Analysis of water environmental quality features in Songhua River Basin

The surface water environmental quality features of the Songhua River Basin during the period from 2006 to 2009,of which the year 2006 was selected as the base year,were analyzed at multiple scales and from various perspectives,based on analysis of the water quality conditions,different water distribution areas,and main indices that exceeded the standards.The results show the following: the water quality in the Songhua River Basin improved in the annual period,the flood period,and the non-flood period,with an increase in the proportion of water with quality of class I to III and a decrease in the proportion of water with quality of class IV to V;the river basin water quality in the flood period was slightly worse than that in the annual period,while the water quality in the non-flood period was slightly better than that in the annual period;the areas polluted seriously(with water quality of class V and inferior to class V) in the river basin have gradually shifted from the Nenjiang River area to the main stream of the Songhua River,and from the cities scattering in the whole basin to a few major cities around the main stream of the basin;and in addition to chemical oxygen demand(COD),permanganate index,and BOD5,ammonia nitrogen was a new water pollution indicator that exceeded the standard.