Nitrogen in Groundwater

Nitrate and nitrite are two types of nitrogen in groundwater that can create health concerns in drinking water.  The maximum contaminant levels (MCL), which are standards set by the United States Environmental Protection Agency (EPA) for drinking water quality is 10 milligrams per liter (mg/L) and 1 mg/l for nitrite.  Of the two types, nitrate is the form of nitrogen that is of greatest general concern in drinking water.

Nitrate is introduced into the environment in a number of ways including agricultural fertilizer, lawn fertilizers, septic systems, and domestic animals in residential areas, urban, and industrial areas. Because it is an important plant nutrient, nitrate is commonly applied on agricultural land in the form of inorganic fertilizer and animal manure or in the form of chemical fertilizer to lawns and landscaping.

While nitrate is an important nutrient for plants, it highly soluble in water and if not applied at an agronomic rate — a rate that matches the amount of nitrogen the plants need and will use — it can easily pass through the soil profile to the groundwater table. Once nitrate is in groundwater it persists. Nitrate in groundwater can increase in concentration over time, and it does not degrade.

Due to Indiana’s extensive use of fertilizers for agricultural, residential, and other landscaping related activities nitrate is a growing concern for groundwater quality statewide.  Nitrate has been found in several places throughout the state at concentrations above the MCL of 10 mg/L. Nitrate in excess of 10 mg/L in drinking water is a health concern for infants under the age of six months and expectant mothers because it can cause methemoglobinemia (blue baby syndrome) in infants.

Members of the InWMC Groundwater Focus Committee are working to investigate the chemical transformation, movement, and occurrence of nitrate in Indiana’s subsurface and groundwater.