Environmental Engineering Reference
In-Depth Information
Figure 4.12 Reduction of sulphur dioxide through emission controls
Source: Various; see text
lake with fish cannot be successful unless some
buffering agent is added. In 1973, several lakes
in the Sudbury area were treated with calcium
carbonate and calcium hydroxide in an attempt
to reduce acid levels (Scheider et al. 1975). Acidity
returned to normal and there was an increase in
nutrient levels, but, in the lakes closest to
Sudbury, copper and nickel remained at
concentrations toxic to fish (Ontario: Ministry
of the Environment 1980). Similar experiments
in Sweden since the mid-1970s have involved the
liming of some 3,000 lakes and 100 streams, and
have provided encouraging results (Porcella et
al. 1990). Reduced acidity is often followed by
recovery among the aquatic biota, Lower
organisms—such as phytoplankton—which
reproduce rapidly recover first, followed
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