Mercury in the Environment: Thinking critically about environmental contaminants

Outline

• Mercury background (5 mins)

• Activity 1: Distribution of mercury in the U.S. (10-15 mins)

• Activity 2: Understanding bioaccumulation (10-15 mins)

• Presentation and discussion (5-10 mins)

Teaching standards

• Common core standards– Hypothesis testing– Write informative/explanatory texts– Conduct short research projects to answer a question

• Environmental science standards– Recognize that humans are part of the global ecosystem

and evaluate the effects of human activities on ecosystems• Next generation science standards– Develop quantitative models to describe elemental cycling

What is Mercury?

• Silvery, liquid metal at room temperature

• Heavy metal

• Highly toxic

• Does not break down into less toxic substances

What are the sources of mercury to the environment?

• Natural– Volcanoes– Weathering of rocks

• Anthropogenic sources– Burning of fossil fuels in

industry– Smelting metals– Use in mining operations

What factors regulate movement of mercury once in the environment?

• Wind

• Humidity

• Temperature

• Precipitation

• Others?

Activity 1

Distribution of mercury in the U.S.

Handout 1 questions

• Which state(s) do you think have the biggest problem with atmospheric mercury?

• Why?

Handout 2 questions

• How do you explain the observed pattern of atmospheric mercury?

• How does the atmospheric map/distribution of mercury compare to the fish advisories map?

• Why would a state like New Mexico have high fish advisories with little atmospheric mercury?

Activity 1 outcomes

• Students should see that atmospheric deposition of mercury (and other pollutants) are higher around urban centers.

• The fish advisories map shows that much of the atmospheric mercury is deposited west of these large cities due to prevailing winds and precipitation.

How do organisms in the environment interact with mercury?

• Biotransformation– Microbes convert elemental

mercury to more or less toxic form?

• Methylmercury– More toxic– Taken up by primary

producers

What happens once mercury is in the food chain?

• Bioaccumulation

• What is the relationship between trophic level and mercury concentration?

Activity 2

Understanding bioaccumulation

Activity 2 questions

• What are some ways mercury might get into your local ecosystem?

• Which organisms in your food web would you expect to have the highest concentration of mercury? Why?

Activity 2 outcomes

• Students should demonstrate an understanding of biotransformation, bioaccumulation, and be able to describe how trophic status influences accumulation of toxic compounds like mercury.