Nitrate is a nutrient needed by all aquatic plants and animals to build protein. The decomposition of dead plants and animals and the excretions of living animals release nitrate into the aquatic system. Excess nutrients like nitrate (and phosphate) increase plant growth and decay, promote bacterial decomposition, and therefore, decrease the amount of oxygen available in the water.

Sewage is the main source of excess nitrate added to natural waters, while fertilizer and agricultural runoff also contribute to high levels of nitrate.

1. Fill the test tube (0106) to the 5 mL line with the water sample.
2. Add one Nitrate Wide Range CTA TesTabs (3703).
3. Cap and mix until the tablet has disintegrated. Bits of material may remain in the sample.
4. Wait 5 minutes for the red color to develop.
   NOTE: If the sample does not develop a red color (sample is colorless or yellow), record the result as 0 (ZERO) ppm.
5. Compare the color of the sample to the Nitrate color chart.
6. Record the result as ppm Nitrate.

• 5 ppm = Fair
• 20 ppm = Poor
• 40 ppm = Poor

The natural level of nitrate in an aquatic system is around 1 mg/L. Lower nitrate results indicate less nutrient enrichment of the water, while higher results indicate nitrate contamination. Excess levels of nitrates can induce hypoxia (low dissolved oxygen) and even be toxic to warm-blooded animals at high concentrations (over 10 mg/L).

Drinking water containing high nitrate levels can affect the ability of our blood to carry oxygen. This is especially true for infants who drink formula made with water containing high levels of nitrate.

You should always have a professional lab test your drinking water for the presence of nitrate. A list of labs certified by the RI Department of Health can be found here