Water PollutionMercury

Explain how the accumulation of mercury, phosphates and nitrates affects the quality of water and the organisms that live in rivers, lakes and oceans.

D24

I can explain why mercury pollution is a problem.

I can differentiate between bioaccumulation and biomagnification.

Learning Targets

An element on the periodic table Metal in a liquid state Has many uses Has serious health effects when released

into the environment

What is Mercury?

Natural Sources◦ Volcanoes◦ Natural mercury deposits◦ Release from the oceans

Human sources◦ Coal combustion◦ Waste incineration◦ Metal processing

Sources of Mercury

How does mercury enter the food chain?

Mercury from power plants, waste incinerators, smelting plants and natural sources is released into the air.

These particles are released as rain drops, and deposited in soil or water.

These airborne particles can travel thousands of miles.

Bacteria take in inorganic mercury and convert it to a different form called methyl-mercury◦ This form is more toxic and is harder for

organisms to eliminate The bacteria release the methyl-mercury,

where it enters the food chain by being absorbed by phytoplankton

Fish

What organism is most likely to be contaminated with Hg?

How are these fish becoming so contaminated when the

atmospheric levels of mercury are so low?

OrHow do fish in remote lakes

become contaminated?

What does this mean?

This is the process by which organisms build up mercury in their bodies. They take in mercury more quickly than they can get rid of it.

Over time, the organism will accumulate mercury, until it can even reach toxic levels.

Mercury undergoes Bioaccumulation

Mercury increases at each step in a food chain, because each organism takes the mercury from the organism that it eatswhich has taken in the mercury from the organisms that it ate …and so on … and so on

It also undergoes Biomagnification

The highest levels of mercury are found at the highest levels of the food chain.

Bigger fish, older fish, and carnivorous fish will have the highest levels of mercury.

And, the mercury concentrates in the muscles of the fish, which is the part that humans eat

Biomagnification

Mild cases have the following symptoms:◦ Reduction in motor skills◦ Dulled sense of touch, taste and sight

Pregnant women should avoid ingesting mercury at all costs, as unborn babies are very sensitive to mercury poisoning.

Mercury Poisoning in Humans

Deterioration of the nervous system Impaired hearing, speech, vision Difficulty walking Tremors, or involuntary muscle movements Corrosion of skin and mucous membranes Difficulty with chewing and swallowing

Effects of more advanced mercury poisoning

How Are Animals Affected?

Mercury can accumulate in fish and in the food chains that they are part of.

The effects that mercury has on animals are kidney damage, stomach disruption, damage to intestines, reproductive failure and DNA alteration.

Human activities have doubled or tripled mercury levels.

This also is increasing by about 1.5% per year

Current levels of Mercury

Reduced the amount of coal use

Take part in Hazardous Household Waste Disposal days

What can we do to help?

Why is Hg pollution a problem? What is the difference between

bioaccumulation and biomagnification?

Learning Target Checkpoint

Krabbenhoft, D. P., & Rickert, D. A. (2008). Retrieved from U.S. Geological Survey website: http://pubs.usgs.gov/fs/1995/fs216-95

Reference