). Because of this time lag and the ability for these pollutants to be carried by wind to different locations, what was once a local concern can now become a regional or even a transboundary problem.

 

 Dry Deposition

 

Dry deposition occurs during a shorter period of time, often within 2-3 days and usually within close proximity of the emission source (3).  This deposition takes place in the form of gases and salts.

While it is important to remember that even unpolluted rainfall is slightly acidic by nature (an average pH of 5.6 as compared to a neutral balance of 7.0), the pH for polluted waters can be as low as 1.8! (4), thereby cementing the link between primary and secondary pollutants.

Notwithstanding an annual precipitation of just slightly more than one centimeter, Cairo does become humid during the summer months. It is during this time that wet deposition would be most likely to occur, while dry deposition would be more prominent during the dry winter months.  Acid deposition will continue to threaten Cairo’s environment in the following ways:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Agriculture

 

Although much is dependent upon the plant type and age, sunlight, humidity, and the presence of other pollutants (5), acid deposition can be exceptionally harmful when pH levels fall below 5.1. Types of agricultural damage include:

-depletion of nutrients from the soil, impacting plant and crop productivity damage to the waxy coating on leaves which in turn restricts the plants ability to absorb water and gases

-reduction in the plant’s ability to fight off diseases, insects, harmful mosses and effects of drought