--------"'
~
Lesson7
pH ... Potential Horrors
of Acid Rain
Assessing the effects of pH on the growth and
development of Fast Plants
Part I: A buffering blanket of soil
Part II: Germination-the first step
Part Ill : Growth and development
Overview
Acid rain, a major environmental concern, results from high concentrations of sulfur pollutants in the atmosphere.
Different regions of the world and different areas in the U.S. experience varying amounts of acid rain depending on the climate, geography, wind patterns and degree of industrialization. Acid rain concentrations also vary from place to place due to the frequency of natural
occurrences such as lightning and volcanic activity.
In this experiment, students will investigate interactions between soil
and acid rain, and look at the germination, growth and development of
plants in an acid environment.
Biological
and
ag ricu ltu ral
concepts
Plant growth and development
Water cycle
Acids and bases
Data collection and interpretation
Soil science
Acid Rain I
7-1
Lesson 7
The
teachable
moment
Teacher material
Both biology and agriculture teachers can use this activity in an plant
or crop science unit. This activity can also illustrate the practice of data
collection, data analysis and preparation of solutions. Biology teachers
may find this activity useful for a unit in ecology, while an agriculture
teacher may use it for a forestry or soils unit.
This activity may also be followed with discussion of what is being
done to reduce the damage caused by acid rain, and what actions are
being taken globally to reduce sulfur emissions.
Background
The fundamental attraction to an issue such as global warming, deforestation or acid precipitation is in the delivery or "packaging" presented to students. This could take the form of a question: "How
might taking a shower or turning on a light here in the United States
kill fish in Sweden?" Adding an international perspective to the question provides a framework for further investigation. Students are
motivated to challenge the notion that such profound relationships
could exist. They begin to realize that their actions go far beyond the
classroom activities they carry out. They are able to appreciate the
complexity of the world they live in and formulate opinions regarding
global sustainability.
While acid rain, snow, sleet or hail might not keep the postal carrier
from delivering, they have been linked to changes in the ecosystems
they fall on. Since acid precipitation is formed by interactions in the
upper atmosphere, it can travel great distances and the effects can be
far removed from the causes. The socioeconomic/ ethical implications
of this are thus far-reaching and teachers are encouraged to pursue
these avenues as support for the following lab.
The two major chemicals that make up acid rain are S02 (sulfur dioxide) and NOx (nitrogen oxides, made up of NO and N02, nitric oxide
and nitrogen dioxide). These pollutants have been produced naturally
by volcanic action, decaying organic matter, lightning and sea spray.
This relatively small amount of acid can be removed from the air
through interaction with vegetation and the ocean. Pollutants from
industry, car emissions, and the burning of fossil fuels are so great that
natural processes of removing the acid cannot keep up.
Most acid rain is caused by the burning of high-sulfur fuels. When
these fuels are burned, S02 (sulfur dioxide) is formed. S02 then reacts
with the oxygen of the air, forming S03 (sulfur trioxide), which in turn
reacts with the water vapor of the air, to form a sulfuric acid solution
(~S04 ), or acid rain.
7-2
I Acid Rain
Teacher material
Lesson 7
Burning of coal
S + 0 2 = S02
2S02 + 02 = 2S03
so3 + }\0 = }\S04
A pH scale designates the acidity of water in terms of the concentration of H+ in solution. On a pH scale, the lower the number, the greater
the acidity, the higher the number the greater the alkalinity. A pH of 4
is ten times as acidic as a pH of 5. A pH of 4 is 100 times as acidic as a
pH of 6. Distilled water is neutral, having a PH of 7. Naturally occurring rainfall has a PH of 5.6. Acid precipitation often has a pH of 4.04.5 but has been observed as low as 1.5. Strong bases can reach a pH of
14.
Acid precipitation, which can carry acid in rain, snow, hail, sleet, fog or
dew, was first observed in England in the 1600s when the country was
deforested, wood became scarce and coal became the predominant
energy source. The term "acid rain" was coined in 1872 by Robert
Angus Smith, First Chief Alkali Inspector of the British Isles.
