Aerosol Particle Size Distribution Research Articles

Satellite-based identification of aerosol particle species using a 2D-space aerosol classification model

The classification of aerosol types using remote sensing tools is crucial for improving our knowledge on the impacts of aerosol species on global and regional climate. Ground-based classification methods have proven useful though they are limited by discontinuous spatial observations of aerosol optical properties. As such, there is a need to develop methods in aerosol species identification using satellite data. In this study, a 2D-space model suitable for MODIS AOD bands is developed to distinguish aerosol particle species based on aerosol optical depth (AOD) and aerosol relative optical depth (AROD). The model can be used to classify five aerosol types, including biomass burning (BB: AOD470 ≥ 0.45, AROD660/470 < 0.58), urban industry (UI: AOD470 ≥ 0.45, 0.68 > AROD660/470 ≥ 0.58), sub-continental (SB: AOD470 ≥ 0.45, 0.91 > AROD660/470 ≥ 0.68), desert dust (DD: AROD660/470 ≥ 0.91) and continental (CO: AOD470 < 0.45, AROD660/470 < 0.91). AROD values corresponding to different types of aerosols are calculated through Mie scattering theory using the aerosol particle size distribution parameters and spectral complex refractive index. The accuracy and applicability of the model are verified in three steps: 1) we compare aerosol discrimination results of model with ground-based data and the local atmospheric conditions over different regions, 2) we compare aerosol identification results from Moderate Resolution Imaging Spectroradiometer (MODIS) AOD retrieval and ground-based data, and 3) we test our model to validate its use in individual cases studies and regional observations. Our results demonstrate that aerosol species classification for each study region is consistent with the characteristics of their atmospheric conditions, and the classification results using MODIS AOD retrieval are similar to the ground-based observation results. The differences in MODIS versus AERONET AOD, caused by MODIS observation errors, is the major contributor to the differences between ground-based and satellite-based recognition results. Our three-steps validation results indicate that the 2D-space model developed in this paper can accurately identify different types of aerosols and has strong applicability. This provides a basis for the use of satellite data for continuous spatial identification of aerosol type, which greatly promotes research in related fields.

Improved algorithm of aerosol particle size distribution based on remote sensing data.

The optical parameters (extinction or backscatter coefficients) of multi-wavelength beams can be used for the retrieval of the aerosol particle size distribution (APSD). An improved algorithm for APSD and aerosol microphysical parameters (AMPs) is studied and discussed by using only multi-wavelength extinction coefficients data. The regularized algorithm and prior value are combined for the retrieval of APSD and AMPs. The regularization algorithm, based on minimum discrepancy principle and averaging procedure, is used for the retrieval of fine-mode APSD and an averaging procedure that can achieve stable outputs is proposed. The 1% averaging result near the minimum of the discrepancy is selected and verified. Based on the inversion results of fine mode from the regularization algorithm, the lognormal distribution with a prior value (model radius) is applied to reconstruct the coarse mode of APSDs through fitting the data. The comprehensive application of the regularization algorithm and averaging process improves the stability of the inversion in the fine mode, and the use of the prior value broadens the inversion radius range of APSD. The complex refractive index need not be assumed for this method. The inversion error for different types of aerosols is analyzed and studied. The reliability of the algorithm is tested and verified by many typical APSDs and the measured APSDs by particle size spectrometer in different pollution days. The algorithm sensitivity analysis is also provided and discussed. The algorithm can obtain reliable inversion of APSD and AMPs with large radius range.

