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Introduction
Narrative:
Soils
Soil Properties
Soil Horizons
Soil Contaminants
Conclusion
Lesson Plan #1: Introducing the Soils Study Unit
Lesson Plan #2: Student Field Trips to Describe and Sample Soils on Sight
Lesson Plan #3: Testing Soil Texture
Lesson Plan #4: Testing Soil Particle Size Distribution
Lesson Plan #5: Water Movement in Soils: Video, Questions, and Experimentation
Lesson Plan #6: Examining Environmental Influences on Soil Formation
Lesson Plan #7: Testing Properties of Colloids in Soil Environment
Lesson Plan #8: Testing Soil Acidity
Lesson Plan #9: Examining Soil Salinity
Lesson Plan #10: Surveying the South Valley Community for Examples of Soil
Contamination
Lesson Plan #11: Mapping and Completing Soil Survey Reports
Lesson Plan #12: Analyzing an Unknown Soil Sample (Assessment)
Notes
Bibliography
Teacher’s Reference List
Student Reading List
Teacher’s Material List
Appendix A: The Geological Framework of the Albuquerque Basin of New Mexico
Appendix B: The Ecological Framework of the Albuquerque Basin of New Mexico

The early Hispanic families recognized the richness of the Rio Grande River floodplain soils, and the grazing potential of the flanking terraces. They partitioned the best valley lands as large land grants. Isleta Boulevard, a main north-south thoroughfare in the South Valley, is part of the old Camino Real, along which Juan de Onate traveled in 1598, first exploring the area for Spain. Land use and modern settlements in the South Valley today still reflect the historic land grants established by Hispanic families in the 1690-1700’s, in neighborhoods such as Atrisco, Pajarito, and Los Padillas.

The South Valley is a mix today of denser urban population interspersed with rural farms and ranchos. Alfalfa, truck farm vegetables, and fruit orchards, as well as small animal enclosures, compete not only with older neighborhoods and strip mall shopping areas, but with industries, wastewater treatment plants, and new tract housing as well. Much of the South Valley is unincorporated and outside Albuquerque city limits, thus escaping the city zoning laws. Many residents have separate well water and septic systems.

The objective of this nine weeks soil contamination curriculum unit is to enable high school geology students who live in the South Valley to examine, describe and test properties of soils from the South Valley area. Students will also correlate the sources of soil contamination in the South Valley with soil properties. The students will commence this curriculum unit after having studied basic geological principles, the geology of New Mexico, and an introductory chapter on soil properties and soil formation.

Planned activities include field trips to three sites, (the Rio Grande River floodplain, an irrigated field, and the Southwest Mesa terrace), to examine soil properties in the field, measure and describe a soil horizon, and take samples from each site to analyze in laboratory experiments. Students will work in teams of 3 to 4 each, both in the field and in the classroom. Experiments will include analyzing the soil samples for soil texture, particle size distribution, water movement in soils, environmental influences in soil formation, properties of colloids in soil environment, soil acidity, and soil degradation by salinity and sodicity. As students perform the various experiments, they will coordinate their findings with respective area neighborhood surveys of potential and actual contamination sources. As assessment, students will test an unknown soil sample for several properties and also take an essay test based upon their laboratory findings.

Soils provide both nutrients for plant growth and a livable environment for various human activities, such as farming, ranching, building, recreation, and industry. In the Albuquerque Basin, soils form an extensive sand and gravel aquifer, of the Santa Fe Group, providing the water for the entire basin community. Soils also determine the type of vegetative cover, from the southern grasslands, the large Bosque cottonwoods, to the pinyon-juniper covered slopes of the Sandia Mountains pediment.

Soils are influenced by climate, physical and chemical weathering, topography, and ecological and geological settings. Fertile soils, rich with organic matter, can support abundant plant life. Land denuded of soils cannot. Altogether soils form the pedosphere, a layer of disaggregated and decomposed rock debris and organic matter at the surface of the earth.¹

Soils form by different processes: erosion, deposition, organic matter decomposition, weathering, and acidification. Erosion can occur by the action of water, ice, or wind. Physical weathering, to produce rock fragments, can include exfoliation jointing, thermal expansion, biological disintegration associated with plant growth and worm activity, and frost weathering. ² Chemical weathering also contributes greatly to soil formation. Water, other chemical ions, and oxygen react with parent rock material and primary and secondary minerals already in soils to further decompose soils. Water, H₂O, combining with atmospheric carbon dioxide gas, CO₂, forms carbonic acid, H₂CO₃, within soils. This carbonic acid in turn reacts with limestone, calcium carbonate, CaCO₃, dissolving the rock into smaller fragments and forming calcite. Calcite, or caliche, is a common component of arid region soils.

Decaying organic matter also forms acids in soils. Atmospheric nitric and sulfuric gases combine with water to form acids, too, which further decompose soils. Another form of chemical weathering is oxidation. Atmospheric oxygen combines with elements in soils such as iron, Fe, to form iron oxides, FeO, and Fe₂O₃, the characteristic reddish color in many soils. Finally, certain minerals are more soluble than others in soils, and can be removed by water percolating through soils. Potassium, K, calcium, Ca, magnesium, Mg, and sodium, Na, are easily removed by water, while such elements or compounds as aluminum, Al, iron, Fe, and silica, Si, will remain.³

Soils form by the interaction of the lithosphere, hydrosphere, atmosphere, and biosphere. The lithosphere contributes parent rock material. The complex but interesting geological framework of New Mexico has contributed a wide variety of parent rock material to the Albuquerque Basin soils. (Appendix A). The hydrosphere, in the forms of precipitation, stream and river flow, snow, and ice further breaks down rock fragments and aid in transport of soils and sediments. The atmosphere contributes gases such as oxygen, carbon dioxide, nitrogen dioxide, and sulfur dioxide, which combine with water to react chemically within soils. The biosphere contributes decaying plant material and the activities of organisms burrowing through soils.⁴ (Appendix B)

Eminent soil scientist Hans Jenny developed the study of soils as a valid scientific discipline; he derived a soil equation, CLORPT. CL is for climate; O is for organism; R is for relief (slope or topography); P is for parent material; and T is for time.⁵

"Knowing these variables, "he asserted," one should be able to predict the vegetable, animal, soil, and other properties of the ecosystem in question."⁶

