Synthesis,Characterization and Water Absorption Analysis of Highly Hygroscopic Bio-based Co-polyamides 56/66

This study aims to develop highly hygroscopic bio-based co-polyamides(CPs)by melt co-polycondensation of polyamide(PA)56 salt and PA66 salt with varying molar fractions.The functional groups and the chemical structure of the prepared samples were determined by Fourier transform infrared(FTIR)spectroscopy and proton nuclear magnetic resonance(^(1)H-NMR)spectroscopy.The relative viscosity was determined with an Ubbelohde viscometer.The melting behavior and the thermal stability of CPs were investigated by differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA).Furthermore,the water absorption behavior of CP hot-pressed film was studied.The results reveal that the melting point,the crystallization temperature and the crystallinity of CPs firstly decrease and then increase with the molar fraction of PA66 in CPs.The copolymerization of PA56 with PA66 leads to an obvious increase in water absorption.The CPs with PA66 molar fraction of 50%possess a high saturated water absorption rate of 17.6%,compared to 11.6%for pure PA56 and 7.8%for pure PA66.

Response of colour and hygroscopic properties of Scots pine wood to thermal treatment

The effect of heat treatment on the surface colour and hygro- scopic properties of pine wood were investigated in this study. Boards of Scots pine wood （Pinus sylvestris L.） were subjected to thermal treatment at 200℃, for 4, 6, and 8 h. The change of equilibrium moisture content and density values of the specimens in order to facilitate the understand- ing of the treated material behavior. The colour parameters L＊ a＊ and b＊, used to depict the total colour change （dE） of wood surface, were shown to change proportionally to the treatment intensity. Moreover, swelling in the tangential and radial directions and absorption of the specimens ap- peared to be enhanced in great extent by the thermal treatment process. The mean value of swelling percentage in the tangential direction de- creased 10.26%, 17.22%, and 19.60% for specimens treated for 4, 6, and 8 h, respectively, referring to the final measurement after 72 h of immer- sion. In radial direction, mean value of swelling percentage decreased 19.56%, 32.75%, and 34.65% for treated for 4, 6 and 8 h, respectively, after 72 h immersion, which attests the decrease in swelling and im- provement in the hygroscopic behavior of Scots pine wood.

A Multifunctional HTDMA System with a Robust Temperature Control

The hygroscopicity of atmospheric aerosols significantly influences their size distribution, cloud condensation nuclei ability, atmospheric residence time, and climate forcing. In order to investigate the hygroscopic behavior of aerosol particles and serious haze in China, a Hygroscopic Tandem Differential Mobility Analyzers （HTDMA） system was designed and constructed at Fudan University. It can function as a scanning mobility particle sizing system to measure particle size distribution in the range of 20-1000 nm in diameter, as well as a hygroscopicity analyzer for aerosol particles with diameters between 20-400 nm in the range of 20%-90% RH （relative humidity）. It can also measure the effect of uptake of inorganic acids or semiVOCs on the hygroscopic behavior of aerosols, such as typical inorganic salts in atmospheric dust or their mixtures. The performance tests show that the system measured particle size of the standard polystyrene latex spheres （PSLs） is 197 nm, which is in excellent agreement with the certified diameter D=199±6 nm, as well as a standard deviation of the repeated runs SD=8.9×10^-4. In addition, the measured hygroscopic growth factors of the model compounds, （NH4）2SO4 and NaNO3, agree with the Kohler theoretical curves. The results indicate that the HTDMA system is an excellent and powerful tool for studying the hygroscopic behavior of submicron aerosols and meets the demand required for laboratory research and fieldwork on atmospheric aerosols in China.

A Closure Study of Aerosol Hygroscopic Growth Factor during the 2006 Pearl River Delta Campaign

Measurements of aerosol physical, chemical and optical parameters were carried out in Guangzhou, China from 1 July to 31 July 2006 during the Pearl River Delta Campaign. The dry aerosol scattering coefficient was measured using an integrating nephelometer and the aerosol scattering coefficient for wet conditions was determined by subtracting the sum of the aerosol absorption coefficient, gas scattering coefficient and gas absorption coefficient from the atmospheric extinction coefficient. Following this, the aerosol hygroscopic growth factor, f（RH）, was calculated as the ratio of wet and dry aerosol scattering coefficients. Measurements of size-resolved chemical composition, relative humidity （RH）, and published functional relationships between particle chemical composition and water uptake were likewise used to find the aerosol scattering coe？cients in wet and dry conditions using Mie theory for internally- or externally-mixed particle species [（NH_4）_2SO_4, NH_4NO_3, NaCl, POM, EC and residue]. Closure was obtained by comparing the measured f（RH） values from the nephelometer and other in situ optical instruments with those computed from chemical composition and thermodynamics. Results show that the model can represent the observed f（RH） and is appropriate for use as a component in other higher-order models.

