Water PollutionPart 2

Mercury

I can …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

Mercury is a well-known environmental pollutant.

While it has many uses, it has serious health effects when released into the environment.

Human health can be affected when people consume animals exposed to mercury.

What is Mercury?

Fish are often found to be contaminated with mercury.

Fish can be found in streams, wetlands, reservoirs and lakes can have high levels of mercury in their flesh.

A majority of states have issued fish consumption advisories.

What sorts of organisms contain Mercury?

Mercury contamination can be found even in fish from remote lakes.

How are these fish becoming so contaminated when the atmospheric levels of mercury is so low?

So, how are fish in these lakes becoming 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

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

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 plankton

How does mercury enter the food chain?

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

Human sources◦ Coal combustion◦ Waste incineration◦ Metal processing

Sources of Mercury

Human activities have doubled or tripled mercury levels.

This also is increasing by about 1.5% per year

Current levels of Mercury

If emissions could be reduced by 5%, it would take 8 years for changes in fish concentrations would be observed, but the changes would be small.

Due to the bioaccumulation and biomagnification of mercury, this problem will take a long time to be solved.

What can we do to help?

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

Reference