Definitions for "Total Nitrogen"
Total Nitrogen is the sum of nitrate (NO3), nitrite (NO2), organic nitrogen and ammonia (all expressed as N). Note that for laboratory analysis purposes, Total Kjeldahl Nitrogen (TKN) is a test performed that is made up of both organic nitrogen and ammonia.
the sum of all forms of nitrogen (both dissolved and particulate) in water
A measure of all forms of nitrogen (for example, nitrate, nitrite, ammonia-N, and organic forms) that are found in a water sample.
Keywords:  din, gaseous, includes
Includes DIN, PN, but not gaseous N (e.g. N2).