The Stability Research Of Ammonia-nitrogen Nitrite-nitrogen And Nitrate-nitrogen In Water Samples

In the analysis and research of "tri-nitrogen" pollutants in groundwater,the content of "tri-nitrogen" elements in water samples is extremely susceptible to changes due to various factors(temperature,pH,ventilation conditions,etc.)during the process from manual field sampling to laboratory instrument analysis,which often leads to the analysis results not truly reflecting the real situation in groundwater.In this paper,samples collected from groundwater with typical distribution of "tri-nitrogen" content and samples with different concentrations of ammonia-nitrogen,nitrite-nitrogen or nitrate-nitrogen or mixed tris-nitrogen prepared in the laboratory were used as research objects.The effects of germicidal,light,temperature and ventilation conditions on the stability of "tri-nitrogen" in the samples were studied experimentally.The experimental results were analyzed by the comparison between the calculated relative initial value standard deviation of each sample under different conditions with time and the relative standard deviation given in the standard method,and the concentration trend diagram of each sample under different conditions.The factors affecting the stability of "tri-nitrogen" in each sample and the favorable conditions for the preservation of "tri-nitrogen" samples were analyzed.Study found that shading conditions during the test did not affect the stability of the samples of "tri-nitrogen" Sterilization conditions have a significantly influence on the stability of "tri-nitrogen".Secondly,substrate concentration,pH of the samples,temperature and ventilation will also affect the content of "tri-nitrogen" pollutants in water samples.The main factor influencing the stability of the ammonia-nitrogen in water samples is the concentration of the ammonia-nitrogen.Different pH of the samples under the condition of temperature or ventilation may cause the loss of free ammonia in the sample or the interference of free ammonia in the air and rising of ammonium ion concentration during the procedure of moisture to evaporate.The main factors affecting the stability of nitrite-nitrogen are temperature and nitrite-nitrogen concentration,followed by ventilation and matrix conditions.The evaporation of water samples caused by aeration or temperature is the main factor affecting the change of nitrate-nitrogen concentration.Therefore,we believe that the storage conditions of each "tri-nitrogen" element with good stability are as follows: ammonia nitrogen with relatively high concentration(>0.5 mg/L)in the sample is placed close to the sealing condition of 22 room temperature when the sample is acidic.When sample alkaline,placing itin close to 4 cryogenic seal samples.With high nitrite nitrogen concentration(>1 mg/L)samples of single element,placing it in close to 22 seal conditions at room temperature.With different nitrate-nitrogen concentrations(>5 mg/L)of the samples in the experimental period is relatively stable,low temperature and sealing condition can meet the better stability.In this experiment,natural groundwater samples containing high concentration of ammonia-nitrogen and nitrate-nitrogen concentration,appeared the completely purification function and resulted in the accumulation of nitrate nitrogen.The sterilization treatment by 20 kGy cobalt source irradiation can maintain the general stability of the ammonia-nitrogen,nitrite-nitrogen and nitrate-nitrogen in the samples for three months or longer after sterilization.