Changes of water contaminative indexes and its reasons in Tanggu Reach of Haihe River

Water pollution control has become an important part of national environment protection strategy.Correct understanding the change of water quality in the Haihe River has great theoretical and practical significance for the pollution control.Taking the Tanggu Reach of Haihe River of Tianjin as research object,adopted the national control monitoring sections of Dalingzi and Chuanzha's water quality monitoring data,and calculated pollution index(Pi),pollution-sharing rate(fi) and section integrated pollution index of pH,NH3-N,DO,BOD5,Permanganate index,CODCr,total phosphorus,zinc,copper,lead and cadmium and so on 11 pollution factors.From the characteristics of the changes of water pollutions indexes of Haihe River,the comprehensive water quality index gradually decreased from 2001 to 2005.After 2003,the situation improved significantly,and met the Class V requirements.Ammonia,CODCr,BOD5 and dissolved oxygen's exceeding the standards are still the main factors that affected the Haihe River water quality.Pollutions index usually reach its peak in May to June,which is closely related to the surface runoff and the situation of the drain of rainwater.Haihe River dredging project in 2003,making the Haihe River water quality has improved,pollution index decreased significantly, the reduced rate of ammonia is far greater than that of other major pollutants,which indicated that Haihe River dredging project is one of the important measures to improve the water quality.