Reducing SU-8 hygroscopic swelling by ultrasonic treatment

The volume expansion of SU-8 resist brings serious dimensional errors to electroformed structures.Two approaches have been proposed to reduce resist distortions during electroforming:electroforming at room temperature and adding auxiliary features for mask patterns.However,the former method induces higher internal stresses in the electroformed metal layers.And the latter method makes it difficult to predict the expansion behaviors of the resists.In the paper,the thermal expansion of the SU-8 mould is calculated by ANSYS firstly,and the lower thermal expansion value indicates that hygroscopic swelling plays a leading role in SU-8 mould distortions.An original technique is presented to reduce SU-8 hygroscopic swelling by ultrasonic treatment.The dimensional errors of the electroformed structure fabricated on the ultrasonic treatment mould are 50% lower than the one without ultrasonic treatment.Simulation of hygroscopic swelling is conducted by finite element analysis,and the results indicate that the hygroscopic strain ε of SU-8 after electroforming is declined from 6.8% to 3.1% because of ultrasonic.The measurements show that ultrasonic treatment increased the water contact angle of cured SU-8 from 70.8?to 74.9?.Based on these results,the mechanism of ultrasonic effect on hygroscopic swelling is proposed from the view of ultrasonic vibration decreasing the number of hydroxyl groups in SU-8.The research presents a novel method to improve the precisions of electroformed structures.It has no influence on the internal stresses of final structures and does not increase the complexities of mask layouts.

The Effect of Relative Humidity on Continental Average Aerosols

In this paper, the authors extracted and investigated the effect of relative humidity (RH) on some microphysical and optical properties of continental polluted aerosols from OPAC (Optical Properties of Aerosols and Clouds) at the spectral range of 0.25 μm to 2.5 μm and eight relative humidities (0%, 50%, 70%, 80%, 90%, 95%, 98%, and 99%). The microphysical properties extracted were radii, volume, number and mass mix ratios as functions of RH while the optical properties were optical depth, extinction, scattering and absorption coefficients single scattering albedo, refractive indices and asymmetric parameters also at eight RHs. Using the microphysical properties, effective hygroscopic growth factors and effective radii of the mixtures were determined while using optical properties we determined the enhancement parameters, effective refractive indices and angstrom coefficients. Using the effective hygroscopic growth, we determined the dependence of the effective hygroscopicity parameter as a function of RH, while using enhancement parameters;we determined the effect of humidification factor on RH and wavelengths. The effective hygroscopic growth and enhancement parameters were then parameterized using some models to determine the effective hygroscopicity parameter, bulk hygroscopicity and humidification factors. We observed that the data fitted the models very well. The effective radii decrease with the increase in RH while the effective hygroscopic growth increases with the increase in RH, and this is in line with the increase in angstrom parameters, and this shows increase in mode size with the increase in RH. The angstrom coefficients show that the mixture has a bimodal type of distribution with the dominance of fine mode particles.

Effects of Chemical Treatment on the Physical Properties of Typha

Plant-based concretes are produced from plant aggregates and a binder.Plant fibers are mainly composed of saccharides(sugars)and these sugars can decrease the concentration of Ca2+ions in the cement pore solution and delay the formation of hydration products.To improve the interfacial bond between fibers and matrix a chemical treatment is widely used.This study investigates the effect of sodium hydroxide treatment on physical and hygroscopic properties of Typha aggregates.In particular,a 5%sodium hydroxide solution is used to treat these aggregates and their bulk and absolute densities,porosity,water content and water absorption are evaluated accordingly.Results indicate that bulk and absolute densities increase after treatment from 56.44 kg/m^(3) to 122.57 kg/m^(3) and 541.93 kg/m^(3) to 555.17 kg/m^(3),respectively.NaOH treatment reduces porosity of Typha from 89.58%to 77.92%and decreases water content from 1.4%to 1%.The treatment with sodium hydroxide reduces substantially the water absorption of the aggregates.

