Thermodynamic modeling is still themostwidely usedmethod to characterize aerosol acidity,a critical physicochemical property of atmospheric aerosols.However,it remains unclear whether gas-aerosol partitioning should b...Thermodynamic modeling is still themostwidely usedmethod to characterize aerosol acidity,a critical physicochemical property of atmospheric aerosols.However,it remains unclear whether gas-aerosol partitioning should be incorporated when thermodynamicmodels are employed to estimate the acidity of coarse particles.In this work,field measurements were conducted at a coastal city in northern China across three seasons,and covered wide ranges of temperature,relative humidity and NH_(3) concentrations.We examined the performance of different modes of ISORROPIA-II(a widely used aerosol thermodynamic model)in estimating aerosol acidity of coarse and fine particles.The M0 mode,which incorporates gas-phase data and runs the model in the forward mode,provided reasonable estimation of aerosol acidity for coarse and fine particles.Compared to M0,the M1 mode,which runs the model in the forward mode but does not include gas-phase data,may capture the general trend of aerosol acidity but underestimates pH for both coarse and fine particles;M2,which runs the model in the reverse mode,results in large errors in estimated aerosol pH for both coarse and fine particles and should not be used for aerosol acidity calculations.However,M1 significantly underestimates liquid water contents for both fine and coarse particles,while M2 provides reliable estimation of liquid water contents.In summary,our work highlights the importance of incorporating gas-aerosol partitioning when estimating coarse particle acidity,and thus may help improve our understanding of acidity of coarse particles.展开更多
Exploring secondary organic aerosol(SOA)processes is crucial for understanding climate and air pollution in megacities.This study introduces a new method using positive matrix factorization(PMF)to investigate the SOA ...Exploring secondary organic aerosol(SOA)processes is crucial for understanding climate and air pollution in megacities.This study introduces a new method using positive matrix factorization(PMF)to investigate the SOA process by integrating the OA and associated ions previously misidentified as inorganic aerosol in high-resolution aerosol mass spectrometry data.The mass spectra and time series of primary OA(POA)and less oxidized oxygenated OA(OOA)identified by this new method resembled those resolved by traditional PMF.However,more oxidized OOA(MO-OOA)identified by traditional PMF can be further subdivided into multiple OA factors,including nitrogen-enriched OA(ON-OA)and sulfur-enriched OA(OS-OA)in summer,and ON-OA,OS-OA,and OOA in winter.Our findings highlight the significant role of photochemical processes in the formation of OS-OA compared to ON-OA.The compositions of reconstructed MO-OOA varied under different Ox(=O_(3)+NO_(2))and relative humidity conditions,emphasizing the limitations of using a constant mass spectrum.Aged biomass burning OA(BBOA)and coal combustion OA(CCOA),previously misattributed as POA,contributed 9.2%(0.43μg m^(−3))and 7.0%(0.33μg m^(−3))to SOA,respectively.Aged BBOA was more prone to forming OS-OA,whereas ON-OA showed higher correlations with aged CCOA,indicating distinct molecular compositions of SOA from different aged POA sources.Compared to aged BBOA,aged CCOA was more subject to conversion during aqueous phase processing.These results suggest that the variations in mass spectra and compositions need to be considered when simulating SOA processes.展开更多
Heterogeneous oxidation by gas-phase oxidants is an important chemical transformation pathway of secondary organic aerosol(SOA)and plays an important role in controlling the abundance,properties,as well as climate and...Heterogeneous oxidation by gas-phase oxidants is an important chemical transformation pathway of secondary organic aerosol(SOA)and plays an important role in controlling the abundance,properties,as well as climate and health impacts of aerosols.However,our knowledge on this heterogeneous chemistry remains inadequate.In this study,the heterogeneous oxidation ofα-pinene ozonolysis SOA by hydroxyl(OH)radicals was investigated under both low and high relative humidity(RH)conditions,with an emphasis on the evolution of molecular composition of SOA and its RH dependence.It is found that the heterogeneous oxidation of SOA at an OH exposure level equivalent to 12 hr of atmospheric aging leads to particle mass loss of 60%at 25%RH and 95%at 90%RH.The heterogeneous oxidation strongly changes the molecular composition of SOA.The dimer-to-monomer signal ratios increase dramatically with rising OH exposure,in particular under high RH conditions,suggesting that aerosol water stimulates the reaction of monomers with OH radicals more than that of dimers.In addition,the typical SOA tracer compounds such as pinic acid,pinonic acid,hydroxy pinonic acid and dimer esters(e.g.,C17H26O8 and C19H28O7)have lifetimes of several hours against heterogeneous OH oxidation under typical atmospheric conditions,which highlights the need for the consideration of their heterogeneous loss in the estimation of monoterpene SOA concentrations using tracer-based methods.Our study sheds lights on the heterogeneous oxidation chemistry ofmonoterpene SOA andwould help to understand their evolution and impacts in the atmosphere.展开更多
Aerosol hygroscopicity and liquid water content(ALWC)have important influences on the environmental and climate effect of aerosols.In this study,we measured the hygroscopic growth factors(GF)of particles with dry diam...Aerosol hygroscopicity and liquid water content(ALWC)have important influences on the environmental and climate effect of aerosols.In this study,we measured the hygroscopic growth factors(GF)of particles with dry diameters of 40,80,150,and 200 nm during the wintertime in Nanjing.Both the GF-derived hygroscopicity parameter(κ_(gf))and ALWC increased with particle size,but displayed differing diurnal variations,withκ_(gf)peaking around the midday,while ALWC peaking in the early morning.Nitrate,ammonium and oxygenated organic aerosols(OOA)were found as the chemical components mostly strongly correlated with ALWC.A closure study suggests that during midday photo-oxidation and nighttime high ALWC periods,theκof organic aerosols(κ_(org))was underestimated when using previous parameterizations.Accordingly,we re-constructed parameterizations forκ_(org)and the oxidation level of organics for these periods,which indicates a higher hygroscopicity of photochemically formed OOA than the aqueous OOA,yet both being much higher than the generally assumed OOA hygroscopicity.Additionally,in a typical high ALWC episode,concurrently increased ALWC,nitrate,OOA as well as aerosol surface area and mass concentrations were observed under elevated ambient RH.This strongly indicates a coupled effect that the hygroscopic secondary aerosols,in particular nitratewith strong hygroscopicity,led to large increase in ALWC,which in turn synergistically boosted nitrate and OOA formation by heterogeneous/aqueous reactions.Such interaction may represent an important mechanism contributing to enhanced formation of secondary aerosols and rapid growth of fine particulate matter under relatively high RH conditions.展开更多
Water-soluble organic aerosol(WSOA)plays a significant role in air quality and human health.Here we characterized the chemical properties and molecular compositions of WSOA at a rural site in North China Plain during ...Water-soluble organic aerosol(WSOA)plays a significant role in air quality and human health.Here we characterized the chemical properties and molecular compositions of WSOA at a rural site in North China Plain during winter using a high-resolution aerosol mass spectrometer and electrospray ionization high-resolution orbitrap mass spectrometer(ESI-HRMS).Our results show that the mass concentration of WSOA was significantly higher than that observed in Beijing in winter 2020,contributing about 56%of OA on average.CHO compounds(56%-74%)and CHN compounds(66%-80%)dominated in negative mode and positive mode,respectively,while CHON accounted for 15%-41%across both modes.The chemical characteristics of WSOA varied with polluted levels and between day and night.As pollution intensified,the abundance of CHO-compounds with condensed aromatics increased by 9%and the number of highly oxygenated molecules(HOMs)molecular formula detected in server haze was more than double that of clean days.CHO-compounds with ten carbon atoms(C_(10))were more abundant at night while those with nine carbon atoms(C_(9))were higher during the day.High levels of CHN+compounds were linked to nighttime biomass burning,whereas CHON compounds were more abundant during the day.Increased pollution also led to the formation of more complex CHON-compounds,indicating that organonitrates continue to play a significant role in rural pollution.展开更多
