Total Phosphorus

Basic Information about Phosphorus

Phosphorus pollution is the greatest threat to clean water in the Missisquoi River Basin and Lake Champlain, in general. Phosphorus is a nutrient that stimulates excessive growth of algae, turning the water green (refer to the images below) and in excessive amounts it can be detrimental to the aquatic ecosystem, the taste of drinking water, recreational uses, and aesthetic enjoyment. There are some cases where these algal blooms, particularly cyanobacteria, can be harmful to animals and people. Eroded soils and runoff from farm fields, barnyards, roads, parking lots, and streambanks are all major sources of phosphorus that contribute to the problems along the Missisquoi.


Blue-green algae blooms, like this on in July 2012 at Burlington’s North Beach, can contain dangerous toxins and should be avoided
VT Department of Health


Types & Measurement of Phosphorus

Phosphorus exists in water in either a particulate phase or a dissolved phase. Particulate matter includes living and dead plankton, precipitates of phosphorus, phosphorus adsorbed to particulates, and amorphous phosphorus. The dissolved phase includes inorganic phosphorus and organic phosphorus.

There are several forms of phosphorus that can be measured, but for the purpose of our sampling program, we measure Total Phosphorus (TP), which is a measure of all forms of phosphorus, dissolved or particulate, that are found in a sample. Nutrient concentrations, in our reports, are recorded as micrograms per liter of water (µg/L), which is equivalent to parts per billion (ppb).

Total Phosphorus Sampling for 2014

Above is a map of the U.S. municipalities in the Missisquoi River Basin, including the 21  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 phosphorus for a specific site; for example, the site in Swanton (T-HBW) is a large red circle because its average total phosphorus is greater than 90.1 µg/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 green averaged below 25 µg/L Phosphorus in 2014; the sites highlighted in yellow had concentrations of Phosphorus between 25.1 – 50.0 µg/L; the sites highlighted in orange had concentrations of Phosphorus between 50.1 – 90.0 µg/L; and finally the sites highlighted in red had concentrations of Phosphorus more than 90.1 µg/L. To put this all in perspective, the Vermont Agency of Natural Resources (VTANR) water quality standard is 20 µg/L. This standard represents the maximum amount of phosphorus allowed in a water body while still being able to naturally function. To summarize this data, a majority of the sampling sites were not even close to meeting the VTANR water quality standard of 20 µg/L, therefore it is obvious that these sites need to be re-evaluated & best management practices need to be implemented.

2014 Total Phosphorus