Coal contains substantial amounts of mercury. When coal is burned to generate heat or electricity, the mercury is released into the atmosphere. Most of this mercury is eventually deposited in the ocean or other aquatic environments
What happens to the mercury once it is deposited in the ocean?
What will be an ideal response?
Answer: Answers could include a diagram similar to that shown in Figure 20.16 (page 645). In aquatic environments, bacteria convert mercury (Hg2+) into methylmercury (CH3Hg+) or dimethylmercury (CH3Hg+ CH3), which are extremely toxic and absorbs through the skin into the flesh of aquatic organisms (such as fish or sharks). These compounds bioaccumulate and are concentrated as they pass up the food chain, potentially causing problems for humans that eat large quantities of fish (such as large tuna, salmon, or sharks). Bacteria in anoxic environments can detoxify the methymercury compounds where they could be buried as mercuric sulfide (HgS). If the sediments are oxidized, the mercury will be released back into the overlying water.
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