The impact of aerosols on clouds,which remains one of the largest aspects of uncertainty in current weather forecasting and climate change research,can be influenced by various factors,such as the underlying surface t...The impact of aerosols on clouds,which remains one of the largest aspects of uncertainty in current weather forecasting and climate change research,can be influenced by various factors,such as the underlying surface type,cloud type,cloud phase,and aerosol type.To explore the impact of different underlying surfaces on the effect of aerosols on cloud development,this study focused on the Yangtze River Delta(YRD)and its offshore regions(YRD sea)for a comparative analysis based on multi-source satellite data,while also considering the variations in cloud type and cloud phase.The results show lower cloud-top height and depth of single-layer clouds over the ocean than land,and higher liquid cloud in spring over the ocean.Aerosols are found to enhance the cumulus cloud depth through microphysical effects,which is particularly evident over the ocean.Aerosols are also found to decrease the cloud droplet effective radius in the ocean region and during the mature stage of cloud development in the land region,while opposite results are found during the early stage of cloud development in the land region.The quantitative results indicate that the indirect effect is positive(0.05)in the land region at relatively high cloud water path,which is smaller than that in the ocean region(0.11).The findings deepen our understanding of the influence aerosols on cloud development and the mechanisms involved,which could then be applied to improve the ability to simulate cloud-associated weather processes.展开更多
Aerosol acidity(pH)plays an important role in the multiphase chemical processes of atmospheric particles.In this study,we demonstrated the seasonal trends of aerosol pH calculated with the ISORROPIA-II model in a coas...Aerosol acidity(pH)plays an important role in the multiphase chemical processes of atmospheric particles.In this study,we demonstrated the seasonal trends of aerosol pH calculated with the ISORROPIA-II model in a coastal city of southeast China.We performed quantitative analysis on the various influencing factors on aerosol pH,and explored the responses of aerosol pH to different PM_(2.5)and O_(3)pollution levels.The results showed that the average aerosol pH was 2.92±0.61,following the order of winter>spring>summer>autumn.Sensitivity tests revealed that SO_(4)^(2−),NH_(x),T and RH triggered the variations of aerosol pH.Quantitative analysis results showed that T(37.9%-51.2%)was the main factors affecting pH variations in four seasons,followed by SO_(4)^(2−)(6.1%-23.7%),NH_(x)(7.2%-22.2%)and RH(0–14.2%).Totally,annual mean meteorological factors(52.9%)and chemical compositions(41.3%)commonly contributed the aerosolpH in the coastal city.The concentrations of PM_(2.5)was positively correlated with aerosol liquid water content(R^(2)=0.53)and aerosol pH(R^(2)=0.26),indicating that the increase in pH was related with the elevated NH_(4)NO_(3)and decreased SO_(4)^(2−),and also the changes of T and RH.The O_(x)(O_(3)+NO_(2))was moderately correlated with aerosol pH(R^(2)=-0.48),attributable to the fact that the proportion of SO_(4)^(2−)increased under high T and low RH conditions.The study strengthened our understanding of the contributions of influencing factors to aerosol pH,and also provided scientific evidences for chemical processes of atmospheric particles in coastal areas.展开更多
Nitrate renoxification significantly influences atmospheric nitrogen cycling and global OH budgets.Although numerous nitrite acid(HONO)formation pathways from nitrate photolysis have been widely reported,the influence...Nitrate renoxification significantly influences atmospheric nitrogen cycling and global OH budgets.Although numerous nitrite acid(HONO)formation pathways from nitrate photolysis have been widely reported,the influence of various environmental factors and aerosol properties on reactive nitrogen production remains largely unclear.In this work,we employed NaNO_(3)/humic acid(HA)as a model nitrate photosensitization system to investigate the crucial roles of aerosol acidity,organic fraction,and dissolved oxygen in the production of HONO,NO_(2),and NO_(2)^(-).The presence of HA at 10 mg/L resulted in a remarkable increase in HONO production rates by approximately 2–3 times and NO_(2)^(-) concentration by 3–6 times across a pH range of 5.2 to 2.0.Meanwhile,the molar fraction of gaseous HONO in total N(Ⅲ)production increased from4%to 69%as bulk-phase pH decreased from 5.2 to 2.0.The higher organic fraction(i.e.,20 and 50 mg/L HA concentration)instead inhibited HONO and NO_(2) release.The presence of dissolved oxygen was found to be adverse for reactive nitrogen production.This suggests that the HA photosensitizer promoted the secondary conversion of NO_(2) to HONO mainly via reduced ketyl radical intermediates,while superoxide radical formation might exert a negative effect.Our findings provide comprehensive insights into reactive nitrogen production from photosensitized nitrate photolysis mediated by various external and internal factors,potentially accounting for discrepancies between field observations and model simulations.展开更多
Carbonaceous aerosol,including organic carbon(OC)and elemental carbon(EC),has significant influence on human health,air quality and climate change.Accurate measurement of carbonaceous aerosol is essential to reduce th...Carbonaceous aerosol,including organic carbon(OC)and elemental carbon(EC),has significant influence on human health,air quality and climate change.Accurate measurement of carbonaceous aerosol is essential to reduce the uncertainty of radiative forcing estimation and source apportionment.The accurate separation of OC and EC is controversial due to the charring of OC.Therefore,the development of reference materials(RM)for the validation of OC/EC separation is an important basis for further study.Previous RMs were mainly based on ambient air sampling,which could not provide traceability of OC and EC concentration.To develop traceable RMs with known OC/EC contents,our study applied an improved aerosol generation and mixing technique,providing uniform deposition of particles on quartz filters.To generate OC aerosol with similar pyrolytic property of ambient aerosol,both water soluble organic carbon(WSOC)and water insoluble organic carbon(WIOC)were used,and amorphous carbon was selected for EC surrogate.The RMs were analyzed using different protocols.The homogeneity within the filter was validated,reaching below 2%.The long-term stability of RMs has been validated with RSD ranged from 1.7%–3.2%.Good correlationwas observed between nominal concentration of RMswithmeasured concentration by two protocols,while the difference of EC concentration was within 20%.The results indicated that the newly developed RMs were acceptable for the calibration of OC and EC,which could improve the accuracy of carbonaceous aerosol measurement.Moreover,the laboratory-generated EC-RMs could be suitable for the calibration of equivalent BC concentration by Aethalometers.展开更多
With the rapid development of the world economy,complex air pollution has increasingly become a serious threat;for example,with haze events occurring frequently in various regions of the globe.Recent evidence has indi...With the rapid development of the world economy,complex air pollution has increasingly become a serious threat;for example,with haze events occurring frequently in various regions of the globe.Recent evidence has indicated that secondary aerosols play an important role in haze formation,and that heterogeneous processes are among the main forces driving their explosive growth.In this regard,this paper reviews recent advances in the understanding of the impact of heterogeneous processes on haze chemistry,including the impact on NO_(2)chemistry,marine aerosols,and the hygroscopicity and optical properties of atmospheric aerosols.It is distinguished from past reviews on this topic by focusing mainly on new insights from the past five years.We summarize the main findings of the impacts of heterogeneous processes on NO_(2)chemistry,marine aerosols,and the physicochemical properties of atmospheric aerosols,and propose several future research directions.展开更多
