Pollution assessment and source identification of basin groundwater in typical agricultural areas in Northeast China

Due to limitations of traditional grey relation alanalysis, an improved evaluation method of ground water quality by weighted-grey relational analysis (WGRA) was proposed. This new method was used to characterize basin ground water pollutions of Lalin River, a typical agricultural area of the Chinese Northeast. WGRA results were compared with classical assessment methods (comprehensive index, fuzzy mathematics and traditional grey relational analysis). Positive matrix factorization (PMF) was employed for source identification. Evaluation with single factor analysis revealed iron, manganese, ammonia and nitrate to be the main pollution factors on the Lalin River. WGRA evaluation indicated that 66.7% of groundwater was of class V, only 33.3% met drinking water standards. Compared to other methods, the WGRA results were closer to the environmental data of the area. PMF identification showed that potential sources to affect groundwater quality of Lalin River are agricultural nonpoint sources (pesticide chemical, fertilizer application) and natural geological background, with contributions of 38.5% and 61.5% from each.