Seasonal and spatial variability of the ammonium nitrogen content in the Amur River near Khabarovsk in 2018-2019
The results of observations over the content of ammonium nitrogen in the water of the Amur River near Khabarovsk in 2018-2019 are presented. The maximum values were determined in the right-bank and middle parts of the riverbed in 2018 at the beginning of ice formation (0.37 mg of N/dm3) and in 2019 at the end of ice formation (0.32 mg of N/dm3). The minimum values were observed in winter in the left-bank part of the Amur riverbed due to effect of the regulated rivers of Zeya and Bureya. The gradual decline in the concentration of ammonium nitrogen 1.5 times during the winter season of 2018 and growth 2.4 times in 2019 are shown. The decrease in concentrations 1.9 times during the winter runoff low of 2018-2019 in comparison with period of 2011-2013 was revealed which gives evidence of the water quality improvement in Sungari River and, respectively, in the middle reaches of Amur River. In the period of free channel, the content of ammonium nitrogen is lower in comparison with the same during winter low-water level and does exceed 0.1 mg of N/dm3. The maximum values are observed in the right-bank and middle parts of the riverbed during high water and on the rise of floods formed in the catchments of the Ussuri and Sungari Rivers. It was demonstrated that in the top of the catastrophic flood formed in the Trans-Baikal Territory in 2018 and very strong flood in 2019, the content of ammonium nitrogen did not exceed 0.05 mg of N/dm3. It has been established that the content of ammonium nitrogen in the left-bank part of riverbed and in the peak-flood interval across the whole width of the Amur River is below detection limit.