Peculiarities of suspended matter distribution on the geochemical barrier water-atmosphere on transoceanic sections

The article contains the results of the study of surface waters (31 cruise of the R/V “Akademik Nikolai Strakhov”, December 2015–January 2016) and the particle size distribution of aerosols and surface waters (42 cruise of the R/V “Akademik Boris Petrov”, January–April 2017). It was found that aerosol flows increased in arid regions of the Arabian Peninsula and the number of particles 0.3–0.5 µm decreased in the sequence (particles/l, 2017): Bab El-Mandeb Strait (135190)&gt;Gulf of Aden (102854)&gt;Red Sea (91612)&gt;North, Baltic Sea (76468)&gt;Indian Ocean (64113)&gt;Malacca Strait (46491)&gt;Mediterranean Sea (28397)&gt;East Atlantic (14803). The biotic factor between the distribution of suspended matter and organic compounds prevails in the open waters of the Indian Ocean, in the northeastern part of the Atlantic Ocean, as well as in areas with increased water productivity (the Arabian Sea). Circumcontinental zonality led to the dominance of the terrigenous component in the suspension of coastal waters. The transition of the phytoplankton community from the winter (2016) to the spring (2017) led to a decrease in the suspension content, in 8 times on average. The absence of the correlation between the content of the suspension and organic compounds in some areas indicated different sources of their forming. Despite the high concentrations of hydrocarbons in individual samples in 2016 (up to 50–70 µg/l), their average content remained almost unchanged: 10.5 µg/l (2016), 8.7 µg/l (2017). The determination in the composition of hydrocarbons of weathered petroleum alkanes indicated the influence of petroleum pollutants.

Characterization of oil injected screw compressors and air/oil separators at realistic operating pressures

AbstractAn experimental setup to determine the particle size distribution (PSD) of a pressurized oil aerosol (p<10 bar) was validated. The combination of optical particle counter (OPC) and scannin...

2018년 11월 광주 지역에서 발생한 미세먼지 고농도 사례 시 수용성 성분의 크기 분포 조사

In this study, mass size distributions of ambient aerosol particles and their water-soluble organic and inorganic species were investigated under high pollution episode. To achieve the aim of this study, 24-hr integrated size-segregated aerosol samples were collected at an ubran site of Gwangju between November 02 and 16, 2018, and analyzed for mass, water-soluble organic carbon (WSOC), and ionic species. During study period, a high pollution episode of fine particulate matter (PM) occurred between November 02 and 07, possibly due to high pressure developed around Korean peninsula, extremely stable air conditions, and long-range transportation of aerosol particles from North Korea and northeastern China region. On November 02~03 when influence of local pollution dominated, ambient aerosol particles, WSOC, NO3-, SO₄2-, and NH4+ exhibited bi-modal size distributions with a condensation mode at a particle size of 0.32 μm and a droplet mode at a particle size of 1.0 μm in PM1.8. While, between November 05 and 07 when long-range transportation of PM was mixed with locally-produced pollution, they showed very pronounced droplet mode size distributions at 1.0 μm, without a condensation mode. NO3- concentration in PM1.8 during pollution episode increased significantly from 5.9 μg/m³ on November 02 to 21.5μg/m³ on November 06, while SO₄2- in PM1.8 increased from 1.6 to 5.8 μg/m³, indicating the dominance of local pollution during pollution episode. Furthermore, for WSOC, NO3-, SO₄2-, and NH4+, fraction of droplet mode size (PM0.55-1.8) to PM1.8 increased gradually as PM pollution got increased, while the condensation mode (PM0.17-0.32) contribution decreased. In addition, it was demonstrated that relative humidity could be an important factor promoting formation of droplet mode WSOC, NO3-, and SO₄2-.

Accuracy calculation for lidar ratio and aerosol size distribution by dual-wavelength lidar

This paper presents a method to obtain aerosol-lidar ratio and particle-size distribution simultaneously with a dual-wavelength lidar, when the aerosol particle-size distribution is to be approximated by a Junge distribution. The manuscript analyzed the relationship between the aerosol particle ratio, particle-size distribution, and particle complex refractive index. The results show that the particle properties have a great impact on the lidar ratio. If the selected lidar ratio is not suitable, the extinction coefficient obtained from the Fernald method will cause a great uncertainty in the inversion of particle-size distribution. A lidar-ratio iteration method was introduced to solve the influence of improper lidar-ratio selection on particle-size distribution inversion, and then conducted simulation calculations and analysis. The simulation results show that the lidar-ratio iteration method effectively solves the problem of uncomfortable lidar ratio, and can obtain relatively accurate lidar ratio and particle-size distribution parameters at the same time; the uncertainty of iteration method was discussed in the manuscript.