Acid precipitation can have a devastating impact on an ecosystem.
Unfortunately, this serious impact is often subtle and indirect. Plants
and trees exposed to acid rain are deprived of vital nutrients when
calcium, magnesium, and potassium are leached from the soil. Aluminum, abundant in the soil in a non-toxic form, changes to a toxic
soluble form in the presence of acid. Hence one of the serious effects of
acid precipitation on plants is aluminum toxicity.
As acidification becomes more severe, direct ecosystem effects begin to
appear. Lakes with pH levels below 4.7 cannot support fish reproduction. Tree damage from acid rain in the U.S. extends from the
Adirondack Mountains in New York to the Appalachian Mountains in
Georgia. Billions of dollars have been lost due to crop damage. Ecosystems in the Scandinavian countries, central Europe and eastern
North America all suffer from acidification. Humanmade cultural
attractions such as the Taj Mahal, the Sphinx, the Parthenon, and the
cathedral in Cologne are also affected as they corrode and dissolve in
the face of acid precipitation.
A common, though short-sighted, local solution to the acid rain problem is to make smokestacks taller so that emissions are carried farther
away. This is not a long-term solution in that emissions are simply
carried to other areas and not eliminated. S02is naturally taken out of
the environment as it runs through soil and is acted upon by microorganisms. Tall smokestacks, erected to promote dilution of emissions,
Acid Rain I
7-3
Lesson 7
Teacher material
force emissions high into the air, allowing them to react for longer
periods of time with oxygen in the air, increasing the problem.
There are three parts to this unit. Each part can be done separately.
• Part I : Buffering capacity of soil
• Part IT : Effects of acid on plant germination
• Part Ill : Effects of acid on plant growth and development
This experiment uses either acetic acid (C~C02H) or dilute sulfuric
acid (~504), which in concentrated form, and if handled incorrectly,
can be dangerous. Therefore, we recommend that a teacher prepare all
the acid dilutions in advance. However, if this activity is used with
more advanced students, you may want to have students prepare
dilutions and in so doing teach the need for precise and accurate measurement and safe laboratory practices.
Teacher
management
Preparing the solutions using concentrated sulfuric acid (H2 S04):
You will need the following materials:
• six 2-liter bottles for dilutions
• 500 or 1000 ml beaker
• stirring rod
• hotplate
• pH paper, range 1-7
• tweezers
Directions:
1. Always add acid to water, not the reverse.
2. Stir each solution carefully. Rinse stirring rod, eye dropper and
beaker after each use.
3. In using the dilution table below, note the following:
• Create your solutions in the order indicated
• To get the correct pH you may need to add slightly less or
slightly more than the amounts indicated depending on the
strength of your concentrated sulfuric acid.
7-4
I Acid Rain
Lesson 7
Teacher material
Volume needed:
• Part I (need 300 ml/ group)
• Part IT (need 200 ml/per acid level tested))
• Part Ill (need 200 ml per group)
Total volume of
200-300mls
(for Part I, II, or III)
Total Volume of
700mls
( for Parts I, II and ill)
pH2
10 dr.}\504 /500 ml}\0
15 dr. ~504 /750 m1 ~0
pH3
40 dr. pH 2 soln /360 ml ~0
75 dr. pH 2 soln I 675 m1 ~04
pH4
40 dr. pH 3 soln /360 ml}\0
75 dr. pH 3 soln /675 m1 ~0
pHS
40 dr. pH 4 soln /360 ml}\0
75 dr. pH 4 soln /675 ml ~0
4. To make a pH 7.0, boil distilled water (which will have a pH about
5.6) for 5-10 minutes to remove dissolved C02 from water. Cover
loosely to prevent C02 reabsorption, yet allowing steam to escape.
Allow to cool 20 minutes.
5. Pour each solution into appropriately labelled 1-liter bottles. A
plastic cap with many holes punched in it will convert this storage
container into a sprinkling device for easier application of your acid
solutions.
Sources for
materials
Bottles: redemption centers, your students, acquaintances, etc.