Soils can be identified and described by examining their physical, organic, chemical, and water related properties. Soils are also characterized by their layered position at a site and their topography. Soil physical properties include the amount of pore space between soil grains, the structure (or aggregation), color, compaction, density and strength, presence of cracks or crusts, resistance to penetration, permeability and porosity, and temperature and texture. Organic properties include odor, presence of decomposing organic matter, content and type of organisms present, and type of vegetative cover. Chemical properties include acidity or alkalinity, salinity or sodicity. Soil composition affects, in turn, the amount of water that can infiltrate, the water holding capacity, and the water content. Another important consideration is where soils occur geographically, and at what level in a horizon.⁷

When soils develop in place, they form layers, or horizons, each with its own distinctive characteristics. Soil horizons form a vertical arrangement called a soil profile. Different climates, parent rock material, topography, and vegetative cover can contribute to varying soil profiles. The uppermost soil horizon is the O Horizon, composed of decaying organic matter, which forms a humus layer, black, brown or tan in color. Underlying the O Horizon is the A Horizon, composed of mineral materials, clays, silts, sands, and some organic materials. The A Horizon can, like the O, show evidence of the activity of organisms, for example burrowing. The B Horizon underlies the A Horizon; it contains clays, leached minerals, and elements or compounds, such as aluminum, iron, and silica. Color changes, in the form of banding, can occur in this horizon. Certain desert soils develop calcium carbonate bands in the B Horizon. Finally, the lowermost C Horizon may or may not lie on bedrock; it usually has weathered rock material from the underlying bedrock, or can be composed of materials such as sand or gravel alluvium. ⁸

The U.S. Department of Agriculture has devised a soil classification system of 12 soil orders, with further subdivisions of suborders, great groups, subgroups, families, series and types. These soil orders reflect variations in temperature, precipitation, topography, horizon thickness, and clay content. Soil maps, moreover, reflecting these orders, are available from Soil Conservation Services. The soil orders include Alfisols, Andisols, Aridisols, Entisols, Histosols, Inceptisols, Mollisols, Oxisols, Spodosols, Ultisols, and Vertisols. In the Southwestern United States, Aridisols and Mollisols are more common. ⁹

Most soils of the Albuquerque Basin can be characterized as desert soils with calcic horizons and very little or no O (organic) Horizon. They are often referred to as caliche soils. Some soils in the Albuquerque Basin look like cake layers, with clay rich, reddish horizons above white calcic horizons.

"These clay rich layers are called argillic horizons, formed over long periods of time when clay particles, suspended in water, are carried downward into the soil and accumulate."¹⁰

Argillic horizons can be a dusty brick red, produced by the oxidation of iron bearing minerals, such as biotite and hornblende, which are derived from igneous or metamorphic rocks.¹¹

Soil Contaminants

Soils respond differently to various contaminants, depending upon type of soil composition, pore space, acidity or alkalinity, available water flow, and contaminant concentration levels, source and type. Coarser sandy soils have a lower water retention rate than fine textured soils with more humus and /or clay; therefore contaminants will percolate much more quickly through coarse soils than finer soils. An example would be the action of a common pesticide contaminant atrazine:

"The fate of the pesticide atrazine applied to soil, is of primary environmental concern and is linked to the organic content of soil. Sorption of atrazine by soil components, primarily organic matter, reduces its solution concentration, and lessens potential leaching hazards."¹²

Clays, or colloids, because they have so much surface area and are negatively charged at their outer particle perimeters, can attract and swell to many hundred times their original particle size with water contaminated with toxic metallic ions, such as lead, cadmium, chromium, or mercury. Clays in soils also form a barrier and can trap hydrocarbon contaminants, such as gasoline or cleaning solvents. ¹³

Atmospheric pollutant gases, such as nitrogen dioxide, NO₂, sulfur dioxide, SO₂, or excess carbon dioxide can go into solution with water and percolate through soils, increasing soil acidity. Soil acidity, in turn, can increase absorption of other elements and compounds.

Human activity can negatively impact the soil environment in a number of ways:

depletion of soil nutrients, such as nitrogen by planting the same crops and not rotating crops; dumping wastes illegally; accelerating erosion by poor construction planning; clearing soil surfaces of covering vegetation; compacting and covering soils with concrete, asphalt, or other impervious cover; fostering organic matter loss by not mulching; and accelerating acidification of soils. ¹⁴

Finally, agriculture activity frequently leads to soil contamination, in the use of excess fertilizers or improper disposal of animal wastes; both activities contribute phosphorus and excess nitrates to soils. Such contamination eventually leaches through soils and can lead to eutrophication of streams, ponds, lakes, and rivers.

The South Valley of the Albuquerque Basin has numerous example of soil contamination, from leaking underground gasoline tanks, leaking private septic systems, excess fertilizer use, illegal dumping, industrial pollution, and animal waste contamination. For example, creosote and oil, used in the treatment of wood products, was removed as contaminated oil sludge from an EPA Superfund site. There was concern that contamination from the 6" of sludge, a very complex mixture of polycyclic aromatic hydrocarbons, and 1,100 cubic yards in volume, would infiltrate the groundwater supply in the upper Santa Fe aquifer.¹⁵

The Natural Resource Conservation Service defines soil quality as

"…the capacity of soils to function. Soil will function to filter the water that falls on it and the air that flows through it, while supporting the biological ecosystems that function within and on it. When we degrade soils, the capacity to function is diminished."¹⁶

"A soil is not a pile of dirt. It is a transformer, a body that organizes raw materials into tissues. These are the tissues that become mother to all organic life."¹⁷

In the Albuquerque Basin, soils, not only provide still fertile farmland, landfills, and building sites, but also filter and contain the basin's water supply in the Santa Fe Aquifer.

"Virtually all fresh water falls on soil and travels over, through, evaporates from, is stored in, or interacts with soil to drive several chemical and biological processes."¹⁸

Human activity can impact soils negatively through urban and agricultural runoff, municipal and industrial discharge, river overflow, feedlot wastes, illegal dumping, heavy fertilizer use, and removal of vegetative cover. Once damaged, it is difficult for soils to recover.