Optical characterization of cloud and aerosol of the temperate zone

Aerosol and cloud optical data of the network AERONET/PHOTONS are in major importance in climate change and air quality studies. Sun photometers allow the determination of cloud and aerosol optical depths and the particle size distribution of aerosol for many sites distributed over large four zones belongs to the temperate areas: Mediterranean, maritime, humid subtropical, and continental and dry. The histograms of cloud occurrence frequencies reveal the dominance variation in the interval (20.100) relating to Stratus and Altostratus, maximum reaches (~ 70%) recorded at eastern Asia (China). For values below 20, the histograms are different from those of Equatorial zone but modeled into two classes, staircase and non-staircase shapes, depending on the weather conditions. The monthly aerosol optical depth averages at 0.5 μm show the highest values in summer, a maximum reach 1.6 at Eastern Asia and coincides with the highest cloud optical depth particularly for Asian sites. Seasonal average of aerosol particle size distribution records larger amplitudes of both fine and coarse modes in the Asian sites especially in the East two to three times higher than those in other zones. The average radius of fine mode is around 0.17 μm expressing high anthropogenic local pollution. The coarse mode around 2.75 μm is very important in Western India with a maximum concentration in summer as seasonal desert dust advections concern.

Stratospheric aerosol characteristics from space-borne observations: extinction coefficient and Ångström exponent

Abstract. Stratospheric aerosols are of a great importance to the scientific community, predominantly because of their role in climate, but also because accurate knowledge of aerosol characteristics is relevant for trace gas retrievals from remote-sensing instruments. There are several data sets published which provide aerosol extinction coefficients in the stratosphere. However, for the instruments measuring in the limb-viewing geometry, the use of this parameter is associated with uncertainties resulting from the need to assume an aerosol particle size distribution (PSD) within the retrieval process. These uncertainties can be mitigated if PSD information is retrieved. While occultation instruments provide more accurate information on the aerosol extinction coefficient, in this study, it was shown that limb instruments are more sensitive to the smaller particles in the visible–near-infrared spectral range. However, the sensitivity of occultation instruments improves if the UV part of the wavelength spectrum is considered. A data set containing PSD information was recently retrieved from SCIAMACHY limb measurements and provides two parameters of the unimodal lognormal PSD for the SCIAMACHY operational period (2002–2012). In this study, the data set is expanded by aerosol extinction coefficients and Ångström exponents calculated from the retrieved PSD parameters. Parameter errors for the recalculated Ångström exponents and aerosol extinction coefficients are assessed using synthetic retrievals. For the extinction coefficient the resulting parameter error is within ±25 %, and for the Ångström exponent, it is better than 10 %. The SCIAMACHY aerosol extinction coefficients recalculated from PSD parameters are compared to those from SAGE II. The differences between the instruments vary from 0 % to 25 % depending on the wavelength. Ångström exponent comparison with SAGE II shows differences between 10 % at 31 km and 40 % at 18 km. Comparisons with SAGE II, however, suffer from the low number of collocated profiles. Furthermore, the Ångström exponents obtained from the limb-viewing instrument OSIRIS are used for the comparison. This comparison shows an average difference within 7 %. The time series of these differences do not show signatures of any remarkable events (e.g., volcanic eruptions or biomass burning events). In addition, the temporal behaviour of the Ångström exponent in the tropics is analyzed using the SCIAMACHY data set. It is shown that there is no trivial relation between the Ångström exponent value at a single wavelength pair and the PSD because the same value of Ångström exponent can be obtained from an infinite number of combinations of the PSD parameters.

Size Distribution and Depolarization Properties of Aerosol Particles over the Northwest Pacific and Arctic Ocean from Shipborne Measurements during an R/V Xuelong Cruise.

