Environmental Engineering Reference
In-Depth Information
coral reefs is one approach to reducing the amount of surge
during storms, which are predicted to become more severe in
the future. Vegetation and reefs can reduce current speeds and
dissipate some of the energy because these organisms provide
drag force in the water. Another approach is to retreat—to
move houses and communities back from the shore, a strategy
that runs into considerable political opposition. Perhaps if it
were called something else—perhaps “move-back”—it would
not sound like defeat and cause so much opposition.
What is pH?
The pH is a scale from 0 to 14 used to measure of hydrogen
ion concentration in water. A pH of 7 is neutral, and repre-
sents equal amounts of hydrogen ion (H
+
) and hydroxide ion
(OH
-
). Pure water is neutral. Solutions with a pH less than 7
have more H
+
than OH
-
and are acidic, while solutions with a
pH above 7 are basic or alkaline; 0 is as strong as an acid can
be, and 14 is the strongest alkali. Seawater is slightly alkaline,
with a pH around 8.2. Since pH is a logarithmic scale, a dif-
ference of one pH unit is equivalent to a tenfold difference in
hydrogen ion concentration. So a pH decrease from 8.2 to 8.1
represents a 30% increase in acidity (even though the water is
not really acidic, but is less alkaline).
What is ocean acidification?
When CO
2
from fossil fuel burning enters the atmosphere,
about 1/3 of it ends up dissolving in the ocean. While this is
good for us since it slows down global warming, it is bad for
the ocean. In the ocean, the CO
2
combines with water to form
carbonic acid, which becomes bicarbonate ions (HCO
3
-
) and
hydrogen ions (H
+
), reducing the pH of the water by making
it more acidic. Since the industrial age began, the pH of the
oceans has declined by 0.1 pH unit, which, because the scale
is logarithmic, represents a 30% increase in acidity. This is
Search WWH ::
Custom Search