"In some parts of the world today, rates of erosion due to human activity are 18 to 100 times greater than the natural rate of soil renewal. In the 1980's, the World Watch Institute, a research group in Washington D C, projected a 32% decline in the amount of topsoil per person between 1984 and 2000." ¹⁹

Soil formation, moreover, is a process which requires time. Only about 0.02-0.11mm of soil forms per year; soils to a depth of several meters requires 10,000-50,000 years.²⁰

This soils curriculum unit should enable students to examine soil properties and soil contamination in an investigative and experimental approach. This curriculum unit also addresses the need to teach and assess several New Mexico State geology and environmental science core curriculum standards not otherwise met in traditional high school science classes.

Objective: Students will determine the soil properties to be measured and review which field techniques to use.

Introduction:

Teacher introduces the Soils Unit with a demonstration prior to lecture and discussion. Teacher assembles three different soil samples in funnels on ring stands, one each of humus, sandy loam, and a soil with high clay content, with beakers underneath each funnel of each ring stand. Teacher asks students to help in the demonstration, as each person pours the same small amount of blue colored water, 25mL, into each funnel.

Teacher asks students to predict which soil will hold the most liquid, and which soil might retain the most color. Teacher asks students why and how soils can trap liquids.

Teacher then lectures briefly on soil properties, writing key concepts on the chalkboard or on an overhead. Teacher explains that observing soils in the field is like detective work and qualitative in nature. Teacher reviews required field kits with students, obtains written permission slips, and assigns student teams of 3-4 each, prior to trip. Field kit for each student team will include the following:

• Per student: field notebook, pens, ruler, water bottle, hat, sunscreen, and sensible shoes
• Per team: small shovel, small plastic bottle for 1M Hydrochloric acid, hand lens, and soil thermometer, 4-6 plastic collecting bags for samples.
• Per class: Munsell color chart and soil maps

Objective: Students will evaluate soil properties in the field using a number of measuring parameters and criteria. Students will also determine and use the appropriate measuring device for each soil property. Students will record soil property information in an orderly and systematic manner in their field notebooks.

Estimated Class Time: Three separate field trips to three different sites, of ½ day each, with each geology class.

Introduction:

Teacher will guide geology students, one class at a time, on each field trip of ½ day duration, to three different sites on three different days:

• Field Trip #1: Rio Grande River Bosque Floodplain
• Field Trip #2: South Valley Irrigated Field
• Field Trip #3: Southwest Mesa

At each site, student teams will measure, describe, and evaluate soil properties according to the following list and descriptions of soil properties, and record information in their field notebooks:

Soil Properties, Field Notes:

Soil Aeration: Use your hand lens to check soil for the presence and size of pore spaces.

Soil Aggregation (Structure): What type of soil grains can you see in your sample? Are they sand, silt, or clay sized? Use your grain size chart as a guide.²¹ Record what type of minerals you see as well. Describe the structure of the soil grains according to the following structure criteria:

• Granular: cubical, pea or smaller sized
• Blocky: cubic, larger than granular with sharp or rounded edges
• Prismatic: columnar shaped
• Platy: flat shaped
• Single grained: as in loose sands
• Massive: powdery, or irregularly shaped

Color: Use the Munsell color chart, as demonstrated by the teacher, to compare the soil sample and record color.

Cracks and Crusting: Note and describe the presence of any cracks in soil surface, or crusting, compact, hard or a brittle surface. Do you see any dry spots in the soil, where the vegetation appears wilted?

Horizon: Record from which horizon level the soil you are sampling came from. Do you see any distinct layers within any horizon? Describe and measure in centimeters the height of each horizon.

Odor: Does the soil sample have any noticeable odor? Smell a freshly exposed sample and describe. Odors can be evidence of volatile organic compounds, contamination, rotting vegetation, microbe activity, pesticides, ammonia, and/or petroleum products. Indicate possible source of odor.

Organic Matter: Humus is black, brown to tan in color and is composed of decomposing vegetation. Describe the color carefully. Do you see any evidence of organisms? Any roots or rootlets?

Porosity: Use your hand lens to examine soil for abundance and relative size of pore spaces between soil grains. Describe and record.

Salinity: Do you detect the presence of any white or gray crusty deposits in the soil? Take a fresh soil sample and drop 3-4 drops of Hydrochloric acid onto the sample. If it fizzes, then calcium carbonate,CaCO₃, is present.

Soil Sample Position: Describe the general topographical location of your sample. (i.e. floodplain, slope, terrace, arroyo, etc.)

Temperature: Using the soil thermometer, take the temperature of the soil where you took your samples for other testing and record in degrees Celsius.

Texture: In order to determine the relative percentage of sand, silt, or clay in your soil, perform the following field test:

• Moisten a golf ball sized ball of soil to a putty consistency.
• Work the soil between thumb and forefinger, flattening it into a ribbon.
• Allow ribbon to hang.
• If ribbon is less than 1", there is very little clay.
• If ribbon is between 1-2.5", there is a moderate amount of clay.
• If ribbon is more than 2", there is a lot of clay.

Thatch and Vegetative cover: Describe the presence or absence of any thatch, nondecomposed, or partially decomposed layer of organic matter. Check for the presence of any insects or rodents, fungi, algae, or mold. Describe the type, quality and abundance of any plants that your soil supports. Use your guides to help you identify plant species.

Water Content: How well does your sample hold water? Squeeze a small, flattened lump of soil in your hand and knead it with your finger. Evaluate its wetness according to the following:

• Excessively wet: soil will flow together and release liquid water, or feel sticky, a sign of high clay content.
• Wet: Soil will feel plastic and keep a molded shape; there is some clay content.
• Moist: Soil will crumble.
• Moderately Dry: Soil will show cloddiness or dustiness.
• Dry: Soil will crumble.

LAST STEP: Carefully collect 4 soil samples, about 1 cup each, from the same horizon and position from which you’ve taken your measurements. Label sample bags with your team members’ names, class, date, and LOCATION. You will be using these samples for your experiments in the coming weeks.

Modified after Soil Science, by Thien and Graveel, 1997

Objective: Students will compare, contrast, and recognize the significance of soil texture as a soil property.

Materials:
Water
Three different soil samples collected in field
Sand, silt, and clay percentage content triangle from geology text
Exercise #2 from Soil Science, pp. 21-32, by Thien and Graveel, 1997

Estimated Class Time Required: 2-3, 50 minute class periods.

Introduction:
Teacher briefly introduces topic of soil classification and demonstrates use of soil classification textural triangle.²² Teacher asks students to consider the following questions as they examine their soil samples for percentages of sand, silt, and/or clay:

• What is the relationship between soil texture and color?
• What is the relationship between soil wetness and soil texture?
• How would each soil react to a hazardous spill, such as gasoline?
• What could account for the difference in absorption rate for each soil?

