Study On The Screening Of Priority Pollutants And Environmental Criteria In Liaodong Bay

Liaodong Bay is one of the most important fishery bases and the coastal economic zone in China.With constant economic growth,the rapid development of bay coastal cities,high population density,and well-developed industry and agriculture,as the estuary of many rivers,Liaodong bay has overloaded carrying land-source pollution for years,especially the offshore sea area,where pollution is more serious,raising concerns about its ecological environment.In order to control the pollution situation of Liaodong Bay,China is currently implementing the target total amount control management of land-based pollutants,and the emission reduction indicators are only limited to the emission reduction amount of pollutants entering the sea approved according to the equal proportion of administrative regions.Although the total amount of pollutants entering Liaodong Bay has decreased,the water quality of Liaodong Bay has not improved accordingly.With the further strengthening and deepening marine environmental protection and management in Liaodong Bay,in a bid to monitor,manage,control,and reduce the potential and high-risk pollutants with more targeted measures,it is imperative to carry out the screening of the main priority control pollutants and the study of water quality criteria in Liaodong Bay.This study mainly adopted the composite scoring method and the potential risk index method to screen the pollutants under priority control.Over the course of the screening process,it was compared with the Seawater Quality Standard of China(GB3097-1997),and the US EPA recommended water quality criteria and HC5 that protect95% of aquatic species were taken into account.Indigenous and model species of five phylums and eight families of Liaodong Bay were selected as experimental subjects for acute toxicity experiments in the laboratory.At the same time,1 794 acute toxicity data of Cu were collected.Having screened,the toxicity data of 23 species met the screening principle.The water quality criteria of Cu in Liaodong Bay were derived by using the toxicity percentile rank method,the species sensitivity distribution(SSD)method,and the acute-chronic ratio method.The main conclusions are as follows:(1)Based on the water quality monitoring data of major pollutants in LiaodongBay,inorganic nitrogen,active phosphate,Pb,and Cu exceed the second level standard according to “Seawater Water Quality Standard” GB 3097-1997,and these four pollutants should be included in the list of priority pollutants in Liaodong Bay.Although the over-standard rate of Cu is not high,the average detected concentration of Cu exceeds the HC5 value and the CCC of the National recommended water quality standard of the United States.So Cu should be included in the list of priority pollutants in Liaodong Bay.In addition,12 kinds of pollutants were screened by the composite scoring method and the potential risk index method.The results showed that Cd is the common level I pollutant screened by the two methods and should be included in the list of priority pollutants in Liaodong Bay.Finally,five priority pollutants were screened as inorganic nitrogen,active phosphate,Pb,Cd,and Cu.(2)Based on the basic principles of species selection prescribed by US EPA,acute toxicity tests were carried out on indigenous species and model species from five phylums and eight families in Liaodong Bay to obtain experimental results of acute toxicity of Cu.Among them,48 h-EC50 of Phaeodactylum tricornutum Bohlin was15.080 μg/L,72 h-EC50 of Chaetoceros curvisetus Cleve was 160.086 μg/L,24 h-LC50 of Brachionus plicatilis was 161.010 μg/L,and 96 h-LC50 of Mactra veneriformis Reeve was 1 227.330 μg/L.96 h-LC50 of Ruditapes philippinarum were 152.891 μg/L,96 h-LC50 of Tigriopus japonicus was 204.173 μg/L,96 h-LC50 of Trachidermus fasciatus was 1 150.787 μg/L and 96 h-LC50 of Cynoglossus semilaevis was 769.740μg/L.There were significant differences among different species.(3)In accordance with the data obtained in conclusion(2),combined with the toxicity percentile rank method,the CMC and CCC of Cu were 3.87 μg/L and 2.56μg/L,respectively.Based on laboratory data and collected data as well as the toxicity percentile rank method,Cu CMC and CCC were 3.31 μg/L and 2.18 μg/L respectively.In the meanwhile,the SWQC of Cu in Liaodong Bay was 4.99 μg/L and the LWQC was 3.30 μg/L by the SSD method.In accordance with the above studies,in a gesture to protect a wider range of aquatic organisms,the SWQC and LWQC of Cu in Liaodong Bay should be 3.31 μg/L and 2.18 μg/L respectively.This paper fills in the blanks of water quality criteria research on Liaodong Bay area in China and provides an important basis for the determination of total control target of pollutants in Liaodong Bay,which also serves as a basis and reference for the development of environmental & ecological protection and environmental pollution control countermeasures in Liaodong Bay.