Acid Rain and Maryland Streams

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Activities 2 and 3Activity 1

Activities 5 and 6Activity 4

Introduction

Introduction

When precipitation reaches the surface, most of it flows down slope either beneath or along the surface. It eventually becomes part of a stream. The stream water continues its downhill flow, merging with other streams along the way until it reaches sea level. Thus, the land ‘sheds’ the water, giving us the term ‘ watershedwatershed’.

Most of Maryland lies within the Chesapeake Bay watershed, which is shaded yellow on the map below. This watershed also includes large areas in New York, Pennsylvania, Delaware, and Virginia.

Maryland’s human population continues to grow and expand into previously undeveloped areas of Maryland’s watersheds. In this task, you will investigate one way in which increased human activity impacts the pH of Maryland streams. You will also investigate how certain aquatic organisms may be affected by the changes in pH of the water they inhabit.

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Understanding pHUnderstanding pHandand

the formation of acid rainthe formation of acid rain

pH is a numerical measure of the acidity or alkalinity of a solution. A scale from 1 to 14 is used to determine weather something is acidic or alkaline (basic). Solutions that register less than 7 on the pH scale are considered acids. Solutions that register above 7 on the pH scale are said to be bases. A reading of 7 would be considered neutral.

Activity 1To the left, you will see 4 different

substances. Identify each substance as either acidic, neutral or alkaline. Click on each to find the pH of the

substance.Record your answer in the Activity

1 section of your packet.

Lemon JuiceLemon Juice

Normal Rain WaterNormal Rain Water

Pure WaterPure Water

AmmoniaAmmonia

All rain is slightly acidic because of the carbon dioxide in the air. This has always existed and is considered normal. However, in recent years, the rainfall in many parts of the world has become more acidic.

The main cause of acid rain is the burning of fossil fuels. Coal and oil are burned to operate automobiles and other vehicles, as well as small gasoline powered engines, electric power generating plants and other industries. Exhaust emissions from these and other sources put acid producing gases such as oxides of nitrogen, carbon and sulfur into the air.

When it rains, these oxides of nitrogen, carbon, and sulfur mix with the water in the air to form nitric acid, sulfurous acid, and carbonic acid.

Images from: http://www.elmhurst.edu/~chm/onlcourse/ chm110/molimages/

The acidic water precipitates to the surface. It soaks into the ground and flows into streams and lakes making them more acidic.

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A watershed with New Mexico underwent a rapid growth in population in recent years. Along with the larger numbers of people, came a big increase in the burning of fossil fuels. Scientists collected pH data from streams in the watershed, before and after the rapid population change.

Activity 2

Click on the white button to see the pH readings from New Mexico before the land was developed.Then click on the green button to see the pH readings five years after the land was developed.

Before proposed land development

After land development

After viewing the two land diagrams, click here to move on.

Below is the section of Maryland watershed planned for development.Streams in the watershed currently have the following pH readings as shown in the tan boxes.

Activity 3. Step A. think about the river in New Mexico and how increased human activity affected its pH. Predict the pH of each site in the Maryland watershed below when increased use of fossil fuels by a growing population takes place. Then record your prediction for that site in your packet.

Step B. In your packet, explain how you made your predictions.

Site ApH = 6.4 Site C

pH = 6.2

Site BpH = 5.9

Site DpH = 6.4

Site EpH = 6.3

Site GpH = 5.9

Site FpH = 6.4

Step C. Describe two advantages and two limitations of using the New Mexico example to make predictions about the Maryland watershed.

The chart below is very important. Copy it into your packet for Activity 6.

Site A Present pH =6.4 Predicted pH =

Site B Present pH =5.9 Predicted pH =

Site C Present pH =6.2 Predicted pH =

Site D Present pH =6.4 Predicted pH =

Site E Present pH =6.3 Predicted pH =

Site F Present pH =6.1 Predicted pH =

Site G Present pH =5.9 Predicted pH =

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If the water’s pH changes, it may or may not affect the populations of different organisms. Click on each pH below to learn more about their population success in waters of different pH levels. Make a data chart for each organism on the worksheet found in your packet.

6.0 5.5 5.0 4.5 4.0 3.56.5

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How pH affects Maryland’s streamsHow pH affects Maryland’s streams

Activity 5Activity 5Step A. In your packet, list the aquatic organisms that will be most greatly affected by the change in stream pH. Review your predictions from Activity 3A and the chart from the previous activity to help you decide.

Step B. Use the information to support your answer.

Activity 6Activity 6Suppose you live within a Maryland watershed that is growing rapidly with new homes, businesses, roads and people. Use what you know and have learned from this task to think about the relationship between human activity, acid rain, and stream pH. Be sure to explain how each change would have an impact.

You have completed this investigation of acid rain and Maryland streams!