Students will work in their respective teams to characterize the soils. Teacher circulates continuously among student teams, anticipating questions, and monitoring student progress.

Objective: Students will examine and apply the principle of dispersion and sedimentation through calculating particle flow rates using Stokes Law.

Materials:
Soil Hydrometer, ASTM, # 152H with Bouyoucos scale in grams per liter
Sedimentation cylinder, with 1000mL mark
Dispersing solution: Dissolve 35.7g technical grade sodium hexametaphosphate, (NaPO₃)₆, and 7.9g sodium carbonate,Na₂CO₃, in about 900mL of deionized water. Adjust pH to 8.3 with additional sodium carbonate. Bring final volume to 1000mL.
Thermometer
Balance
Mechanical Mixer with stirring cup
30% Hydrogen peroxide, H₂O₂, for optional procedure only
Sieve, 300 mesh, (50µ m openings), for optional procedure only
Exercise #3, pages 33-42, from Soil Science, by Thien and Graveel, 1997

Estimated Class Time Required: 4, 50 minute class periods

Introduction:
Teacher reviews key concepts, key terms, and experimental procedure on first class day with students. Key terms include dispersion, aggregates, primary particles, polyvalent cations, suspension, sedimentation, and flocculation (of clays).

Teacher reviews concept and application of Stokes Law:

V = kD² , where V equals velocity of particle, k equals a constant, 11241 (@ 30^oC), and D equals particle diameter. Stokes Law demonstrated the relationship between the settling rate of a particle and its size. Small particles, with high specific surface areas, settle more slowly than larger particles.

"Stokes’ Law accurately predicts the fall velocity of particles whose Reynolds number, Vgdp/µ , is less than about 0.5. This corresponds to silt-size and finer quartz-density particles in water."²³

Teacher relates field application of Stokes’ Law to particles in suspension in moving water. A moving flow rate keeps particles in suspension; as water slows down, heavy sand particles drop out of suspension first, then silt sized particles, then, as flow rate stops, clay sized particles.²⁴

Teacher also demonstrates the use of a hydrometer. This part of the experiment requires at least two hours; a member of each team will have to return later in the day to take required measurements, after suspension has settled, about 2 hours time. Since hydrometers and sieves are relatively expensive, student teams will have to alternate their use.

Students should be wearing safety goggles, chemistry aprons, and disposable gloves while performing the experiment with the dispersion medium.

Objective: Students will observe and examine types of water movement in soils.

Materials:
Video: "How Water Moves Through Soil", by Jack Watson, 1994, available through
College of Agriculture, University of Arizona, 715 North Park Avenue, Tucson, Arizona, 85719
Exercise #6, pages 73-88, from Soil Science, by Thien and Graveel
Three soil samples: clay loam, sandy loam, and silty loam
Beakers, 3 per team
Graduated cylinders, 3 per team
Glass tubes, 3 per team
Ring stand 1 per team
Soda straws, 3 per team
Sponges, 3 per team

Estimated Class Time Required: 2, 50 minute class periods

Introduction:
Teacher begins with a demonstration. Teacher asks students to predict how much water a dry sponge will hold. Teacher wets sponge from large beaker of water, and then asks student to squeeze the sponge into an empty beaker, and to pour the water into a graduated cylinder to measure.

Teacher equates a full sponge as supersaturated, a damp sponge as saturated, and a dry sponge as unsaturated. Teacher asks students how these terms might apply to soil water content and which type of soil would hold more water.

Teacher briefly introduces video on first day, reminding students to apply concepts of video to their experimentation on second day.

Students will perform experiments on the second day in their respective teams.

Objective: Students will demonstrate, through experimentation, weathering processes on soils and infer how human activity might affect the way soils interact with their environment.

Materials:
Hot plate
Erlenmeyer flasks
Beakers
Test tubes
pH meter, or pH indicator papers
Exercise #7 from Soil Science, pages 89-100, by Thien and Graveel, 1997
Sucrose
Drinking straws
Soils: acid soil, neutral soil, and red soil
Mortar, pestle
20 and 60 mesh sieves
Fluorapatite, Ca₅(PO₄)₃F
Ammonium molybdate: Dissolve 5g (NH₄)MO₄ in 50mL deionized water. Heat and filter if turbid, then add 50mL concentrated nitric acid and 100mL deionized water
Stannous chloride: For stock solution, dissolve 10g SnCl₃*2H₂O in 25mL concentrated Hydrochloric acid and store in a brown glass bottle. Then each day, make a fresh solution by combining 3mL stock solution and 97mL deionized water.
Phenolphthalein indicator: dissolve 0.5g indicator in 800mL ethyl alcohol and bring to 100mL with deionized water.
Solutions: dissolve the following amount of chemical in deionized water. Bring to 1000mL volume.
0.1 N hydrochloric acid: 8.3mL concentration HCL
1.0 N ammonium hydroxide: 35g NH₄OH
Saturated ammonium oxalate: 50g (NH₄)₂C₂O₄*H₂O
Saturated calcium hydroxide: add Ca(OH)₂ until excess solid is evident
1 M sodium carbonate: 86g Na₂CO₃
1 M sodium chloride: 58.4g NaCl
1 M calcium chloride: 147g CaCl₂*2H₂O
1 M aluminum chloride: 241.5g AlCl₃*6H₂O

Estimated Class Time Required: 3, 50 minute class periods

Introduction:

Teacher introduces topic and reviews experimental procedures and lab safety with student teams. Teacher also reviews key concepts with students: types of physical and chemical weathering, hydration, hydrolysis, carbonation, and oxidation-reduction. Students will be demonstrating and evaluating each of these concepts in their experimentation.

Teacher reviews with students how human activity can greatly affect soil properties. Contamination, depletion, pollution, erosion, and/or compaction of soils can result from negative human impact of such activities as dumping illegally, wastewater runoff, toxic leaching, and hydrocarbon pollution.

Teacher reminds students that they are surveying their neighborhood sectors for such examples, and others, of such soil pollution.

Students perform experiments in their respective teams and should wear safety goggles, chemistry aprons, and disposable gloves.

Objective: Students will demonstrate, through experimentation, how soil colloids can absorb and exchange cations and how colloids, both organic and mineral, absorb water. Students will also examine how the special properties of colloids contribute to the retention of contaminants.