Understanding the variations and potential source of air pollution is essential for implementing targeted mitigation actions.However,the distribution and long-term trends of Aerosol Optical Depth(AOD)and its component...Understanding the variations and potential source of air pollution is essential for implementing targeted mitigation actions.However,the distribution and long-term trends of Aerosol Optical Depth(AOD)and its components over the Fenwei Plain(FWP)have not been thoroughly investigated.Furthermore,the potential source contribution of AOD loading is still unclear.Thus,maximum synthesis and Mann-Kendall trend(MK)test with Sen's Slope methods are employed to reveal the spatiotemporal variation characteristics of AOD over the FWP.The Potential Source Contribution Function(PSCF)model was applied to analyze the potential source contribution of AOD over the FWP.Results demonstrated that the AOD in spatial pattern exhibited consistency with the topography.AOD over the FWP fluctuated annually from 2000 to 2020,with an increase in the previous decade followed by a gradual decline after 2011.There was a significant monthly variation in AOD with higher values in August(0.47±0.21)and lower in November(0.29±0.12).A positive AOD trend was confirmed from 2000 to 2010 yet a negative trend is identified from 2011 to 2020.The sulfate aerosol(AODSU)exhibited an increasing trend over an extended period.Clear-sky radiation shows a negative trend at the surface and the top of the atmosphere(TOA)from 2000 to 2010,which is consistent with the trend in AOD.The AOD in FWP was primarily influenced by local emissions,with contributions from northern and northwestern sources.This research offers an enhanced overarching comprehension of the distribution and regional climate effects of aerosols over the FWP.展开更多
It is highly challenging to precisely compare the impacts of anthropogenic pollutants on the photooxidation of isomeric volatile organic compounds with respect to molecular compositions and particle number/mass concen...It is highly challenging to precisely compare the impacts of anthropogenic pollutants on the photooxidation of isomeric volatile organic compounds with respect to molecular compositions and particle number/mass concentrations of secondary organic aerosols(SOAs).In this study,we conducted a series of well-defined indoor chamber experiments to compare the effects of NO_(x)(NO and NO_(2))on the photooxidation of isomeric monoterpenes ofβ-pinene and limonene.For the photooxidation ofβ-pinene with NO_(x),the increase of the initial concentrations of NO([NO]_(0))shows a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a monotonous enhancement of the particle mass concentration.For the photooxidation of limonene with NO_(x),the increase of[NO]_(0) exhibits a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a parabolic trend of the particle mass concentration.Utilizing a newly developed vacuum ultraviolet free electron laser(VUV-FEL),the online threshold photoionization mass spectrometry reveals a series of novel compounds at molecular weight(MW)=232 and 306 for theβ-pinene+NO_(x) system and MW=187,261,280,and 306 for the limonene+NO_(x) system.The molecular structures and formation pathways of these species were inferred,which led to the prediction of the diversity and difference of SOA products(i.e.,ester and peroxide accretion products)formed from different monoterpene precursors.To improve the predictions of future air quality,it is recommended that climate models should incorporate the NO_(x)-driven diurnal photooxidation of monoterpenes for SOA formation mechanisms.展开更多
1.Background Air pollution is a global environmental problem and has serious impacts on human health,climate change,and ecological systems.From the lessons learned by developed countries,the use of various energy type...1.Background Air pollution is a global environmental problem and has serious impacts on human health,climate change,and ecological systems.From the lessons learned by developed countries,the use of various energy types can result in different types of air pollution,such as smoke from coal burning and photochemical smog from gasoline/diesel vehicle emissions.Meanwhile,in China,rapid development in the last several decades has led to a drastic increase in coal consumption and the number of vehicles;and consequently,air pollution in China is complicated by the coexistence of high concentrations of primary and secondary trace gases and aerosol particles from multiple sources.The concept of an“air pollution complex”was first proposed by Xiaoyan TANG in 1997 to characterize the complexity of the formation mechanisms of air pollution,and calls for science-based control strategies(Zhu,2005).展开更多
Up-conversion(UC)luminescent materials doped with Ln^(3+)ions possess excellent optical properties and extensive applications in the formulation of multifunctional fluorescence ink.Printing technology offers various m...Up-conversion(UC)luminescent materials doped with Ln^(3+)ions possess excellent optical properties and extensive applications in the formulation of multifunctional fluorescence ink.Printing technology offers various methods for the preparation of UC fluorescent inks.This study introduced the optical properties of luminescent materials doped with Ln^(3+)ions,including luminescence characteristics and spectral characteristics,which provide a basis for the subsequent printing process.We also reviewed different printing techniques,including direct writing,screen printing,laser printing,inkjet printing,and aerosol jet printing(AJP),developed so far in the literature and explored the printing process of ink characteristics.However,the printing process of inks was explored and their potential for various applications was maximized.Therefore,the printing technology of UC fluorescent inks still faces challenges in different aspects.This review also points out the direction for future in-depth research,which is expected to promote further development and innovation in the field.展开更多
In this study, a variety of high-resolution satellite data were used to analyze the similarities and differences in horizontal and vertical cloud microphysical characteristics of 11 tropical cyclones(TCs) in three dif...In this study, a variety of high-resolution satellite data were used to analyze the similarities and differences in horizontal and vertical cloud microphysical characteristics of 11 tropical cyclones(TCs) in three different ocean basins.The results show that for the 11 TCs in different ocean basins, no matter in what season the TCs were generated when they reached or approached Category 4, their melting layers were all distributed in the vertical direction at the height of about 5 km. The high value of ice water contents in the vertical direction of 11 TCs all reach or approach about 2000 g cm^(–3).The total attenuated scattering coefficient at 532 nm, TAB-532, can successfully characterize the distribution of areas with high ice water content when the vertical distribution was concentrated near 0.1 km^(–1)sr^(–1), possibly because the diameter distribution of the corresponding range of aerosol particles had a more favorable effect on the formation of ice nuclei,indicating that aerosols had a significant impact on the ice-phase processes and characteristics. Moreover, by analyzing the horizontal cloud water content, the distribution analysis of cloud water path(CWP) and ice water path(IWP) shows that when the sea surface temperature was at a relatively high value, and the vertical wind shear was relatively small, the CWP and the IWP can reach a relatively high value, which also proves the importance of environmental field factors on the influence of TC cloud microphysical characteristics.展开更多
