Environmental Engineering Reference
In-Depth Information
Can objects in the water cause pollution?
Antifouling paints on vessels are designed to reduce attach-
ment of organisms like barnacles and algae, and do so by
being toxic. The chemicals are released slowly from the boat
paint and thus deter settlement by the planktonic stages of
these organisms. However, the chemicals are also toxic to
other organisms nearby. The most popular antifouling chemi-
cal that was used in the past was tributyltin (TBT), which is
now banned throughout most of the world (and will be dis-
cussed in detail in later chapters). Other antifoulants include
copper, which is especially toxic to mollusks and algae (it is
used as an algicide and molluscicide). Since bans and restric-
tions on TBT came into effect, researchers have developed
and produced new types of chemicals. Irgarol is now a com-
mon antifoulant, and is highly toxic to nontarget plants. It is
found in water and sediments near marinas at levels that may
be high enough to cause changes in phytoplankton commu-
nities. Another antifouling biocide, diuron, is also found in
water and sediments.
When wooden structures are placed in the water in the
form of dock pilings or bulkheads, they are subject to decay
by microbes and destruction by wood-boring animals such
as some amphipods (gribbles) and shipworms (which are
really mollusks). Therefore, the wood gets treated with
high concentrations of toxic chemicals, such as creosote or
chromated-copper-arsenate (CCA), to prevent this destruc-
tion. These chemicals also leach from the wood and can accu-
mulate in the environment and get taken up by nearby plants
and animals, causing toxic effects.
How can aquaculture cause pollution?
Aquaculture is the raising of marine organisms for food—
farming the sea—similar to agriculture on land. Fish farms,
especially open cage culture of salmon, have been found to
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