Screening of priority pollutants in Liaodong Bay

Liaodong Bay is an important coastal economic zone in China and has carried a large number of pollutants discharged from coastal areas for many years. Heavy metal and organic pollution are serious in coastal waters. The composite scoring method and potential risk index method were used to screen the priority pollutants based on the 12 pollutants of water quality monitoring data in the coastal waters of Liaodong Bay in 2016-2018. The results showed that the total score of the 12 pollutants using the composite scoring method was 29.4-83.2. There were three types of class Ⅰ pollutants, including Hg (83.2), Cd (83.2) and Pb (75.8), and there were three categories of class Ⅱ pollutants, namely Cu (68.4), Cr (63.2) and As (60.8). The results of potential risk index method ranged from 4 to 22. There were three types of class Ⅰ pollutants, including Cd (22), Cu (20) and As (20), and there were three categories of class Ⅱ pollutants, including Hg (19), Cr (19) and Pb (19). Combining the two grading methods, considering that the common primary pollutant screened by the two methods was Cu and the average detected concentrations of Hg, Pb, Cr, As and Cu in Liaodong Bay was 0.04, 2, 7.1, 1.8, 3.8 μg/L, respectively, while the corresponding water quality criterion continuous concentration recommended by US EPA was 0.94, 5.6, 50, 36, 3.1 μg/L, respectively, only Cu exceeded the water quality criterion continuous concentration. At the same time, the average concentration of Cu (3.8 μg/L) in Liaodong Bay was much higher than the set value of harmful concentration (1.90 μg/L) that protected 95% aquatic species. Therefore, Cd and Cu were proposed to be included in the list of priority pollutants for control in Liaodong Bay.