Rivers are like living organism in that they have many different mechanisms
to keep themselves healthy. You can dump sludge into a river and, up to a
point, the river can detoxify itself and remain in good health. For
example, turbulence in the river mixes water with oxygen, a powerful
purifier and germicide, as is ultraviolet light from the sun. Also, many
of
the plants that grow in rivers, both algae and higher plants, can remove
contaminants from water. But if you keep dumping sludge, at some point
you
will exceed a critical level where natural purification mechanisms become
overwhelmed and break down. Plants and beneficial microorganisms die,
flow
patterns change, the river becomes sick.
The river that appears hopelessly polluted is not beyond help. If you
will
simply stop putting bad substances into it, eventually the levels of
contamination will drop to a point where the natural healing mechanisms
revive. Oxygenation increases, sunlight penetrates to deeper levels,
beneficial organisms return, and the river cleans itself up.
Terry
a3587s@[EMAIL PROTECTED]
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