What are nitrates?
Nitrates (NO3-) are chemical compounds made from the elements nitrogen
(N2) and oxygen (O2). When plants and animals die, proteins are broken
down by bacteria to form ammonia (NH3). Ammonia is broken down by other
bacteria to form nitrite (NO2-). Nitrite is then consumed by a third
type of bacteria to form nitrates (NO3-).
What factors influence the amount of nitrate in your watershed?
1. As decomposition of plants and animal occurs, dissolved oxygen levels
decrease. This will cause nitrate levels to increase.
2. Aerobic bacteria can break down large protein molecules into ammonia.
Ammonia combines with oxygen to form nitrates and nitrites.
3. Normally, only small amounts of nitrates are found naturally, but
an increase in nitrate levels can come from man-made sources such as
septic systems, fertilizer runoff and improperly treated wastewater.
4. Much nitrogen is released in the wastes produced by humans and animals.
Ducks and geese contribute a heavy load of nitrogen through their feces.
What is the optimal amount of nitrate in a watershed?
1. Nitrates in river water often ranges from 0.01-3.0 mg/L.
2. A nitrate-nitrogen reading that is less than 1.0 mg/L is considered
3. A nitrate-nitrogen reading that is 1.1-3.0 mg/L is considered good.
4. A nitrate-nitrogen reading that is 3.1-5.0 mg/L is considered fair.
5. A nitrate-nitrogen reading that is greater than 5.0 mg/L is considered
poor and unsafe for drinking water. Some sewage treatment plants may
have levels in excess of 20 mg/L.
6. Nitrate-nitrogen concentrations that exceed 10.0 mg/L (44 mg/L nitrogen)
may cause methemoglobinemia (blue baby syndrome) in bottle-fed infants.
Nitrite affects the ability of red blood cells to carry oxygen.
What factors are affected by the amount of nitrate in a watershed?
1. An increase in nitrates may cause an increase in phosphate levels.
As phosphates increase, there will be an excess of plant growth (eutrophication)
and decomposition. Consequently, dissolved oxygen levels will decrease
and negatively affect the quality of aquatic animal life.
2. Nitrogen is needed by all plants and animals in order to make proteins,
to grow, and to reproduce.
3. High nitrite levels can cause serious illnesses in fish.