Ground water in its natural state tends to be relatively free of contaminants in most areas. Because it is a widely used source of drinking water, we must protect it.
Pesticides and herbicides applied to agricultural crops can find their way into ground water when rain or irrigation water leaches the poisons downward into the soil. Fertilizers are also a concern. Rain can also leach pollutants from city dumps into ground-water supplies, e. g. toxic mercury from a broken thermometer may eventually find its way to the ground-water supply. Heavy metals such as mercury, lead, chromium, copper, and cadmium, together with household chemicals and poisons, can all be concentrated in ground-water supplies beneath dumps. Liquid and solid wastes from septic tanks, sewage plants, and animal feed lots and slaughterhouses may contain bacteria, viruses, and parasites that can contaminate ground water. Liquid wastes from industries and military bases can be highly toxic, containing high concentrations of heavy metals and compounds. Deep wells may be safe for liquid waste disposal if they are deep enough, but contamination of drinking water supplies and even surface water has resulted in some localities from improper design of disposal wells. Acid mine drainage from coal and metal mines can contaminate both surface and ground water. It is usually caused by sulphuric acid formed by the oxidation of sulphur in pyrite and other sulphide minerals when they are exposed to air by mining activity. Fish and plants are often killed by the acid waters draining from long-abandoned mines. There must be a better way how to treat our nature...