Soil Filtration as an Ecosystem Service - Teacher Pages

I recently created a lab for a 7th grade unit that included Ecosystem Services. I thought I should share what I learned, because it was a cool lab and a ton of work to invent from scratch. Others (you) should be able to learn from my experience.

The reason I created this lab is because this unit didn’t seem to have many lab options available for it. One ecosystem service that lends itself toward a lab is Soil Filtration.

Downloads: Powerpoint: Soil Ecosystem Services Video: Video of soil water filter assembly

Background:

Since 1908 the United States has been putting Chlorine into municipal drinking water to kill microorganisms. This practice is sound from a disease-prevention standpoint, especially G.I. diseases. However, some people are concerned about this practice because of potential long-term health risks of ingesting chemicals, or because of the odor and taste of Chlorine. They may choose to filter their water in the home to remove Chlorine and other contaminants.

One ecosystem service that the soil provides to humans is water filtration. Similar to home water filters, the soil can filter chemicals such as Chlorine out of water. In this lab, the students construct a water filter and test how much Chlorine a soil-based filter is able to remove from a water sample.

Since you’re curious, here’s just a little bit more background on Chlorine’s health consequences. Some naturally occurring byproducts of chlorinated water are bromoform and dibromochloromethane. “Studies in animals indicate that long-term intake of either bromoform or dibromochloromethane can cause liver and kidney cancer.”1 However, the World Health Organization recommends chlorination of municipal water because the “risks to health from these by-products are extremely small in comparison with the risks associated with inadequate disinfection.”2

One other thought is that most of our municipal (Chlorinated) water doesn’t ever pass through the soil. It can go one of three places. 1) Typically, after it is used the water exits the house through the sewer system and travels directly to the sewage treatment facility, never entering the soil. 2) If you wash your car, etc., the water

travels down the gutter to the storm drain to the creek, never entering the soil. 3) If you water your lawn, etc., the Chlorinated water does pass through the soil before joining the water table and eventually the creek. Even if we aren’t asking for much Chlorine filtration from the soil, it filters this chemical and other contaminants without our asking. That’s an ecosystem service!

Overview:

1. Students construct homemade water filters from a small water bottle, a cotton ball and a filtering substance (sand, clay, potting soil, charcoal, etc.).

2. The teacher creates a Chlorine solution by adding bleach to a gallon jug of water.

3. Students test the concentration of Chlorine in the solution with test strips (initial reading).

4. Students run water through their filter(s). 5. Students test the concentration of Chlorine in the water that has passed

through the filter with test strips (final reading). 6. Students compare the initial and final readings to determine how much

Chlorine was removed by the filter.

Materials List: Each student creates 1 filter (a group of 2 would make 2 filters, etc.)

1 water bottle per student 1 cotton ball per student 2 Chlorine Test Strips per student

Filter Substance Choices: Sand, Dirt, Clay, Charcoal, ? Chlorinated water (take a gallon jug of water and add 3 mL bleach)

Tips and thoughts on materials:

For the water bottles I used the smallest, cheapest ones available. I didn’t reuse them between classes but you could.

It just takes one cotton ball per filter. One bag of cotton balls was more than enough.

Other filters I saw online had different layers of materials, but I don’t see the point of layers for this lab. It fact, layers could confound things.

For the soil and sand I just bought a bag at Home Depot. For the clay, I found out that kitty litter is made of clay. In fact, the cheapest,

non-scented, non-clumping kitty litter is pure ground clay. So I bought a bag of that.

The charcoal was labor intensive and I’d recommend against it. I sat on my back porch pulverizing charcoal briquettes with a hammer and it was messy and difficult. I used charcoal as a substance since Brita filters include “activated carbon”.

For the chlorine test strips I bought a vial with 200 of them on amazon. They had gradations of 10, 50, 100 and 200ppm.

For the chlorine water I used 3mL of bleach for 1 gallon of water. That’s what it took to just barely crack 200ppm. I used a little child’s medicine dropper syringe for accuracy. You might have to play around with that to get it just right. I wanted it to be at the top of the readings on the strips “without going over” by too much so that students could see an interesting drop in concentration.

What my students learned was that all 4 substances filtered out most of the Chlorine (that was amazing to me). It was a bit inconclusive which substance was best. I had steered them toward the testable question of “Does ___ filter out more Chlorine than ___. In retrospect, an equally relevant testable question that I would have approved would have been “Does ____ filter Chlorine out of water?”, asked for each substance. I still think the first question is better, but the second one is both interesting and testable.

I left the lab sheet fairly open-ended because I’m trying to train the students to think through all the hypothesis, testable question, IV and DV stuff. I would encourage you to adapt it for your students and your instructional goals.

Works Cited:

1. Agency for Toxic Substances and Disease Registry, “Public Health Statement for Bromoform and Chlorodibromomethane” (March 2011) http://www.atsdr.cdc.gov/phs/phs.asp?id=711&tid=128 (retrieved 4-17-2014). 2. World Health Organization, “Guidelines for Drinking Water Quality” (2006) http://www.who.int/water_sanitation_health/dwq/gdwq0506.pdf.

Soil Filtration as an Ecosystem Service – Student Pages – KEY Ecosystem Services Name _________________________

What are Ecosystem Services?

Different ways that an ecosystem provides _________ to ________.

Benefits to humans

Types of Ecosystem Services

Provisioning

Production of ______ and ________

Food and water

Regulating

Control of climate, disease or _________ Flooding

Supporting

___________ __________ and Crop Pollination

Nutrient cycles

Cultural

Spiritual and Recreational benefits

What Ecosystems Servies ARE NOT

Ecosystem Services ARE NOT things that humans do to ___________ the environment. protect

Ways that humans DISRUPT Ecosystem

Services

Pollution Removal of plants causes erosion of soil

Overuse of water can cause drought and harm to plants

Development can cause reduction of biodiversity

Deforestation reduces plants available for photosynthesis: Less __________ produced and

more _____________ ____________ in the atmosphere.