The Effect of Hygroscopic Growth on Continental Aerosols

In this paper, the authors investigated some microphysical and optical properties of continental clean aerosols from OPAC to determine the effect of hygroscopic growth at the spectral range of 0.25 μm to 2.5 μm and eight relative humidities (RHs) (0%, 50%, 70%, 80%, 90%, 95%, 98% and 99%). The microphysical properties extracted were radii, volume mix ratio, number mix ratio and mass mix ratio as a function of RH while the optical properties are scattering and absorption coefficients and asymmetric parameters. Using the microphysical properties, growth factors of the mixtures were determined while using optical properties the enhancement parameters were determined and then parameterized using some models. We observed that the data fitted the models very well. The angstrom coefficients show that the mixture has bimodal type of distribution with the dominance of fine mode particles.

The Effect of Relative Humidity on Maritime Tropical Aerosols

The present work focused on the effect of relative humidity (RH) on some microphysical and optical properties of maritime tropical aerosols from the software package OPAC (Optical Properties of Aerosols and Clouds) data at the spectral range of 0.25 μm to 2.5 μm and eight relative humidities (0%, 50%, 70%, 80%, 90%, 95%, 98%, and 99%). The microphysical properties extracted were radii, volume mix ratio, number mix ratio and mass mix ratio as a function of RH while the optical properties were optical depth, extinction, scattering and absorption coefficients single scattering albedo, refractive indices and asymmetric parameters. The hygroscopic growth and enhancement parameters were then parameterized by using some models to determine the hygroscopicity, bulk hygroscopicity, humidification factors and some other parameters that depend on RH and/or wavelengths. The results showed that the data fitted our models very well and can be used to extrapolate the hygroscopic growth at any RH and enhancement parameters at any RH and wavelengths. The importance of determining gfmix(RH) as a function of RH and volume fractions, mass fractions and number fractions, and enhancement parameters as a function of RH. The effective radii increases with the increase in RH, while Angstrom coefficients decrease with the increase in RH and this signifies the dominance of coarse mode particles. The angstrom coefficients show that the mixture has bimodal type of distribution and the mode size increases with the increase in RH.

Effect of Varying Aerosol Concentrations and Relative Humidity on Visibility and Particle Size Distribution in Urban Atmosphere

Atmospheric aerosol concentrations have been found to change constantly due to the influence of source,winds and human activities over short time periods.This has proved to be a constraint to the study of varied aerosol concentrations in urban atmosphere alongside changing relative humidity and how it affects visibility and aerosol particle size distribution.In this research simulation was carried out using Optical Properties of Aerosols and Clouds(OPAC 4.0)average concentration setup for relative humidity(RH)0-99%at visible wavelength 0.4-0.8μm to vary the concentrations of three aerosol components:WASO(Water-soluble),INSO(Insoluble)and SOOT.The Angstrom exponents(α),the curvatures(α2)and atmospheric turbidities(β)were obtained from the regression analysis of Kaufman’s first and second order polynomial equations for visibility.The research determined the mean exponent of the aerosol size growth curve(μ)from the effective hygroscopic growth(geff)and the humidification factors(γ)from visibility enhancement f(RH,λ).The mean exponent of aerosol size distributions(υ)was determined fromμandγ.The results showed that with varied WASO,INSO and SOOT concentrations respectively at different RH,aerosol particle size distributions showed bimodal characteristics with dominance of fine mode particles.Hazy atmospheric conditions prevailed with increasing turbidity.

Investigating the effect of volatility on the hygroscopicities of acetate nanoparticle aerosols by surface plasmon resonance microscopy

