1.19: Lab 19 - Pedology

This lab contains potentially inaccessible interactive resources. Please work with your instructor and local campus resources to identify accommodations for these resources.

Learning Objectives

• Describe the physical and chemical properties of soils.
• Compare the twelve soil orders found in the United States.
• Use geographic information systems (GIS) to analyze soils.
• Identify methods of soil conservation.
• Analyze soil contamination using an environmental justice GIS.

Introduction

Soils are a vital natural resource that serve many functions. Soils provide a foundation for buildings and a medium for plants to grow in. Soils are fascinating ecosystems. In one teaspoon of healthy agricultural soil, there are more microorganisms than people on Earth. Soils are important components of the biogeochemical cycles. For example, as part of the carbon cycle, soils hold three times more carbon than plants and other living organisms (Figure 19.1). Soil conservation and restoration projects demonstrate how soils remove carbon dioxide from the atmosphere, which is one way to combat climate change. On Figure 19.1, numbers show the stores and flows of the fast carbon cycle in gigatons of carbon per year. White numbers indicate stored carbon, yellow are natural fluxes, and red are anthropogenic contributions.

Figure 19.1: The Carbon Cycle. Figure by NASA Earth Observatory is in the public domain

Pedology is the study of soils. In this lab, you will learn the basic characteristics of soils and the main soil classification system used in the United States. You will analyze your local soils and determine how soil conservation efforts increase the resiliency of our ecosystems.

Think About It…Don’t Call It Dirt

When we think of natural resources, most of us think of air and water. Soil is often neglected even though it is interconnected with the health of our water and the atmosphere. Why do you think so many of us take soil for granted?

Part A. Soil Properties

Soils are composed of mineral matter from weathered parent material, organic material, water, and air. Soil properties are the physical and chemical characteristics of soils. These properties develop over time and are influenced by variables such as climatic conditions, topography, and the biological activity of the soil location. These variables influence the rate of weathering, which is the breakdown of parent material by physical processes, chemical processes, and biological activity.

Physical Properties of Soil

Soil Horizons

The first physical soil property you will investigate is soil horizons. As shown in Figure 19.2, soil layers—called soil horizons—form over time. Younger soils have fewer horizons. Soils in tropical environments will have more developed soil horizons because of the increased rates of weathering. The physical properties of the parent material—the rocks that weather to form the mineral matter of the soils—also play a role in the formation of soil horizons.

Figure 19.2: Soil Formation. Figure by Jeremy Patrich is licensed under CC BY-NC-SA 4.0

Exercise \(\PageIndex{1}\)

1. Refer to Figure 19.2. List the major changes that you notice from the soil column on the far-left to the soil column on the far-right.

The process of soil formation generally involves the downward movement of clay, water, and dissolved ions. The common result of that is the development of chemically and texturally different layers known as soil horizons (Figure 19.3). The commonly developed soil horizons are as follows:

➢ O: the layer of organic matter

➢ A: the layer of partially-decayed organic matter mixed with mineral material

➢ E: the eluviated (leached) layer from which some of the clay and iron have been removed to create a pale layer that may be sandier than the other layers

➢ B: the layer of accumulation of clay, iron, and other elements from the overlying soil

➢ C: the layer of incomplete weathering^[338]

➢ R: the parent material or bedrock

Figure 19.3: Soil Horizons. Figure by Jeremy Patrich is licensed under CC BY-NC-SA 4.0. Note that not all soils have all of the soil horizons present.

Exercise \(\PageIndex{2}\)

2. Based on the descriptions provided in Table 19.1 below, label the soil horizons shown on each of the four soil profile diagrams.

Have you ever wondered where the aluminum comes from in a cold beverage can? Bauxite is an ore of aluminum commonly found in tropical and subtropical forests. The high levels of precipitation help to concentrate aluminum oxides in the B and C soil horizons after they have been leached from upper horizons.

