Urban Ecology

How do scientists study the environment?

by David Wright

The world around us is called the environment. Our environment is filled with things to study. Physical scientists study the non-living parts of the environment. Life scientists study the living things. Ecologists study the relationships between the living and non-living things.

All scientists use a special tool when they study. That tool is called the scientific method. It kind of works like this:

Step 1: Ask a question.
The goal of the research is to answer this question: Does mercury pollute the environment?

Step 2: Explain why this question is important.
If mercury harms the environment, we need to be careful with how we use and discard mercury.

Step 3: In general terms, describe the system to be studied.
In this case, the environment and pollution are the system.

The environment provides all that we consume. It receives all that we discard. The environment is made of energy, air, water, land and living things.

Pollution is anything that harms the environment. Pollutants come from natural and human sources. Most pollutants circulate widely. They can become diluted in the air, water, and soil. Most pollutants are present in trace amounts. But even small amounts of very toxic substances can be harmful. And some pollutants can build up in the food chain. This is called bioaccumulation.

Step 4: Describe the topic.
Mercury is a toxic metal. It is a liquid at room temperature and evaporates quickly when heated. Mercury is extracted from the mineral cinnabar. It reacts with other metals to form amalgams. It also reacts with other substances to form compounds that can be very toxic. When handled properly, mercury and its compounds are safe. However, accidental spills or improper disposal can release mercury into the environment.

Step 5: Select a site to study and collect samples.
A good study site might be a lake near a factory where large amounts of mercury are used.

Scientists often collect many samples over time so they may observe changes in the environment. Sometimes nature does the sampling for us. In animals and people, hair absorbs substances from the body as it grows. These substances provide a record of any contamination in the recent past.

Scientists collect samples of the air, water, soil and plants. They also collect tissue, fluids, or hair from animals and people. Each sample is stored in a clean container and labeled with the date, time, and location. The condition of plants and animals are recorded. If people are tested, the scientists describe where these people live, what they do, and how they feel.

Step 6: Examine the samples. In this case, analyze them for mercury.
Samples are tested in a laboratory. Experts decide which testing methods to use for each kind of sample. In some cases, samples can be tested at the collection site with portable scientific instruments.

Step 7: Understand the results.
Scientists use quantitative analysis to measure how much mercury is present in a sample.

When testing air, the concentration is reported in micrograms of mercury per cubic meter of air (µg/m3). A microgram is one one-millionth of gram. A paperclip weighs about one gram.

Mercury levels in air are usually less than 0.02 µg/m3. Near active volcanoes, mercury levels in the air might be as high as 18 micrograms per cubic meter. In cinnabar mines with poor ventilation, mercury levels can climb to 5,000 micrograms per cubic meter!

When testing water, soil, plants, and animals, mercury levels are reported in micrograms of mercury per kilogram of sample (µg/kg). One µg/kg is one part-per-billion (ppb). Natural waters usually contain less than 0.01 ppb of mercury. However, the sediment in the bottom of a contaminated lake may have levels as high as 250 ppb. In contaminated fish, levels have been as high as 10,000 ppb. Hair samples from people who ate these fish and became sick had levels as high as 500,000 ppb!

Scientists use qualitative analysis to identify what forms of mercury are present.

Air samples may contain mercury vapor or microscopic droplets of liquid (mercury dust) floating in the air. Air may also contain compounds that evaporate easily. Water may contain very small amounts of mercury compounds that dissolve slightly in water. Soil may contain mercury metal and compounds of mercury. Mercury can accumulate in plants, animals and people.

Step 8: Summarize the results.
Mercury is not normally present in the environment. But in contaminated areas, mercury may be present in air, water, soil, plants, animals, and people. Mercury changes from one chemical form to another as it moves through the environment.

Certain bacteria convert mercury to deadly organo-mercury compounds. These compounds can accumulate in the food chain. Plants and animals can sicken and die. If people eat food that is tainted with mercury, they can become very sick for a long time.

Step 9: Answer the question.
If present, mercury and its compounds pollute the environment. This pollution harms living things.

Make a recommendation based on this answer.
We should avoid releasing mercury to the environment.

Share all information with other scientists.
Scientists describe their research at meetings and in written reports. Other scientists review the work to be sure it was done properly. Scientists all over the world read the published reports. They might try the same study in other locations. Or, they might try a brand new study of the environment.

Step 10: Ask another question! Good science always raises new questions to explore.

David Wright is an associate research professional at ASU’s Center for Solid State Science. He visits schools throughout Arizona doing demonstrations as part of the Science is Fun! program.