Page 153 - Fundamentals of Air Pollution

IV. Effects on Animals 121

altered by acid deposition. Decreased pH in some lakes and streams in the
affected areas was observed in the 1960s (17) and further evidence shows
this trend.
When a forest system is subjected to acid deposition, the foliar canopy
can initially provide some neutralizing capacity. If the quantity of acid
components is too high, this limited neutralizing capacity is overcome. As
the acid components reach the forest floor, the soil composition determines
their impact. The soil composition may have sufficient buffering capacity
to neutralize the acid components. However, alteration of soil pH can
result in mobilization or leaching of important minerals in the soil. In some
instances, trace metals such as Ca or Mg may be removed from the soil,
altering the Al tolerance for trees.
This interaction between airborne acid components and the tree-soil
system may alter the ability of the trees to tolerate other environmental
stressors such as drought, insects, and other air pollutants like ozone. In
Germany, considerable attention is focused the role of ozone and acid
deposition as a cause of forest damage. Forest damage is a complex problem
involving the interaction of acid deposition, other air pollutants, forestry
practices, and naturally occurring soil conditions.

IV. EFFECTS ON ANIMALS

Acid deposition and the alteration of the pH of aquatic systems has led
to the acidification of lakes and ponds in various locations in the world.
Low-pH conditions result in lakes which contain no fish species.
Heavy metals on or in vegetation and water have been and continue to
be toxic to animals and fish. Arsenic and lead from smelters, molybdenum
from steel plants, and mercury from chlorine-caustic plants are major of-
fenders. Poisoning of aquatic life by mercury is relatively new, whereas
the toxic effects of the other metals have been largely eliminated by proper
control of industrial emissions. Gaseous (and particulate) fluorides have
caused injury and damage to a wide variety of animals—domestic and
wild—as well as to fish. Accidental effects resulting from insecticides and
nerve gas have been reported.
Autopsies of animals in the Meuse Valley, Donora, and London episodes
described in Chapter 16, Section III, revealed evidence of pulmonary edema.
Breathing toxic pollutants is not, however, the major form of pollutant
intake for cattle; ingestion of pollution-contaminated feeds is the primary
mode.
In the case of animals we are concerned primarily with a two-step process:
accumulation of airborne contaminants on or in vegetation or forage that
serves as their feed and subsequent effects of the ingested herbage on
animals. In addition to pollution-affected vegetation, carnivores (humans