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WHAT
IS IT?
pH
is a measure of the hydrogen ion (H+) concentration in water.
The pH scale ranges from 0 (acidic) to 14 (basic). Pure water
is made up of water molecules (H20), hydrogen ions
(H+) and hydroxyl ions (OH-). Chemically, H20 = H+
+ OH- .
Rivers
have their own unique balances in the numbers of H20
molecules, H+ ions and OH- ions. If there are equal numbers of
each ion (H+ and OH-), water has a pH of 7 (neutral). When more
H+ is present than OH-, the water becomes acidic and has a pH
value less than seven (0-7). When more OH- is present than H+,
the water becomes more basic and has a pH value greater than
seven (7-14).
Very Acidic
Neutral
Very Basic
(Lots more H+)
H20
(Lots
more OH-)
0----------------------------------7---------------------------------14/
(Note: This scale is logarithmic; a change between
numbers is not one unit of change but a tenfold change.)
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WHY
IS IT IMPORTANT?
1. pH affects
what can live in water by influencing the blood's ability to
hold oxygen. Many aquatic animals breathe oxygen in the water
and use it to run chemical processes in their bodies. If the
pH is too low or high they cannot get enough oxygen in their
blood to fuel these chemical processes, which are essential to
life.
CHART: Tolerant pH ranges for aquatic
organisms
| Most Acidic |
Neutral |
Most Basic |
| 0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
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Bacteria |
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Plants (algae, rooted, etc.) |
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carp, suckers,catfish, some
insects |
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bass,
bluegill crappie |
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Snails,clams,mussels |
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Largest
variety of animals (Trout, mayfly and stonefly nymphs, caddisfly
larvae) |
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Mitchell,
M. &W.B. Strapp, 1988 Field Manual for Water Quality Monitoring
2. pH can effect
the state of an ion, and its influence on aquatic life. For example,
at a certain pH Fe2+ could be harless to aquatic life,
while at a certain pH the ion becomes Fe3+ and is
harmful to aquatic life.
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WHAT
INFLUENCES IT?
1. Acid Rain:
Cars and coal plants create emissions which, when mixed in the
atmosphere, fall back to earth as acid rain. (The most acidic
snow in the Rocky Mountains falls in northern Colorado in the
Mount Zirkle Wilderness)
2. Acid Mine
Drainage: Mining brings sulfur-containing rocks and minerals
from deep within the Earth to its surface. Once exposed, these
rocks and minerals react with rainwater and groundwater to form
acidic water that runs into local rivers and streams./
3. Temperature.
4. pH fluctuates
both daily and seasonally as the result of temperature changes.
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