Exercise \(\PageIndex{3}\)

Table 19.1: Soil Horizon Labeling Exercise. Figures by Waverly Ray are licensed under CC BY-NC-SA 4.0

Profiles and Descriptions	Profiles and Descriptions
Soil Profile 1. Few horizons have formed because the parent material was recently exposed to weathering. There is some biological weathering activity initiated by moss growth.	Soil Profile 2. This is an arid environment with low rates of weathering. Caliche (calcium carbonate) deposits are found in the B horizon.
Soil Profile 3. This is a well-developed soil in a temperate environment.	Soil Profile 4. This is a soil in a tropical environment with aluminum oxide deposits (bauxite) in the B and C horizons.

3. Apply What You Learned: List the impacts that the extraction of bauxite from tropical regions has on the local environment and population.

Think About It…Interconnectedness and Social Responsibility

With an understanding of how aluminum is produced, how are you interconnected to people working and living at bauxite mines? Would a wider understanding of aluminum production and its impacts encourage people in your community to recycle aluminum beverage cans?

Soil Color

Soil color is another physical property of soil. The mineralogy of the parent material and the rates of weathering are the two main factors that determine a soil’s color (Table 19.2).

Table 19.2: Minerals and Common Soil Colors. Adapted from USDA Natural Resources Conservation Service

Material	Formula	Common Soil Color
goethite	FeO(OH)	yellow, strong brown
hematite	Fe2O3	red
lepidocrocite	FeO(OH)	reddish-yellow, red
ferrihydrite	Fe(OH)3	dark red
glauconite	K(SixAl4-x)(Al,Fe,Mg)O10(OH)2	dark gray
iron sulfide	FeS	black
pyrite	FeS2	black (metallic)
jarosite	KFe3(OH)6 (SO4)2	pale yellow
todorokite	MnO4	black
calcite	CaCO3	white
dolomite	CaMg(CO3)2	white
gypsum	CaSO4×2H2O	very pale brown
quartz	SiO2	light gray
humus	Humus is not a mineral but it influences soil color, especially in the upper horizons. Humus is organic material that forms in a soil when living organisms decay.	black

Exercise \(\PageIndex{4}\)

4. Refer to Table 19.2.

1. What colors are commonly seen when iron (Fe) is present in the parent material of a soil?

2. What color is commonly seen when calcium (Ca) is present in the parent material of a soil?

Soil Texture

Soil texture refers to the sizes of the mineral materials in a soil. All soils can be classified by the amount of sand (<2 to 0.05 millimeters), silt (0.05 to 0.002 millimeters), and clay (<0.002 millimeters) found in them. Figure 19.4 shows the relative sizes of these three particles.

Figure 19.4: Relative Sizes of Sand, Silt, and Clay. Figure by College of the Canyons ZTC Team is licensed under CC BY 4.0

The soil texture triangle (Figure 19.5) provides the names to classify soils with varying percentages of sand (bottom side of triangle), silt (right side of triangle), and clay (left side of triangle.

Guided Practice: Using the Soil Texture Triangle

Watch a tutorial video on how to use the soil texture triangle. (Video length is 2:21).

Figure 19.5: Soil Texture Triangle. Figure by Mikenorton is licensed under CC-BY-SA-4.0

Exercise \(\PageIndex{5}\)

5. Refer to Figure 19.5.

1. What is the soil name for a soil that has 10% silt, 80% sand, and 10% clay?

2. What is the soil name for a soil that has 30% silt, 35% sand, and 35% clay?

3. What is the soil name for a soil that has 75% silt, 10% sand, and 15% clay?

Each of the three soil textures have different characteristics. Table 19.3 summarizes their different properties.

