Ground water is a resource found under the earth’s surface. Most ground water comes from rain and melting snow soaking into the ground. Water fills the spaces between rocks and soils, making an “aquifer”. About half of our nation’s drinking water comes from ground water. Most is supplied through public drinking water systems. But many families rely on private, household wells and use ground water as their source of fresh water. Ground water — its depth from the surface, quality for drinking water, and chance of being polluted — varies from place to place. Generally, the deeper the well, the better the ground water. The amount of new water flowing into the area also affects ground water quality.
Ground water may contain some natural impurities or contaminants, even with no human activity or pollution. Natural contaminants can come from many conditions in the watershed or in the ground. Water moving through underground rocks and soils may pick up magnesium, calcium and chlorides. Some ground water naturally contains dissolved elements such as arsenic, boron, selenium, or radon, a gas formed by the natural breakdown of radioactive uranium in soil. Whether these natural contaminants are health problems depends on the amount of the substance present.
The biggest concern for nitrates come if there is a pregnant woman in the residence, or plans for children in the near future. Regular testing for nitrate is also a good indicator of surface water contamination and potential bacterial contamination of well water. High nitrate is often an indicator of a nearby septic system.
Nitrates at a basic level are pollutants are found in human and animal wastes. Septic tanks can cause bacterial and nitrate pollution. So can large numbers of farm animals. Both septic systems and animal manures must be carefully managed to prevent pollution. Sanitary landfills and garbage dumps are also sources. Children and some adults are at extra risk when exposed to water-born bacteria. These include the elderly and people whose immune systems are weak due to AIDS or treatments for cancer. Fertilizers can add to nitrate problems. Nitrates cause a health threat in very young infants called “blue baby” syndrome. This condition disrupts oxygen flow in the blood.
The natural nitrate content of most ground water sources is below 0.1 mg/L, although a few natural sources have been found to contain as much as 3 mg/L. However, it is extremely rare for ground water to contain more than 10 mg/L, the drinking water standard set by EPA for nitrate-nitrogen. So regular approved testing for nitrates in well water is recommended.