Atmospheric aerosols over polar regions have attracted considerable attention for their pivotal effects on climate change. In this study, temporospatial variations in single-particle-based depolarization ratios (δ: s-polarized component divided by the total backward scattering intensity) were studied over the Northwest Pacific and the Arctic Ocean using an optical particle counter with a depolarization module. The δ value of aerosols was 0.06 ± 0.01 for the entire observation period, 61 ± 10% lower than the observations for coastal Japan (0.12 ± 0.02) ( Pan et al. Atmos. Chem. Phys. 2016 , 16 , 9863 - 9873 ) and inland China (0.19 ± 0.02) ( Tian et al. Atmos. Chem. Phys. 2018 , 18 , 18203 - 18217 ) in summer. The volume concentration showed two dominant size modes at 0.9 and 2 μm. The supermicrometer particles were mostly related to sea-salt aerosols with a δ value of 0.09 over marine polar areas, ∼22% larger than in the low-latitude region because of differences in chemical composition and dry air conditions. The δ values for fine particles (<1 μm) were 0.05 ± 0.1, 50% lower than inland anthropogenic pollutants, mainly because of the complex mixtures of submicrometer sea salts. High particle concentrations in the Arctic Ocean could mostly be attributed to the strong marine emission of sea salt associated with deep oceanic cyclones, whereas long-range transport pollutants from the continent were among the primary causes of high particle concentrations in the Northwest Pacific region.

Efficiency of electrostatic precipitation of NiO nanoparticles dispersed by atomization

ABSTRACT The dispersion of metal oxide nanoparticles by pneumatic atomization of oxide suspensions has rarely been used in laboratory-scale research on electrostatic precipitation, due to the insolubility of the oxides under ambient conditions, the particle agglomeration and sedimentation in aqueous mixtures. Therefore, the aim of this work was to evaluate the performance of a wire-plate electrostatic precipitator in the collection of NiO nanoparticles produced by nebulization of suspensions pretreated with ultrasonic bath, which resulted in reproducible aerosol concentrations and particle size distributions. Increase of the voltage and decrease of the gas flow rate improved the charging and collection efficiencies.

Determination of Passive Dry Powder Inhaler Aerodynamic Particle Size Distribution by Multi-Stage Cascade Impactor: International Pharmaceutical Aerosol Consortium on Regulation & Science (IPAC-RS) Recommendations to Support Both Product Quality Control and Clinical Programs.

The multi-stage cascade impactor (CI) is the mainstay method for the determination of the aerodynamic particle size distribution (APSD) of aerosols emitted from orally inhaled products (OIPs). CIs are designed to operate at a constant flow rate throughout the measurement process. However, it is necessary to mimic an inhalation maneuver to disperse the powder into an aerosol when testing passive dry powder inhalers (DPIs), which constitute a significant portion of available products in this inhaler class. Methods in the pharmacopeial compendia intended for product quality assurance initiate sampling by applying a vacuum to the measurement apparatus using a timer-operated solenoid valve located downstream of the CI, resulting in a period when the flow rate through the impactor rapidly increases from zero towards the target flow rate. This article provides recommendations for achieving consistent APSD measurements, including selection of the CI, pre-separator, and flow control equipment, as well as reviewing considerations that relate to the shape of the flow rate-sampling time profile. Evidence from comparisons of different DPIs delivering the same active pharmaceutical ingredients (APIs) is indicative that the compendial method for APSD measurement is insensitive as a predictor of pharmacokinetic outcomes. Although inappropriate for product quality testing, guidance is therefore provided towards adopting a more clinically realistic methodology, including the use of an anatomically appropriate inlet and mimicking patient inhalation at the DPI while operating the CI at constant flow rate. Many of these recommendations are applicable to the testing of other OIP classes.

Precise size distribution measurement of aerosol particles and fog droplets in the open atmosphere.