To investigate the seasonal characteristics in air pollution in Chengdu,a single particle aerosol mass spectrometry was used to continuously observe atmospheric fine particulate matter during one-month periods in summ...To investigate the seasonal characteristics in air pollution in Chengdu,a single particle aerosol mass spectrometry was used to continuously observe atmospheric fine particulate matter during one-month periods in summer and winter,respectively.The results showed that,apart from O_(3),the concentrations of other pollutants(CO,NO_(2),SO_(2),PM_(2.5)and PM_(10))were significantly higher in winter than in summer.All single particle aerosols were divided into seven categories:biomass burning(BB),coal combustion(CC),Dust,vehicle emission(VE),K mixedwith nitrate(K-NO_(3)),Kmixed with sulfate and nitrate(K-SN),and K mixedwith sulfate(K-SO_(4))particles.The highest contributions in both seasons were VE particles(24%).The higher contributions of K-SO_(4)(16%)and K-NO_(3)(10%)particles occurred in summer and winter,respectively,as a result of their different formation mechanisms.S-containing(KSO_(4)and K-SN),VE,and BB particles caused the evolution of pollution in both seasons,and they can be considered as targets for future pollution reduction.The mixing of primary sources particles(VE,Dust,CC,and BB)with secondary components was stronger in winter than in summer.In summer,as pollution worsens,the mixing of primary sources particles with 62[NO_(3)]−weakened,but themixing with 97[HSO_(4)]−increased.However,in winter,the mixing state of particles did not exhibit an obvious evolution rules.The potential source areas in summer were mainly distributed in the southern region of Sichuan,while in winter,besides the southern region,the contribution of the western region cannot be ignored.展开更多
Ultrasonic humidifiers are commonly used in households to maintain indoor humidity and generate a large number of droplets or spray aerosols.However,there have been various health concerns associated with humidifier u...Ultrasonic humidifiers are commonly used in households to maintain indoor humidity and generate a large number of droplets or spray aerosols.However,there have been various health concerns associated with humidifier use,largely due to aerosols generated during operation.Here,we investigated the size distribution,chemical composition,and charged fraction of aerosol particles emitted from commercial ultrasonic humidifiers.Heavy metals in water used for humidifiers were found to be highly enriched in the ultrasonic humidifier aerosols(UHA),with the enrichment factors ranging from 102 to 107.This enrichment may pose health concerns for the building occupants,as UHA concentrations of up to 106 particles/cm^(3) or 3 mg/m^(3) were observed.Furthermore,approximately 90%of UHA were observed to be electrically charged,for the first time according to our knowledge.Based on this discovery,we proposed and tested a newmethod to remove UHA by using a simple electrical field.The designed electrical field in this work can efficiently remove 81.4%of UHA.Therefore,applying this electrical field could be an effective method to significantly reduce the health risks by UHA.展开更多
Ultrabright femtosecond X-ray pulses generated by X-ray free-electron lasers(XFELs)enable the high-resolution determination of nanoparticle structures without crystallization or freezing.As each particle that interact...Ultrabright femtosecond X-ray pulses generated by X-ray free-electron lasers(XFELs)enable the high-resolution determination of nanoparticle structures without crystallization or freezing.As each particle that interacts with the pulse is destroyed,an aerodynamic lens(ADL)is used to update the particles by focusing them into a narrow beam in real time.Current single-particle imaging(SPI)experiments are limited by an insufficient number of diffraction patterns;therefore,optimized ADLs are required to improve the hit rate and signal-to-noise ratio,particularly for small particles.Herein,an efficient and simple method for designing ADLs and a new ADL specifically designed for SPI using this method are presented.A new method is proposed based on the functional relationship between a key parameter and its influencing parameters in the ADL,which is established through theoretical analysis and numerical simulations.A detailed design process for the new ADL is also introduced.Both simulations and experiments are performed to characterize the behavior of the particles in the ADL.The results show that particles with diameters ranging from 30 to 500 nm can be effectively focused into a narrow beam.In particular,particles smaller than 100 nm exhibit better performance at lower flow rates than the injector currently used in SPI.The new ADL increases the beam density and reduces the gas background noise.This new method facilitates the design of ADLs for SPI and has potential applications in other fields that utilize focused aerosol beams.展开更多
Nitrous acid(HONO)is a crucial source of OH radicals in the troposphere,significantly enhancing secondary pollutants like secondary organic aerosols(SOA)and peroxyacetyl nitrates(PAN).While prior research has examined...Nitrous acid(HONO)is a crucial source of OH radicals in the troposphere,significantly enhancing secondary pollutants like secondary organic aerosols(SOA)and peroxyacetyl nitrates(PAN).While prior research has examined HONO sources and their total impacts on secondary pollution,the specific enhancement capacity of each individual HONO source remains underexplored.This study uses observational data from 2015 to 2018 for HONO,SOA,and PAN across six sites in China,combined with WRF-Chem model adding six potential HONO sources to evaluate their capacity:traffic emissions(E_traffic),soil emissions(E_soil),indoor-outdoor exchange(E_indoor),nitrate photolysis(P_nit),and NO_(2) heterogeneous reactions on aerosol and ground surfaces(Het_a,Het_g).The simulated HONO contributions near the ground in urban Beijing were:12%from NO+OH(default source),10%-20%from E_traffic,1%-12%from P_nit,2%-10%from Het_a,and 50%-70% from Het_g.For SOA and PAN,we calculated incremental contributions enhanced by each HONO source and derived enhancement ratios(ERs)normalized against HONO’s contribution:~7 for P_nit,~2 for Het_a,~0.9 for Het_g,~0.8 for E_soil,~0.3 for E_traffic,and~0.1 for E_indoor.HONO sources’capacity to enhance secondary pollutants varies,being larger for aerosol-related sources.Vertical analysis on HONO concentration,spatial distribution,RO_(x) radical cycling rates,and OH enhancements revealed that aerosol-related HONO sources,especially P_nit,contribute more to secondary pollution.Future research should focus more on assessing real-world impacts of HONO sources,besides identifying their budgets.Additionally,uptake coefficient(γ)and nitrate photolysis frequency(J_(nitrate))critically affect HONO and secondary pollutant formation,necessitating further investigations.展开更多
Over the past decade,biomass burning has emerged as one of the main polluting events in northern India.It is one of the major sources of brown carbon(Br C),the light-absorbing organic carbon component of PM_(2.5).Most...Over the past decade,biomass burning has emerged as one of the main polluting events in northern India.It is one of the major sources of brown carbon(Br C),the light-absorbing organic carbon component of PM_(2.5).Most studies on the impact of biomass burning in India are based on source locations or urban areas;very little is known about its effects on a regional background location.We examine the effect of biomass burning on regional air quality and co-occurring meteorological factors.Year-long PM_(2.5)levels and light absorption by carbonaceous aerosols at 880 nm and 370 nm were measured at Rohtak,a regional background location.Results showed that post-harvest biomass burning in the Punjab-Haryana region affects the regional air quality with a lead of one to two days.A comparison of dispersionnormalized concentrations showed that open-field biomass burning not only affects regional air quality in the post-monsoon season(kharif crops)but is also a dominant source of PM_(2.5)in the post-harvest summer season(rabi crop).A significant(p<0.05)difference is observed in PM_(2.5),b_(abs-880),and b_(abs-370)between biomass burning days and non-biomass burning days during the kharif and rabi harvest seasons.Regression analyses confirm that in summer,regional PM_(2.5)and light absorption by aerosols are influenced more strongly by post-harvest burning of rabi crops.However,adverse meteorology plays a more dominant role in the post-monsoon season than biomass burning.These findings underscore the need for better policy interventions to curb biomass burning and improve air quality during both harvest seasons.展开更多
基金supported by the National Natural Science Foundation of China (Nos.42022050 and 42277088)the Guangdong Basic and Applied Basic Research Fund Committee (Nos.2021A1515011248 and 2023A1515012010)the Guangdong Foundation for the Program of Science and Technology Research (No.2020B1212060053).
