Annual variation of major water quality indices of Yixing and Liyang′s rivers and their causes

Yixing and Liyang′s rivers are taken for case study to explore the evolutional trend of the water environment of the watershed and main factors affecting the evolution of the water environment.The results show that the annual variation of TN and TP does not show any ascending trend,but that of COD_Mn does otherwise.Industrial point-source pollution is the main factor affecting COD_Mn concentration in the water,whereas high rates of fertilizer application is the major non-point source pollution affecting TN index,and domestic pollution is the major factor affecting TP index in the water.