Environmental Science

Leaf traits can help students identify trees with a dichotomous key. A dichotomous key is a nature ID tool that works by choosing between two characteristics at each step. The word dichotomous comes from two Greek words that mean "to divide into two...

Forest tree density sampling can be done with the point-centered quarter method. This field method helps measure the density, frequency, and coverage of tree species in a forest. It also helps estimate how many individual trees are present, how often a tree species appears, how common it is compared with other trees, and the size of the trees.

The point-centered quarter method is useful because it is more efficient than standard plot analysis. In fixed-area plot sampling, only a small part of...

GIS helps map urban forests and the many trees found in cities. Urban forests include urban parks, street trees, landscaped boulevards, public gardens, river and coastal promenades, greenways, river corridors, wetlands, nature preserves, natural areas, shelterbelts of trees, and even working trees at industrial brownfield sites. These spaces are more than decoration. They are part of city infrastructure and support human life in ways similar to food, housing, and other public utilities.

Urban...

Proton exchange membrane fuel cells use hydrogen gas to make electric current. They are part of the search for cleaner energy sources that can help replace non-renewable fuels used for electricity, transportation, industry, and homes. The United States now uses about 97.5 quadrillion BTUs of energy each year, and about 90% still comes from non-renewable sources.

Hydrogen is one possible renewable energy carrier. It is abundant in the universe, but on Earth it is found in compounds such as...

Ethanol can be produced from plant waste such as corn stalks, leaves, and grasses. In this lab, cellulosic material is used as the feedstock, which means it is the starting plant material for the reaction. The process shows how biomass can be turned into a fuel product.

The material is first pretreated by grinding and heating it. It is then digested with enzymes, which break the material down further. Next, yeast ferments the sample and ethanol forms during the reaction.

Ethanol production is...

Food DNA can be tested for genetically modified material by using PCR and gel electrophoresis. This experiment shows how food DNA is identified so students can better understand the science behind GMOs and the concerns linked to health and environmental safety.

Polymerase chain reaction, or PCR, is used to amplify the DNA from food samples. Amplifying the DNA makes it possible to test for the presence of genetically modified DNA. The method gives a clear way to compare test foods with known...

Turbidity and total solids are two ways to measure water clarity in surface waters. Turbidity is an indirect measure. It shows how much light can pass through the water. Total solids are measured directly by weight and show the amount of solid particles suspended in the water.

High turbidity and high total solids can come from soil erosion, waste discharge, runoff, or changes in ecological communities. Algal growth and the abundance of benthic organisms can also disturb sediment and mix it...

Dissolved oxygen in surface water helps support life in lakes, rivers, and oceans. Fish, such as bluegill and bass, need it to survive. Decomposer species also depend on it to recycle biogeochemical materials in the ecosystem.

When dissolved oxygen drops below normal levels, water quality declines and organisms begin to die. Low oxygen can happen during eutrophication, when excess nutrients trigger a fast algal bloom. The bloom forms dense mats at the surface and blocks two key oxygen sources:...

Nitrogen and phosphorus are important nutrients in aquatic ecosystems. Water quality tests often monitor both because too much of either can create serious water quality problems.

Nitrogen in water is usually measured as nitrate, written as NO3-. Nitrate dissolves in water and is easily taken up by photosynthesizers such as algae. Phosphorus is usually measured as phosphate, written as PO43-. Phosphate can be found dissolved in water, and it also binds strongly to sediment particles.

When...

Tropospheric ozone is an air pollutant found in the lower atmosphere. It is a form of elemental oxygen, O3, made of three oxygen atoms in a highly reactive structure. In the troposphere, ozone contributes to photochemical smog and can harm people, plants, and materials.

Ozone also exists in the stratosphere, about 10 to 50 km above Earth’s surface. There, it forms the ozone layer and helps block harmful UV rays from reaching the ground. Tropospheric ozone is different because it occurs near...

Car exhaust releases nitrogen oxides, or NOx, that help drive smog formation in the lower atmosphere. In the troposphere, sunlight splits nitrogen dioxide (NO2) into nitric oxide (NO) and oxygen atoms. Those oxygen atoms then combine with O2 to make ozone (O3). Ozone can also react with NO to reform NO2 and O2, so this cycle does not create a net gain of ozone on its own.

Problems begin when fossil fuel combustion adds extra NO, NO2, and volatile organic compounds (VOCs) to the air. Motor...

Lead contamination in soil can be measured with atomic absorption spectroscopy. Lead is a naturally occurring element in soil, usually at 10 to 50 ppm. But soil near old paint, gasoline use, or industrial pollution can contain much higher levels. In some urban areas, lead can reach 10,000 ppm.

Lead stays in soil because it does not biodegrade. That makes it a long-term hazard. Children are at particular risk from lead exposure. Millions of children in the U.S. may contact soil that contains...

Carbon and nitrogen in soil can be measured by elemental analysis. Environmental samples such as soils are often studied for these two ecologically important elements. Scientists use these results to understand the elemental makeup of a material.

This method uses flash combustion to analyze the sample. The sample is oxidized with a catalyst in a high-temperature chamber. The combustion products are then reduced to nitrogen gas (N2) and carbon dioxide (CO2). A thermal conductivity detector...

Soil fertility can be measured by testing the macronutrients nitrogen, phosphorus, and potassium. These three nutrients are major parts of soil fertilizer, and their levels help show how well soil can support plant growth.

The experiment uses chemical extraction to pull each nutrient out of the soil and into a solution. Color-based reagents are then added to the extracted samples. The nutrients are analyzed by color and turbidity, which is the cloudiness of a solution, to estimate how much of...

Earthworm populations can be sampled from soil with mustard. The mustard draws Lumbricus terrestris earthworms up from deeper soil layers. This method lets scientists collect data without disturbing the landscape or using toxic chemicals.

After sampling, the earthworms are counted. The counts can then be used for data analysis and statistical testing. A bar graph and a student’s t-test help compare the results.

Monitoring earthworm populations is important in environmental science. Many...