The Transport,Fate And Biouptake Of Silver Nanoparticle And Silver Nitrate In The Model Of Rice Plant (Oryza Sativa L.) And Pond Microcosm

Due to their unique physicochemical properties,nanoparticles such as silver nanoparticles(AgNPs),are widely used in industry and consumer products.Metallic silver has been used since ancient times for the conservation of water and food due to its sustained release of silver ion(Ag+)with antibacterial effect.With the increase production,use,recycling and handling,silver are inevitably released into the environment and become potential contaminants.Therefore,extensive and growing interests in the field of environmental health and safety have been focused on the transport,transform,fate and toxicity of silver.Studying on the toxicity and bioaccumulation of AgNPs and Ag+ are usefull to evaluate their environmental behaviors.This thesis focuses on the transport,fate and bioavailability of AgNPs and Ag+ under a relative real environmental,the main point of this study as follows:(1)The wide use of silver ion(Ag+)and silver nanoparticles(AgNPs)and their inevitable release into the environment have led to great concern on their environmental risks.Evaluation of the toxicity and accumulation of Ag+ and AgNPs on/in organism is helpful to fully understand their environmental impacts.This study reported the influence of chloride ion(Cl-),iron plaque,and dissolved iron on the phytotoxicity,accumulation and translocation of Ag+ and AgNPs by rice plant(Oryza sativa L.).With Cl-in treatment medium,the formation of AgCl greatly retains Ag+on the root surface,which decreases the bioavailability of Ag+.However,AgNPs,due to the Trojan horse effect,can be assimilated and translocated more effectively by rice than Ag+,which makes AgNPs more toxic than Ag+.Generally,iron plaque on rice root increases the uptake and toxicity of AgNPs by rice,while minor influence of dissolved iron is observed.(2)We investigated the differential distributions and bioavailabilities of Ag+ and AgNP in pond microcosms by using isotope tracer.It was observed that the half-life of Ag+(<1 h)in water column is much shorter than that of AgNP(~3 h),possibly owning to the formation AgCl precipitation.Accordingly,the uptake of AgNP by floating plants(Pistia stratiotes and Salvinia natans)was much higher than that of Ag+.While,for submerged plant(Ceratophyllum demersum),the uptake of AgNP was comparable with that of Ag+.Pseudorasbora parva can accumulate more AgNP than Ag+,with higher concentration in liver and brain than other tissues.However,the uptake of Ag+by freshwater snail(Procambarusclarkia)was much higher than that of AgNP.Our findings highlighted the importance of more realistic scenarios in evaluation of the transformation,uptake and toxicity of Ag+and AgNPs in the environment.