Risk assessment for sediment associated heavy metals using sediment quality guidelines modified by sediment properties.

Abstract

Sediment quality guidelines (SQGs) are a fundamental component of sediment quality assessment framework, frequently used in the first tier of assessment to predict the potential risks of contaminants in sediment. A recognized weakness of SQGs concerns the bioavailability of sediment contaminants, which may vary considerably with different physical-chemical properties. To better evaluate the ecological risks and predict the toxicity of the heavy metals (Cd, Cu, Ni, Pb, Zn) in the sediments of Haihe River of China, the risk quotients derived from total metal concentrations and SQG values were modified using multiple linear regressions with sediment properties, i.e. total organic carbon (TOC), acid-volatile sulfide (AVS), and particle size distribution (PSD). Then, the sediment toxicity was tested with the benthic organisms of chironomids and tubificids, and the relationships between the observed toxicity with the modified risk quotients were investigated. We found that the risk quotient modified with TOC and AVS displayed significantly improved relationship with the toxicity (p<0.001) compared to the original risk quotient without modification (p=0.062-0.074>0.05). Risk assessment indicated that although the heavy metals in the sediments of Haihe River of China are at a relatively low level, potential ecological risks caused by Ni and Zn still exist in some area, especially in the lower reaches along the estuary. The results indicated that the risk quotient and SQG values modified with sediment properties are promising for risk assessment of the metal contaminants in sediments.