A global review and evaluation on the derivation and application of sediment quality criteria to protect aquatic ecosystem and humanhealth

Sediment Quality Guidelines (SQGs) serve as scientific benchmarks, or reference points of chemical contaminants levels for evaluating the possibility of occurrence of adverse biological responses in the aquatic environment. SQGs are important because the quality of sediment has significant influences on the health of aquatic organisms, and the use of SQGs is a critical means to protect and manage various aquatic ecosystems. In this study, nine conventional derivation methods are described and contrasted. Their uses and limitations, which in general reduce the ecological relevance of SQGs in applications, are discussed. Improvements can be made through implementing elements like site-specific, field-based, chemical mixtures assessments, etc. in the SQG derivation process. The Hong Kong sediment management system, which focuses on classification of dredged sediment for their disposal options, is reviewed. I suggest that the current system shall be subject to major review. First, SQG values (i.e., LCEL and UCEL) shall be reviewed with the establishment of a new database. Second, a new set of guidelines shall be derived site-specifically for the disposal area. Third, the chemical priority list shall be expanded to include other contaminants of environmental concerns. Forth, a tier of evaluating bioavailability of the target contaminant can be incorporated in the classification framework in order to assess the portion of chemicals that causes toxicity in the sediment. Finally, the biological test can be improved by using ecologically relevant local species. The need of the site-specificity in SQG derivation is justified in this study, by deriving two sets of SQGs (i.e., ERL, ERM, TEL, PEL and AET) using data from two geologically distinct areas in Hong Kong, which are the Hong Kong-Zhuhai-Macao Bridge (HZMB) area and the Kai Tak development area. The derived SQGs of arsenic, chromium, nickel and zinc are higher in the HZMB areas, but those of copper, mercury, lead and silver are higher in the Kai Tak area. In addition, the incidence rates of effect data with the same contaminants concentrations are different between the HZMB and Kai Tak area. The discrepancies among the derived SQGs and the incidence rates indicate that site-specific SQGs are essential. Furthermore, the analysis of incidence rates of effect data with different contaminants concentrations shows that the HKSQG (i.e., LCEL and UCEL) has to be reviewed, especially for arsenic, because high toxicity is not resulted at a high arsenic concentration range in the dataset.

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Contaminated sediments - China - Hong Kong - Testing.

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