You would die
mercury
Water pollution; it is important to know the quantity spilled, the possibility of dilution, the estimated concentration, if it is irradiated uranium, etc.
the amount of dissolved oxygen would decrease.
The river would flood cities near the Mississippi River.
it falls lol
well first of all if there is too much irrigation the river would get dirty and animals would die
For Benzene exposure, the medical attention you would need is to go a hospital immediately. At the moment, there is no antidote for Benzene exposure.
If you could add a pair of hydrogen ions to any double bond of the benzene ring it would not be benzene anymore, on the one hand.
If your topic is oil spills in the ocean 'How was oil spilled in the Mississippi River?' is not a good question to ask.
it can be pollution
The river would flood downstream.