In cation exchange, the ions of calcium, magnesium, potassium,
and other metals are attached to the clay and humus particles
in the soil. The attractive forces of positive metal ions to
the negatively charged clay particles is strong enough to hold
the metal ions in the soil despite the passage of water through
Effect of Acid: The hydrogen ions in the sulfuric acid
trade places with the metal ions. The hydrogen ions are retained
and neutralized by the soil. The calcium, potassium, and magnesium
ions are leached or washed out of the top soil into lower inaccessible
subsoil. These ions are then not available as nutrients or fertilizers
needed for tree and plant growth.
Effects on Soils - Related to Tree Growth Leaching Nutrients:
Trees derive their nutrition primarily from element ions such
as calcium, Ca, magnesium, Mg, and potassium, K that have dissolved
from rocks into the soil.
Acid deposition adds hydrogen ions, which displace these important
nutrients in a process called leaching. Leaching means
that the ions are washed deeper into the subsoil or washed out
of the top soil. If ions are leached from the soil, they are
no longer available to the roots of the plants.
Calcium ion is used in the cells of a tree for cell formation
and in the processes that transport sugars, water, and other
nutrients from the roots to the leaves.
Magnesium ion is a vital element in photosynthesis and as
a carrier of phosphorus which is important in the production
of DNA. These ions may be unavailable to the tree roots because
they have been leached away.