Materials:
Funnels, funnel rack, test tubes, test tube rack, medium speed filter paper (e.g. Whatman no.2)
Soil samples collected in the field
0.2% bentonite suspension: slowly sift 2g bentonite into 1000mL deionized water while vigorously stirring
Bentonite and kaolinite clay in dry powder form
Petri dish, 60 x 15 mm
500mL plastic beakers, spatula
Balance
Solutions: dissolve the following amount of chemical in deionized water. Bring to 1000mL volume.
        0.02 N barium acetate: 2.55g Ba(C₂H₃O₂)₂
        Saturated potassium dichromate: 100g K₂Cr₂O₇
        0.2 N potassium chloride: 14.9g KCl
        N sodium chloride: 5.84gNaCl
        Saturated ammonium oxalate: 50g (NH₄)₂C₂O₄*2H₂O
        N potassium chloride: 7.46g KCl
        N hydrochloric acid: 8.3mL concentrated HCl
        N calcium chloride: 7.35g CaCl₂*2H₂O
        0.1 N magnesium chloride: 10.2g MgCl₂*6H₂O
        N aluminum chloride: 8.05g AlCl₃*6H₂O
        Dilute benzyltrimethylammonium chloride: 5g C₆H₅CH₂N(CH₃)₃Cl
        Exercises #8, pages 101-116, from Soil Science, by Thien and Graveel

Estimated Class Time Required: 3, 50 minute class periods

Introduction:

Teacher introduces topic and reviews experimental procedures, key terms and concepts with students. Key terms include cation, anion, cation exchange, and flocculation.

Both organic (humus) and mineral (clay) colloids have the ability to swell greatly with absorbed water because their constituent particles have large specific surface areas where they can store cations, such as calcium, Ca, magnesium, Mg, and potassium, K. Colloids, since they are negatively charged at their outer perimeters, repel other negatively charged particles and attract positive cations. Colloids greatly affect soil pH, by freeing excess hydrogen ions from water, and thus affect soil acidity.²⁵

Objective: Students will examine the mechanisms of soil acidity by using a pH meter, by using a displacing solution to extract hydrogen ions, and by applying fundamentals of neutralization reactions in acid-base chemistry.

Materials:
Soil samples
pH meter and standard solutions for pH calibration
small glass beakers or paper cups
filtration funnels
0.5 N barium acetate: dissolve 63.8g Ba(C₂H₃O₂)₂ in deionized water and bring to 1000mL volume
Phenolphthalein indicator: dissolve 0.5g phenolphthalein in 800mL ethyl alcohol and bring to a final volume with 1000mL deionized water
N sodium hydroxide: dissolve 0.4g NaOH in deionized water and bring to1000mL volume. Titrate against a standard acid solution to determine exact normality
Exercise #9, from Soil Science, pages 117-126, by Thien and Graveel

Estimated Class Time Required: 2, 50 minutes class periods

Introduction:

Teacher introduces topic, reviews key concepts, key terms, and experiment procedure with students prior to experiment. Key concepts include pH scale, acid-base chemical reactions and chemical equations. Key terms include acidity, basicity, buffer, buffering capacity, and neutralization reaction. Students should perform these experiments wearing safety goggles, chemistry aprons, and disposable gloves.

Soil acidity is measured by its pH, or level of exchangable hydrogen ions. Various soil chemical and biochemical activities, such as soil reactivity, plant availability, compound solubility, and toxicity are affected by soil acidity levels. Clays and/or organic matter serve as buffers in soils resisting change in pH. Optimal soil pH for most plant growth is 6.8pH, a slightly acidic soil. The pH of acidic soils can be altered by adding neutralizing agents, such as lime, calcium carbonate.²⁶

Objective: Students will perform experiments to determine soil salinity and sodicity.

Materials:
Balance
Three soil samples: normal, saline, and sodic, 100g each
Deionized water
pH meter, or pH indicator papers
Buchner funnel
Funnels, 3 per team
Ring stands, 3 per team
Medium speed filter paper
0.5% calcium chloride, CaCl₂, solution
0.5% sodium chloride, NaCl, solution
4mm sieve
Solid sodium chloride crystals
6, 1kg samples of normal soil
Various seeds: barley or bermuda grass (salt tolerant), oats, cabbage, or wheat (moderately salt tolerant), and red clover, tomato, or celery (low salt tolerant)
15 small clay or plastic pots
Exercise #11, pages 141-152, from Soil Science, by Thien and Graveel

Introduction:

Teacher introduces topic and reviews key concepts, key terms, and lab safety, with students. Students perform experiments in their respective teams.

Soil salinity, or too much soluble salt, can adversely affect plant growth in soils. Soil salinity also lessens water content. Sodicity, too many exchangable sodium ions, renders soils impermeable to air and water. Soil runoff and erosion can result. When poor quality irrigation water is used in dry climates, soil salinity can increase.

Salinity is a measure of high salt levels in soils formed by certain cations: calcium, Ca²⁺, magnesium, Mg²⁺, and sodium, Na⁺, forming compounds with anions: chloride, Cl^-, sulfate, SO₄^2-, and bicarbonate, HCO₃^-. Soil pH, in conjunction with an electrical conductivity test, measures the concentration of these saline ions in soils.

Soil salinity increases osmotic water tension and limits available soil water. Seeds that are trying to germinate have more difficulty extracting the water. In arid climates, salts can accumulate in soils because much of the water infiltrating into soils evaporates. Salinity in soils can increase soil pH and reduce other plant nutrients as well. ²⁷

Objective: Students will investigate, describe, and record the impact various human activities have on soils.

Materials:
South Valley map, 1 per team
Survey questions
Student field book

Introduction:
Teacher introduces topic briefly and brainstorms with students on possible sources of contamination in the South Valley. Teacher and students compile list on overhead and/or chalkboard. Teacher recommends that students conduct survey in their respective teams, work in assigned survey area, record information on maps and in field books, in daylight hours only, and that students should be polite while in other neighborhoods.

Possible contamination sources would include business dumping or littering, septic system leaks, industry pollution, illegal dumping and/or landfill, irrigated fields, animal wastes, and wastewater runoff.

