Total Nitrogen

Basic Information about Nitrogen

Nitrogen is a nutrient that is naturally abundant in the atmosphere and is essential for plant and animal growth. Unfortunately, there are ways that nitrogen can be added in excess, such as through sewage and fertilizers. Nitrogen, in the form of nitrate or ammonium, is essential for plant growth, therefore with excess nitrogen in a water body it can overstimulate the growth of aquatic plants and algae. Excess growth of aquatic plants and algae decrease the amount of dissolved oxygen available as they decompose, which makes it very difficult for aquatic organisms to survive. For example, Lake eutrophication can occur, which produces a thick layer of algae on the water surface, which can lead to fish deaths and can even “kill” a lake by depriving it of oxygen. Excess nitrogen can overall decrease plant & animal diversity along with affecting our use of the water for recreational activities, such as fishing, swimming, and boating.


A kayak paddles over thick weeds covered in algae in St. Albans Bay  
Photo by: St. Albans Area Watershed Association

Type & Measurement of Nitrogen

Total Nitrogen is the sum of nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), ammonia-nitrogen (NH3-N) and organically bonded nitrogen. Since nitrogen can be found in all of the four major forms, whether it be from wastewater or fertilizers, each of the four can be analyzed separately and then summed up for a total nitrogen level, which is measured in milligrams per liter (mg/L).


Above is a map of the U.S. municipalities in the Missisquoi River Basin, including the 22 sampling sites, located along the mainstem and tributaries of the Missisquoi River, that were monitored in 2014. The color-coded circles represents the average total nitrogen for a specific site; for example, the site in Enosburgh (T-ETYB) is a large red circle because its average total nitrogen is more than 0.901 mg/L. The letters located next to each sampling site (marked by the colored circles) is a code to represent the sampling site (i.e. T-HBW stands for a site on a tributary to Hungerford Brook, along Woods Hill Rd., and M-NTBF stands for a site along the mainstem, in North Trow, below Big Falls). See the table below for more detailed location information for each of the coded sites highlighted in yellow averaged less than 0.45 mg/L; the sites highlighted in orange averaged between 0.45 – 0.90 mg/L; and the sites highlighted in red averaged more than 0.901 mg/L. Unlike phosphorus, there is not State water quality standard for nitrogen, but this data is still relevant in the mission for clean water in the Missisquoi and Lake Champlain, in general.

Total Nitrogen Levels 2014