Nitrate (NO3) versus Nitrate-Nitrogen (NO3-N)

Laboratories sometimes differ in the basis for reporting the concentration of nitrate in water. Some report as mg NO3>/L and some report mg N/L as nitrate. Because N weighs 14 g/mole and nitrate weighs 44.3g/mole, the two methods differ by a factor of 4.43.

Nitrate result on water test report can differ depending on the way of expression used by the testing laboratory; whether it is as "total nitrate or nitrate ion (NO3)" or "nitrate as nitrogen (NO3-N)". The concentrations in both cases are usually expressed in milligrams per liter (mg/L) or parts per million (ppm). In most cases, it is reported as "NO3-N"; that means 'nitrate as nitrogen', which is the amount of the element nitrogen (N) in the nitrate ion (NO3). However, it is seldom reported as "total nitrate," which is the actual nitrate ion (NO3).

Conversion between these two methods of expression: 1 mg/L nitrate-nitrogen (NO3-N) = 4.43 mg/L nitrate (NO3). The EPA's maximum contaminant level (MCL) for NO3-N is 10 mg/L, which is equal to 10 x 4.43 or 44.3 mg/L nitrate (NO3).

Occasionally, testing is also performed for total Nitrite (NO2) and Nitrate (NO3) together. In this case, concentrations are reported as (NO2 + NO3-N) or "nitrite plus nitrate as nitrogen."

Nitrite (NO2) versus Nitrite-Nitrogen (NO2-N)

As for nitrate, the nitrite result on water test report can differ depending on the way of expression used by the testing laboratory; whether it is as "total nitrite or nitrite ion (NO2)" or "nitrite as nitrogen (NO2-N)". The concentrations in both cases are usually expressed in milligrams per liter (mg/L) or parts per million (ppm). In most cases, it is reported as "NO2-N"; that means 'nitrite as nitrogen', which is the amount of the element nitrogen (N) in the nitrite ion (NO3). However, it is seldom reported as "total nitrite," which is the actual nitrite ion (NO2).

Conversion between these two methods of expression: 1 mg/L nitrite-nitrogen (NO2-N) = 3.28 mg/L nitrite (NO2). So for instance, a water test result of 5 ppm NO2-N is the same as 16.4 ppm NO2.

Occasionally, testing is also performed for total Nitrite (NO2) and Nitrate (NO3) together. In this case, concentrations are reported as (NO2 + NO3-N) or 'nitrite plus nitrate as nitrogen'

Explanation of Units

mg/L (ppm): milligrams per liter, or parts per million.
Equivalent to 1 pound of an element dissolved in 1,000,000 pounds of water.
µg/L (ppb): micrograms per liter, or parts per billion.
Equivalent to 1 pound of an element dissolved in 1,000,000,000 pounds of water.
CFU: colony forming units
A rough estimate of the number of viable bacteria or fungal cells in a sample.
MPN: most probable number
NTU: nephelometric turbidity units
mg CaCO3/L: milligrams calcium carbonate per liter
pCi/L: picocuries per liter

UGA Extension - Agricultural & Environmental Services Laboratories
Drinking Water
Interpretation and Recommendations
Uttam Saha, Rick Hitchcock, and Leticia Sonon http://aesl.ces.uga.edu/water/recommendations

An estimated 1.7 million people in Georgia rely on 640,000 private wells for their drinking water supply. The Georgia Environmental Protection Division enforces EPA's drinking water quality standards for human consumption in public water supplies according to the Federal Safe Drinking Water Act. However, private wells are not regulated. Consequently, private well water users are responsible for ensuring the quality and safety of their water supplies for domestic, livestock, and irrigation use.

This web page provides interpretation and recommendations for drinking water quality. Enter results from a water testing laboratory below, select the appropriate units, and click "Interpretation and Recommendations" to see an interpretation of your results and necessary recommendations (if any). The interpretation is made only on the data provided.

If you are a well owner but have not had your water tested, consider doing so. For a list of recommended water tests and testing strategies, consult your local Extension office and our educational circular Testing for Water Quality.

All tests below can be analyzed by our labs except for the ones highlighted. You can view prices in our Fee Schedule.

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