What is ammonia nitrogen? Dangerous to fish? How to detect? multiple methods

What is ammonia nitrogen? Ammonia nitrogen refers to the compound nitrogen that exists in the form of ammonia or ammonium ions, that is, the nitrogen that exists in the form of free ammonia (NH3) and ammonium ions (NH4+) in water. The compound nitrogen in the form of free ammonia (NH3) and ammonium ion (NH4+) is called ammonia nitrogen. Ammonia nitrogen is a nutrient in water, which can lead to eutrophication. It is the main oxygen-consuming pollutant in water and is poisonous to fish and some aquatic organisms. Ammonia nitrogen detection methods usually include Nessler colorimetric method, phenol-hypochlorite (or salicylic acid-hypochlorite) colorimetric method and electrode method. Nessler's reagent colorimetric method has the characteristics of easy operation and sensitivity. For the interference determination of calcium, magnesium and iron and other metal ions, sulfides, aldehydes and ketones, color, and turbidity in water, corresponding pretreatment is required. The chlorate colorimetric method has the advantages of sensitivity and stability, and the interference and elimination methods are the same as those of Nessler's reagent colorimetric method. The electrode method usually does not require pretreatment of the water sample and has the advantages of a wide measurement range. When the ammonia nitrogen content is high, the distillation-acid titration method can still be used.