Effect Of Natural Organic Matter In Water Bodies On The Photoconversion Process Of Metal Ions

The environmental processes of fine metal particles in aquatic systems have long been of great interest to researchers,and the influence of natural organic matter（NOM）in this environmental process has been a hot topic of research.NOM is widely distributed in soils,natural waters and sediments,and the environmental processes of fine metal particles affected by NOM mainly include redox,adsorption-desorption and photodegradation reactions,etc.Under the conditions of light irradiation,NOM can produce a variety of reactive oxygen species（ROS）,including singlet oxygen（¹O₂）,hydroxyl radicals（·OH）and superoxide radicals（O₂^-）,etc.These reactive oxygen species can chemically react with the coexisting metal fine particles in natural water bodies,and then affect the environmental transformation and homing of metal fine particles.Humic acid（HA）,as the main component in NOM,contains a large number of carboxyl groups,phenolic hydroxyl groups and other oxygen-containing functional groups,which are important catalysts for indirect photolysis of pollutants in the aqueous environment.Under the action of solar light,humic acid can produce ROS such as·OH,O₂^-,¹O₂,etc.Moreover,humic acid has strong complexation and adsorption ability for heavy metals and hydrophobic organic pollutants,and it can be used as an exogenous oxidizing/reducing agent to accelerate electron transfer and participate in redox reactions,therefore,the effect of HA on the photoreduction of fine metal particles The effect of HA on the phototransformation reaction of fine metal particles is therefore complex and multiple.Dissolved black carbon（DBC）is one of the highly photoactive components of NOM,which contains higher aromaticity and richer oxygen-containing functional groups compared with humic acid,and DBC can also effectively generate ROS and adsorb heavy metal ions,.Therefore,the photochemical properties of DBCs will have a significant impact on the environmental fate of organic pollutants and the morphology of metals in aquatic systems.Based on the fact that both organic substances have certain photochemical activity,however,the strength of photochemical activity of DBC and HA has not been explored in comparison,and the mechanism of the influence of these two NOMs on the photoconversion process of fine metal particles is relatively complex,and there are few relevant studies at this stage.Therefore,this paper will take precious metal nanoparticles（including gold and silver nanoparticles,with emphasis on silver nanoparticles）as the research object,and investigate the effect of DBC on the photoconversion process of metal fine particles and compare the ability of DBC and SRHA to photoreduce Ag⁺by conducting photochemical experiments,adsorption experiments,characterization of silver nanoparticles,and determination of reactive oxygen groups,etc.,and take commercial cadmium-based pigments as the research object by The photochemical experiments,inhibition tests,characterization of humic acid and determination of ROS were conducted to investigate the mechanism of HA on the phototransformation process of fine metal particles,and to provide experimental data and theoretical basis for the risk assessment and pollution control of fine metal particles in natural water bodies.