Identification of the Songhua River Water Quality Using Fuzzy Synthetic Evaluation and GIS Approach

According to the principle of fuzzy set theory,water quality of the Songhua River was assessed based on 13 kinds of pollutants which were selected from monitoring data of 15 monitoring sections in the Songhua River during 1990-2006.GIS method was also used to investigate the trend of water pollution and temporal-spatial changes from industrial structure characteristics in the Songhua River.The results showed that water quality of the Songhua River was improved,and varied significantly with different seasons.For example,water quality in the Nen River was mainly polluted by area-source pollution;the pollution was worse in the high water period than in the low water period.Water of the Second Songhua River and the mainstream of the Songhua River were more polluted during the low water period,and the main pollution sources were industrial sewage and domestic sewage.The spatial difference in water quality in the Songhua River basin was that water pollution in branch streams was greater than in the mainstream and greater in urban areas than other water areas.The major pollutants in the Songhua River basin were oil pollutants,COD_ Mn,BOD_5,ammonia-N and chromium (Ⅵ) in Songhua River basin.