The novel complex photocatalytic material was prepared by coating TiO2 nanoparticles on tourmaline using the sol-gel method, and used in the degradation of the herbicide 2,4-D. The results indicated that coating TiO2 with tourmaline enhanced the photocatalytic activity significantly. Based on the research of a simplified model for the average light intensity in the photoreactor, the influence of the concentration of photocatalyst, and the initial concentration of 2,4-D, a model for the degradation of 2,4-D by the tourmaline-coated TiO2 nanoparticles was established. Further tests showed that results calculated from this model were close to those obtained in the actual experiments.

The present article attempts to use freshwater bivalves Anodonta woodiana for monitoring the pollution of hexachlorocyclohexane isomers (alpha-, beta-, gamma-, delta-HCH), dichlorodiphenyltrichloroethanes (o, p', p, p'-DDT) and metabolites (p, p'-DDE, p, p'-DDD) in the Taihu Lake, China. A total of 36 bivalves were sampled from 4 sites of Huzhou city, Dapu of Yixing city, Xueyan of Changzhou city, and Wulihu of Wuxi city around the lake in August-October 2004. The organochlorines were detected in all bivalves, and the mean concentration of SigmaDDTs (7.07 ng/g wet weight) was significantly higher than that of SigmaHCHs (2.37 ng/g wet weight). Overall, SigmaHCHs are at the highest concentrations in the bivalves from the Dapu and Huzhou site, whereas SigmaDDTs are at highest concentrations in the bivalves from the Wulihu site. Compositions of SigmaHCHs were predominated by alpha- and gamma-HCH isomers in the bivalves from all four study sites. Among these sampling sites, p, p'-DDT exhibited the highest percentage in the bivalves from Huzhou site. Furthermore, significant regional variations in compositions of both SigmaDDTs and SigmaHCHs had been identified. The residue levels of SigmaDDTs and SigmaHCHs in the bivalves of the present study were much lower than the corresponding residue limits for aquatic products of Ministry of Agriculture of China, FDA, and FAO/WHO. These findings suggest that Anodonta woodiana could serve as a unique bioindicator to monitor the HCH and DDT pollutions in the freshwater environment.