Table 19.3: Soil Texture and Related Properties

Property	Sand	Silt	Clay
Soil Fertility: Ability to sustain plant growth	Low	Moderate-High	Moderate-High
Porosity: Air spaces (gaps between particles)	High	Moderate-High	Low
Permeability: Ability for water to flow through the soil	High	Moderate-High	Low
Water Holding Capacity: Ability to hold water against the force of gravity	Low	Moderate-High	High

Exercise \(\PageIndex{6}\)

6. Loam is the ideal soil texture for most vegetable crops. From Figure 19.5, determine the relative amounts of silt, sand, and clay for loam soils and use Table 19.3 to describe the characteristics that you would expect to find in loam soils.

Soil Structure

Another physical property of soils is soil structure. Soil structure is the way in which the components of a soil aggregate together. There are several common structures called “peds” (Figure 19.6). The soil peds influence how water permeates through the soil.

Figure 19.6: Soil Structures. Figure by USDA Natural Resources Conservation Service is in the public domain

Exercise \(\PageIndex{7}\)

7. Refer to Figure 19.6.

1. Apply What You Learned: Which soil structures would have the highest levels of permeability? Explain your response in one to two sentences.

2. Apply What You Learned: Which soil structures would have the lowest levels of permeability? Explain your response in one to two sentences.

Chemical Properties Of Soils

Cation Exchange Capacity (CEC)

Cation exchange capacity (CEC) refers to the capacity of soils to hold on to cations. Cations are positively charged ions such as aluminum (Al³⁺), calcium (Ca²⁺), hydrogen (H⁺), magnesium (Mg²⁺), and sodium (Na⁺). Negatively charged particles such as clays and organic matter attract positively charged cations through electrostatic forces. A soil’s CEC represents the total amount of exchangeable cations that it can absorb.

When there are high levels of CEC, more nutrients are available to plants. If the cations do not find a negatively charged particle (called an anion), they can be washed away or leached. The more organic matter in a soil and the higher the clay content of that soil, the higher the CEC and thus the higher number of nutrients available for plants to utilize.

Exercise \(\PageIndex{8}\)

8. Use Your Critical Thinking Skills: Review the four physical properties of soil (horizons, color, texture, and structure). Which characteristics of those physical properties would you expect to increase the CEC of a soil? Explain your response in one to two sentences.

Soil Ph

pH is a measure of hydrogen ions in a substance. pH is a logarithmic scale; acids range from 0 to 6.9, 7 is neutral, and 8 to 14 are alkaline. So, a pH of 3 is ten times more acidic than a pH of 4. For most crops, a pH of 6.0 to 6.8 is ideal. At this pH, many nutrients are dissolved when water permeates the soil. This allows plants to uptake the nutrients through their roots in part because this range of pH is favorable to the microbes that help plants to uptake nutrients.

Exercise \(\PageIndex{9}\)

9. Use Your Critical Thinking Skills: Based on what you know about cation exchange capacity, why are soils with higher levels of clay and organic matter less likely to have fluctuations in pH levels when compared to sandy soils? Explain your response in one to two sentences.

Let’s Review: The Physical and Chemical Properties of Soils

Exercise \(\PageIndex{10}\)

10. Complete Table 19.4. In your own words, briefly summarize the four physical properties and two chemical properties of soils.

Table 19.4: Summary of Soil Properties

Physical or Chemical Property?	Property Name	Property Description

11. List the variables that greatly influence the physical and chemical properties of a soil:

Local Soil Properties

For this section of the lab, you will use the California Soil Resource Lab Soil Properties GIS from the University of California, Davis.

Guided Practice: Local Soil Properties

Watch a tutorial video on how to navigate the soil properties GIS website. (Video length is 4:03).

Step 1

Go to the California Soil Resource Lab at UC Davis Soil Properties web app.

Step 2

On the left-hand sidebar, click on the Location tab.

Step 3

Click on the Use My Current Location button, or use the text box to type in your “city, state”, “zip code”, or a nearby “landmark” and click on the Go button. Note: your professor may instruct you to use a particular location for this activity.

Step 4

Click on the Properties tab.

Step 5

Select a Property by clicking on Physical. This should open a menu of physical property options.

Step 6

Click on Sand. Then, click on the question mark icon and read the information about this variable.

