Study on persistent organic pollutants in the areas around Bohai Sea, North Yellow Sea and the Yangtze River Delta, China

Bohai Sea, the shallow northwestern arm of the Yellow Sea, off the North China coast, is enclosed by the Liaodong Peninsula (northeast) and the Shandong Peninsula (south). The gulf's maximum dimensions are 480 km from northeast to southwest and 306 km from east to west. The strait leading to the gulf is about 105 km in width. The mean depth of Bohai Sea is about 18 m. The Yellow River, China's second longest river, discharges into the gulf. Two other major rivers draining into the Bohai Sea include the Hai River System and Liao River System, which constitute two of the five river systems in China. The gulf has long been used as a source of prawns and salt. There are both onshore and offshore petroleum deposits, and several oil refineries are located there. The Bohai region is one of the most important economic zones with its GDP growing more than tenfold in the past 12 years. The Bohai region has covered some major cities from three provinces and two municipalities, such as Dalian (in Liaoning Province), Tangshan (in Hebei Province), Dongying (in Shandong Province), Tianjin and Beijing. The Bohai Sea is a relatively closed bay; the interchange of seawater with ocean outside is weak, and thus the water quality of this area is influenced seriously by human activity.