Spatial Distribution and Pollution Level Evaluation of Nutrients in the Songhua River Basin

In this research, 122 samples were obtained from the Songhua River Basin to investigate spatial distribution and pollution of nutrients in river water using the comprehensive pollution index method in combination with the results of the 2-year field survey of aquatic ecosystems from 2013 to 2014. The results showed that the percentages of the excellent, good, moderate, poor and terrible grades of nutrient assessment were respectively 10.66%, 15.57%, 20.49%, 28.69% and 24.59%. The lowest scores of nutrient assessment were found in the Nenjiang River, the Mudan River, the Songnen Plain, the Sanjiang Plain and the Second Songhua River Basin. Nutrient pollution was less in the tributaries than in the main streams. The pollution of the nutrients in river water was in order of the main stream of the Songhua Riverthe Second Songhua Riverthe Mudan Riverthe Nen River. The three nutrient indicators(TN, TP and NH3-H)were significantly different.The assessment method based on grades divided by the same standards was feasible. Land use had profound impacts on nutrient pollution in river water, especially the non-point source pollution of agriculture that affected nitrogenous pollution more significantly.