Temporal characteristics of eutrophication and pollution source analysis in Yuqiao reservoir

Based on the records of water quality and precipitation data from 2000 to 2010,the paper used hierarchical cluster analysis,backward discriminant analysis and positive matrix factorization model( PMF) to systematically assess the temporal characteristics of eutrophication and the potential pollution sources in Yuqiao Reservoir. The results indicated that the key exceeded standard factor of eutrophication is N,and the limit factor is P. At temporal scale,eutrophication of water bodies can be divided into period I( from July to September) and period Ⅱ( from April to June,October to November),and there is a delay for the response of water quality to precipitation. Moreover,the concentrations of SS,CODMn,CODCr,BOD5 and TP in period I are much higher than that in period Ⅱ,and the concentrations of DO,TN and NO3-N in period I are much lower than that in period Ⅱ,while NH3-N in both periods is similar.These findings revealed that eutrophication in period I is more serious than that in period Ⅱ,and the influence of non-point source pollution on eutrophication is higher than that of point source pollution. The results of PMF identified six possible pollution sources of eutrophication in Yuqiao Reservoir such as agricultural non-point source phosphorus pollution,nitrogen industrial wastewater,reservoir sediment,agricultural non-point source nitrogen pollution,village sewage,and organic industrial wastewater.