文摘Thermodynamic modeling is still themostwidely usedmethod to characterize aerosol acidity,a critical physicochemical property of atmospheric aerosols.However,it remains unclear whether gas-aerosol partitioning should be incorporated when thermodynamicmodels are employed to estimate the acidity of coarse particles.In this work,field measurements were conducted at a coastal city in northern China across three seasons,and covered wide ranges of temperature,relative humidity and NH_(3) concentrations.We examined the performance of different modes of ISORROPIA-II(a widely used aerosol thermodynamic model)in estimating aerosol acidity of coarse and fine particles.The M0 mode,which incorporates gas-phase data and runs the model in the forward mode,provided reasonable estimation of aerosol acidity for coarse and fine particles.Compared to M0,the M1 mode,which runs the model in the forward mode but does not include gas-phase data,may capture the general trend of aerosol acidity but underestimates pH for both coarse and fine particles;M2,which runs the model in the reverse mode,results in large errors in estimated aerosol pH for both coarse and fine particles and should not be used for aerosol acidity calculations.However,M1 significantly underestimates liquid water contents for both fine and coarse particles,while M2 provides reliable estimation of liquid water contents.In summary,our work highlights the importance of incorporating gas-aerosol partitioning when estimating coarse particle acidity,and thus may help improve our understanding of acidity of coarse particles.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0760200)the National Natural Science Foundation of China(Grant No.42377101,91744207).
文摘Exploring secondary organic aerosol(SOA)processes is crucial for understanding climate and air pollution in megacities.This study introduces a new method using positive matrix factorization(PMF)to investigate the SOA process by integrating the OA and associated ions previously misidentified as inorganic aerosol in high-resolution aerosol mass spectrometry data.The mass spectra and time series of primary OA(POA)and less oxidized oxygenated OA(OOA)identified by this new method resembled those resolved by traditional PMF.However,more oxidized OOA(MO-OOA)identified by traditional PMF can be further subdivided into multiple OA factors,including nitrogen-enriched OA(ON-OA)and sulfur-enriched OA(OS-OA)in summer,and ON-OA,OS-OA,and OOA in winter.Our findings highlight the significant role of photochemical processes in the formation of OS-OA compared to ON-OA.The compositions of reconstructed MO-OOA varied under different Ox(=O_(3)+NO_(2))and relative humidity conditions,emphasizing the limitations of using a constant mass spectrum.Aged biomass burning OA(BBOA)and coal combustion OA(CCOA),previously misattributed as POA,contributed 9.2%(0.43μg m^(−3))and 7.0%(0.33μg m^(−3))to SOA,respectively.Aged BBOA was more prone to forming OS-OA,whereas ON-OA showed higher correlations with aged CCOA,indicating distinct molecular compositions of SOA from different aged POA sources.Compared to aged BBOA,aged CCOA was more subject to conversion during aqueous phase processing.These results suggest that the variations in mass spectra and compositions need to be considered when simulating SOA processes.
基金supported by the National Natural Science Foundation of China (Nos.22022607 and 42005090)the Shanghai Pujiang Program (No.20PJ1407600)。
文摘Heterogeneous oxidation by gas-phase oxidants is an important chemical transformation pathway of secondary organic aerosol(SOA)and plays an important role in controlling the abundance,properties,as well as climate and health impacts of aerosols.However,our knowledge on this heterogeneous chemistry remains inadequate.In this study,the heterogeneous oxidation ofα-pinene ozonolysis SOA by hydroxyl(OH)radicals was investigated under both low and high relative humidity(RH)conditions,with an emphasis on the evolution of molecular composition of SOA and its RH dependence.It is found that the heterogeneous oxidation of SOA at an OH exposure level equivalent to 12 hr of atmospheric aging leads to particle mass loss of 60%at 25%RH and 95%at 90%RH.The heterogeneous oxidation strongly changes the molecular composition of SOA.The dimer-to-monomer signal ratios increase dramatically with rising OH exposure,in particular under high RH conditions,suggesting that aerosol water stimulates the reaction of monomers with OH radicals more than that of dimers.In addition,the typical SOA tracer compounds such as pinic acid,pinonic acid,hydroxy pinonic acid and dimer esters(e.g.,C17H26O8 and C19H28O7)have lifetimes of several hours against heterogeneous OH oxidation under typical atmospheric conditions,which highlights the need for the consideration of their heterogeneous loss in the estimation of monoterpene SOA concentrations using tracer-based methods.Our study sheds lights on the heterogeneous oxidation chemistry ofmonoterpene SOA andwould help to understand their evolution and impacts in the atmosphere.
基金supported by the National Natural Science Foundation of China(Nos.42275116 and 41975172).
文摘Aerosol hygroscopicity and liquid water content(ALWC)have important influences on the environmental and climate effect of aerosols.In this study,we measured the hygroscopic growth factors(GF)of particles with dry diameters of 40,80,150,and 200 nm during the wintertime in Nanjing.Both the GF-derived hygroscopicity parameter(κ_(gf))and ALWC increased with particle size,but displayed differing diurnal variations,withκ_(gf)peaking around the midday,while ALWC peaking in the early morning.Nitrate,ammonium and oxygenated organic aerosols(OOA)were found as the chemical components mostly strongly correlated with ALWC.A closure study suggests that during midday photo-oxidation and nighttime high ALWC periods,theκof organic aerosols(κ_(org))was underestimated when using previous parameterizations.Accordingly,we re-constructed parameterizations forκ_(org)and the oxidation level of organics for these periods,which indicates a higher hygroscopicity of photochemically formed OOA than the aqueous OOA,yet both being much higher than the generally assumed OOA hygroscopicity.Additionally,in a typical high ALWC episode,concurrently increased ALWC,nitrate,OOA as well as aerosol surface area and mass concentrations were observed under elevated ambient RH.This strongly indicates a coupled effect that the hygroscopic secondary aerosols,in particular nitratewith strong hygroscopicity,led to large increase in ALWC,which in turn synergistically boosted nitrate and OOA formation by heterogeneous/aqueous reactions.Such interaction may represent an important mechanism contributing to enhanced formation of secondary aerosols and rapid growth of fine particulate matter under relatively high RH conditions.
基金supported by the National Natural Science Foundation of China(No.42307139)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0760200)。
文摘Water-soluble organic aerosol(WSOA)plays a significant role in air quality and human health.Here we characterized the chemical properties and molecular compositions of WSOA at a rural site in North China Plain during winter using a high-resolution aerosol mass spectrometer and electrospray ionization high-resolution orbitrap mass spectrometer(ESI-HRMS).Our results show that the mass concentration of WSOA was significantly higher than that observed in Beijing in winter 2020,contributing about 56%of OA on average.CHO compounds(56%-74%)and CHN compounds(66%-80%)dominated in negative mode and positive mode,respectively,while CHON accounted for 15%-41%across both modes.The chemical characteristics of WSOA varied with polluted levels and between day and night.As pollution intensified,the abundance of CHO-compounds with condensed aromatics increased by 9%and the number of highly oxygenated molecules(HOMs)molecular formula detected in server haze was more than double that of clean days.CHO-compounds with ten carbon atoms(C_(10))were more abundant at night while those with nine carbon atoms(C_(9))were higher during the day.High levels of CHN+compounds were linked to nighttime biomass burning,whereas CHON compounds were more abundant during the day.Increased pollution also led to the formation of more complex CHON-compounds,indicating that organonitrates continue to play a significant role in rural pollution.
基金supported by the National Natural Science Foundation of China(Grant No.42230601).
