Ozonolysis Of Vinyl Ethers With The Participation Of Sea Spray Aerosol

The oceans and atmosphere are interconnected through the release and deposition of chemical species.Sea spray aerosols(SSA)represent the largest global aerosol source and plays a major,largely undetermined role in affecting our atmosphere.As a component of aerosols,vinyl ethers have been widely used in chemical industry.They are commonly used as fuels and fuel additives,which finally discharged into the atmosphere.Most of these vinyl ethers emitted to the atmosphere are small molecules with 4 to 6 carbons.However,there are few studies on the effects of reactions of vinyl ethers to secondary organic aerosols(SO As)in the atmosphere,and the mechanism has not been fully understood.At the same time,some studies have shown that with the large-scale emission of vinyl ethers,the atmospheric chemical reactions are significantly affected by sea salt,triggering more complex reactions.Therefore,it is necessary to study the generation and evolution of SSA,and the atmospheric evolution under the presence of vinyl ethers.In this work,a self-made sea spray aerosol generator device was used to generate submicron sea spray aerosols.Then,using the smog chamber system and matrix isolation technology,the gas-phase kinetics and reaction mechanism of vinyl ethers were explored.Finally,the effects of sea spray aerosols on SOA generated from the ozonolysis of vinyl ethers were systematically simulated.Our main work include the followings:(1)The formation of sea spray aerosols.Different combinations of NaCl,MgSO4,malonic acid(MA),D-fructose and sodium malonate were used to explore the effect of MA on submicron SSA generation.SSA particles were produced at room temperature by bubble bursting from an adjustable home-built SSA generator equipped with sintered glass filters.We found that MA could promote the generation of SSA particles and make the geometric mean diameter(GMD)to decrease for MA concentrations ranging between 8 and 32 mM and then,to increase for MA concentrations in the range of 64-60 mM.D-fructose could improve the generation of SSA with increasing GMD.Interestingly,sodium malonate could significantly enhance the production of SSA,with the change of morphology.Besides,different parameters including flow rate,underwater depth,pore size and size span of sintered glass filter and salinity of water were tested to obtain the characterization of our self-made adjustable SSA generator.Three modes could be found among different SSA generation methods,and they exhibited an obvious accumulation mode around 100 nm.The SSA generation under different conditions was compared with oceanic measurements from the literature,which showed that the sintered glass filter has advantages in generating submicron SSA from film drops.(2)The study of Criegee mechanism.The matrix isolation technique combined with infrared spectroscopy has been used to characterize Criegee intermediates(CI)and other products formed during the ozonolysis reactions of ethyl vinyl ether and n-butyl vinyl ether.Twin jet deposition at 14 K led to a number of new bands indicating the formation of products,with an intensity increase of?150%to 400%when annealing to 30 K.All the infrared absorptions could be assigned to different bands,which provided direct evidence for the formation of primary ozonides,CI and secondary ozonides in the systems investigated.Theoretical calculations at the B3LYP-D3/aug-cc-pVTZ level were carried out to complement the experimental observations.Experimental and theoretical results demonstrate that the studied ozonolysis reactions predominantly follow the Criegee mechanism.The current results will allow a better assessment of the potential environmental impacts of vinyl ethers.(3)Study on the kinetics and mechanism of ozonolysis of vinyl ethers.Rate coefficients at ambient temperature and atmospheric pressure for the reaction of ozone with 2-methoxypropene(2-MPE)and 2-ethoxypropene(2-EPE)were determined in a 100 L Teflon reaction chamber using absolute and relative rate methods.The product analysis experiments were carried out using a 50 L Teflon reaction chamber in conjunction with FTIR as the detection technique.The rate coefficients(k in unit cm3 molecule-1s-1)obtained are(1.18±0.13)×10-17 and(1.89±0.23)×10-17 for reactions with 2-MPE and 2-EPE,respectively.The effects of the alkoxy group on the gas-phase reactivity of alkyl vinyl ethers toward ozone are compared and discussed.The major ozonolysis products are methyl acetate,formaldehyde and CO2 for 2-MPE,and ethyl acetate,formaldehyde and CO2 for 2-EPE.Possible mechanisms for the two vinyl ethers are proposed based on the observed reaction products.Additionally,atmospheric lifetimes of 32 h and 21 h for 2-MPE and 2-EPE were estimated based on the measured rate constants and the tropospheric concentration of ozone,respectively.The obtained lifetimes indicate that the reaction with ozone is an important loss process for these vinyl ethers in the atmosphere,especially in polluted areas.(4)Study on SOA formation from the ozonolysis of vinyl ethers.Two kinds of seeds(NaCl and the mixture of NaCl and MA)were generated by SSA generator.The impacts of molecular structure,relative humidity(RH),OH scavenger and particle acidity on the formation of SOA from four alkyl vinyl ethers(EVE,2-EPE,2-MPE and BVE)ozonolysis were examined.The molecular structure of vinyl ethers influenced the formation of SOA.The yield from high to low are n-BVE?2-EPE?EVE and 2-MPE,which means vinyl ethers with longer carbon chain will have higher SOA yield.Meanwhile,the vinyl ethers with a linear chain have higher SOA formation rate than those with the branched chain.This result means the reaction of n-BVE with O3 has the highest SOA yield and formation rate.Increased RH appeared to suppress the formation.of SOA in moderate RH range(42%).This highlights the importance of competition between H2O and O3 in reacting with the stabilized Criegee intermediate in vinyl ethers ozonolysis at ambient RH.OH scavenger will remove OH radical generated in vinyl ethers ozonolysis and thus suppress the formation of SOA,which means the reaction associated with OH radicals facilitate the formation of SOA.Increased particle acidity mainly contributed to the change reaction path of vinyl-ethers-dominated SOA and thus reduce SOA formation.The results presented here extend previous analysis of vinyl-ethers-derived SOA and further aid our understanding of SOA formation potential of vinyl ethers ozonolysis under highly complex pollution conditions.Furthermore,the submicron sea spray aerosol can affect the atmospheric reaction process as seed aerosols.The influence of sea spray aerosol in the atmosphere cannot be ignored,especially considering its complex composition.