Natural Causes of Acidity:
Soils and surface waters such as streams and lakes receive
acid from a variety of natural sources.
Natural sources of acids include:
sulfur oxides/sulfuric acid from volcanoes, forest fires, decomposition
of plants and animals, carbon dioxide in air forms carbonic acid,
lightning bolts convert nitrogen molecules in air to nitrogen
oxides to nitric acid.
A research project, called the Integrated Lake Watershed Acidification
Study conducted by the Electric Power Research Institute, studied
three Adirondack lakes located so close to each other that they
received the same rain and snow.
One of the lakes was healthy (basic), another was acidic,
and the third cycled back and forth from basic to acidic. It
was found that the acid rain and snow probably played only a
very small part in the whether the lakes are acidic or basic.
Types of soil, trees, and decaying leaves which surround a
lake have the strongest influence on the whether a lake is acidic
or basic. Water drains from the surrounding land into a lake.
Water from rain and snow comes into contact with materials surrounding
the lake before it drains into the lake.
The layers of decaying leaves, called humus, are rich in organic
matter and produce acids similar to vinegar. The pH of water
in contact with humus is generally very acidic.