Chemicals: Carolina Biological or other supply houses.
Film canisters: film developing centers
Tips and
safety
1. Always add acid to water, never the reverse.
2. Safety goggles and lab aprons should always be worn when
working with acids.
3. In case of acid contact with skin, flush area under cool water.
4. Heat sources such as a propane torch or Bunsen burners should be
carefully supervised by the teacher if not actually used by the
teacher in ad vance.
Acid Rain I
7-5
Lesson 7
Teacher material
5. Divide your class into groups of three to four. Each group will test
a certain pH range. Test pH 2, 3, 4, 5 and 7. If you have enough
students, test 4.5 and 5.5 also.
7. A class can do Parts I, TI and III singly. Part ill, growth and
development, can be terminated after the flowers have finished
flowering at two weeks or can be run to day 40 and total seed
harvest can be calculated.
Key terms
Acid: a chemical that produces excess H+ ions when dissolved in
water
Acid Rain: atmospheric precipitation (rain, snow, fog, frost, sleet) that
has a pH of less than 5. Dew is 30 times more acidic than any other
form of precipitation
Dilution: lowering the concentration of a solution by the addition of
water
pH: the measure of acidity or alkalinity
Solution: a homogeneous mixture of one or more liquids
References
Jacob, Anthony T., Acid Rain, (Madison, Wisconsin: University of
Regents, 1991).
Corson, Walter H., ed., Global Ecology Handbook (Boston, MA, Beacon
Press, 1990).
Steger, Will, and John Bowermaster, Saving the Earth (New York, NY,
Alfred A. Knopf, Inc., 1990).
Canadian Embassy; Science News, Ontario Ministry of the Environment, Pacific Northwest Laboratory, 1990).
Hinrichsen, Don, Acid Rain and Forest Decline, in Edward Goldsmith
and Nicholas Hildyard (eds.), The Earth Report (Los Angeles: Price
Stern Sloan, 1988), p. 67.
Whelpdale, D.M., "Acid Deposition: Distribution and Impact, Water
Quality Bulletin, Vol. 8, 1983, p. 72.
7-6 I Acid Rain
Part 1: Teacher material
Lesson 7
Part 1: A buffering blanket of soil
Introduction
Teacher
management
In this portion, students will explore the interactions between acid and
soils. A soil's buffering capacity, that is its ability to neutralize an acid,
is a significant factor in the effect that acid precipitation has on an
ecosystem. Buffering capacity of a soil depends on the mineral makeup of the soil, the organic content and physical properties such as
density and particle size. A solution of a given pH will usually be
neutralized to some degree by contact with the soil. However, after
prolonged contact with the acid, a soil will lose its buffering capacity.
A more in-depth soils background can be found in the background
section of Chapter 9 in this manual, "Down and Dirty, A study of
water movement through soils."
In this experiment, students will examine and compare the buffering
effects of one or more soils. Ideally, the soil should be collected locally.
After the experiment, students should be encouraged to think about
the ecosystems that provided the soil. What do their results say about
the vulnerability of that ecosystem to acid precipitation?
Preparation
If you want to examine different types of soil, results from a local soil
survey, available through your local extension office or Soil Conservation Service office, will be useful in selecting soil samples. Virtually
every county in the U.S. has a completed soil survey map available for
the asking. These reports map the soil types in local areas and describe
how these soils will respond when used. A soil survey will explain the
variability of soils from community to community and will describe
the reasons for such variation. If local soils are unavailable, potting
soils or potting mixes can be used. The buffering capacity of potting
mixes is dramatic!
Activity time
Day 1- build and set up columns
Day 2- run experiment
Students can work in groups of one to three. Have at least six groups
(to test pH 2, 3, 4, 5, 7 and distilled water). If there is an ample supply
of soil and bottles, make the groups as small as possible. Each group
will construct a column and run one pH solution through its column.
Data Table #1, "Classroom pH Values," should be at the front of the
room. Litmus paper results from each group should be recorded on
that classroom data table.