文摘The impact of aerosols on clouds,which remains one of the largest aspects of uncertainty in current weather forecasting and climate change research,can be influenced by various factors,such as the underlying surface type,cloud type,cloud phase,and aerosol type.To explore the impact of different underlying surfaces on the effect of aerosols on cloud development,this study focused on the Yangtze River Delta(YRD)and its offshore regions(YRD sea)for a comparative analysis based on multi-source satellite data,while also considering the variations in cloud type and cloud phase.The results show lower cloud-top height and depth of single-layer clouds over the ocean than land,and higher liquid cloud in spring over the ocean.Aerosols are found to enhance the cumulus cloud depth through microphysical effects,which is particularly evident over the ocean.Aerosols are also found to decrease the cloud droplet effective radius in the ocean region and during the mature stage of cloud development in the land region,while opposite results are found during the early stage of cloud development in the land region.The quantitative results indicate that the indirect effect is positive(0.05)in the land region at relatively high cloud water path,which is smaller than that in the ocean region(0.11).The findings deepen our understanding of the influence aerosols on cloud development and the mechanisms involved,which could then be applied to improve the ability to simulate cloud-associated weather processes.
基金supported by the National Natural Science Foundation of China(Nos.42277091 and U22A20578)Xiamen Youth Innovation Fund Project(No.3502Z20206094)+1 种基金Fujian Provincial Environmental Protection Science&Technology Plan Projects(No.2023R004)Xiamen Atmospheric Environment Observation and Research Station of Fujian Province.
文摘Aerosol acidity(pH)plays an important role in the multiphase chemical processes of atmospheric particles.In this study,we demonstrated the seasonal trends of aerosol pH calculated with the ISORROPIA-II model in a coastal city of southeast China.We performed quantitative analysis on the various influencing factors on aerosol pH,and explored the responses of aerosol pH to different PM_(2.5)and O_(3)pollution levels.The results showed that the average aerosol pH was 2.92±0.61,following the order of winter>spring>summer>autumn.Sensitivity tests revealed that SO_(4)^(2−),NH_(x),T and RH triggered the variations of aerosol pH.Quantitative analysis results showed that T(37.9%-51.2%)was the main factors affecting pH variations in four seasons,followed by SO_(4)^(2−)(6.1%-23.7%),NH_(x)(7.2%-22.2%)and RH(0–14.2%).Totally,annual mean meteorological factors(52.9%)and chemical compositions(41.3%)commonly contributed the aerosolpH in the coastal city.The concentrations of PM_(2.5)was positively correlated with aerosol liquid water content(R^(2)=0.53)and aerosol pH(R^(2)=0.26),indicating that the increase in pH was related with the elevated NH_(4)NO_(3)and decreased SO_(4)^(2−),and also the changes of T and RH.The O_(x)(O_(3)+NO_(2))was moderately correlated with aerosol pH(R^(2)=-0.48),attributable to the fact that the proportion of SO_(4)^(2−)increased under high T and low RH conditions.The study strengthened our understanding of the contributions of influencing factors to aerosol pH,and also provided scientific evidences for chemical processes of atmospheric particles in coastal areas.
基金supported by the National Key R&D Program of China(No.2022YFC3701102)the National Natural Science Foundation of China(Nos.22376029,22176038,91744205 and 21777025)the Natural Science Foundation of Shanghai City(No.22ZR1404700).
文摘Nitrate renoxification significantly influences atmospheric nitrogen cycling and global OH budgets.Although numerous nitrite acid(HONO)formation pathways from nitrate photolysis have been widely reported,the influence of various environmental factors and aerosol properties on reactive nitrogen production remains largely unclear.In this work,we employed NaNO_(3)/humic acid(HA)as a model nitrate photosensitization system to investigate the crucial roles of aerosol acidity,organic fraction,and dissolved oxygen in the production of HONO,NO_(2),and NO_(2)^(-).The presence of HA at 10 mg/L resulted in a remarkable increase in HONO production rates by approximately 2–3 times and NO_(2)^(-) concentration by 3–6 times across a pH range of 5.2 to 2.0.Meanwhile,the molar fraction of gaseous HONO in total N(Ⅲ)production increased from4%to 69%as bulk-phase pH decreased from 5.2 to 2.0.The higher organic fraction(i.e.,20 and 50 mg/L HA concentration)instead inhibited HONO and NO_(2) release.The presence of dissolved oxygen was found to be adverse for reactive nitrogen production.This suggests that the HA photosensitizer promoted the secondary conversion of NO_(2) to HONO mainly via reduced ketyl radical intermediates,while superoxide radical formation might exert a negative effect.Our findings provide comprehensive insights into reactive nitrogen production from photosensitized nitrate photolysis mediated by various external and internal factors,potentially accounting for discrepancies between field observations and model simulations.
基金supported by the National Natural Science Foundation of China(No.22206180)the funds for establishing basic quality and technology capabilities(No.ANL2203)the special fund for basic scientific research business of central public research institutes(No.AKYZD2207-4)。
文摘Carbonaceous aerosol,including organic carbon(OC)and elemental carbon(EC),has significant influence on human health,air quality and climate change.Accurate measurement of carbonaceous aerosol is essential to reduce the uncertainty of radiative forcing estimation and source apportionment.The accurate separation of OC and EC is controversial due to the charring of OC.Therefore,the development of reference materials(RM)for the validation of OC/EC separation is an important basis for further study.Previous RMs were mainly based on ambient air sampling,which could not provide traceability of OC and EC concentration.To develop traceable RMs with known OC/EC contents,our study applied an improved aerosol generation and mixing technique,providing uniform deposition of particles on quartz filters.To generate OC aerosol with similar pyrolytic property of ambient aerosol,both water soluble organic carbon(WSOC)and water insoluble organic carbon(WIOC)were used,and amorphous carbon was selected for EC surrogate.The RMs were analyzed using different protocols.The homogeneity within the filter was validated,reaching below 2%.The long-term stability of RMs has been validated with RSD ranged from 1.7%–3.2%.Good correlationwas observed between nominal concentration of RMswithmeasured concentration by two protocols,while the difference of EC concentration was within 20%.The results indicated that the newly developed RMs were acceptable for the calibration of OC and EC,which could improve the accuracy of carbonaceous aerosol measurement.Moreover,the laboratory-generated EC-RMs could be suitable for the calibration of equivalent BC concentration by Aethalometers.
基金supported by the National Key Research and Development Program of China(No.2022YFC3701000)the National Natural Science Foundation of China(Nos.42130606 and 41931287)+1 种基金the Beijing National Laboratory for Molecular Sciences(BNLMS-CXXM-202011)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.Y2021013).
文摘With the rapid development of the world economy,complex air pollution has increasingly become a serious threat;for example,with haze events occurring frequently in various regions of the globe.Recent evidence has indicated that secondary aerosols play an important role in haze formation,and that heterogeneous processes are among the main forces driving their explosive growth.In this regard,this paper reviews recent advances in the understanding of the impact of heterogeneous processes on haze chemistry,including the impact on NO_(2)chemistry,marine aerosols,and the hygroscopicity and optical properties of atmospheric aerosols.It is distinguished from past reviews on this topic by focusing mainly on new insights from the past five years.We summarize the main findings of the impacts of heterogeneous processes on NO_(2)chemistry,marine aerosols,and the physicochemical properties of atmospheric aerosols,and propose several future research directions.
