ABSTRACT

Both nitrate (NO3-N) and ammonia (NH4-N) concentrations are in general highly variable during a lake’s seasonal cycle.During the growing seasonal peak, such concentrations can be very low due mainly to its’ sequestration by phytoplankton.

With the aim to study NO3-N and NH4-N mean concentration variation along the increase of the trophic state of lakes, this study simultaneously analyses the information for more than 400 lakes worldwide. Both forms of nitrogen are directly related to the trophic state of a lake when lakes are compared with total phosphorous concentration (TP) ranging across five magnitude levels. However, in lakes a pronounced non-linearity dominates the relationships among the different forms of nitrogen and phosphorous. Our results suggest that the empirical basis for both the limiting resource and inorganic nitrogen hypotheses are related. The NO3-N: NH4-N ratio is directly related to the TN: TP ratio for lakes in general and shallow ones in particular. Source :Limnetica 22(1-2): 37-50 (2003...PDF enclosed

Thank you sir.

The USEPA(United States Environmental Protection Agency

) recommends a limit of 0.02 ppm as NH3 in freshwater or marine environments. Total ammonia levels, at this limit, can range from 160 ppm at pH 6 and temperature of 5 degrees C to 0.06 ppm at pH 9 and temperature of 25 degrees C.

 Nitrites: Nitrites occur in water as an intermediate product in the biological breakdown of organic nitrogen, being produced either through the oxidation of ammonia or the reduction of nitrate. The presence of large quantities of nitrites is indicative of waste water pollution. The level considered ideal for marine fish is between 0.01 and 0.04 ppm.

 Nitrates occur in water as the end product in the biological breakdown of organic nitrogen, being produced through the oxidation of ammonia . Although not particularly toxic to fish, excess nitrates in the water is often used as an indicator of poor water quality. Under anaerobic conditions, such as in the sludge or soil at the bottom of a pond, lake or aquarium, denitrification can be used to convert nitrate back to nitrite and from there to nitrogen gas, removing total nitrogen from the aquatic system. In marine environments, levels of 0.1 to 0.2 are considered ideal.