Step 7

Move the transparency slide bar on the upper-left of the map to the right to find a specific location to investigate. Using the light gray lines representing roads and river features may help you to pinpoint one location. Note: you are unable to zoom in when using this dataset.

Exercise \(\PageIndex{11}\)

12. Describe the location that you selected to investigate. For example, the intersection of Interstate 5 and the Sacramento River.

13. Slide the transparency bar to the left so that you can see the percentage of sand found at your location. What is the range for the percentage of sand found there?

Step 8

Repeat the same steps to find the percentages of silt and clay found at your location.

Exercise \(\PageIndex{12}\)

14. What is the range for the percentage of silt found at our location?

15. What is the range for the percentage of clay found at your location?

16. Use the soil texture triangle (Figure 19.6) to determine the name for the soil type found at the location. Note: there may be more than one type, depending on the ranges of sand, silt, and clay found at your location.

Step 9

Click on Avail. Water Holding Capacity. Then, click on the question mark icon and read the information about this variable.

Exercise \(\PageIndex{13}\)

17. What is the available water holding capacity (AWC) at your location?

18. Apply What You Learned: How does the soil texture at your location help to explain the water holding capacity at your location?

Step 10

On the left-hand sidebar, click on Soil Color. Then, click on the question mark icon and read the information about this variable.

Step 11

Click on Soil Color (10 cm), then Soil Color (25 cm), Soil Color (75 cm), and Soil Color (125 cm).

Exercise \(\PageIndex{14}\)

19. Describe how the soil colors change from a 10-centimeter (10 cm) depth to a depth of 125 centimeters (125 cm).

20. Apply What You Learned: What would explain the differences in soil color at different depths?

Step 12

On the left-hand sidebar, click Chemical.

Step 13

Click on Cation Exchange Capacity. Then, click on the question mark icon and read the information about this variable. Note that the unit of measurement is centimoles per kilogram (cmol(+)/kg), which basically measures the number of cations per kilogram of soil.

Exercise \(\PageIndex{15}\)

21. What is the range for the cation exchange capacity at your location?

22. Based on your answer to the previous question, would you expect the soil at this location to have high levels of fertility (the ability to support plant growth)? Explain your response.

Step 14

Click on pH. Then, click on the question mark icon and read the information about this variable.

Exercise \(\PageIndex{14}\)

23. What is the range and reaction class name for the pH found at your location?

24. Describe the spatial pattern of pH across the map. Are there any places where there are very strongly acidic or extremely acidic soils found? Are there any places where there are very strongly alkaline or strongly alkaline soils found?

25. Use Your Critical Thinking Skills: What do you think explains the spatial variability of pH on your map? Explain your response.

Part B. Soil Orders

In the United States, soils are classified into twelve categories called soil orders. This taxonomy is based on the dominant physical and chemical characteristics that make each soil order unique. Like many taxonomies (classification systems) within each category, there are subdivisions. You may be familiar with the taxonomy of living organisms from a biology course: domain, kingdom, phylum, class, order, family, genus, and species. With the soil taxonomy, order is the largest grouping, which can be further divided into suborder, great group, subgroup, family, and soil series. So, soil order is the largest grouping and soil series is the smallest grouping.

Before we review the key characteristics of each soil order, let’s analyze the Global Soil Regions map (Figure 19.7).

Figure 19.7: Global Soil Regions Map. Figure by USDA Natural Resources Conservation Service is in the public domain

Exercise \(\PageIndex{15}\)

26. Refer to Figure 19.7.

1. Which two soil orders are most common along the equator?

2. Which two soil orders are most commonly found in the world’s desert regions?

3. Which soil order is most common in the highest latitudes of the northern hemisphere?

Soil Order Descriptions

Check It Out! Soil Order Photographs

Check out photographs of the soil orders at the University of Idaho website.