Oxygen and Carbon dioxide

Describe in your own words what an Ecosystem Service is. __________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

Describe how human activity can threaten Ecosystem Services. Give at least two

examples.

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

Which of the following are examples of Ecosystem Services? (there may be several

correct responses)

a. Flood Prevention b. Recycling of cans and bottles by humans c. Water filtration by the soil

d. Protection of stream and river channels from erosion e. Research by Ecologists on Biodiversity

f. Halting of development of residential and commercial buildings in natural spaces

g. Pollination of crops

h. Installing an asphalt surface for a shopping center parking lot

Mitigation means to reduce the seriousness or painfulness of something. One

Ecosystem Service is mitigation of droughts and floods. What is another example

of an Ecosystem Service that involves mitigation?

a. Development of drugs that come from plants or microbes

b. Cycling and movement of nutrients c. Reduction of soil erosion in stream and river channels

d. Dispersal of seeds

Which of the following is a correct description of an Ecosystem Service

a. A benefit the natural environment provides to humans b. Something that humans do to protect the environment

Correct responses for item 1: a, c, d, g 2: c (because it’s reduction) 3: a

Soil Filtration as an Ecosystem Service Ecosystem Services Name _________________________

What are Ecosystem Services?

Different ways that an ecosystem provides _________ to ________.

Types of Ecosystem Services

Provisioning

Production of ______ and ________

Regulating

Control of climate, disease or _________

Supporting

___________ __________ and Crop Pollination

Cultural

Spiritual and Recreational benefits

What Ecosystems

Servies ARE NOT

Ecosystem Services ARE NOT things that humans do to

___________ the environment.

Ways that humans

DISRUPT Ecosystem Services

Pollution

Removal of plants causes erosion of soil Overuse of water can cause drought and harm

to plants Development can cause reduction of biodiversity Deforestation reduces plants available for

photosynthesis: Less __________ produced and more _____________ ____________ in the

atmosphere.

Describe in your own words what an Ecosystem Service is. __________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

Describe how human activity can threaten Ecosystem Services. Give at least two

examples.

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

Which of the following are examples of Ecosystem Services? (there may be several

correct responses)

i. Flood Prevention j. Recycling of cans and bottles by humans k. Water filtration by the soil

l. Protection of stream and river channels from erosion m. Research by Ecologists on Biodiversity

n. Halting of development of residential and commercial buildings in natural spaces

o. Pollination of crops

p. Installing an asphalt surface for a shopping center parking lot

Mitigation means to reduce the seriousness or painfulness of something. One

Ecosystem Service is mitigation of droughts and floods. What is another example

of an Ecosystem Service that involves mitigation?

e. Development of drugs that come from plants or microbes

f. Cycling and movement of nutrients g. Reduction of soil erosion in stream and river channels

h. Dispersal of seeds

Which of the following is a correct description of an Ecosystem Service

c. A benefit the natural environment provides to humans d. Something that humans do to protect the environment

Water Filter Inquiry Name ________________________

In this investigation we are going to explore the Ecosystem Service of Water

Filtration by the Soil. We will create a filter out of different materials and test

how much Chlorine remains in the water after passing through the filter.

Materials: Water Bottle, Cotton Ball

Filter Substance Choices: Sand, Dirt, Clay, Charcoal

Chlorine Test Strips

Chlorinated water

Procedure:

1. Assemble your filter using a water bottle, cotton, and substance of your choice.

2. Use the Chlorine test strip to test the amount of Chlorine in the water before filtration (just do this once).

3. Run the water through your filter.

4. Use the Chlorine test strip to test the amount of Chlorine in the water after filtration.

Diagram:

Testable Question:__________________________________________________

__________________________________________________________________

Reasonable Hypothesis: ____________________________________________

__________________________________________________________________

__________________________________________________________________

Independent Variable: _________________________

Dependent Variable: _________________________

Controlled Variables: __________________ __________________

__________________ __________________

__________________ __________________

Data Table: Construct a data table in the space below that would compare the IV

and DV. The data table should be designed so that other students could use it to

record and analyze the data collected ruing the experiment. Be sure to label rows

and columns appropriately.

Graph: Use the data from

your table to construct a

line/bar graph on the grid

below.

Be sure to provide:

An appropriate title

A label for each axis

with appropriate units

Appropriate number

scales (line graph)/An

appropriate number

scale and category

labels (bar graph) Correctly plotted data

Conclusion: ______________________________________________________

__________________________________________________________________

__________________________________________________________________

Scoring Guide:

Testable Question (1 pt. possible):

1pt. “Which substance filters the most Chlorine out of water?”

0pts. “What substance makes the best water filter?”

Hypothesis (1 pt. possible):

1pt. “If sand is used in a water filter, then it will remove more Chlorine than clay or

charcoal.”

1pt. “A charcoal filter will remove the most Chlorine, a sand filter will remove less

Chlorine, and a clay filter will remove the least Chlorine.”

0pts. “Sand filters better than clay or charcoal.”

0pts. “Charcoal removes the most Chlorine.”

Graph (4 pts. Possible):

4pts.

Note: your title should mention both the IV and DV

Conclusion (2 pts. possible)

2pt. “Using a clay filter removes the most Chlorine from water compared to

charcoal or sand filters. Also, charcoal filters remove more chlorine than sand.”