The National Atmospheric Deposition Program (NADP) currently monitors ammonium (NH₄) in National Trends Network (NTN) and Atmospheric Integrated Research Monitoring network (AIRMON) wet deposition samples. Ammonium is analyzed by colorimetric detection at 630nm by Flow Injection Analyzer (FIA) using Lachat HACH instruments. Nitrogen can be present in multiple forms such as ammonia/ammonium, nitrate and nitrite, amino acids, proteins and urea. Total nitrogen (TN) is the sum of all forms of nitrogen that are present in water samples.

This study will investigate the use of a total nitrogen method using nitrogen persulfate digestion (EPA method 353.2 and Wisconsin State Laboratory of Hygiene (WSLH), inorganic department Method ESS INO Method 240.0). Nitrate (NO₃) in the samples is reduced to nitrite (NO₂) through a copperized cadmium column. The nitrite (originally present plus the reduced nitrate) is then determined by diazoting with sulfanilamide and coupling with N-(1-naphthyl) ethylenediamine dihydrochloride, forming a colored azo dye which is measured by colorimetric detection at 520nm.

This study will investigate sample preparation and analysis for total nitrogen in NADP samples. The first step is to establish a protocol for the determination of total nitrogen, and then to determine the fraction of organic nitrogen in the National Atmospheric Deposition Program (NADP) samples.