Entisols and Inceptisols

The two soil orders with the least soil weathering and development are entisols and inceptisols. Entisols are soils that are recent and they have the least number of horizons than any other soil order. For example, very thin O or A horizons may be present in an entisol. Entisols are found in many different environments such as dunes, steep slopes, or a location in which parent materials have been only recently exposed to weathering. Inceptisols are a little more developed than entisols. Inceptisols have a few more horizons present, or thicker O and A horizons, compared to an entisol. Inceptisols lack characteristics (such as clay accumulation) that are found in the other soil orders.

It is estimated that entisols cover 18% of the world’s ice-free land surface while inceptisols cover about 15%. Additionally, inceptisols support the largest percentage of the world’s population when compared to other soil orders. Twenty percent of the world’s population lives on inceptisols.

Exercise \(\PageIndex{16}\)

27. Return to question 2 at the beginning of this lab (Table 19.1). Which one of the four soil profiles that you labeled best represents an inceptisol?

28. Use Your Critical Thinking Skills: Given that one in five people live on an inceptisol, what impact do you think that would have on the functions of soil? Hint: explain your response based on agricultural and construction uses of soil. Your response should be one to two sentences in length.

Oxisols and Ultisols

While entisols and inceptisols are the result of weak weathering, oxisols and ultisols have very high weathering rates. Oxisols and ultisols are found in humid environments and have advanced rates of physical, chemical, and biological weathering. Oxisols are found in tropical and subtropical regions. Oxisols have low cation exchange capacity and commonly have quartz, aluminium oxides, or iron oxides present. Oxisols are common on stable land surfaces in the tropical regions of the world. Ultisols have clay-enriched subsoils along with quartz, aluminum oxides, or iron oxides present.

Oxisols cover 7.5% of the global ice-free land surface while ultisols cover 8.1%.

Exercise \(\PageIndex{17}\)

29. Return to question 2 at the beginning of this lab (Table 19.1). Which one of the four soil profiles that you labeled best represents an oxisol?

30. Refer to the global soil regions map (Figure 19.7). Which soil order is most common in the southeastern United States?

Andisols, Aridisols, and Gelisols

Andisols, aridisols, and gelisols are soil orders that are connected to specific geologic environments. Andisols are found in volcanic landscapes, aridisols are found in desert landscapes, and gelisols are associated with permafrost. Andisols make highly productive soils because of their nutrient availability and water-holding capacity. Aridisols have limited soil development but can accumulate caliche and other materials that are usually leached out of soils in environments that have higher rates of precipitation.

Andisols cover about 1% of the world’s ice-free land area, aridisols cover about 12%, and gelisols cover about 8.3%.

Exercise \(\PageIndex{18}\)

31. Return to question 2 at the beginning of this lab (Table 19.1). Which one of the four soil profiles that you labeled best represents an aridisol?

32. Refer to the global soil regions map (Figure 19.7). Both aridisols and entisols are found across the Sahara Desert. In one to two sentences, explain why these two soil orders are commonly found there.

Alfisols and Spodosols

Alfisols and spodosols are common in forest environments. Alfisols are found in humid and temperate climates and spodosols are found in cooler climates with coniferous forests. Alfisols are rich in nutrients and make productive agricultural soils. In contrast, spodosols are more acidic and have low rates of fertility.

Alfisols cover about 10% of the global ice-free land surface while spodosols cover 4%.

Exercise \(\PageIndex{19}\)

33. Return to question 2 at the beginning of this lab (Table 19.1). Which one of the four soil profiles that you labeled best represents an alfisol?

34. Refer to the global soil regions map (Figure 19.7). Which regions of the United States have alfisols?

35. Refer to the global soil regions map (Figure 19.7). Which regions of the world have spodosols?

Histosols, Mollisols, and Vertisols

Histosols are found in wetlands and mollisols are common in grasslands. Vertisols are not associated with a specific landscape—they are distinct from other soil orders because vertisols have large amounts of clays. Key ideas about these three soil orders are as follows:

➢ Given their wetland environment, histosols have high levels of organic content when compared to other soil orders. Little drainage in wetland areas allows for organic materials to accumulate over time.

