Assessment of Water Quality in the Northern Sea Area of Zhanjiang Bay in Winter

Based on the water quality investigation data of December in 2009,the water environment quality in the northern sea area of Zhanjiang Bay was assessed using single water quality parameter model, integrated water quality index model, organic pollution index model and eutrophication assessment model. The results showed that the key pollutants were dissolved inorganic nitrogen (DIN) and phosphate (PO₄-P), with their average concentrations of 0.99 and 0.033mg/L.The averages of their single parameter pollution index were 2.47and 1.09. And DIN was the most important one. Its concentration was unable to meet the third standard of seawater quality, and decreased gradually from inner bay to outer bay. Under the effects of the inputting of Suixi River and land-based pollutants, most parts of the northern sea area in Zhanjiang Bay were polluted lightly. The averages of single parameter pollution index, integrated water quality index, organic pollution index and eutrophication index were 0.94, 1.87, 2.84 and 20.1, respectively, which also decreased gradually from inner bay to outer bay.