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Brook pH, Aluminum, and Viability
Name: Dale W.
Status: Student
Age: 15
Location: N/A
Country: N/A
Date: September 23, 2004
Question:
My Dad and I are trying to find out why the brook in our
neighbourhood is dying. There is a lot of algae and silt building in the
brook and fish are no longer migrating here.
We showed our Department of Environment the brook and they tested the
water. The tests showed "low pH and elevated aluminum." We understand the
pH and how this originates, but not the elevated aluminum.
This is a residential area, all along the brook with no industrial sites
at all. Can this much aluminum, to kill a brook, be a natural occurrence?
The city said they were going to check their storm drains. Does this make
sense?
Replies:
My guess is the low pH is leaching aluminum from the rocks. As for the
algae, blooms of algae often occur when run off from farms or even local
lawns cause excess nutrients to dump into the local waters.
Peter Faletra
Algae are often associated with elevated phosphate and/or nitrate levels.
These result from fertilizers applied to lawns followed by runoff from
rain. I am not aware of "elevated" aluminum being a pollution source from
residential runoff.
Vince Calder
Dear Dale,
Aluminum is naturally occurring in soils but its mobility is increased by
low pH water. A typical problem with acid rain therefore is the
increased levels of aluminum in soils which then leach into the water
and adversely affect aquatic life. Sort out the cause of the low pH,
eliminate it and the aluminum problem should go away.
Jim Tokuhisa
Dale,
These issues can be very complex. I once dealt with a home in Wisconsin
whose well was pumping acidic water. Although near some industry, there
was no contamination affecting the water table. The issue was caused by
natural occurrences.
You have not indicated what "elevated aluminum" is. Aluminum is
naturally occurring in the soils and can be leached out by the low pH.
There could be other factors at work here as well. How much dissolved
oxygen is in the brook? What is the source of the Brook? Does it come
from surface runoff or from underground spring?
The city storm drains can also move contaminants from far away into the
brook. It sounds like this issue needs more investigation.
Bob Hartwell
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Update: June 2012
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