➢ Mollisols also have higher levels of organic materials due to the activity of plant roots in grassland ecosystems. Mollisols are productive agricultural soils.

➢ Vertisols shrink and swell due to their clay content. When wet, clay absorbs moisture and swells. When dry, clay shrinks and cracks. Histosols cover about 1.2% of the world’s ice-free land area, mollisols cover about 7%, and vertisols cover about 2.4%.

Exercise \(\PageIndex{20}\)

36. Peat is partially decayed organic matter. Which soil order would likely be a source of peat?

37. Refer to the global soil regions map (Figure 19.7). Where in the United States are mollisols common?

38. Apply What You Learned: In one to two sentences, explain why building in vertisols can be challenging.

Part C. Soil Order Exploration

For this section of the lab, you will use the California Soil Resource Lab SoilWeb GIS from the University of California, Davis. Note: this is a different GIS than you used to investigate soil properties earlier in the lab.

Guided Practice: Soil Order Exploration

Watch a tutorial video on how to navigate the SoilWeb GIS website. (Video length is 2:02).

Step 1

Go to the California Soil Resource Lab at UC Davis SoilWeb app.

Step 2

Read the information in the pop-up box and click OK.

Step 3

Zoom out so that you can see all of the United States, including Alaska and Hawai’i.

Step 4

Think about the twelve soil orders that you learned about in the previous section. Select one of the soil orders and zoom in on a location where you think you would find this soil order.

Exercise \(\PageIndex{21}\)

39. Which soil order did you select?

40. Which location did you select?

Step 5

Zoom into the location until you see the yellow lines, which represent boundaries between soil series. Recall that soil series are the smallest taxonomic grouping for soils (soil orders are the largest taxonomic grouping).

Step 6

Double-click on one of the areas on the map.

Step 7

A box to the left of the screen opens and may list several soil series. Select one of the soil series shown. Click on the name (it is shown in blue underlined text).

Exercise \(\PageIndex{22}\)

41. Which soil series did you select? (What is it called?)

Step 8

Click Description and read the information shown about the soil series.

Exercise \(\PageIndex{23}\)

42. What are three ideas listed in the description that connect to the information that you learned earlier in the lab? Your response should be at least three sentences in length.

Step 9

Click Close.

Step 10

Look at the information listed under the Soil Taxonomy heading in the box on the left.

Exercise \(\PageIndex{24}\)

43. Which soil order does this soil series belong to?

44. Is this the same soil order that you expected to find in this location? If yes, explain why you expected to find this soil order here. If not, explain why you think another soil order is present at this location. Note: it’s okay if you did not select a location that matched your soil order. You made an hypothesis and it was either proven or disproven—either outcome is okay! Your response should be one to two sentences in length.

Step 11

In the box on the left of your screen, click on Series Extent Explorer shown at the top.

Exercise \(\PageIndex{25}\)

45. How many acres does this soil order cover? For reference, one acre is about 90% of the size of a football field.

Part D. Soil Conservation and Contamination

Soil conservation refers to the practices of maintaining healthy soils. In many regions, it takes hundreds of years to form just one inch of topsoil (this is the top five to ten inches of a typical soil). The U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS) works to use current scientific techniques to analyze and manage soils. “Originally known as the Soil Erosion Service in 1933 then the Soil Conservation Service starting in April of 1935, the agency was created in response to the high rates of soil erosion seen across the Great Plains during the Dust Bowl of the 1930s (NRCS n.d., n.p.)”. In addition to co-creating soil GIS like the ones that you utilized earlier in this lab, the NRCS provides recommendations that prevent soil erosion, ensure healthy soil microbes, and prevent mineral depletion in soils. The NRCS also recommends improved farming practices that will prevent water contamination (Figure 19.8).

