| Based on the recent monitoring results, the concentration and distribution of persistent toxic substances in the benthic mussels from the coastal areas of Bohai Sea and North Yellow Sea were determined. The results indicated that,at over 36% of the total sampling sites, the tissue concentrations of petroleum hydrocarbons were higher than the Category Ⅰ value (15 μg/g, wet weight) of the national marine biological quality standards, especially at the sites near Dalian Bay and Xincun in Hebei Province, the tissue concentrations even exceeded the Category Ⅲ level (80 μg/g, wet weight). Moreover, higher tissue concentration of PHCs (over the Category Ⅰ level) during recent years remained in the most monitoring sea areas. At minor sites (mariculture zone in Yantai and Laizhou Bay), the tissue concentrations of As and Pb were relatively higher, and the high levels of Cd (above the Category Ⅱ value of 2000 ng/g, wet weight) and Hg (above the Category Ⅱ value of 100 ng/g, wet weight) in mussel bodies presented at several sites situated in coastal areas near Dalian Bay and Xincun of Hebei Province. Additionally, at the sampling sites near Liaodong Bay and Shandong Peninsula, the tissue concentration of Hg showed an annual increase during recent years. At all the monitoring sites, the tissue concentrations of PCBs and HCHs were usually low, while as the case of Hg, the tissue concentrations of PCBs and HCHs in Liaodong Bay increased gradually in these years. The new monitoring results indicated that, most sites with DDTs levels in benthic mussels higher than the Category Ⅰ value (10 ng/g, wet weight) were located in the coastal areas of Hebei Province belonged to Bohai Bay (such as Zhaojiapu and Xincun). The continuous monitoring in these sea areas demonstrated that, in addition to the historical residues, there may be some fresh input sources of DDT nearby. Consequently, in the neighboring sea areas of Dalian Bay and Xincun, the tissue concentrations of PHCs, Cd and Hg were fairly high (all over their Category Ⅱ values), and these sea areas could be of relatively stronger potential ecological risk. In view of the gradual increases in tissue concentrations (e.g., Hg, PCBs and HCHs) during the recent years, the coastal areas, for example, of Liaodong Bay and Shandong Peninsula should be addressed with sufficient concern. |