Survey:

1. Describe the geographic location of your survey area, with respect to perimeter boundaries, and label on map and describe in your field books.
2. Are there any businesses and/or industry in your survey area? If so, describe and locate on your maps.
3. Do you find any evidence of contamination from older businesses in your survey area, ones that are no longer in operation? If so, describe and locate on your maps.
4. Do any of the residents in your survey area have animal enclosures, irrigated fields, orchards, or large gardens? Do you find evidence of excess fertilizer use or animal waste dumping? Describe and label on your survey map.
5. Do any of the residents have their own water wells and/or septic systems? Describe and locate on your map.
6. Do you find any other evidence of soil contamination? Describe and locate on your map.

Objective: Students will utilize soil maps to inventory and evaluate soils in their survey areas. Students will correlate their earlier experimental results with predictions of possible contaminant levels and sources in their respective survey areas.

Materials:

Soil Survey of Bernalillo County and Parts of Sandoval and Valencia Counties, New Mexico, published by the Natural Resources Conservation Service, U.S.          Department of Agriculture
Student field books and survey maps
Soil Survey report form

Estimated Class Time Required: 1-2, 50 minute class periods

Introduction:

Teacher introduces topic and demonstrates the use of soil maps. Teacher reviews key terms with students: map units, soil association, soil series, soil phases, and soil complex.

Students correlate their respective survey areas with soil maps to find the type of soils within their survey area. Students then compare their own experimental results with what contaminants they found in their areas, and predict how each soil type might contain and/or release contaminant.

Objectives: Students will test and evaluate an unknown sample of soil using their acquired lab skills. Students will also develop a model for tracking change in soil type with respect to predicted environmental impacts. Students will also develop a cost-risk benefit analysis in the context of environmental issues of soil contamination.

Materials:
Beakers, graduated cylinders, ring stands, and funnels
Medium weight filter paper
pH meter, or pH indicator papers
Munsell color chart
Unknown soil sample, in quantity
Various chemicals for testing soils (see appropriate lab for each relevant test)

Estimated Class Time Required: 2, 50 minute class periods

Introduction:
Teacher sets up 6 testing stations to examine unknown soil sample for one type of test at each of the following soil color, soil grain size, soil wetness, soil acidity, soil salinity, and soil composition (constituent grains, percentage of sand, silt, or clay, and organic matter content). The procedure for each station will be written on the examination. Only one student at a time should be at each station; students should rotate stations until all experiments have been performed. While at their desks, each student should work independently to answer other short essay questions on test. Essay questions should be representative of soils unit overall, require critical thinking skills, (such as evaluation, synthesis, and analysis), and should number minimum 6 to maximum 10.

Notes:

Bibliography

1.Anderson, Wes, Bancroft, Anne, Cully Anne, Ellis, Lisa, Graybill, Alice, Gunckel, Kristen, Hardage, Bill, Morris, Letitia, Parker, Don, Rosenthal, Laurie, Scheib, Gregory, Schneider, Maryann, Soergel, Heidi, Stolz, Gary M., Stever, Mary, Tierney, Gail, Tolisano, Jim, Trujillo, Diana, Trujillo, Don, Tydinga, Rebecca, Voldahl, Mary, and Woods, Ann, 1995, Bosque Education Guide, The Middle Rio Grande Initiative, U. S. Fish and Wildlife Service, Albuquerque, NM, pages 1-35.

2.Compton, Robert R., 1985, Geology in the Field, John Wiley and Sons, New York, NY, pages 197-217.

3.Cordell, Linda, 1996, "Heritage and Human Environment", Albuquerque’s Environmental Story, http://www.cabq.gov/aes/s3pueblo.html.

4.Hacker, Leroy W., 1977, Soil Survey of Bernalillo County and parts of Sandoval and Valencia counties, New Mexico, Natural Resources Conservation Service, U. S. Department of Agriculture, pages 1-8,88-97, and soil maps 30, 31, 40, 41,46, 47, 49, 50, and 54.

5.Hawley, John W., 1999, "Hydrogeologic Framework of the Rio Grande Rift Basins, Central and Southern New Mexico", New Mexico Bureau of Mines and Mineral Resources, New Mexico Tech, 2500 Yale Blvd, SE, Albuquerque, NM, abstract.

6.Herrera, Dolores, May 1999, "AT &SF Albuquerque Superfund Site, Update", San Jose Community Newsletter, Albuquerque San Jose Community Awareness Council, Inc, P. O. Box 12297, Albuquerque, NM, 87195-2297, Vol. 10, No. 19, pages 1-5

7.Ivey, Robert Dewitt, 1983, Flowering Plants of New Mexico, a Sketchbook, published by Author, 9311 Headingly Ct., NE, Albuquerque, NM, 87111, pages 40-187.

8.Keeney, Daniel, 1999, "Soil quality: A Call for Action", Conservation Voices, Soil and Water Conservation Society, 7515 NE, Ankeny Rd., Ankeny, Iowa, Vol. 12, Issue 2, page 4.

9.Kelly, Vincent C., 1977, Geology of the Albuquerque Basin, New Mexico Memoir 33, New Mexico Bureau of Mines and Mineral Resources, New Mexico Tech, Socorro, NM, pages 7-54.

10.Leeder, M. R., 1982, Sedimentology, Process and Product, George Allen and Unwin, Boston, MA, pages 35-43, 67.

11.Logan, William Bryant, 1992, "Ecstatic Skin of the Earth", Conservation Voices, Soil and Water Conservation Society, 7515 NE, Ankeny Road, Ankeny, Iowa, Vol. 12, Issue, 2, pages 16-17.

12.Logan, William Bryant, 1992, "Hans Jenny and the Pygmy Forest", Orion, The Myrin Institute, 136 east 64^th St., New York, NY, 10021, Vol. 11, No. 2, pages17-29.

13.McAuliffe, Joseph R., 1999, "Desert Soils", Desert Botanical Garden publication, Phoenix, AZ, pages 1-24.

14.Merritts, Dorothy, DeWet, Andrew, and Menking, Kirsten, 1997, Environmental Geology, W.H. Freeman and Company, New York, NY, pages 1-188, 220-227.

15.Molles, Jr., Manuel C., 1999, Ecology, Concepts and Applications, McGraw Hill Boston, MASS, pages 1-99.

16.Pazzaglia, Frank J., Woodward, Lee A., Lucas, Spencer G., Anderson, Orin J., Wegmann, Karl W., and Estep, John, 1999, Phanerozoic Geologic Evolution of the Albuquerque Area, 1999, in press, pages 1-25, and Figures A-J.