Under high relative humidity(RH)conditions,the release of volatile components(such as acetate)has a significant impact on the aerosol hygroscopicity.In this work,one surface plasmon resonance microscopy(SPRM)measurement system was introduced to determine the hygroscopic growth factors(GFs)of three acetate aerosols separately or mixed with glucose at different RHs.For Ca(CH_(3)COO)_(2) or Mg(CH_(3)COO)_(2) aerosols,the hygroscopic growth trend of each time was lower than that of the previous time in three cyclic humidification from 70% RH to 90% RH,which may be due to the volatility of acetic acid leading to the formation of insoluble hydroxide(Ca(OH)_(2) or Mg(OH)_(2))under high RH conditions.Then the third calculated GF(using the Zdanovskii-Stokes-Robinson method)for Ca(CH_(3)COO)_(2) or Mg(CH_(3)COO)_(2) in bicomponent aerosols with 1:1 mass ratio were 3.20% or 5.33% lower than that of the first calculated GF at 90% RH.The calculated results also showed that the hygroscopicity change of bicomponent aerosol was negatively correlated with glucose content,especially when the mass ratio of Mg(CH_(3)COO)_(2) to glucose was 1:2,the GF at 90% RH only decreased by4.67% after three cyclic humidification.Inductively coupled plasma atomic emission spectrum(ICP-AES)based measurements also indicated that the changes of Mg^(2+)concentration in bicomponent was lower than that of the single-component.The results of this study reveal thatduring the efflorescence transitions of atmospheric nanoparticles,the organic acids diffusion rate may be inhibited by the coating effect of neutral organic components,and the particles aging cycle will be prolonged.

Atmospheric Particle Hygroscopicity and the Influence by Oxidation State of Organic Aerosols in Urban Beijing

A hygroscopic tandem differentialmobility analyser(H-TDMA)was used to observe the sizeresolved hygroscopic characteristics of submicron particles in January and April 2018 in urban Beijing.The probability distribution of the hygroscopic growth factor(HGF-PDF)in winter and spring usually showed a bimodal pattern,with more hygroscopic mode(MH)being more dominant.The seasonal variation in particle hygroscopicity was related to the origin of air mass,which received polluted southerly air masses in spring and clean northwesterly air masses in winter.Particles showed stronger hygroscopic behaviour during heavy pollution episodes(HPEs)with elevated concentrations of secondary aerosols,especially higher mass fraction of nitrate,which were indicated using the PM2.5(particulate matter with diameter below 2.5μm)mass concentration normalised by CO mass concentration.The hygroscopic parameter(κ)values were calculated using H-TDMA(κhtdma)and chemical composition(κchem).The closure study showed thatκchem was overestimated in winter afternoon when compared withκhtdma,because the organic particle hygroscopic parameter(κorg)was overestimated in the calculations.It was influenced by the presence of a high concentration of hydrocarbon-like organic aerosol(HOA)with a weak water uptake ability.A positive relationship was observed betweenκorg and the ratio of oxygenated organic aerosol(OOA)and HOA,thereby indicating that the strong oxidation state enhanced the hygroscopicity of the particles.This study revealed the effect of local emission sources and secondary aerosol formation processes on particle hygroscopicity,which is of great significance for understanding the pollution formation mechanism in the North China Plain.

Moisture electricity generation:Mechanisms,structures,and applications

With the increasing concern of energy crisis and global warming,the whole globe is in an urgent need to develop clean energy that comes from renewable sources and does not harm the environment to fulfill the carbon neutralization and green earth commitments.Water is the most abundant substance on earth and has been historically used as the major energy carriers in watermill,water wheel,hydroelectricity.Moisture electricity generation is another emerging technology that can convert lowgrade energy in the widely-accessible moisture to electricity simply by the integration of moisture,electrodes,deliberatelydesigned hygroscopic films.Recent research on moisture electricity generators(MEGs)led to the creation of a series of selfpowered sensors and in some occasions they have replaced conventional batteries to power miniaturized devices.In this review,the basic mechanisms of MEGs are firstly clarified,three categories of them,i.e.,gradient structure,homogeneous structure,and heterogeneous structure depending on the structure of hygroscopic films,are then introduced.Furthermore,recent advances in the fabrication,characteristics,performance of MEGs are summarized,MEGs with continuous or transient output that could be applied in self-powered sensors and power sources are discussed.Finally,some remaining challenges and our perspectives on MEGs are highlighted.

Wet‑Spinning Knittable Hygroscopic Organogel Fibers Toward Moisture‑Capture‑Enabled Multifunctional Devices

