Soil—Nature’s Freshwater Filter
Soil has been shown to remove metals, toxic chemicals, organic waste, and other contaminants from water that flows down through the ground. By the time the water settles in bedrock aquifers, it can even be safe to drink.
Physical Filtering
Sand and rock particles act like a fine sieve, catching some contaminants.
Biological Filtering
Microorganisms living in soil can neutralize substances that would otherwise be toxic to humans. Some bacteria can even break down toxic oils into carbon dioxide and water.
Chemical Filtering
Soils with a slight electric charge can capture toxic chemicals that have the opposite charge. Negatively charged clay particles, for instance, can remove positively charged particles of corrosive ammonium from water.