How are chemical reactions used to remediate environmental effects of chemical spills?
When the deep-sea oil well blew out in the Gulf 2 years ago, one of the control methods was to spray the spreading slicks with chemicals, since the water was too rough to contain the spill with booms. The chemicals broke down the oil into less toxic tar and hydrocarbons, making the spill easier to clean up, and minimizing the damage to the environment.
Spills of Mercury, Arsenic, and other poisonous substances usually involve hard to contain water soluble compounds containing these elements. Exposing these compounds to other more reactive metals result in displacement reactions that change their forms into insolubles, that are easier to track, and collect, minimizing how much of the poison gets into the environment.