Acid Rain I
7-7
Lesson 7
Safety and tips
Part 1: Teacher material
Use soils that are slightly damp but not dripping
Crush the dry soil samples to destroy any remaining soil structure.
Sand samples that are single grained rarely require this; however, you
will need to process finer grained samples, like clays, in this manner.
If you want to work with a heavy clay sample, the experiment will
probably take longer than two class periods to run. If that will cause
scheduling problems, test your most finely grained sample to determine if the experiment can be completed in two class sessions. If the
sample is too heavy, mix in sand to a 3:1 ratio (3 parts fine-grained to
1 part sand).
Make sure that each column is constructed using two bottles of the
same brand name since bottle size varies slightly.
If you are teaching a unit on soils, the number of soil types can be
increased and the types more carefully determined.
Horticulture instructors may wish to demonstrate the properties of
the components of professional soil mixes using this design.
Materials
For each group (1-3 students):
• 500 ml soil
•
•
•
•
•
•
•
•
two 2-liter bottles, one with cap
Exacto knife, razor blade or other cutting blade
grease pencil
scissors
300 ml appropriate acid stock solution
graduated cylinder or bottle
tweezers
film can
For the classroom (only one set necessary):
•
•
•
•
7-8
I Acid Rain
tape
hole punch
nail poke or awl
hot water or hair dryer
Lesson 7
Part 1: Student material
Part I: A buffering blanket of soil
Introduction
While acid rain, snow, sleet or hail might not keep the postal carrier
from delivering, they have been linked to changes in the ecosystems
they fall on. Since acid precipitation is formed by interactions in the
upper atmosphere, it can travel great distances and the effects can be
far removed from the causes. The socioeconomic/ ethical implications
of this are thus far-reaching.
The two major chemicals that make up acid rain are S02 (sulfur dioxide) and NOx (nitrogen oxides, made up of NO and N02, nitric oxide
and nitrogen dioxide). These pollutants have been produced naturally
by volcanic action, decaying organic matter, lightning and sea spray.
This relatively small amount of acid can be removed from the air
through interaction with vegetation and the ocean. Pollutants from
industry, car emissions, and the burning of fossil fuels are so great that
natural processes of removing the acid cannot keep up.
Most acid rain is caused by the burning of high-sulfur fuels. When
these fuels are burned, S02 (sulfur dioxide) is formed. S02 then reacts
with the oxygen of the air, forming S03 (sulfur trioxide), which in turn
reacts with the water vapor of the air, to form a sulfuric acid solution
(}\S04), or acid rain.
Burning of coal
S + 0 2 = S02
2S02 + 02 = 2S03
so3 + }\0 = ~so4
A pH scale designates the acidity of water in terms of the concentration of hydrogen ions in solution. On a pH scale, the lower the number,
the greater the acidity, the higher the number the greater the alkalinity.
A pH of 4 is ten times as acidic as a pH of 5. A pH of 4 is 100 times as
acidic as a pH of 6. Distilled water is neutral, having a PH of 7. Naturally occurring rainfall has a PH of 5.6. Acid precipitation often has a
pH of 4.0-4.5 but has been observed as low as 1.5. Strong bases can
reach a pH of 14.
Acid precipitation, which can carry acid in rain, snow, hail, sleet, fog or
dew, was first observed in England in the 1600's when the country was
deforested, wood became scarce and coal became the predominant
energy source. The term "acid rain" was coined in 1872 by Robert
Angus Smith, First Chief Alkali Inspector of the British Isles.
Acid Rain I
7-9
Lesson 7
Part 1: Student material
Acid precipitation can have a devastating impact on an ecosystem.
Unfortunately, this serious impact is often subtle and indirect. Plants
and trees exposed to acid rain are deprived of vital nutrients when
calcium, magnesium, and potassium are leached from the soil. Aluminum, abundant in the soil in a non-toxic form, changes to a toxic
soluble form in the presence of acid. Hence one of the serious effects
of acid precipitation on plants is aluminum toxicity.