A precise measurement for the aerosol particle size distribution and fog droplet size distribution simultaneously in the open atmosphere is proposed. The extinction coefficient and small-angle forward scattering measurement are integrated into the detection for particle size distribution in the open atmosphere, and can achieve the fine detection of the particles in the atmosphere with radius between 0.1 to 30 μm. The key technology including optimal scattering angle in small-angle forward scattering measurement and optimal wavelengths selection are discussed and solved in detail. The fourteen different particle size distributions including aerosol size distributions and fog droplet size distributions are used for the determination of optimal forward scattering angle and wavelengths. The optimal forward scattering angle is calculated to be 1.1°. Seven wavelengths for extinction coefficients and five wavelengths for forward scattering coefficients are chosen for the retrieval of particle size distribution in the measurement. The regularization inversion of optical parameters for the retrieval of particle size distribution is described. The aerosol particle size distributions measured by particle spectrometer and actual fog particle size distributions are used for the method test and the reconstructions of particle size distributions. The inversion results show that the method can achieve the precise measurements of aerosol particle size distribution and fog droplet size distribution. The error influence on the inversion results of distributions is discussed. Based on the sensitivity analysis of inversion results, the feasibility of measurement in the real atmosphere is analyzed and discussed, and the scheme of detection system is provided.

Size distribution and concentration of aerosol particles in Yinchuan area, China

ABSTRACTThe size distribution and concentration of atmospheric aerosol particles are important parameters that characterize the physical and optical properties of aerosols. Understanding the spectral distribution of atmospheric particles is fundamental for studying particulate pollution. Based on observational data acquired by an aerodynamic particle sizer APS-3321 and a laser dust meter LD-5 from September 2017 to July 2018, the temporal evolution of particle size distribution and concentration of aerosols were studied at the North Minzu University in Yinchuan (38°29’52"N 106°06’28"E), China. By cluster analysis of particle surface area distribution in different weathers, seven clusters were obtained and discussed. The experimental results showed that the particle number and mass concentrations were different in the four seasons of the year. Compared with the unimodal distribution of the particle number concentration and the doublet mass concentration distribution in sunny weather conditions, there were great differences in the particle spectrum distribution in haze, snowfall, and dusty weather conditions. The particle surface area distributions of the seven clusters were clearly different from each other and influenced by meteorological conditions. Additionally, the PM2.5 value has a relationship with the meteorological elements. The research is helpful to reveal the formation mechanism and source of aerosols in Yinchuan, China.

The Impact of Changes in Cloud Water pH on Aerosol Radiative Forcing

AbstractOxidation of sulfur dioxide (SO2) in cloud water by reaction with ozone is an important sulfate aerosol formation mechanism and strongly dependent on the acidity of cloud water. Decadal reductions in Northern Hemisphere sulfur emissions have contributed to higher cloud water pH, thereby altering sulfate formation rates. Here we use a global composition‐climate model to show that changes in cloud water pH over the 1970–2009 period strongly affects the aerosol particle size distribution, cloud condensation nuclei concentrations, and the magnitude of aerosol radiative forcing. The simulated all‐sky aerosol radiative forcing (1970–2009) over the North Atlantic is +1.2 W m−2 if pH remains constant at 5.0, as in many climate models. However, the forcing increases to +5.2 W m−2 if pH is assumed to increase by 1.0 unit over this period. Global composition climate models need to account for variations in cloud water pH to improve the representation of sulfate aerosol formation and aerosol radiative effects.

Inversion algorithm for non-spherical dust particle size distributions

Dust particles are the main aerosol component of the atmosphere, and can influence human, environmental, and ecological health. Particle size distribution is an important aerosol micro-physical parameter that denotes the concentration distribution of particles of different radii and can determine the extinction characteristics of these particles. In traditional inversion algorithms, the aerosol is generally assumed to be spherical according to Mie theory, and the relationship between aerosol optical thickness and particle size distribution is described by the Fredholm integral equation of the first kind. For non-spherical dust particles, this spherical assumption is obviously unreasonable and yields unreliable results. Therefore, we developed an algorithm assuming non-spherical particles for inversion of dust particle size distributions. In the case of non-spherical particles, the extinction efficiency factor kernel functions of the ellipsoid were calculated using the anomalous diffraction approximation method, and the kernel function of Mie scattering theory was substituted with these new kernel functions. Moreover, the Phillips–Twomey method was employed to solve the Fredholm integral equation of the first kind using aerosol optical thickness data from a CE-318 sun photometer. To verify the feasibility of the anomalous diffraction approximation method, experiments were carried out under sunny, dusty, windy and hazy weather conditions. These experiments showed that the extinction kernel function for non-spherical particles obtained using the anomalous diffraction approximation method is suitable for inversion of non-spherical dust particle size distributions under different weather conditions in the Yinchuan area.