基金supported by the National Natural Science Foundation of China(No.41905016)the Key Research and Development Program of Shaanxi Province(No.2024SF-YBXM-583)+1 种基金the Key Research and Development Project of Shaanxi Province(No.2021ZDLSF-05-07)the National Key Research and Development Plan of China(No.2017YFC0212206).
文摘Understanding the variations and potential source of air pollution is essential for implementing targeted mitigation actions.However,the distribution and long-term trends of Aerosol Optical Depth(AOD)and its components over the Fenwei Plain(FWP)have not been thoroughly investigated.Furthermore,the potential source contribution of AOD loading is still unclear.Thus,maximum synthesis and Mann-Kendall trend(MK)test with Sen's Slope methods are employed to reveal the spatiotemporal variation characteristics of AOD over the FWP.The Potential Source Contribution Function(PSCF)model was applied to analyze the potential source contribution of AOD over the FWP.Results demonstrated that the AOD in spatial pattern exhibited consistency with the topography.AOD over the FWP fluctuated annually from 2000 to 2020,with an increase in the previous decade followed by a gradual decline after 2011.There was a significant monthly variation in AOD with higher values in August(0.47±0.21)and lower in November(0.29±0.12).A positive AOD trend was confirmed from 2000 to 2010 yet a negative trend is identified from 2011 to 2020.The sulfate aerosol(AODSU)exhibited an increasing trend over an extended period.Clear-sky radiation shows a negative trend at the surface and the top of the atmosphere(TOA)from 2000 to 2010,which is consistent with the trend in AOD.The AOD in FWP was primarily influenced by local emissions,with contributions from northern and northwestern sources.This research offers an enhanced overarching comprehension of the distribution and regional climate effects of aerosols over the FWP.
基金supported by the National Natural Science Foundation of China(Nos.22125303,92361302,92061203,22103082,22273101,22288201,and 21327901)the National Key Research and Development Program of China(No.2021YFA1400501)+3 种基金the Innovation Program for Quantum Science and Technology(No.2021ZD0303304)Dalian Institute of Chemical Physics(No.DICPI202437)Chinese Academy of Sciences(No.GJJSTD20220001)the International Partnership Program of CAS(No.121421KYSB20170012)。
文摘It is highly challenging to precisely compare the impacts of anthropogenic pollutants on the photooxidation of isomeric volatile organic compounds with respect to molecular compositions and particle number/mass concentrations of secondary organic aerosols(SOAs).In this study,we conducted a series of well-defined indoor chamber experiments to compare the effects of NO_(x)(NO and NO_(2))on the photooxidation of isomeric monoterpenes ofβ-pinene and limonene.For the photooxidation ofβ-pinene with NO_(x),the increase of the initial concentrations of NO([NO]_(0))shows a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a monotonous enhancement of the particle mass concentration.For the photooxidation of limonene with NO_(x),the increase of[NO]_(0) exhibits a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a parabolic trend of the particle mass concentration.Utilizing a newly developed vacuum ultraviolet free electron laser(VUV-FEL),the online threshold photoionization mass spectrometry reveals a series of novel compounds at molecular weight(MW)=232 and 306 for theβ-pinene+NO_(x) system and MW=187,261,280,and 306 for the limonene+NO_(x) system.The molecular structures and formation pathways of these species were inferred,which led to the prediction of the diversity and difference of SOA products(i.e.,ester and peroxide accretion products)formed from different monoterpene precursors.To improve the predictions of future air quality,it is recommended that climate models should incorporate the NO_(x)-driven diurnal photooxidation of monoterpenes for SOA formation mechanisms.
基金the National Natural Science Foundation of China(Grant No.91844000)is acknowledged.
文摘1.Background Air pollution is a global environmental problem and has serious impacts on human health,climate change,and ecological systems.From the lessons learned by developed countries,the use of various energy types can result in different types of air pollution,such as smoke from coal burning and photochemical smog from gasoline/diesel vehicle emissions.Meanwhile,in China,rapid development in the last several decades has led to a drastic increase in coal consumption and the number of vehicles;and consequently,air pollution in China is complicated by the coexistence of high concentrations of primary and secondary trace gases and aerosol particles from multiple sources.The concept of an“air pollution complex”was first proposed by Xiaoyan TANG in 1997 to characterize the complexity of the formation mechanisms of air pollution,and calls for science-based control strategies(Zhu,2005).
基金Project supported by National Natural Science Foundation of China(51962006)the High-level Talents Research Initiation Project of JXUST(205200100545)+1 种基金the Young Elite Scientists Sponsorship Program by CAST(2022QNRC001)Jiangxi Natural Science Foundation of China(20224BAB214029,20232BAB204021)。
文摘Up-conversion(UC)luminescent materials doped with Ln^(3+)ions possess excellent optical properties and extensive applications in the formulation of multifunctional fluorescence ink.Printing technology offers various methods for the preparation of UC fluorescent inks.This study introduced the optical properties of luminescent materials doped with Ln^(3+)ions,including luminescence characteristics and spectral characteristics,which provide a basis for the subsequent printing process.We also reviewed different printing techniques,including direct writing,screen printing,laser printing,inkjet printing,and aerosol jet printing(AJP),developed so far in the literature and explored the printing process of ink characteristics.However,the printing process of inks was explored and their potential for various applications was maximized.Therefore,the printing technology of UC fluorescent inks still faces challenges in different aspects.This review also points out the direction for future in-depth research,which is expected to promote further development and innovation in the field.
基金National Natural Science Foundation of China(42192554, 42175008)Shanghai Typhoon Research Foundation(TFJJ202201)+1 种基金S&T Development Fund of CAMS (2022KJ012)Basic Research Fund of CAMS (2022Y006)。
文摘In this study, a variety of high-resolution satellite data were used to analyze the similarities and differences in horizontal and vertical cloud microphysical characteristics of 11 tropical cyclones(TCs) in three different ocean basins.The results show that for the 11 TCs in different ocean basins, no matter in what season the TCs were generated when they reached or approached Category 4, their melting layers were all distributed in the vertical direction at the height of about 5 km. The high value of ice water contents in the vertical direction of 11 TCs all reach or approach about 2000 g cm^(–3).The total attenuated scattering coefficient at 532 nm, TAB-532, can successfully characterize the distribution of areas with high ice water content when the vertical distribution was concentrated near 0.1 km^(–1)sr^(–1), possibly because the diameter distribution of the corresponding range of aerosol particles had a more favorable effect on the formation of ice nuclei,indicating that aerosols had a significant impact on the ice-phase processes and characteristics. Moreover, by analyzing the horizontal cloud water content, the distribution analysis of cloud water path(CWP) and ice water path(IWP) shows that when the sea surface temperature was at a relatively high value, and the vertical wind shear was relatively small, the CWP and the IWP can reach a relatively high value, which also proves the importance of environmental field factors on the influence of TC cloud microphysical characteristics.
基金supported by the Basic Research Cultivation Support Plan of Southwest Jiaotong University(No.2682023ZTPY016)the Natural Science Foundation of Sichuan Province(No.2022NSFSC0982)the National Natural Science Foundation of China(Nos.U23A2030,42205100,and 41805095).
