Transformation Of Silver Nanoparticles And Impact On Heavy Metals Of Sediment In The Xiangjiang River

With the widely use of silver nanomaterials in clinical medicine,food packaging,water purification,beauty products,textile products,and many other areas.The chance of silver nanomaterials release into water environment is getting bigger.Silver nanomaterial is a new kind of environmental pollutants,which not only can produce toxicity to all kinds of organisms,but also may affect the form and distribution of other heavy metals in water.In this study,the water and sediment of the Xiangjiang River which was polluted by heavy metals,was chosen as the experimental object to study the migration and transformation of silver nanomaterials in heavy metal polluted water and sediment,and to investigation the effect of silver nanomaterial on heavy metals in sediment pore water.This study used chemistry method to synthesis the bare AgNPs、Citrate coated AgNPs and Tween 80 coated AgNPs.The data from ultraviolet(UV)-visible light spectroscopy,dynamic light scattering demonstrated that the hydrodynamic diameter of the three synthesized silver nanoparticles were 26.10 ± 0.94,27.46±0.91 and 30.12±0.76 nm with a negative surface charge-25.6 mV、-15.2 mV and-6.7 mV respectively.The migration and transformation of silver nanoparticles in the heavy metal polluted water and sediment were studied using the successful synthesized silver nanoparticles and found that the coating material significantly influences the transport and transformation of silver nanomaterial in heavy metal polluted water and sediment from Xiangjiang River.Tween 80 coated silver nanoparticles can exist longer in water without aggregation and react with organic matter,on the other hand,bare silver nanoparticles and citrate coated silver nanoparticles will react with organic matter easier and to aggregate.The vertical distribution of silver in sediment demonstrated that Tween 80 coated silver nanoparticles can penetrate into the deep layers of sediment,while bare silver nanoparticles and citrate coated silver nanoparticles mainly end up in the surfacial sediment,however,most of the three kinds of silver nanoparticles were in the surface 0-3 cm depth area.Through the concentration of copper,zinc,lead,cadmium and mercury in sediment pore water,combined with environmental scanning electron microscope spectrum analysis showed that,silver nanomaterial in the sediment pore water caused heteroaggregation and adsorption which would affect the concentration and speciation of heavy metals,electron microscopy energy spectrum analysis results show that content of mercury and silver of particles in sediment pore water have good linear relationship,indicated formation of silver amalgam.