Acid Acid Rain

ACID DEPOSITION AND ACID RAIN:

Acid deposition is caused by acidic particles and gases that deposit or fall to the Earth. Acid deposition can be wet or dry. Wet deposition is deposition of acidic gases such as oxides of sulfur and nitrogen and acidic particles brought down as precipitation by rain, fog and snow. Dry deposition is dry deposition of acidic gases in the absence of rain or precipitation.

Acidity is measured using a scale called the pH scale. This scale goes from 0 to 14. 0 is the most acidic and 14 is the most alkaline (opposite of acidic). Something with a pH value of 7, we call neutral, this means that it is neither acidic nor alkaline.

Very strong acids will burn if they touch your skin and can even destroy metals. Acid rain

H+ ions make the rain acidic. A change of 1 in pH means the H+ concentration has increased 10 times; pH 4.2 means H+ concentration is 25 times greater than pure rain water. In Los Angeles in December 1982, pH 1.7 was recorded but that much acidity is rare. Industrialized areas of the world have H+ concentration about 4 to 40 times greater than the pure rain water. This corresponds to pH 4to to 5when compared pure rain water of pH 5.6. A pH of 4 in the lakes is sufficient to kill fish life and in North America there are such dead

SO2 (g) + H2O (l) → H2SO3 (aq)

In the presence of O2 and O3 sunlight, sulfur dioxide is oxidized to sulfur trioxide.

SO2 (g) + 1/2 O2 (g) → SO3(g)

With moisture, sulfur oxides can be converted to sulfuric acid, which is a strong acid.

2 SO2 (g) + O2(g) + 2 H2O(l) → H2SO4 (aq)

SO3(g) + H2O (l) → H2SO4 (aq)

As well as oxides of sulfur, oxides of nitrogen also cause acid rain:

In the absence of oxygen, nitrogen dioxide can dissolve in water and produce a mixture of nitrous acid (HNO2 ) which is a very weak acid and nitric acid (HNO3) which is a strong acid.

2NO2 (g) + H2O (l) → HNO2 (aq) + HNO3 (aq)

In the presence of oxygen and moisture, nitrogen dioxide can be converted to nitric acid through a series of complicated reactions. This can be summarized as:

4NO2 (g) + 2H2O (l) + O2(g → 4 HNO3 (aq)

EFFECTS OF ACID RAIN:

Acid rain affects humans, aquatic life, materials, soil, vegetation and visibility. If we consider them separately:

Effects on humans: Breathing air containing fine acid droplets irritates the whole respiratory tract from the mucous membranes in the nose and throat to the lung tissues. It may also cause severe irritation of