Acid Deposition - Air Pollution and Global Warming: History, Science, and Solutions - page 231

Acid deposition destroys crops in the same way that it
destroys forests.
Not all damage to forests and crops is a result of acid
deposition. Ozone also reacts with leaves, increasing
plant and tree stress and making plants and trees more
susceptible to disease, infestation, and death. Soot par-
ticles smother leaves, increasing plant and tree stress.
PA N d i s colors the leaves of plants and trees.

to the lake. A neutralizing agent increases the pH of an
acidified lake toward that of natural rainwater. Certain
natural chemicals in soil and aerosol particles also act
as neutralizing agents, preventing some soils and lakes
from acidifying.

10.6.1. Ammonium Hydroxide
One anthropogenic neutralizing agent is ammo-
nium hydroxide [NH 4 OH(aq)], obtained by dissolv-
ing ammonia gas [NH 3 (g)] in water. The net effect of
adding NH 4 OH(aq) to acidified water is

10.5.3. Effects on Buildings and Sculptures
Acid deposition erodes materials. In particular, acids
erode sandstone, limestone, marble, copper, bronze, and
brass. Of note are buildings and sculptures of histori-
cal and archeological interest, such as the Parthenon in
Greece, that have decayed, partly as a result of acid
deposition and partly as a result of other pollutants
in the air. Ozone, for example, reduces the detail in
statues. Figure 10.6 shows an example of statue ero-
sion, due both to acid deposition and other types of air
pollution.

H +
Hydrogen
ion

NH 4
Ammonium
ion

NH 4 OH
Ammonium
hydroxide

(aq) + + H 2 O(aq)

Liquid
water
(10.15)

which reduces the H +

molarity, reducing acidity and

increasing pH.

10.6.2. Sodium and Calcium Hydroxide
When lye [NaOH(aq), sodium hydroxide ], the
common component of “Drano,” or slaked lime
[Ca(OH) 2 (aq), calcium hydroxide ]isadded to an acid-
ified lake, it reacts with H + to form water, decreasing

10.6. Natural and Artificial Neutralization
of Lakes and Soils
One way to reduce the effect of acid deposition on lakes
is to add a neutralizing agent (often called a buffer )

Figure 10.6. Sandstone figure over the portal of a castle, built in 1702, in Westphalia, Germany, photographed
in 1908 (left) and in 1968 (right). The erosion of the figure is due to a combination of acid deposition and air
pollution produced from the industrialized Ruhr region of Germany. Photo courtesy of Herr Schmidt-Thomsen,
available from www.ultranet.com/ ∼ jkimball/BiologyPages/A/AcidRain.html#westphalia.