Figure 19.8: Nutrients and Water Quality. Figure adapted from USDA Natural Resources Conservation Service is in the public domain

Exercise \(\PageIndex{26}\)

46. In one to two sentences, explain how soils are connected to other components of the biosphere.

Soil contamination refers to the occurrence of substances in soils that pose human health risks and exceed naturally-occurring levels. Soil contamination can result from a variety of intended, accidental, or naturally occurring activities and events such as manufacturing, mineral extraction, abandonment of mines, national defense activities, waste disposal, accidental spills, illegal dumping, leaking underground storage tanks, hurricanes, floods, pesticide use, and fertilizer application. Nationally, there are thousands of contaminated sites of varying size and significance in settings ranging from abandoned buildings in inner cities to large areas contaminated with toxic materials from past industrial or mining activities. Contaminated lands include the following:

➢ Sites contaminated by improper handling or disposal of toxic and hazardous materials and wastes.

➢ Sites where toxic materials may have been deposited as a result of natural disasters or acts of terror.

➢ Sites where improper handling or accidents resulted in release of toxic or hazardous materials that are not wastes.^[347]

Contaminated lands can pose a variety of health and environmental hazards. Some contaminated sites pose little risk to human health and the environment, because the level of contamination is low and the chance of exposure to toxic or hazardous contaminants is also low. Other contaminated sites are of greater concern because of the chemicals that may be present and their propensity to persist in or move through the environment, exposing humans or the environment to hazards. These sites must be carefully managed through containment or cleanup to prevent hazardous materials from causing harm to humans, wildlife, or ecological systems, both on- and offsite:

➢ Contaminated soils can leach toxic chemicals into nearby ground or surface waters, where these materials can be taken up by plants and animals, contaminate a human drinking water supply, or volatilize and contaminate the indoor air in overlying buildings.

➢ In dry areas, contamination in soil can be further distributed through wind-borne dust. Once soil contamination migrates to waterways, it may also accumulate in sediments, which can be very difficult to remediate, and may also affect local ecosystems and human health.

➢ Humans can be harmed by contact with toxic and hazardous materials on a contaminated site via exposure to contaminated land, air, surface water, and groundwater.

➢ When contaminated lands are not properly managed, humans and wildlife can be exposed to contaminants through inhalation, ingestion, or dermal contact. The risks of human exposure are site-specific and difficult to generalize at the national level. Potential effects may be acute or chronic.^[348]

Exercise \(\PageIndex{27}\)

47. List the causes of soil contamination.

48. List the effects of soil contamination.

Environmental justice is the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income, with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies. This goal will be achieved when everyone enjoys the following:

➢ the same degree of protection from environmental and health hazards, and

➢ equal access to the decision-making process to have a healthy environment in which to live, learn, and work.^[349]

CalEnviroScreen is a mapping tool that helps identify California communities that are most affected by many sources of pollution, and where people are often especially vulnerable to pollution’s effects. CalEnviroScreen includes a list of indicators (variables) in four categories:

➢ Exposure indicators are based on measurements of different types of pollution that people may come into contact with. These include:

• Air quality: ozone and PM2.5
• Diesel particulate matter
• Drinking water contaminants
• Pesticide use
• Toxic releases from facilities
• Traffic density

➢ Environmental effects indicators are based on the locations of toxic chemicals in or near communities. These include:

• Cleanup sites
• Groundwater threats
• Hazardous waste generators and facilities
• Impaired water bodies
• Solid waste

➢ Sensitive population indicators measure the number of people in a community who may be more severely affected by pollution because of their age or health. These include:

• Asthma
• Cardiovascular disease
• Low birth weight infants

➢ Socioeconomic factor indicators are conditions that may increase people’s stress or make healthy living difficult and cause them to be more sensitive to pollution’s effects. These include:

• Educational attainment
• Housing burden
• Linguistic isolation
• Poverty
• Unemployment^[350]

The indicators are aggregated so that each location has a percentile score. The higher the score, the higher the environmental burden.

