LaMotte ACID RAIN STUDY OUTFIT ARO - Manual (Page 7)

TESTING THE pH OF OTHER SO LU TIONS
The *Wide Range Indicator (2218) included in this kit can be used to measure the
pH of solutions ranging from 3.0 to 10.0 pH. Surface water, tap water, foods and
household products can be tested.
TESTING THE pH OF STREAMS, LAKES, AND PONDS
1. Select a sampling location where the water sample is typical of the water source
and does not represent a localized condition. For example, a water sample taken
next to a discharge pipe may not contain the same types and amounts of
substances that would be found in a sample collected away from the discharge
pipe.
2. Record the date and time of day, weather and other observations such as water
color, the presence of aquatic plants, algae, insects, or fish.
3. Keep the water sample free of foreign matter such as aquatic plants or sediment
from the bottom.
4. Use a clean, plastic or glass water sample container that has a suitable cap. The
container should hold enough water to conduct all of the tests.
5. Unless the sample is going to be tested immediately, the water sample container
should be filled until it overflows and then capped. Avoid air bubbles in the
sample that can cause chemical changes in the water. Water samples should be
tested as soon as possible.
6. Pour water sample into a clean test tube (0230) to the 5mL line.
7. Holding the bottle in a vertical position, add 10 drops of *Wide Range Indicator
(2218) to the sample (figure 3). Cap and mix.
8. Place the test tube in the Octet Comparator (2193) and record the pH value
from the color standard in the comparator that most closely matches the sample
tube color. (figure 4).
9. When the color observed in your sample is between two colors on the
comparator, the value may be reported to the nearest 0.25 unit. If the color
produced by your sample is not in the range of the color standards in the
comparator, use the following chart to estimate the pH of the sample:
pH 7 apple green
pH 8 green
pH 9 blue-green
pH 10 blue
pH 11 purple
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EF FECTS ON AQUATIC LIFE
The pH of natural waters does not fall evenly as acid contamination proceeds. The
natural buffering materials in water slow the decline of pH to around 6.0. This
gradual decline is followed by a rapid pH drop as the bicarbonate buffering capacity
is used up. At pH 5.5, the buffering capacity is very low and pH drops further with
additional acid. Sensitive species and immature animals are affected first. As food
species disappear, even larger, resistant animals are affected.
pH EFFECT ON AQUATIC LIFE
6.0 Freshwater shrimp absent
5.5 Bottom-dwelling bacteria (decomposers) begin to die
Leaf litter and detritus begin to accumulate, locking up essential
nutrients and interrupting chemical cycling
Plankton begin to disappear
Snails and clams absent
Mats of fungi begin to replace bacteria in the substrate
Metals (aluminum, lead) normally trapped in sediments are
released into the acidified water in forms toxic to aquatic life
5.0 Mayfly and many other insect eggs will not hatch
Most fish will not hatch
4.5 All fish, most frogs, insects absent
Sphagnum moss may invade, covering the substrate and inhibiting
nutrient cycling
EF FECTS ON PLANTS AND SOILS
The leaves of living plants are covered with a protective waxy cuticle. Acid
deposition (dust, rain, fog, dew) damages this coating, permitting desiccation of leaf
tissues and leaching important nutrients directly from the leaves. Damaged plants
become more vulnerable to drought and disease.
The pH of soil affects the availability of nutrients to plants growing in the soil.
When acid precipitation infiltrates forest soils, important cations such as potassium
(K
+ ) and calcium (Ca ++ ) may be displaced by the hydrogen ions of the acid. The
cations can then be “leached” away by groundwater and surface runoff. In areas
where the soil contains limestone or calcite, much of the acidity can be neutralized.
However, in areas with thin soils overlying granite rocks, the runoff of acid
precipitation to lakes and streams will be acidic and may contain ions leached from
the soil, such as aluminum, which is toxic to fish at levels less than 1 part per
million.
Soil acidification also inhibits helpful soil bacteria, limiting nitrogen fixation and
nitrification in the soil and slowing the decomposition of organic matter.
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