Contribution to column-integrated aerosol typing based on Sun-photometry using different criteria

This study analyses the aerosol optical and microphysical properties obtained by the Aerosol Robotic Network (AERONET) in seven different sites operating in the Iberian Peninsula during three coincident years (2010−2012) with the objective of studying different aerosol typing approaches. This area is of interest due to its location between the Sahara desert (the largest source of natural aerosols in the world) and mainland Europe (a relevant source of anthropogenic aerosols). In particular, we study the aerosol optical depth (AOD), Angström parameter (α440–870) and fine mode fraction (FMF), which are estimated from direct sun irradiance measurements. Additionally, the single scattering albedo (ωo) and aerosol particle size distribution (PSD), which are computed using additional sky radiances measurements under cloudless skies, are used in our analyses. The analyses show aerosol seasonal patterns in the AOD with maximum values in summer/spring and minimum values in winter/autumn for all the analysed stations. For α440–870, there are differences from site to site, with maximum values in winter and minimum values in summer for the southern locations, while there is not a remarkable pattern for the eastern locations close to the Mediterranean coast. The frequent and intense Saharan dust outbreaks over the southern Iberian Peninsula and the intense anthropogenic activity in the eastern urban locations are behind these seasonal patterns in the AOD and α440–870. In this work, two of the most employed classification schemes of aerosol type in the literature are used: one is based on the AOD and α440–870, the other one is based on ωo at 440 nm and the FMF and a new classification scheme based on ωo at 440 nm and FMF is proposed. The results revealed that the new classification method is more appropriate for distinguishing the aerosol types that affect the Iberian Peninsula. The relationship derived here between Δωo = ωo (440)- ωo (1020) and the FMF is demonstrated to be useful for aerosol type classification when no measurements of the sky radiances, and consequently of ωo(440), are available. Alternatively, the relationship between the ratio Δωo/ωo(440) and the FMF can be used because (Δωo/ωo) provides information about both the spectral ωo and the absolute values.

Characteristics of size distributions and sources of water-soluble ions in Lhasa during monsoon and non-monsoon seasons

To understand the physical and chemical characteristics, particle size distribution and sources of size-separated aerosols in Lhasa, which is located on the Tibetan Plateau (TP), six sizes of aerosol samples were collected in Lhasa in 2014. Ca2+, NH4+, NO3−, SO42− and Cl− were the dominant ions. The ratio of cation equivalents (CE) to anion equivalents (AE) for each particle size segment indicated that the atmospheric aerosols in Lhasa were alkaline. SO42− and NO3− could be neutralized by Ca2+, but could not be neutralized by NH4+, according to the [NH4+]/[NO3− + SO42−] and [Ca2+]/[NO3− + SO42−] ratios. Mobile sources were dominant in PM0.95–1.5, PM1.5–3 and PM3–7.2, while stationary sources were dominant in the other three size fractions according to the [NO3−]/[SO42−] ratios. The particle size distribution of all water-soluble ions during monsoon and non-monsoon periods was characterized by a bimodal distribution due to the different sources and formation mechanisms, and it was revealed that different ions had different sources in different seasons and different particle size segments by combining particle size distribution with correlation analysis. Source analysis of aerosols in Lhasa was performed using the Principal component analysis (PCA) for the first time, which revealed that combustion sources, motor vehicle exhaust, photochemical reaction sources and various types of dust were the main sources of Lhasa aerosols. Furthermore, Lhasa's air quality was also affected by long-distance transmission, expressed as pollutants from South Asia and West Asia, which were transmitted to Lhasa according to backward trajectory analysis.

