Some are very poisonous at low concentrations. Inorganic Chemicals Inorganic chemicals and mineral substances, solid matter, and metal salts commonly dissolve into water. They often come from mining and manufacturing industries, oil field operations, agriculture, and natural sources. They also corrode expensive water treatment equipment and increase the cost of boat maintenance. The major source of pollution from agriculture comes from surplus fertilizers in the runoff.
Fertilizers contain nitrogen and phosphorous that can cause large amounts of algae to grow.
The large algae blooms cover the water's surface. The algae die after they have used all of the nutrients. Once dead, they sink to the bottom where bacteria feed on them. The bacterial populations increase and use up most of the oxygen in the water. Once the free oxygen is gone, many aquatic animals die.