[Effect of nano-TiO2 on the release and activation of mercury in sediment]

To investigate the effects of nano-TiO2 on mercury release and activation in sediment, flooding simulation experiments were conducted. The impacts of nano-TiO2 on total mercury and methylmercury concentrations in overlying water were analyzed. And the influences of nano-TiO2 on the migration and transformation of mercury were discussed based on changes of mercury speciation in sediment. The results indicated that nano-TiO2 promoted the release of mercury in sediment, leading to more mercury released into the water. Compared with the control, 4 g x kg(-1) TiO2 nanoparticles increased the total mercury by 91.32%, when the concentration of total mercury in overlying water was the highest. Release of mercury in soil was increased by approximately 10% finally. The main reason may be that the dissolution of oxidation state mercury was improved by nano-TiO2. It indicated that the risk of mercury contamination in water may increase. Moreover, under the experimental conditions, nano-TiO2 may reduce the formation of methylmercury in sediment in the short-term, but no significant effects in the long-term. Generally, the effects of nano-TiO2 on the release and transformation of mercury in sediment showed concentration dependence. Thus, with increasing nano-TiO2 content in sediment or soil, its impact on the geochemical cycle of mercury may increase.