Study On The Transformation Mechanism Of Nano Silver In The Groundwater Environment In Northeast China

Silver nanoparticles(AgNPs),as one of the most widely used metal nano materials,can enter the water and soil environment through various channels to produce toxicity to aquatic organisms,which can damage the ecological environment of water.Understanding the transformation and fate of AgNPs in water environment is very important for water quality management and ecological environment protection.The toxicity of AgNPs in groundwater environment is mainly determined by two factors:(1)the toxicity of AgNPs itself;(2)the transformation of AgNPs.The groundwater environment in real time due to the different physical and chemical properties,toxicity and influence on the transformation of AgNPs pH,ionic strength,organic matter content and dissolved oxygen and other water quality situation will change.In the groundwater environment,the toxicity of AgNPs is determined by two factors:(1)the toxicity of AgNPs itself;(2)the transformation of AgNPs.The physicochemical properties of the real groundwater environment will change with time and location,and the toxicity and transformation of AgNPs in groundwater flow and churning hydrological conditions and pH,ionic strength,organic matter content and dissolved oxygen of water quality will be affected.This experiment simulated the transformation process of AgNPs and silver ions in the groundwater environment in different regions of Northeast China,and identified the factors that affect the morphological transformation,and provided the theoretical basis for the prediction of the environmental ecological risk of AgNPs in the groundwater.The following conclusions can be drawn from the experimental data:(1)after the addition of AgNPs or silver ions,the coagulation deposition process can be combined with other ions to form a common precipitation;(2)the background fluid with the same concentration of AgNPs and silver ions,the background solution containing AgNPs particles in the settling velocity is greater than the addition of silver ion in water samples,which may be due to calcium ion on the nanoparticle coagulation effect.However,in the case of high dissolved oxygen,pH less than 7,AgNPs may first dissolve the silver ions released in order to lead to a reduction in the rate of AgNPs deposition;(3)in spite of the fact that AgNPs will eventually flocculation settling after entering the environment,AgNPs will still have a certain influence on the microorganism in the environment before fully flocculation sedimentation.If AgNPs is the first release of silver ions into the groundwater environment,not only the resulting silver ions will pose a threat to the water environment,but also to extend the AgNPs settling time.In addition,the silver ion into the aqueous environment can also react to produce coagulation sedimentation and chloride ion in the environment,and this process is relatively greater than AgNPs settlement process,This proves that the said silver ions in the water environment after entering will exist in the form of ion for a period of time,it will cause certain environmental threats.