文摘To investigate the seasonal characteristics in air pollution in Chengdu,a single particle aerosol mass spectrometry was used to continuously observe atmospheric fine particulate matter during one-month periods in summer and winter,respectively.The results showed that,apart from O_(3),the concentrations of other pollutants(CO,NO_(2),SO_(2),PM_(2.5)and PM_(10))were significantly higher in winter than in summer.All single particle aerosols were divided into seven categories:biomass burning(BB),coal combustion(CC),Dust,vehicle emission(VE),K mixedwith nitrate(K-NO_(3)),Kmixed with sulfate and nitrate(K-SN),and K mixedwith sulfate(K-SO_(4))particles.The highest contributions in both seasons were VE particles(24%).The higher contributions of K-SO_(4)(16%)and K-NO_(3)(10%)particles occurred in summer and winter,respectively,as a result of their different formation mechanisms.S-containing(KSO_(4)and K-SN),VE,and BB particles caused the evolution of pollution in both seasons,and they can be considered as targets for future pollution reduction.The mixing of primary sources particles(VE,Dust,CC,and BB)with secondary components was stronger in winter than in summer.In summer,as pollution worsens,the mixing of primary sources particles with 62[NO_(3)]−weakened,but themixing with 97[HSO_(4)]−increased.However,in winter,the mixing state of particles did not exhibit an obvious evolution rules.The potential source areas in summer were mainly distributed in the southern region of Sichuan,while in winter,besides the southern region,the contribution of the western region cannot be ignored.
基金supported by the National Natural Science Foundation of China (Nos.42077193 and 21976034)the National Key R&D Program (Nos.2022YFC3702600 and 2022YFC3702601)the Shanghai Natural Science Foundation (23ZR1479700).
文摘Ultrasonic humidifiers are commonly used in households to maintain indoor humidity and generate a large number of droplets or spray aerosols.However,there have been various health concerns associated with humidifier use,largely due to aerosols generated during operation.Here,we investigated the size distribution,chemical composition,and charged fraction of aerosol particles emitted from commercial ultrasonic humidifiers.Heavy metals in water used for humidifiers were found to be highly enriched in the ultrasonic humidifier aerosols(UHA),with the enrichment factors ranging from 102 to 107.This enrichment may pose health concerns for the building occupants,as UHA concentrations of up to 106 particles/cm^(3) or 3 mg/m^(3) were observed.Furthermore,approximately 90%of UHA were observed to be electrically charged,for the first time according to our knowledge.Based on this discovery,we proposed and tested a newmethod to remove UHA by using a simple electrical field.The designed electrical field in this work can efficiently remove 81.4%of UHA.Therefore,applying this electrical field could be an effective method to significantly reduce the health risks by UHA.
基金supported by the Major State Basic Research Development Program of China(No.2022YFA1603703)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB 37040303)+1 种基金National Natural Science Foundation of China(No.12335020)Shanghai Soft X-ray Free Electron Laser Facility beamline project.
文摘Ultrabright femtosecond X-ray pulses generated by X-ray free-electron lasers(XFELs)enable the high-resolution determination of nanoparticle structures without crystallization or freezing.As each particle that interacts with the pulse is destroyed,an aerodynamic lens(ADL)is used to update the particles by focusing them into a narrow beam in real time.Current single-particle imaging(SPI)experiments are limited by an insufficient number of diffraction patterns;therefore,optimized ADLs are required to improve the hit rate and signal-to-noise ratio,particularly for small particles.Herein,an efficient and simple method for designing ADLs and a new ADL specifically designed for SPI using this method are presented.A new method is proposed based on the functional relationship between a key parameter and its influencing parameters in the ADL,which is established through theoretical analysis and numerical simulations.A detailed design process for the new ADL is also introduced.Both simulations and experiments are performed to characterize the behavior of the particles in the ADL.The results show that particles with diameters ranging from 30 to 500 nm can be effectively focused into a narrow beam.In particular,particles smaller than 100 nm exhibit better performance at lower flow rates than the injector currently used in SPI.The new ADL increases the beam density and reduces the gas background noise.This new method facilitates the design of ADLs for SPI and has potential applications in other fields that utilize focused aerosol beams.
基金supported by the National Natural Science Foundation of China(Nos.92044302,42075108,42107124,41822703,91544221,91844301,and 22222610)Beijing National Laboratory for Molecular Sciences(No.BNLMS-CXXM-202011)the Natural Science Foundation of Yunnan Province(No.202302AN360006)。
文摘Nitrous acid(HONO)is a crucial source of OH radicals in the troposphere,significantly enhancing secondary pollutants like secondary organic aerosols(SOA)and peroxyacetyl nitrates(PAN).While prior research has examined HONO sources and their total impacts on secondary pollution,the specific enhancement capacity of each individual HONO source remains underexplored.This study uses observational data from 2015 to 2018 for HONO,SOA,and PAN across six sites in China,combined with WRF-Chem model adding six potential HONO sources to evaluate their capacity:traffic emissions(E_traffic),soil emissions(E_soil),indoor-outdoor exchange(E_indoor),nitrate photolysis(P_nit),and NO_(2) heterogeneous reactions on aerosol and ground surfaces(Het_a,Het_g).The simulated HONO contributions near the ground in urban Beijing were:12%from NO+OH(default source),10%-20%from E_traffic,1%-12%from P_nit,2%-10%from Het_a,and 50%-70% from Het_g.For SOA and PAN,we calculated incremental contributions enhanced by each HONO source and derived enhancement ratios(ERs)normalized against HONO’s contribution:~7 for P_nit,~2 for Het_a,~0.9 for Het_g,~0.8 for E_soil,~0.3 for E_traffic,and~0.1 for E_indoor.HONO sources’capacity to enhance secondary pollutants varies,being larger for aerosol-related sources.Vertical analysis on HONO concentration,spatial distribution,RO_(x) radical cycling rates,and OH enhancements revealed that aerosol-related HONO sources,especially P_nit,contribute more to secondary pollution.Future research should focus more on assessing real-world impacts of HONO sources,besides identifying their budgets.Additionally,uptake coefficient(γ)and nitrate photolysis frequency(J_(nitrate))critically affect HONO and secondary pollutant formation,necessitating further investigations.
基金supported by the Ministry of Environment,Forest and Climate Change(Mo Fand CC),Government of India,under the NCAP-COALESCE project(No.14/10/2014-CC(Vol.II))。
文摘Over the past decade,biomass burning has emerged as one of the main polluting events in northern India.It is one of the major sources of brown carbon(Br C),the light-absorbing organic carbon component of PM_(2.5).Most studies on the impact of biomass burning in India are based on source locations or urban areas;very little is known about its effects on a regional background location.We examine the effect of biomass burning on regional air quality and co-occurring meteorological factors.Year-long PM_(2.5)levels and light absorption by carbonaceous aerosols at 880 nm and 370 nm were measured at Rohtak,a regional background location.Results showed that post-harvest biomass burning in the Punjab-Haryana region affects the regional air quality with a lead of one to two days.A comparison of dispersionnormalized concentrations showed that open-field biomass burning not only affects regional air quality in the post-monsoon season(kharif crops)but is also a dominant source of PM_(2.5)in the post-harvest summer season(rabi crop).A significant(p<0.05)difference is observed in PM_(2.5),b_(abs-880),and b_(abs-370)between biomass burning days and non-biomass burning days during the kharif and rabi harvest seasons.Regression analyses confirm that in summer,regional PM_(2.5)and light absorption by aerosols are influenced more strongly by post-harvest burning of rabi crops.However,adverse meteorology plays a more dominant role in the post-monsoon season than biomass burning.These findings underscore the need for better policy interventions to curb biomass burning and improve air quality during both harvest seasons.
