The College Board requires the AP Environmental Science course to have a laboratory and field investigation component that will complement students’ learning about the environment. Although there is no formal lab manual for the course, teachers are expected to provide lab experiences that ultimately incorporate test concepts and principles learned throughout the course. These experiences must also help you design experiments, collect data, apply mathematical routines and methods, and refine testable explanations and predictions.

• The variety of different labs that can be performed gives students opportunities to explore various topics in environmental science; this also allows instructors the freedom to adapt their course laboratories to their geographic locations, which can make the course more interesting for students.

• On the AP Environmental Science Exam, you could be asked a number of different types of questions in which the lab component from your class will be helpful.

• However, you won’t be able to get full credit simply by remembering the details of what you did in a particular lab. You will have to use your critical thinking skills to answer these questions.

SOME COMMON AP ENVIRONMENTAL SCIENCE LABS

Below, we’ve listed some of the common labs performed during an AP Environmental Science course, a summary of the procedures you might follow, and the take-home message of each.

Remember that each AP Environmental Science course is different; you may have performed some of these labs, but you probably have not completed all of them. It’s a good idea to review all of these labs and understand their basic workings as well as their intent.

Soil Analysis Lab

• Soil Testing Laboratory: In this lab, soil is tested for physical traits and chemical properties, which provide information about the soil’s condition and suitability for crops, septic fields, or other purposes. All of the factors tested are listed below.

Chemical Properties

• pH—Clay soil requires more lime (calcium oxide) or alum (aluminum sulfate) to alter its pH than do sandy or loam soils. Iron necessary for plant growth is unavailable when the soil becomes alkaline. Gymnosperms (pine, fir, etc.) grow better in mildly acidic soil.

• Nitrogen—common plant nutrient component

• Phosphorus—common plant nutrient component

• Potash—common name for a compound that contains one of the potassium oxides

Physical Characteristics

• Soil type—Sand, silt, clay. Use mesh screen, cheese cloth, and soil settling in water tubes to determine the percent of each type of particle in the sample.

• Water-holding capacity—Because of the small pores between clay particles, water moves very slowly through clay. Therefore, clay has a greater holding capacity than silt or sand.

• Permeability—the movement of gas or liquid through the soil

• Friability—Good soil is rich, light, and easily worked with fingers, which is good for plant growth because roots can easily grow through it.

• Percent humus—A measure of soluble organic constituents of soil; the higher the number, the better. Organic soil has qualities of both sand and clay.

• The small particles of organic soil come together to form larger clusters. Water can be retained inside a cluster, but can move between clusters to percolate. Organic material is also high in nutrients.

• Buffering capacity—Resilience of different types of bedrock, such as marble, granite, and basalt, when exposed to acid. Marble has high calcium content and is a better buffer than other rocks.

Water Analysis Lab

Water Chemical and Physical Analysis: Water can be tested from many different sources. Sample kits have tools for many different tests—for example, the LaMotte kit and the spectrophotometer type kit. Below are some commonly performed tests and some of the expected results. It is probably not necessary for you to memorize all the standards, but you should be familiar with them.

• pH—Normal pH of water is between 6.5–8.5.

• DO—Measure of dissolved oxygen in water. Warm-water fish require a minimum of 4 ppm and cold-water fish require 5 ppm.

• Turbidity—Measurement of water clarity. Higher turbidity means there will be low clarity, and little sunlight will be able to penetrate the water. A Secchi Disk may be used to measure turbidity, but a more accurate measure can be made with a turbidity unit.

• Phosphate—An important plant nutrient, typically found in fertilizer and runoff from agricultural lands. Too much leads to eutrophication of water, high BOD, and low DO levels. Levels should not exceed 0.025 mg/L in still water and 0.05 mg/L in flowing water.

• Measure of compounds that shift the pH toward the alkaline. There are no EPA standards, but normal is between 100–250 ppm.

• BOD—Biological oxygen demand, which is required for the aerobic organisms in a body of water. Unpolluted natural waters have a concentration of 5 mg/L or less. High nutrient levels or lots of biological material ready for decomposition are associated with high BOD, and vice versa.

• Chlorine—EPA standards dictate that Cl cannot exceed 250 mg/L. NaCl is applied to roads and parking lots and can run off into streams. Other sources of excess Cl are animal waste, potash fertilizer (KCl), and septic tank effluent. Chlorine is associated with limestone deposits but is not common in other soils, rocks, or minerals.

• Hardness—A measure of salts composed of calcium, magnesium, or iron. Most water testing kits test for CaCl2. Hard water is more than 121 ppm, and soft water is less than 20 ppm.

• Iron—Normal range is 0.1–0.5 ppm.