Exercise \(\PageIndex{28}\)

49. Which of the indicators listed above relate to soil contamination? Go to the Indicators Overview webpage to read the definitions of the indicators. Explain why you selected these indicators.

Let’s explore CalEnviroScreen 3.0 in order to analyze soil contamination in California through an environmental justice framework. Note that the data is provided by census tract, which is a spatial scale that averages about 4,000 people.

Step 1

Go to the CalEnviroScreen 3.0 website and click OK.

Step 2

Zoom in on your location and click on the map. This opens a pop-up window with the indicators used in the CalEnviroScreen model.

Exercise \(\PageIndex{29}\)

50. What is the number for this census tract?

51. What is the population of this census tract?

52. What is the CalEnviroScreen 3.0 percentile for this census tract?

53. What is the pollution burden percentile for this census tract?

54. What is the population characteristics percentile for this census tract?

55. Use Your Critical Thinking Skills: Are you surprised by these percentiles? Why or why not?

56. Scroll down in the pop-up window to see the individual percentiles for each indicator. Do you think soil contamination is a problem in this census tract? Why or why not? Be sure to cite the data provided in the pop-up window in your response.

Step 3

Close the pop-up window and zoom out so that you can see the entire state of California.

Exercise \(\PageIndex{30}\)

57. Which regions of the state have the highest CalEnviroScreen 3.0 percentiles?

57. Use Your Critical Thinking Skills: What factors likely contribute to the high scores in these regions? Explain your response in two to three sentences.

Check It Out! More About Environmental Justice

Learn more about the environmental justice movement at the U.S. Environmental Protection Agency webpage. The webpage has an interactive timeline that traces the environmental justice movement from grassroots organizing by communities of color to actions in recent years.

Part E. Wrap-Up

Consult with your geography lab instructor to find out which of the following wrap-up questions you should complete. Attach additional pages to answer the questions as needed.

Exercise \(\PageIndex{31}\)

59. What is the most important idea that you learned in this lab? In two to three sentences, explain the concept and why it is important to know.

60. What was the most challenging part of this lab? In two to three sentences, explain why it was challenging. If nothing challenged you in the lab, write about what you think challenged your classmates.

61. What is one question that you have about what you learned in this lab? Write your question along with one to two sentences explaining why you think your question is important to ask.

62. Review the learning objectives on page 1 of this lab. How would you rate your understanding or ability for each learning objective? Write one sentence that addresses each learning objective.

63. Sketch a concept map that includes the key ideas from this lab. Include at least five of the terms shown in bold-faced type.

64. Create an advertisement to educate your peers on the important information that you learned in this lab. Include at least three key terms in your advertisement. The advertisement should be about half a page in size (about 4 inches by 6 inches).

65. One way to think of physical geography is that it is the study of the relationships among variables that impact the Earth's surface. Select two variables discussed in this lab and describe how they are related.

66. How does what you learned in this lab relate to your everyday life? In two to three sentences, explain a concept that you learned in this lab and how it relates to your day-to-day actions.

67. How does what you learned in this lab relate to current events?
    1. Write the title, source, and date of a news item that relates to this lab.
    2. In two to three sentences, discuss how the news item relates to what you have learned in this lab.
    3. In one to two sentences, discuss whether or not the news item accurately represents the science that you learned. Tip: consider whether or not the news item includes the complexity of the topic.

68. Search O*NET OnLine to find an occupation that is relevant to the topics presented in today's lab. Your lab instructor may provide you with possible keywords to type in the Occupation Quick Search field on the O*NET website.
    1. What is the name of occupation that you found?
    2. Write two to three sentences that summarize the most important information that you learned about this occupation.
    3. What is one question that you would want to ask a person with this occupation?

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^[338] Physical Geology - 2nd edition by Steven Earle is licensed under a CC BY 4

^[347] Text by US EPA is in the public domain

^[348] Text by US EPA is in the public domain

^[349] Text by the US EPA is in the public domain

^[350] Text by California EPA is in the public domain