Identification of Ah receptor agonists in sediment of Meiliang Bay, Taihu Lake, China.

Deterioration of ecosystem and water quality in Taihu Lake, the third largest freshwater lake in China, is of great concern in China. However, most evaluations on water and sediment were carried out by chemical analysis, which could hardly gain information on the risk stressors affecting the system. Sediment samples from Meiliang Bay, Taihu Lake were assayed for AhR-mediated EROD induction using a rat hepatoma cell line (H4IIE). The known AhR agonists including PCDD/Fs, PCBs, and PAHs were analyzed by instruments. The cause-effect relationship between the observed EROD activity and chemical concentrations of AhR agonists and their dose-effect relationship were examined. Our results showed that sediment extracts could induce significant AhR effects, and the chemical-derived TCDD equivalents (TEQ(cal)) were significantly correlated to bioassay-derived TCDD equivalents (TEQ(bio)) (R = 0.85, p < 0.01). Among different contributors, PAHs could account for 70-93% and PCDD/Fs could contribute less than 30% of TEQ(cal). PCBs exhibited almost no contribution. Therefore, integration of EROD bioassay and chemical analysis provided an effective way for identifying the potential risk stressors. Underthis circumstance, a quantitative dose--effect relationship between TEQ(PAH) and EROD activity could be established, suggesting that the observed AhR effect was mostly derived from PAHs. The implication is that the EROD assay and the identified risk stressors (PAHs) may be used in lieu of detailed environmental analysis to follow the progression of a remediation strategy.