| Fine particulate matter has always been the focus of atmospheric science research due to its abundant content in the atmosphere,high reactivity,and important impact on the atmospheric chemical processes.Among them,mineral particles are easy to react heterogeneously with trace gases(such as hydrogen peroxide and oxygenated volatile organic compounds),which greatly increases the complexity of atmospheric chemical processes while changing the balance of trace gases or free radicals in the atmosphere.The physical and chemical properties of particulate matter will be changed by this heterogeneous reaction,which will affect the environmental effect of particulate matter.Due to their tiny size,atmospheric fine particulate matter can easily penetrate the bronchi and lungs by the way of inhalation,and cause damage throughout the body via the circulatory system.In addition,pollutant molecules in the atmosphere can be carried into the human body by fine particles,thereby increasing the intracellular bioaccessibility of pollutant molecules,which is called the "Trojan horse" effect.Understanding the mechanism and kinetics of heterogeneous reactions is crucial for a comprehensive understanding of atmospheric chemical behavior and the development of effective strategies to mitigate air pollution.On the other hand,knowing the transformation and fate of fine particles on the cell membrane is of great significance to correctly assess the ecological risk and toxicological effects of fine particles.In this paper,mineral particles and plastic particles were selected as fine particle models,and their heterogeneous reaction mechanisms with trace gases were studied by means of multiscale computational chemistry.On this basis,the transformation and fate of single-component atmospheric particles,heterogeneously modified atmospheric particles,and pollutant-carrying atmospheric particles on the cell membrane were explored,and their cytotoxicity was evaluated.The main research findings of this study are summarized as follows:(1)Heterogeneous reaction between hydrogen peroxide and silica particlesHydrogen peroxide(H2O2)is an oxidant that was widely present in the atmosphere.Due to its role as both a source and sink of free radicals,H2O2 influences the circulation and redistribution of free radicals,which in turn affects the atmospheric chemical reactions.In this study,the mechanism of the heterogeneous reaction between H2O2 and the typical mineral particle-SiO2 was investigated by using reactive molecular dynamics.Our results indicate that H2O2 molecules were adsorbed onto the surface of mineral particles through physical and chemical adsorption.The humidity level can significantly influence the heterogeneous reaction between H2O2 and SiO2 due to competition for reaction sites.As the heterogeneous reaction occurs,SiO2 particles collided with each other to form new particles.The rate of new particle formation at different humidity levels was calculated.It is found that the increase in humidity suppressed the new particle formation process.(2)Heterogeneous reaction between formic acid and mineral particle componentsFormic acid,as the most abundant carboxylic acid in the atmosphere,an important component of oxygenated volatile organic compounds,and an important contributor to atmospheric acidity,is responsible for controlling many atmospheric reactions.This study investigated the uptake process and heterogeneous mechanism of formic acid on SiO2 and TiO2 by using quantum chemical calculation and molecular dynamics simulation.It is found that electrostatic interaction and dispersion interaction were the primary factors responsible for the adsorption of formic acid onto the surface of these mineral particles.The Ti-OH and Ti-OCHO bonds were formed at the surface during the heterogeneous reaction stage.The coordination surface modes were dominated by the monodentate formate mode rather than bidentate formate mode.Most importantly,due to the water competed with formic acid for interaction sites on the TiO2 surface,the uptake process of formic acid on TiO2 particles was inhibited by water molecules and the suppression effect increases with the increase of humidity.(3)Absorption of typical heterogeneously modified mineral particle components on phospholipid bilayersBased on the above-mentioned heterogeneous reaction,molecular models of five different SiO2 particles that were heterogeneously modified were constructed,and their interaction with phospholipid bilayers was studied using molecular dynamics simulations.The studies demonstrated that SiO2 particles modified through the heterogeneous reaction with formic acid exhibit an increased interaction with phospholipid membranes.This interaction results in a reduction of the order parameter of the phospholipid molecules and reduced fluidity of the phospholipid membranes.As a result,the cytotoxicity of SiO2 particles increased following the heterogeneous modification with formic acid.Furthermore,it was observed that the integrity of the cell membrane was more severely compromised with increasing particle size.This effect may be attributed to the stronger interaction of larger SiO2 nanoparticles with the DPPC bi layer.which enables them to overcome the bending of the lipid bilayer and adapt the energy to the binding energy required for the SiO2 nanoparticles.(4)Effects of plastic particles on the integrity and fluidity of phospholipid membranesThe impact of five different flexible nanoplastics on the integrity and fluidity of phospholipid membranes was investigated using molecular dynamics simulations.Unlike rigid particles.plastic particles undergo a degree of deformation when attached to the phospholipid membrane.Some plastic particles can also penetrate the interior of the cell membrane and dissociate molecular chains inside.The adsorbed plastic particles have a significant impact on the fluidity of the phospholipid membrane,the average surface area of the phospholipid head,the compressibility coefficient,and the roughness.Additionally,the effects of different plastic particles on the integrity of phospholipid membranes were assessed,and the mechanisms by which two plastic particles reduced the thickness of phospholipid membranes were summarized.(5)Mechanism of atmospheric nanoparticles and trace gas synergistically adhering to biofilmsBased on the single-particle coating mechanism described above,we have constructed a SiO2 particle model carrying three trace gases,namely formic acid,methyl vinyl ketone,and methyl acrolein,at the molecular level.These trace gases have all been shown to have adverse effects on human health.Our research indicates that SiO2 particles carrying pollutants exhibit the same coating mechanism as single SiO2 particles.However,SiO2 particles can affect the attachment and distribution of trace gases on phospholipid membranes,with the specific mechanism being the "waterwheel model".That is,SiO2 particles first attach to the cell membrane,then transport pollutant gas molecules from the aqueous phase to the DPPC bilayer surface like a water wheel,and aggregate around the particle.This means that in addition to the commonly accepted "Trojan horse" effect,SiO2 particles may also increase their biological hazards by regulating the local concentration of pollutants. |
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