RESEARCH ON THE CHANGING TREND OF WATER QUALITY IN THE MIDDLE REACHES OF HEILONGJIANG RIVER

To investigate water pollution in the middle reaches of Heilongjiang River (Fuyuan Section), and to analyze the changing trend of the physical and chemical factors, the water quality indexes of Heilongjiang River from 2004 to 2019 were detected, including total phosphorus, un-ionized ammonia, permanganate index, petroleum pollutants, volatile phenol, copper and so on. Statistical method was used to analyze the changing trend of these indexes. The results suggest that from 2004 to 2011, permanganate index and total phosphorus were the leading two pollutants, with contents higher than the standard for China's Class III surface water but returning below the standard after 2011. As suggested by the monitored pH values of Heilongjiang River's Fuyuan Section, Fuyuan Section is in a trend of alkalization. On the whole, water quality in Heilongjiang River has improved remarkably since 2011, but still has the risks of eutrophication and alkalization.