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=Water Test: Nitrate/Nitrogen Test= //Adapted from Project Search//

Nitrogen is present in aquatic ecosystems in several forms, including ammonia, nitrates, and nitrites. The original source of all nitrogen compounds in water is molecular nitrogen (N2) in the atmosphere. Although unusable by most organisms, atmospheric nitrogen is converted or "fixed" by several species of bacteria and blue-green algae (cyanobacteria) into organic nitrogen (Fig. 7.2). Most fixation occurs in aerobic soils, however, nitrogen-fixing organisms are also active in water. As the microbes responsible for fixation die and decay, organic nitrogen is converted to ammonia (NH3). In water, ammonia readily reacts to produce ammonium ions (NH4+), which can then be absorbed by microbes, phytoplankton, or the root systems of plants and converted into organic matter. Ammonium can also adhere to negatively-charged soil particles or be oxidized through a two-step process called nitrification. During the first step of the process, NH4+, and unconverted NH3, are oxidized to nitrites (NO2-) by Nitrosomonas bacteria.

The second step involves the oxidation of nitrites to nitrates (NO3-). Nitrates are highly soluble compounds and can be quickly assimilated by plants into complex proteins and nucleic acids. As plants, and the animals that depend on them, die and decay, these molecules are broken down into NH3 through the process of ammonification. Nitrogen then re-enters the biologic cycle as NH3 is converted to NH4+. If nitrates are not assimilated, certain bacteria can convert nitrates to nitrites and NH4+ through the process of nitrate reduction.

Since nitrate ions are negatively charged, they do not adhere to soil particles as do NH4+. If not reduced or assimilated by plants or microbes, nitrates may be lost through subsurface runoff and ground water flow. If nitrates and nitrites move from oxygenated into anoxic soils, they can be converted, through the process of denitrification, to gaseous nitrous oxide (N2O) and molecular nitrogen. Denitrification, carried out by certain bacteria under anaerobic conditions, is the principal way in which nitrogen is cycled back to the atmosphere.

Nitrates (NO3-) and nitrites (NO2-) are the most abundant forms of dissolved nitrogen in well-aerated streams. Since nitrite readily oxidizes to nitrate, nitrates are by far the most prevalent. Test results for nitrates are often expressed as nitrate- nitrogen (NO3--N), or "nitrogen that was in the form of nitrates." Concentrations of NO3--N rarely exceed 10 mg/l and are usually less than 1.0 mg/l. Elevated levels are primarily associated with human contamination from fertilizers and sewage. High concentrations of nitrates can stimulate the growth of aquatic plants and may be a health hazard to juvenile mammals. In the digestive system, nitrates are reduced to nitrites. As nitrites enter the bloodstream, hemoglobin is oxidized to methemoglobin rendering it incapable of transporting oxygen. Cyanosis due to methemoglobinemia ("blue baby disease") may result from drinking waters with high nitrate concentrations. The maximum allowable level of NO3--N in drinking water has been set at 10.0 mg/l by the U.S. Public Health Service.

1.) How does nitrogen enter the water? 2.) What are the various forms that nitrogen takes? 3.) What is denitrification? 4.) What is the maximum amount of Nitrogen allow in drinking water? 5.) How do you think humans impact the nitrogen levels in Mashamoquet?
 * Prelab**


 * Procedure**


 * Data**

What was the amount of nitrogen for your sample?


 * Analysis**

What is an acceptable amount of nitrogen in your water and how does your sample compare?


 * Conclusion**

What were the challenges that you faced in completing this lab?