As acidification becomes more severe, direct ecosystem effects begin to
appear. Lakes with pH levels below 4.7 cannot support fish reproduction. Tree damage from acid rain in the U.S. extends from the
Adirondack Mountains in New York to the Appalachian Mountains in
Georgia. Billions of dollars have been lost due to crop damage. Ecosystems in the Scandinavian countries, central Europe and eastern
North America all suffer from acidification. Humanmade cultural
attractions such as the Taj Mahal, the Sphinx, the Parthenon, and the
cathedral in Cologne are also affected as they corrode and dissolve in
the face of acid precipitation.
A common, though short-sighted, local solution to the acid rain problem is to make smokestacks taller so that emissions are carried farther
away. This is not a long-term solution in that emissions are simply
carried to other areas and not eliminated. S02 is naturally taken out of
the environment as it runs through soil and is acted upon by microorganisms. Tall smokestacks, erected to promote dilution of emissions,
force emissions high into the air, allowing them to react for longer
periods of time with oxygen in the air, increasing the problem.
In this experiment, you will examine and compare the buffering effects
of one or more soils. Ideally, the soil should be collected locally. After
the experiment, think about the ecosystems that provided the soil.
What do your results say about the vulnerability of that ecosystem to
acid precipitation?
Materials
For each group (1-3 students):
• 500 ml soil
•
•
•
•
•
•
•
•
7-10 1 Acid Rain
two 2-liter bottles, one with cap
Exacto knife, razor blade or other cutting blade
grease pencil
scissors
300 ml appropriate acid stock solution
graduated cylinder or bottle
tweezers
film can
Part I Student material
Lesson 7
For the classroom :
•
•
•
•
Procedure
tape
holepunch
nail poke or awl
hot water or hair dryer
Day 1 - Preparation
1. Mark one bottle at the base for cutting.
Using an Exacto knife or razor blade,
cut a small slit in the bottle and
complete the cut with scissors.
This will serve as the soil
column.
2. Mark another bottle
just below the shoulder
and cut. This will be
the column reservoir.
You may also want to
cut away the base allowing
better viewing.
A
3. Using a hole punch, punch one hole in the bottle base, 2 to 4 em
below the top. The hole allows air to escape from the reservoir
when air is displaced by the pH solution entering the reservoir from
the soil column above. (Be careful not to pour water out the hole
later in the experiment!)
Acid Rain I
7-11
Lesson 7
Part 1: Student material
4. Use a nail poke to make several holes in the center of each of three
caps. Try to make the holes identical in each cap. Place a film
can over each cap. This will prevent
water from flowing out too fast
when you are initially saturating
the column with the pH solution.
5. Place 500 mls of soil in the column.
6. Take an initial pH of your solution. If using litmus paper, hold the
paper with tweezers. Tape the litmus paper on the class data table
and record the initial pH.
7. Slowly, pour 300 mls of the appropriate pH solution on the column.
8. After one minute, carefully remove the film can from the bottle cap
making sure not to unscrew the cap. Pour contents of the film can
into the reservoir.
9. Replace the soil column on the
top of the reservoir and let drain
until most of the solution has
passed through the column.
A
10. Take the pH of the solution that
has drained through the column.
Tape the litmus paper and record
the pH on the classroom data tables.
7-12 I Acid Rain
Part 1: Data sheet
Lesson 7
Classroom pH Values
II
II
pH 2
I put I
I litmus I
1paper1
I here I
I
Iput I
pH
I
II
I put I
I litmus I
1papeq
I here I
llitmusl
1papeq
I here I
pH
J
L
L
pH 5
pH 7
I put
pH
J
I
llitmusl
1papeq
I here I
L
II
I put I
llitmusl
1paper1
I here I
pH
I
I
II
I put I
llitmusl
1paper1
I here I
I put I
llitmusl
1papeq
I here I
I
l
II
I put I
I litmus 1
1paper I
lhere I
I put I
llitmusl
I paper!
