Geology Reference
In-Depth Information
EXERCISE 14
Lake and River Contamination
from Industrial Waste
INTRODUCTION
During the 1970s the public observed pollution and
the effects of pollution from many sources in the
rivers and streams of North America. Detergent foam
covered streams and fish floated on the surface,
dead from toxins or lack of oxygen; beaches were
closed; drinking-water sources were lost; at least one
river burned; and fisheries closed due to mercury or
organic chemical pollution. In this exercise we
explore two areas where industrial wastes resulted in
a decrease in water quality. Although the practice of
dumping industrial wastes directly into surface waters
has decreased markedly in North America since the
1970s there are many places in the world where such
point-source pollution is common. Also, past errors
by industry and the acts of unscrupulous industrial-
waste handling companies have left us with problems
that are still in need of being addressed. In 2007
there were more than 1,600 Superfund sites, the
most serious toxic waste sites, according to the
federal program that is charged with cleaning up
these sites. This exercise shows the impact of poor
waste disposal practices on a river and one of the
Great Lakes and progress in reducing concentrations
of contaminants.
inorganic chemicals (some from agricultural sources)
and trace elements are still a concern in Lake Erie.
Water quality and the health of the fish population in
the lake have shown significant improvement since
the 1970s, but excessive consumption of fish from the
lake is still a hazard. Although detailed fish consump-
tion advisories (e.g., listing type, size, and location of
fish, number of meals per month, and toxins [mercury
and PCBs]) are readily available on the Web and else-
where, some individuals downplay the importance of
health hazards. In addition to the trace element and
organic chemical contamination of the water, sedi-
ments, and biota of the lake, invasive non-native
species (fish, invertebrates, and plants) cause eco-
nomic and environmental damage to the Great Lakes.
The sea lamprey invasion occurred with the opening
of the St. Lawrence Seaway and more recently zebra
mussels have disrupted the ecosystem. The mussel,
which was inadvertently introduced from Europe in
the 1980s, grows rapidly and blocks water intakes for
cities, power plants, and boat motors. Although the
zebra mussels actually improved water quality by fil-
tering, the mussels may eventually cause other prob-
lems because they concentrate pollutants from the
water and remove food needed by other organisms.
The lake will continue to change as other non-native
species enter the system. The round goby has arrived;
the Asian carp is nearby in the Mississippi River
System.
In this part of the exercise we investigate contam-
ination by trace elements. Although this exercise cov-
ers surface-water quality, the focus is actually on
sediments contaminated by trace elements. Trace ele-
ments are defined as those substances that normally
occur in water at concentrations less than 1 milligram
per liter (mg/L or 1 part per million (ppm)). A few
trace elements and their recommended maximum con-
centrations in drinking water are listed in Table 14.1
(see also Table 13.1.). Little is known of the potential
adverse or beneficial physiological effects on humans,
PART A. TRACE ELEMENT (MERCURY
AND CHROMIUM) POLLUTION IN LAKE ERIE
Lakes Erie and St. Clair and the Detroit and St. Clair
rivers were among several areas impacted by mercury
pollution in the 1960s and 1970s. In fact, mercury pol-
lution shut down the fisheries industry in many areas,
and algal blooms caused reduced levels of dissolved
oxygen in other areas. These and other factors caused
some environmentalists to proclaim Lake Erie "dead."
Although the lake is far from dead, organic and
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