Characteristics of single atmospheric particles in a heavily polluted urban area of China: size distributions and mixing states

To investigate the chemical composition, size distribution, and mixing state of aerosol particles on heavy pollution days, single-particle aerosol mass spectrometry was conducted during 9-26 October 2015 in Xi'an, China. The measured particles were classified into six major categories: biomass burning (BB) particles, K-secondary particles, elemental carbon (EC)-related particles, metal-containing particles, dust, and organic carbon (OC) particles. BB and EC-related particles were the dominant types during the study period and mainly originated from biomass burning, vehicle emissions, and coal combustion. According to the ambient air quality index, two typical episodes were defined: clean days (CDs) and polluted days (PDs). Accumulation of BB particles and EC-related particles was the main reason for the pollution in Xi'an. Most types of particle size were larger on PDs than CDs. Each particle type was mixed with secondary species to different degrees on CDs and PDs, indicating that atmospheric aging occurred. The mixing state results demonstrated that the primary tracers were oxidized or vanished and that the amount of secondary species was increased on PDs. This study provides valuable information and a dataset to help control air pollution in the urban areas of Xi'an. Graphical abstract.

On Ash Deposition Rates from Air and Oxy-Combustion of Pulverized Coal, Petroleum Coke, and Biomass

This paper presents a synthesis of a large body of experimental data on growth rates of ash deposits from the air and oxy-combustion of multiple pulverized solid fuels, including coal, biomass, and their blends. The experimental data were obtained from 35 tests in a 100 kW (rated) entrained-flow combustor that allowed for self-sustained combustion of solid fuels. Ash deposition rates were measured using a wall-temperature-controlled ash deposition probe. The collected deposits were divided into tightly bound “inside deposits” adjacent to the heat transfer surface and loosely bound “outside deposits” that grow further out. Ash aerosol particle size distributions (psd’s) and size-segregated compositions were obtained through electric mobility, light scattering, and impactor methods. Rates of ash deposition for both inside and outside deposits are presented. Rates of growth of the inside deposit were proportional to the sub-micrometer particle (PM1) concentration in the flue gas but correlated poorly with th...

Kinetic Parameters of Smoke Aerosols during Combustion of Modified Wood

The most dangerous factors of fire are formation of smoke and thermal decomposition of toxic products. In case of fire, smoke spreads to evacuation routes. In this case, a person may be disoriented and feel panic. Smoke is an aerosol produced by the thermal decomposition of materials. The study object is the wood, which is widely used in construction. Up to date, the influence of wood species and wood surface layer modifiers on the smoke-forming ability has been studied. The effect of wood surface layer modifiers on the properties of aerosols remains insufficiently studied. The objective is to evaluate the effect of the wood surface layer modifiers on the formation and stability of smoke aerosols. In the course of work, the ultimate analysis method was used to assess the modifying effect of selected phosphoric acid esters. It is known that these compounds constitute effective flame retardants and are able to provide the biological stability of the wood. Granulometric analysis was additionally performed to evaluate the aerosol’s properties. To evaluate the energy characteristics of the modified wood surface, the “neutral drop” method was used. As a result of the studies, a percentage phosphorous content was obtained in the surface layer of the wood before and after thermal decomposition. This data made it possible to conclude that the thermal effect of diethyl phosphite is very effective and stable when it is used as a modifier. Based on the granulometric analysis, the size distribution of solid aerosol particles was obtained. When using the selected modifiers, the maximum particle size of the aerosol is reduced, which in turn reduces the optical density of the smoke. Phosphoric acid esters affect the kinetic parameters of the aerosol, which were obtained on the basis of mathematical calculation. Diethyl phosphite produces the greatest effect on the decrease in the aerosol’s stability. The formation of an aerosol having a smaller particle size occurs during thermal decomposition of the modified wood having a thermally stable surface. Therefore, the modification of wood by phosphoric acid esters reduces its propensity to smoke-generating ability, which determines the reduction in death rate of humans in the event of fire.