1here 1
I
I
I
pH
J
II
pH
pH
I
II
pH
pH
J
I put I
llitmusl
1paper1
I here I
I
Distilled water
J
II
I
pH
II
II
I put I
llitmusl
1papeq
I here I
pH
I
Iput I
L
pH 4
I litmus I
1paper1
I here I
I
II
pH 3
Final
Initial
Solution
pH
I
Acid Rain I 7-13
Lesson 7
Results and
discussion
Part I: Student material
1. Did the soil change the pH of the leachate?
2. What kinds of soil would be more likely to raise the pH of acid rain?
3. Graph the pH of the liquids versus the pH of the leachate for each of
the acid concentrations.
Extensions
1. Test different soil types such as sand1 loaml commercial potting mix
or clay.
2. Mix varying amounts of sand with your soil and see how it affects
the pH of the leachate.
3. Try adding various compounds to the soil such as crushed
eggshells~ chalk or limewater. How does this change the acidity of
the leachate?
4. Try adding organic matter such as leaves or grass to the soil. Test
the leachate.
5. Consider changing the length of the soil column.
6. Do other acids of equivalent pHs interact with the soil in the same
way as ~SO4? Try vinegar or hydrochloric acid.
7. What is the pH of rain in your region?
7-14 I Acid Rain
Part II: Teacher material
Lesson 7
Part II: Germination-the first step
Introduction
A mature seed consists of an embryo surrounded by a protective seed
coat. The seed remains dormant until environmental conditions such
as light, water, and temperature are right for germination. The quality
of that water can have a tremendous impact on the germination process. In this experiment, you will examine the effects of a low pH
solution on germination.
Teacher
management
1/2 - 1 hour to gather material, after making the pH solutions.
Preparation
Activity time
One 50-minute class to set up experiment
5-10 minutes of observation and measurement for four days (If plants
other than Wisconsin Fast Plants are used, germination might take
longer.)
Tips and safety
Students can work in groups of one to three. Have at least six groups
(to test pH 2, 3, 4, 5, 7 and distilled water). Each group will test germination for one pH solution. When considering the results, the entire
class' data should be compiled and examined.
Materials
For each group (1-3 students):
•
•
•
•
•
•
petri plate
1 mm plastic grid paper circle
filter paper (9 em , No. 2)
8 radish, turnip or Fast Plant seeds
magnifying glass
200 ml of the appropriate pH solution (for direction for making the
acid dilutions, see page 7-5)
• tweezers
• water reservoir (a bottle bottom does well)
(if only one petri plate is going to be tested for each pH solution, two
extra empty petri plates are needed for support in each reservoir)
Acid Rain I
7-15
Part II: Student material
Lesson 7
Part II: Germination-the first step
Introduction
See introduction to Part I on page 7-9, and the following.
A mature seed consists of an embryo surrounded by a protective seed
coat. The seed remains dormant until environmental conditions such
as light, water, and temperature are right for germination. The quality
of that water can have a tremendous impact on the germination process. In this experiment, you will examine the effects of a low pH
solution on germination.
Materials
For each group (1-3 students):
•
•
•
•
•
•
•
•
•
one petri plate
1 mm plastic grid paper circle (see App. C, p. 16 for template)
filter paper (9 em , No. 2)
8 radish, turnip or Fast Plant seeds
magnifying glass
200 ml of the appropriate pH solution
tweezers
water reservoir (a 2-liter bottle bottom does well)
waterproof tape (black electrical tape works well)
(if only one petri plate is going to be tested for each pH solution, two
extra empty petri plates are needed for support in each reservoir)
Procedure
1. Place the plastic grid in the top of a petri dish.
2. Place the filter paper on top of the grid.
3. Moisten filter paper with the appropriate solution. Press out air
bubbles trapped under the filter paper.
4. Place eight seeds along the
top line of the grid as shown:
7-16 I Acid Rain
Petri plate
seeds
Part II: Student material
Lesson 7
5. Write your name, date and the pH of your solution on the cover of
the petri plate.
6. Cover the dish and tape shut.
7. Tape the hole on the bottom of a 2-liter bottle bottom with water
proof tape.
8. Place petri dish in a 2-liter bottle bottom. The petri plate can lean
back slightly. If you are the only one testing your pH, prop the petri
plate up with two other empty plates as shown.