• Nitrates—As an important plant nutrient, nitrogen is typically found in fertilizer and is a component of runoff from agricultural lands. Too much leads to eutrophication of water, high BOD, and low DO levels. Over 0.10 mg/L is considered elevated, and the EPA limit is 10 mg/L.

• Total solids—Weight of the suspended solids and dissolved solids. All natural waters have some suspended solids, but problem solids are sewage, industrial waste, or excess amounts of algae.

• Total dissolved solids—Naturally occurring in water, but may cause an objectionable taste in drinking water. They are also unsuitable for irrigation because they leave a salt residue on the soil. EPA standard is 500 mg/L, but dissolved solids may range from 20–2,000 mg/L.

• Fecal coliform—Any bacteria that ferments lactose and produces gas when grown in lactose broth. New tests for this are performed by adding a water sample to a specialized media and observing color changes. Drinking water should show no colonies of growth from the water sample.

Air Quality Labs

• Air Quality: Air quality can be assessed using various methods.

• Particulates: Sticky paper can be used to collect air particulates from various sources, and then the paper can be examined under a microscope. It is not possible to see the smallest particulates, but they do color the white paper.

• Ozone: In this lab, an eco badge or a homemade potassium iodide gel sampler is hung or worn in order to collect data on tropospheric ozone. The badge or KI sample changes color in the presence of ozone and becomes more intensely colored as the amount of ozone increases.

• Carbon Dioxide: In this lab, a commercial sampling device is used to determine the amount of carbon dioxide in an air sample. Car exhaust, burning tobacco, or other pollutants can also be sampled.

• Lichen: A lichen survey can be used to judge air quality. Lichens are sensitive to air pollution, particularly sulfur dioxide. The most sensitive lichens are the fruticose types, followed by the foliose, and then the crustose.

• Scrubber Model: A model of a scrubber can be constructed to attempt to remove sulfur contaminates from burning coal. A calcium compound can be used to try to wash the contaminant from the air column.

Biodiversity of Invertebrates: Insects can be counted in an area and then plotted to assess biodiversity. Traps such as fall traps or sticky traps can be set, and bait such as tuna or sugars can be used. The number of different insects captured is counted, and this number divided into the total number captured would give an idea of the biodiversity of the area. A taxonomic key can be used to determine the number of species and their taxonomic name. A similar setup can be used to determine the impact of an invasive species. In this process, native bugs can be trapped and set up in terrariums; the invasive species is then introduced and the effects documented.

• Energy Audit: In this lab, students are asked to use their homes as a laboratory and perform an energy audit, examining the amount of electricity used by their families over a set period of time and then using appliance standards to determine which is the largest energy consumer. A result of this lab is that students suggest how their family’s electrical energy needs could be reduced.

• Food Chain: In this lab, students observe a natural ecosystem and examine the food chain. They identify the organisms that are producers, primary consumers, and secondary consumers and determine how many levels make up the food chain, what organisms act as decomposers, and the presence of symbiotic relationships.

• Mining: Students can construct a model of a mine, representing the rock layers and the mineral deposits.

• Population Growth: Population growth experiments can involve fast-growing populations such as bacteria, duckweed (Lemma minor), roly-polies (sowbugs), or fruit flies (Drosophila) and can involve graphing, as does the analysis of human population data. Population growth can be graphed, with time along the x-axis and population growth on the y-axis. Initially, the curve is a J shape, but it becomes S-shaped. Bacterial growth curves have an extended hook on the J due to the lag time in growth as the bacteria acclimate to the new media.

• Variables: In population growth experiments, often other variables are added to samples of bacteria to compare the growth of a normal population to one that has been altered in some way. This can be used to assess the effect of extra nutrients, such as nitrogen or phosphorus, or the negative effects of certain substances on the organism.

• Turbidity and Bacteria: When studying bacteria, turbidity is commonly observed and recorded. The more turbid (cloudy) the tube, the more growth has taken place. Turbidity can be observed with a spectrophotometer. When the sample tube is inserted into the spectrophotometer, the instrument passes light through the sample tube and measures the amount of light that passed through or was absorbed.

• Population Size: In this type of lab, the size of a population of species such as the gypsy moth, caterpillar, or other insect is studied. Remember that a population is a group of individuals of the same species located in a given area. The experiment can involve a collection box and colored stickers that attract caterpillars. The first day, caterpillars are captured and marked. On the second day, the caterpillars are captured and the new and recaptured individuals are marked. By dividing the number of recaptured insects by the size of the population on day one, an estimate of the population that was originally captured can be obtained. On day three, the total number of caterpillars captured is counted. The total number of caterpillars captured on day