Ask A Scientist General Science Archive

Question:  What are heavy metals? Do they pollute water?
deetta l kambic

Answer 1:
"Heavy metals" are a non-scientific term used to
refer to metals which are in the third period or so
(and higher) of the periodic table.
 
Heavy metals don't pollute the water...people do.
And sure, that's one thing that human activity puts in there.
For example; mining operations on olden days were
notorious for putting heavy metals into the local water
...into the river and so forth.
 
Hope this helps
-topper

Answer 2:
Heavy metals are of real concern in the aquatic environment.
Small amounts of metals are necessary for growth, but at
elevated levels can become toxic.  In my field of
oceanography and phycology (study of algae) metal chemistry
is a hot research item.  Locally, we have trouble with copper
leaching from the the anti-fouling paint on the Navy ships
and precipitating out into the sediments.  From the sediments
the copper will continue to come out into the water and become
a constant source of copper.  Many studies have been done on
marsh plants becasue they take heavy metals up into their
cells and therefore can "cleanse" the water.  However, unless the
plants are harvested, the metals may return to the water as
the plants decompose after death.  So you can see that even
when sources of pollution are identified and stopped, the
polutants can continue to cycle in the system.  In addition, pollution
can cause a shift in the kinds of microalgae that can be supported
in a system, and since these algae are the basis of the food chain,
the kinds of lagae can determine the kinds of animals that can live
there.  Therefore, a non-toxic level of a metal contaminate can alter
the basis of the food chain and therefore alter the types of fisf
and other animals that can be supported in an ecosystem.
Stacie