Petri plates
9. Fill the bottle bottom with approximately 100 ml of the appropriate
pH solution.
10. Place reservoir and petri plates under fluorescent lights.
11. Check the plates in 5-10 minutes to make sure the solutions have
flowed into the petri plate. If not, twist the cover and jiggle the
plates slightly to break a seal which may have formed.
Day 2, 3, and 4:
Observe the seeds and record the data on the data sheets. Add more
pH solution, if necessary.
Acid Rain I
7-17
Part II: Data sheet
Lesson 7
Germination Observations
pH Level._ _ _ __
# of seed coats split
# of embryonic roots
observations
emerged
Day
Day
Day
Length
(in mm)
pH Level_ _ _ __
Seed
#1
Day
Day
Day
7-18 I Acid Rain
Seed
#2
Seed
#3
Seed
#4
Seed
#5
Seed
#6
Seed
#7
Seed
#8
Part II: Data sheet
Lesson 7
Class Data Sheet
/o Germination
0
Average
Root Length
Average
Shoot Length
pH 2
pH 3
pH 4
pH 5
pH 6
distilled water
Acid Rain I
7-19
Part II: Student material
Lesson 7
Results and
discussion
1. What first emerges from the seed?
2. Why do you think the seed coat splits?
3. What percent of seeds germinated?
4. What color is the shoot? the root? Does the color change?
5. Does pH affect germination? How?
6. What do your results tell you about the effect of acid precipitation
on an ecosystem?
7. Can you think of other reasons beside pH which might have caused
the seed not to germinate?
Extensions
1. Compare the effects from various acids at the same pH.
2. Compare germination between different types of seed.
3. Try the activity using rainwater collected in your area.
7-20 I Acid Rain
Part Ill: Teacher material
Lesson 7
Part Ill: Growth and Development
Introduction
How does acid precipitation affect plant growth and development?
There are many aspects of growth and development that could be
affected including height, development time, leaf size, number of
flowers and root growth.
In this experiment, students will watch plants grow while enclosed in a
bottle terrarium. Students will observe water that has evaporated and
condensed on the inside of the terrarium. This water evaporates,
condenses and rewaters the plants similar to the water in our own
water cycle. Does the pH change as the water goes through the "water
cycle?''
Teacher
management
Preparation
After preparation of the pH solutions, preparation of this experiment
should take 1/2 - 1 hour to gather materials.
Activity time
Construction: one or two class periods
Setting up the experiment: one class period
Observations: plants can be observed to flowering (about two weeks)
or until seed harvest (about six weeks). During that time, the observations can be as minimal or extensive as desired.
Students can work in groups of two to four. Have at least six groups
(to test pH 2, 3, 4, 5, 7 and distilled water). Each group will construct a
column and use one pH solution to water its plants. Classroom data
should be compiled.
Tips and
safety
Make sure that each column is constructed using two bottles of the
same brand name since bottle size varies slightly.
Materials
For each group (2-4 students):
•
•
•
•
•
one 2-liter bottle
one 1- liter bottle
scissors
350 mls soil
grease pencil
(continued)
Acid Rain I
7-21
Lesson 7
Part Ill: Teacher material
• Exacto knife, razor blade or other cutting tool
• 200 ml appropriate acid stock solution (for directions for making
acid solutions see page 7-5)
• 5 Fast Plant seeds
• 30 mls of 20-20-20 liquid fertilizer (standard concentration)
For the classroom:
• waterproof tape (electrical tape works well)
• nail poke or awl
• hot water or hair dryer
7-22 I Acid Rain
Part Ill: Student material
Lesson 7
Part Ill: Growth and development
Introduction
See introduction to Part I on page 7-9, and include the following.
How does acid precipitation affect plant growth and development?
There are many aspects of growth and development that could be
affected including height, development time, leaf size, number of
flowers and root growth.
In this experiment you will watch plants grow while enclosed in a
bottle terrarium. You will observe water that has evaporated and
condensed on the inside of the terrarium. This water evaporates,
condenses and rewaters the plants similar to the water in our own
water cycle. Does the pH change as the water goes through the "water
cycle?''