Atmospheric moisture exploitation is emerging as a promising alternative to relieve the shortage of freshwater and energy.Efforts to exploit hygroscopic materials featuring flexibility,programmability,and accessibility are crucial to portable and adaptable devices.However,current two-dimensional(2D)or three-dimensional(3D)-based hygroscopic materials are dif-ficult to adapt to diverse irregular surfaces and meet breathability,which severely hinders their wide applications in wearable and programmable devices.Herein,hygroscopic organogel fibers(HOGFs)were designed via a wet-spinning strategy.The achieved fibers were composed of the hydrophilic polymeric network,hygroscopic solvent,and photothermal/antibacterial Ag nanoparticles(AgNPs),enabling hygroscopic capacity,photothermal conversion,and antibacterial.Owing to the good knittable feature,the HOGFs can be readily woven to adjusted 2D textiles to function as an efficient self-sustained solar evaporator of 4-layer woven HOGF device with a saturated moisture capacity of 1.63 kg m^(-2) and water-releasing rate of 1.46 kg m^(-2) h^(-1).Furthermore,the 2D textile can be applied as a wearable dehumidification device to efficiently remove the evaporative moisture from human skin to maintain a comfortable environment.It can reduce the humidity from 90 to 33.4%within 12.5 min.In addition,the introduction of AgNPs can also endow the HOGFs with antibacterial features,demonstrat-ing significant potential in personal healthcare.

Insight into the interaction between water and surfactant aerosol particles based on molecular dynamics simulations

The ubiquitous surfactant significantly influences the hygroscopic growth of atmospheric aerosol par-ticles.However,knowledge on the morphology of surfactant particles after the adsorption of water is insufficient.In this study,the interaction between water and particles composed of surface active malonic acid(MA)or adipic acid(AA)are simulated based on the molecular dynamics method.The key point is the combined effect of temperature and water content on the structural properties of particles and the surface propensity of surfactants at the equilibrium state.Results show that demixed structure 1 with the adsorption of water clusters on acid grain,mixed structure and demixed structure 2 with acids coating on water droplet can be observed.With temperature increasing from 160 K to 330 K the surface propensity of MA and AA increases first and then weakens.Near the standard atmospheric temperature(280-330 K),the surface propensity of MA and AA increases with increasing water content and alkyl group,and its sensitivity to temperature and water content varies regularly.Moreover,all surfactants at the particle surface orient their hydrophobic groups toward the gas.These findings improve our insight into the surfactant partitioning and further assist in more accurate prediction of the particle hygroscopic growth.

Retrieval of refractive index of ultrafine single particle using hygroscopic growth factor obtained by high sensitive surface plasmon resonance microscopy

When exposed to different relative humidities (RHs),the optical properties of atmospheric aerosols will change because of changes in the aerosol particle size and complex refractive index (RI),which will affect haze formation and global climate change.The potential contributions of ultrafine particles to the atmospheric optical characteristics and to haze spreading cannot be ignored because of their high particle number concentrations and strong diffusibility;measurement of the optical properties of wet ultrafine particles is thus highly important for environmental assessment.Therefore,a surface plasmon resonance microscopy with azimuthal rotation illumination (SPRM-ARI) system is designed to determine the RIs of single particle aerosols with diameters of less than 100 nm in the hygroscopic growth process.Measurements are taken using mixed single particles with different mass ratios.The RIs of mixed single aerosols at different RHs are retrieved by measuring the scattering light intensity using the SPRM-ARI system and almost all the RIs of the bicomponent particles with different mass ratios decrease with increasing water content under high RH conditions.Finally,for each of the bicomponent particles,the maximum standard deviations for the retrieved RI values are only 2.06×10^(-3),3.08×10^(-3)and 3.83×10^(-3),corresponding to the NaCl and NaNO_(3)bicomponent particles with a 3:1 mass ratio at 76.0%RH,the NaCl and glucose particles with a 1:3 mass ratio at 89.0%RH,and the NaCl and OA particles with a 1:1 mass ratio at 78.0%RH,respectively;these results indicate that the high-sensitivity SPRM-ARI system can measure the RI effectively and accurately.

Photothermal hygroscopic hydrogel for simultaneous generation of clean water and electricity

Harvesting water from the air using adsorbents and obtaining fresh water by solar-driven desorption is considered as one of the most effective ways to solve the freshwater crisis in arid and desert regions.Based on a simple and low-cost photothermal hygroscopic hydrogel,a new strategy is proposed to boost solar energy efficiency by coupling solar-driven atmospheric water harvesting technology with thermoelectric power generation technology in this paper.Photothermal hygroscopic hydrogel ink PAM-CaCl_(2)is prepared by in situ polymerization using Acrylamide as monomer,Ammonium persulfate as thermal initiator and CaCl_(2)as hygroscopic component.During the day,the photothermal hygroscopic hydrogel absorbs solar energy and evaporates its own internal water to obtain fresh water.Simultaneously,the residual waste heat is utilized to power the thermoelectric panel,which produces electricity based on Seebeck effect.At night,the hydrogel harvests water molecules in the air to achieve regeneration.This hybrid system can achieve a water production rate of 0.33 kg m^(-2)h^(-1)and an additional electrical energy gain of 124 mW m^(-2)at 1 kW m^(-2)solar intensity.Theoretical model of the hybrid system is developed to understand the heat flow and thermoelectric generation process.The results provide new insights into energy and freshwater replenishment options in arid or desert areas with abundant solar energy.