17.Ritter, Dale, F., 1985, Process Geomorphology, Wm. C. Brown Publishers, Dubuque, IA, pages 84-125, 138-152, 153-204, 220-227.

18.Rosner, Hy and Joan, 1996, "The Albuquerque Environmental Story", http://www.cabq.gov/aes.

19.Stuart, Kevin, 1992, "A Life with the Soil: A Conservation with Hans Jenny", Orion, The Myrin Institute, 136 east 64^th St., New York, NY, 10021, Vol. 11, No.2, pages 30-35.

20.Thein, Steven J., and Graveel, John G., 1997, Soil Science, Agricultural and Environmental Principles, Wm. C. Brown Publishers, Dubuque, IA, pages 1-218.

1.Hacker, Leroy W., 1977, Soil Survey of Bernalillo County and Parts of Sandoval and Valencia Counties, New Mexico, Natural Resource Conservation Service, U.S. Department of Agriculture.

2.Ivey, Robert Dewitt, 1983, Flowering Plants of New Mexico, published by author, 9311 Headingly Ct., NE, Albuquerque, NM, 87111.

3.Merritts, Dorothy, DeWet, Andrew, and Menking, Kirsten, 1997, Environmental Geology, W. H. Freeman and Company, New York, NY.

4.Molles, Jr., Manuel C., 1999, Ecology, Concepts and Applications, McGraw Hill, Boston, MASS.

5.Pazzaglia, Frank J., Woodward, Lee A., Lucas, Spencer G., Anderson, Orin J., Wegmenn, Karl W., and Estep, John, 1999, Phanerozoic Geologic Evolution of The Albuquerque Area, in press. (Guidebook for Geology Conference, Albuquerque, NM, September, 1999).

6.Thein, Steven J., and Graveel, John G., 1997, Soil Science, Agricultural and Environmental Principles, Wm. C. Brown Publishers, Dubuque, IA.

1.High School Geology Text, relevant chapters on physical and chemical weathering processes, mineral composition, water movement.

2.Merritts, Dorothy, DeWet, Andrew, and Menking, Kirsten, 1997, "Soils, Chapter 6", Environmental Geology, W. H. Freeman and Company, Boston, MASS, pages 158-188.

Munsell Color Chart
Bouyoucos hydrometer
Sedimentation cylinder
Mechanical mixer with stirrer
Soil shovels, 6-8 count (small garden trowel or shovel)
Soil thermometers, 6-8 count
Hand lens, 6-8 count
Balances, 6-8 count
Sieves, assorted mesh, from coarse ,4, to fine, 300
Assorted chemistry glassware: beakers, graduated cylinders, funnels, Erlenmeyer flasks,
Ring Stands, 12-18 count
pH meter, or pH indicator papers
City and Soil Survey maps
Geology hammers, optional
Chemicals (note: a complete list of chemicals, for each experiment, is written with each lesson plan involving experiments)
Deionized water, in quantity
Chemistry aprons, safety goggles, and disposable gloves

One important reason for examining the geological framework is that such understanding can determine the composition and source of parent rock material. Such investigations require an elementary understanding of the varied and complex geological processes that have shaped the New Mexico of today. Indeed, many of these processes are still active and ongoing.

The oldest rocks in New Mexico formed about 1.4-1.8 Ga, (Giga annum, 1Ga = 1 billion years). These Precambrian granites can be seen in the Sandias, east of Albuquerque, and in other mountains in New Mexico. When first deposited in the earth’s lithosphere, these granites formed a craton, an ancient continental crust of basement rock.The Sandia Granite today provides much of the quartz, feldspar, and biotite rock parent material for basin soils.²⁸

After a gap, or unconformity of over 1Ga, the next rocks to be deposited and which remained in the Albuquerque area were marine limestones and shales of the Paleozoic Era, some 300Ma, (Million annum, 1MA = 1 million years). The Madera Shale can be seen capping the Sandia Granites; it provides calcium carbonate rock fragments. During the Paleozoic, there were, also, a series of uplifts, folding and faulting of rock layers, of the continental crust, and New Mexico began to develop a more varied topography. In certain areas, the crust began to sink, or subside.²⁹

During the Triassic Period, of the Mesozoic Era, eastward flowing rivers in the western part of the state began to deposit sandstones, siltstones, and mudstones in much of New Mexico. The Chinle Formation of this period left behind some very distinctive red sand, silt and clay deposits. ³⁰

During the Jurassic Period, much of western New Mexico was covered by a vast desert, which produced coarse sands. The Entrada, Todilto, and Morrison Formations form large cliff faces of Jurassic sands in western New Mexico. Some of these further eroded Jurassic sands have been deposited on the Llano de Albuquerque, west of the Albuquerque Basin. ³¹

During the Cretaceous Period that followed, there was relatively little tectonic activity of rock folding and faulting. Much of central and eastern New Mexico was covered by a vast inland sea, the Western Interior Seaway. As the sea alternately rose and fell, it deposited limestones, siltstones and shales. ³²

At the end of the Cretaceous period and the beginning of the Cenozoic period, there was a major episode of mountain building, called the Laramide Orogeny, in which the Rocky Mountains were formed. The Sangre de Cristo Mountains, in northern New Mexico, were also formed at this time.³³

During the Oligocene Epoch, of the Cenozoic, some 30Ma, there was considerable volcanism in New Mexico, in which rocks of the San Juan Mountains formed. At the end of this epoch, some 30Ma, the crust of the Albuquerque Basin area was subject to stretching and thinning stresses, which produced basins. As sediments began to accumulate in these basins, the crust subsided even further. ³⁴

Also during the Oligocene, the entire continental crust of the southwestern area of the United States began to undergo stretching in some areas and compression in others, which resulted in a series of generally north-south trending series of fault blocks alternating with upthrust blocks, and produced what is known as basin and range. In the Albuquerque Basin, a series of north-south trending faults pushed up the Precambrian Granite and Madera Limestone of the Sandia Mountains. The downdropped blocks of the Albuquerque Basin dip more to the east. Overall, the difference in elevation was 20,000 feet, from the top of the Sandias’ Madera Limestone, at over 10,000 feet in elevation, to the same Madera Limestone rock strata buried some 10,000 feet below basin sand and gravel fill.³⁵

