Mercury and the Story of Grassy Narrows Flashcards
How does mercury get into the environment?
Burning of coal (atmospheric deposition). Flooded land (dams / hydro-electric developments). Metal refining (especially gold). Historic contamination from industries. [also volcanoes, forest fires, erosion of rocks that contain mercury]
How does mercury change when it gets into aquatic systems?
Mercury (Hg) is transformed into methyl mercury (MeHg), which makes it bioavailable and toxic.
Where does mercury methylation occur and what causes it?
Microbes methylate the mercury in the anoxic bottom sediments of the lake.
What is bioconcentration and bioaccumulation?
When a substance accumulates in tissues faster than it is excreted. Older, larger organisms accumulate more.
Concentration = from water.
Accumulation = from food and water.
What is biomagnification?
Animals higher in the food chain will have higher concentrations of a substance (i.e. mercury) from eating those lower in the food chain.
There are two fish of the exact same species, but one is twice the size of the other – which will have more mercury, the small or large fish?
Probably the large fish. It’s likely older and has consumed more prey therefore it has accumulated more mercury.
Would the concentration of mercury be higher in zooplankton or in pike (a predatory fish).
It would be much higher in the pike.
What did scientists do to a lake during the METAALICUS study?
They added tiny amounts of traceable mercury to a lake, its surrounding watershed, and a nearby wetland. In total, they added less than a teaspoon of mercury.
In the METAALICUS study, what was learned about how mercury gets into water and fish?
Mercury deposited onto land entered water bodies, converted to methyl mercury, and was taken up by fish. But the majority of mercury uptake was from mercury deposited directly onto bodies of water.
In the METAALICUS study, what happened when scientists stopped adding mercury to the environment? What happened to individuals already exposed to mercury?
Mercury concentrations decreased – most rapidly in smaller organisms and then in the higher trophic level organisms. However the concentrations in individual mercury-exposed fish in many cases, did not drop at all. Once in the muscle tissue methylated mercury tends to stay there for a while.
The amount of mercury released when land is flooded in the creation of reservoirs is dependent on… (two factors).
The amount of land flooded and its organic carbon content.
What can be done to reduce the environmental impacts of building dams?
Remove as much (or flood as little) organic matter as possible to reduces CO2 emissions and the amount of mercury released from such reservoirs.
How can hydroelectric reservoirs affect fish and surrounding communities?
After flooding, mercury increased significantly. Some commercial fisheries have been closed due to elevated mercury levels causing enormous social and economic disruption and problems especially for First Nation Communities.
It takes between ___-___ years or longer for mercury concentrations in fish to drop to levels experienced prior to flooding.
10-20 years.
How much mercury did The Reed Paper Company in Dryden Ontario dump into the Wabigoon River between 1962 and 1970?
9-10 metric tonnes of mercury due to their chlor-alkali pulping process.
What community was affected by the Reed Paper Company dumping mercury into the Wabigoon River?
Grassy Narrows First Nation, over 150km downstream of the paper mill.
How are the lakes and environment downstream of the Reed Paper Company mill affected today?
Mercury concentrations in water and sediments are lower, but still notably high. Also, sulphate and organic carbon currently released by the mill may increase the methylation rate of mercury and its accumulation in fish.
So the mill is still causing problems.
What are some symptoms of mercury poisoning? Try naming 5.
Numbness in extremities, mouth and nose. Constriction of visual field. Impaired hearing and muscle coordination. Slurred speech. Accelerated aging. Hysteria (emotional outbursts). Weak muscles. Brain damage. Coma, and death.
___% of the people in Grassy Narrows still have symptoms of mercury poisoning 50 years later (as of 2014).
90%
What disease have many people from Grassy Narrows been diagnosed with?
Minamata disease (which is caused by mercury poisoning).
What symptoms of mercury toxicity have people in Grassy Narrows experienced?
Premature death, effects on brain development, loss of muscle coordination, vision loss, slurred speech, tunnel vision, poorer youth mental health, more youth suicide attempts.
What were/are the societal effects of the mercury at Grassy Narrows and other issues the community faces?
They were forcibly moved (1961-1963) and affected by residential schools. Mercury in fish caused the main fishing lodge and fisheries to close making most people unemployed. Limited access to healthy food. Alcoholism. Lots of deaths due to homicide and drugs or alcohol. Very high suicide rate.
What did recent research on the concentration of mercury in sediments upstream and downstream of The “Reed Paper Company” show?
The mercury is continuing to be transported on clay particles – it is these that are being remobilized from contaminated riverbanks (?). Sediment concentrations still high in surface sediments, but not increasing.