Hygroscopic growth of aerosol scattering coefficient:A comparative analysis between urban and suburban sites at winter in Beijing

A humidity controlled inlet system was developed to measure the hygroscopic growth of aerosol scattering coefficient in conjunction with nephelometry at an urban site of Chinese Academy of Meteorological Sciences （CAMS） in Beijing and a rural site at Shangdianzi Regional Background Air Pollution Monitoring Station （SDZ） outside Beijing during winter, from December 2005 to January 2006. Measurements were carded out at a wavelength of 525 nm with an Ecotech M9003 nephelometer. The hygroscopic growth function （or factor） of the aerosol scattering coefficientf（RH） increased continuously with increasing relative humidity （RH） and showed no obvious ＂step-like＂ deliquescent behavior at both sites during the experiment. The average growth factorf（RH） at the SDZ site could reach 1.5 when RH increased from less than 40% to 92%, and to 2.1 at the CAMS site when RH increased from less than 40% to 93%. The average hygroscopic growth factor at a relative humidity of 80%, f（RH = 80 ± 1%）, was found to be about 1.26 ±0.15 at CAMS and 1.24 ±0.11 at SDZ. Further analysis indicated that under relatively polluted conditions, the average hygroscopic growth factor was higher at the CAMS site than that at the SDZ site. However, under relatively clean air conditions, the difference between the two sites was small, showing a hygroscopic growth behavior similar to those of burning biomass or blowing dust. These results reflected the different characteristics of aerosol types at the two sites.

An intensive study on aerosol optical properties and affecting factors in Nanjing,China

The optical properties of aerosol as well as their impacting factors were investigated at a suburb site in Nanjing during autumn from 14 to 28 November 2012. More severe pollution was found together with lower visibility. The average scattering and absorption coefficients（B sca and B abs） were 375.7 ± 209.5 and 41.6 ± 18.7 Mm^（-1）, respectively. Higher ？ngstr？m absorption and scattering exponents were attributed to the presence of more aged aerosol with smaller particles. Relative humidity（RH） was a key factor affecting aerosol extinction. High RH resulted in the impairment of visibility, with hygroscopic growth being independent of the dry extinction coefficient. The hygroscopic growth factor was 1.8 ± 1.2 with RH from 19% to 85%.Light absorption was enhanced by organic carbon（OC）, elemental carbon（EC） and EC coatings,with contributions of 26%, 44% and 75%（532 nm）, respectively. The B sca and B abs increased with increasing N_（100）（number concentration of PM_（2.5）with diameter above 100 nm）, PM_1 surface concentration and PM_（2.5）mass concentration with good correlation.

Aerosol optical properties under different pollution levels in the Pearl River Delta(PRD) region of China

To clarify the aerosol hygroscopic growth and optical properties of the Pearl River Delta(PRD)region,integrated observations were conducted in Heshan City of Guangdong Province from October 19 to November 17,2014.The concentrations and chemical compositions of PM2.5,aerosol optical properties and meteorological parameters were measured.The mean value of PM2.5 increased from less than 35(excellent)to 35-75μg/m^3(good)and then to greater than 75μg/m^3(pollution),corresponding to mean PM2.5 values of 24.9,51.2,and 93.3μg/m^3,respectively.The aerosol scattering hygroscopic growth factor(f(RH=80%))values were 2.0,2.12,and 2.18 for the excellent,good,and pollution levels,respectively.The atmospheric extinction coefficient(σext)and the absorption coefficient of aerosols(σap)increased,and the single scattering albedo(SSA)decreased from the excellent to the pollution levels.For different air mass sources,under excellent and good levels,the land air mass from northern Heshan had lower f(RH)andσsp values.In addition,the mixed aerosol from the sea and coastal cities had lower f(RH)and showed that the local sources of coastal cities have higher scattering characteristics in pollution periods.