Beginning in the Miocene, the Albuquerque Basin continued to subside from sediment infill from a variety of waterborne sources: tributary stream, floodplain, river, lacustrine, and piedmont. Collectively, these deposits form the lower part of the Santa Fe Group, which became an aquifer. The water trapped within the lower Santa Fe Group is more saline and not as potable as the water trapped in the upper part of the Santa Fe Group, of Pliocene and Pleistocene sand and gravel. ³⁶

During the late Cenozoic Period, several major volcanic events also occurred in New Mexico, producing varied mountain peaks, claderas, cinder cones and extensive lava flows. A series of mafic basalt flows produced the Santa Anna Benches, some 2.5Ma. The Jemez Mountains, for example, were produced by several successive eruptions during this time, between 1.6-1.8 Ma; one of the more spectacular was the pyroclastic flows which produced the Bandelier Tuff, that formed the Pajarito Plateau upon which Los Alamos is located. Today, the Jemez Mountains are not only the watershed for the Albuquerque Basin, but also provide a lot of parent rock material as well. As recently as 150-160 ka (ka = thousand annum), a series of mafic basalt flows erupted into fault fissures on the western flank of the Albuquerque Basin, again producing a large volume of parent rock material for the basin.³⁷

Alternating with these volcanic eruptions were a series of major depositional events, as the ancient Rio Grande River alternately deposited sediments and excised those sediments. The Sierra Ladrones Formation, of late Miocene to Pleistocene Epoch, forms the upper part of the Santa Fe Group and fills the Albuquerque Basin. It contains varied deposits, from coarsest cross-bedded sandstones with cobble sized grains, to very fine floodplain silts and clays. ³⁸

Up until about 1 Ma, the ancient Rio Grande River did not flow through New Mexico completely, as it does today. During a Pleistocene interglacial warming period, the discharge of headwaters into the Rio Grande increased dramatically, and the ancient river broke through the earlier delta fans it had deposited in the Miocene. The ancient river flowed through many channels, creating a braided stream of several channels, and depositing sands and gravels in broad alluvial terraces, that one can see flanking the current river basin.³⁹

Today, the Rio Grande River still deposits sands, silts, and clays in the Albuquerque Basin. It also is a source of major recharge of the aquifer underlying the city. Unfortunately, as the city has grown along the river, so has the environmental impact of man. The Rio Grande River of today is a very pollution tolerant river, with many introduced species; indigenous species are rapidly disappearing from the Bosque riparian community.⁴⁰

The Albuquerque Basin soils provide the framework for several different biotas, or life zones, in which different plant and animal communities occur in both undisturbed and disturbed areas.

"A natural plant community is the product of all environmental factors, including, but not limited to, climate, soil, and topography". ⁴¹

Excepting the area immediately adjacent to the Rio Grande River, most plant cover is sparse, and usually doesn’t exceed 20%. Evaporation rates are high, precipitation is low, usually 7-14 inches per annum. When vegetation is disturbed, severe erosion results, both from seasonal runoff and blowout by high winds. Agriculture and grazing, too, have removed topsoil layers and much-needed groundcover, which stabilizes slopes.⁴²

The Albuquerque Basin varies in elevation from 4,850-7,000 feet, from steppe, shrub grassland, to pygmy pinyon-juniper on the eastern foothills of the Sandia, Manzanito, and Manzano Mountains. The life zone is generally lower and upper Sonoran.⁴³

The Rio Grande River course is heavily vegetated with riparian cottonwood community, referred to as the Bosque. Along the river course are groves of tamarisk, Russian olive, and several species of willows, in addition to the cottonwoods. In marshes adjacent to the river grow saltgrasses and herbaceous plants. These bottomlands are composed of saline, alkalai, silty clay-loams, silty clays, sandy loams, and loamy sands. Grasses and shrubs include blue grass, western wheatgrass, tobosa, galleta, burrograss, inland saltgrass, and mat muhly. The most abundant shrub is fourwing saltbush.⁴⁴

The Bosque supports an abundance of wildlife and all orders of animals are represented. Migratory and resident birds occur in large flocks. Insects, amphibians, reptiles, and small mammals are plentiful. Many of these species, however, are introduced and are not only more pollution tolerant, but are highly competitive and tend to take over the equivalent niches occupied by rarer, indigenous species.⁴⁵

On terraces flanking either side of the river, some 4,850-6,000 feet elevation, are soils that are sandy, silty, and or loamy in composition. Again, the plant community is a grassland shrub mixture. Dominant plants include Indian ricegrass, blackgrama, various dropseed species, galleta, muhy, and bluestem and bluegrama. These grasses provide 75% of the much needed groundcover for loose, unconsolidated soils. The dominant shrub is sand sagebrush.⁴⁶

The West Mesa is associated with shallow, cobbly, sandy loams, and ranges in elevation from 5,200-5,800 feet. The sparse vegetation cover consists primarily of grasses: galleta, black grama, varies dropseed species, bottlebrush, squirreltail, Indian ricegrass, bush muhly, silver bluestem, three awn, and sideoats grass. The most common shrubs are fourwing saltbush, winterfat, and wolfberry. Creosote, broom snakeweed, althorn, and rubber rabbitbrush are found in some areas. This area receives the least rainfall in the entire Albuquerque Basin, only 7-10 inches per annum.⁴⁷

Where vegetation is still relatively undisturbed, animal life includes many species of snakes, lizards, small mammals and insects, and other arthropods.

The alluvial fans and piedmont terraces east of the Rio Grande River, some 5,000-7,000 feet in elevation, are composed of sandy loams and loamy fine sands, much of it unconsolidated. The dominant grasses are Indian ricegrass, black grama, various dropseed species, New Mexico feathergrass, and galleta. Shrubs include fourwing saltbush, winterfat, wolfberry, Morman tea, and soapweed. ⁴⁸ Pygmy pinyon- juniper woodland covers many undisturbed slopes, from 6,000-7,000 feet, part of the upper Sonoran lifezone.⁴⁹

In addition to supporting many vertebrate species, the soils of the Albuquerque Basin support much invertebrate live below ground level.

"Soils contain over a thousand different species of lower animals, the earthworms, pill bugs, nematodes, millipedes, termites, ants, and amoebas, not to mention the millions of molds and bacteria."…"When I add up the live weight, exclusive of roots, I find more living biomass below ground than above it."⁵⁰