Materials
For each group (2-4 students):
•
•
•
•
•
•
•
•
•
•
•
•
one 2-liter bottle
one 1- liter bottle
one extra 1-li ter bottle base
scissors
350 mls soil
grease pencil
Exacto knife, razor blade or other cutting tool
200 ml appropriate acid stock solution
5 Fast Plant seeds
30 mls of 20-20-20 liquid fertilizer
sharp needle
150-200 mls of Jiffy Mix potting soil
For the classroom:
• waterproof tape (electrical tape works well)
• nail poke or awl
• hot water or hair dryer
Acid Rain I 7-23
Part Ill: Student material
Lesson 7
Procedure
Construction of terrarium:
1. Remove the label and base of a 2-liter bottle.
2. Tape the holes of the base with electrical tape.
3. Cut bottle 2 em above the shoulder.
I
:~
based
removed
4. With the sharp needle, punch approximately 100-150 holes in the
bottom and sides of the bottle. (When inverted, this will be the top.)
5. By inverting the bottle and putting it into the base, you have the
terrarium.
,
./
7-24 I Acid Rain
. . .. . .
...··.. : .. :: ....·
...
/
I
/
I
Part Ill: Student material
Lesson 7
Making the inner column:
1. Cut a delabelled 1-liter bottle
2 em below the shoulder.
··-------·--- 4--
Cut
!~-Cut away
the base
2. Cut away the sides of the base.
3. With the sharp needle, poke
50-100 holes around the base
of the bottle.
·/~'/'/%
/,;/ ~-Extra base
~jf
l~-Punch
)
holes
4. With the awl, punch approximately 25 small holes in the bottom of
an extra bottle base. Tape up the large holes with waterproof tape.
5. Assemble the construction
as shown.
2-liter dome
+---1--+-- 1-liter bottle
/
.
Acid Rain I 7-25
Lesson 7
Planting the seeds:
1. Dampen the Jiffy Mix slightly. Fill the upper 1-liter base to the rim.
2. Water gently with distilled water until the water runs through.
3. Sow five Fast Plant seeds.
4. Cover lightly with a thin layer of potting soil.
5. Gently resaturate the soil with distilled water.
6. Add 10 drops of the appropriate pH solution.
Each day after planting:
1. Add 10 drops of the appropriate pH solution each school day for
two weeks.
2. Add more water if the soil looks dry. It is very important not to let
the plants dry out.
3. Record observations on data sheet, noting color, height and
abnormalities.
4. Occasionally measure the pH of the condensation ("acid rain") on
the inside of your terrarium.
5. When the plants grow too tall for the terrarium, take out the inner 1liter bottle and cut it down until it lowers the plants sufficiently.
6. Fertilize with 5 mls of fertilizer on day 3 after planting, 12 mls on
day 7, and 12 mls on day 14.
7-26 I Acid Rain
Part Ill: Data sheet
Lesson 7
Growth and Development Data Sheet
pH _ _ __
Plant
#1
Plant
#2
Plant
#3
Plant
#4
Plant
#5
Height
(Day 7)
Height
(Day 14)
Number of
Flowers
(Day 14)
Acid Rain 1 7-27
Part Ill: Student material
Lesson 7
Discussion
and results
1. Which dilutions caused the least amount of damage? Compare
plants with the control group.
2. Could varying your soil types change your results?
3. Would different seeds act the same as Brassica rapa?
4. How else would you have done this experiment?
Extensions
1. What are the effects of acid rain on other plants?
2. What would happen if you grew your seeds in an alkaline soil?
3. Would seeds of the Brassica that grew in the lowest pH produce a
more resistant plant?
4. Would these resistant plants grow and develop at the same rate as
previous generations?
5. Could you change the pH during the growth cycle to improve
growth? What would you add?
6. What would happen to fish or insects in an acidic rain?
7. Can you change your pH by adding some soil amendment? If so,
what could you add? Experiment further.
7-28 I Acid Rain