Characterization Of Atmospheric Aerosols Research Articles

Characterization of atmospheric aerosols using MFRSR measurements

Measurements by multifilter rotating shadowband radiometers (MFRSRs) constitute a valuable global data set with contributions from hundreds of instruments deployed worldwide. The geographical coverage of MFRSR networks is complementary to that of AERONET and often provides better spatial density of measurement sites, especially in the United States. We describe our recently updated analysis algorithm for MFRSR data that allows partitioning of the spectral aerosol optical depth (AOD) into fine and coarse mode AOD and retrieval of the fine mode effective radius. Our recent sensitivity study demonstrated that for a typical measurement accuracy 0.01 of AOD, the trade‐offs between the spectral aerosol extinction and NO2 absorption in the visible range effectively prevent unambiguous retrieval of NO2 column from MFRSR data and may also bias aerosol size distribution retrievals. This has prompted us to adopt a new retrieval approach, which utilizes climatological NO2 (based on SCIAMACHY satellite retrievals) and uses column ozone from TOMS measurements. The performance of this new approach was evaluated using the long‐term data set from the Southern Great Plains (SGP) site operated by the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program. We present a detailed intercomparison of total, fine, and coarse mode AOD and fine mode effective radius between two MFRSRs located at the SGP's Central Facility and with the correlative AERONET Sun‐sky inversion results (Version 2) derived from a collocated CIMEL Sun photometer. The comparison between two MFRSRs demonstrated good consistency of both the measurements and the analysis. Agreement with AERONET inversions is remarkably good, in that differences in AOD components do not exceed the expected measurement accuracy of 0.01, while the retrieved values of fine mode effective radius show no relative bias and only 0.03 μm random error (standard deviation of the differences). We show that if only data with large enough AOD (more than 0.06 at 870 nm) are selected, this error is reduced by a factor of two, becoming about 10% of a typical fine mode effective radius value.

Physico-chemical characterisation of atmospheric aerosols in Tanzania, with emphasis on the carbonaceous aerosol components and on chemical mass closure

Physico-chemical characterisation of atmospheric aerosols in Tanzania, with emphasis on the carbonaceous aerosol components and on chemical mass closure

Optimization of a novel method for the organic chemical characterization of atmospheric aerosols based on microwave-assisted extraction combined with stir bar sorptive extraction

A practical analytical methodology based on coupling microwave-assisted extraction–stir bar sorptive extraction–thermal desorption-gas chromatography–mass spectrometry (MAE–SBSE–TD–GC–MS) was developed and validated for the characterization of several SVOC in atmospheric particulate matter (PM). The high enrichment capacity of SBSE makes it a powerful tool for improving detection limits and MAE has been useful for overcoming the long extraction times and high volumes of extraction solvent used in traditional methodologies. Relative to Soxhlet extraction followed by GC–MS analysis (EPA Methods 3540 and 8270C), the MAE–SBSE–TD–GC–MS methodology resulted with approximately 10 4 times better detection limits. Detection limits ranged from 0.3 to 8.3 pg m −3 for pp′-DDD and decachlorobyphenyl, respectively in PM2.5, 24 m 3 air sample. The performance of the optimized methodology gave good precisions, with R.S.D. less than 30% for most of the standards, and linearity within the range tested of 0.1–15 μg L −1. Analysis of real PM samples resulted in the identification of compounds in the ng L −1 range.

Characterization of atmospheric aerosols at Monte Cimone, Italy, during summer 2004: Source apportionment and transport mechanisms

Atmospheric aerosols in the PM10 and PM1 fractions have been sampled at the Global Atmospheric Watch station Mount Cimone, Italy (2165 m above mean sea level) for 3 months during summer 2004, and simultaneous size distributions have been derived by means of an optical particle counter. Samples have been analyzed by X‐ray fluorescence, ion chromatography, and thermal‐optical methodology in order to quantify their elemental, ionic, and carbonaceous constituents. The concentration of PM10 was 16.1 ± 9.8 μg m−3 (average and standard deviation). Source apportionment allowed us to identify, quantify and characterize the following aerosol classes: anthropogenic pollution (10 μg m−3), mineral dust (4 μg m−3), and sea salt (0.2 μg m−3). Pollution has been further split into ammonium sulfate (44%), organic matter (42%), and other compounds (14%). The nitrate/sulfate ratio in the polluted aerosol was 0.1. Fine particles have been completely related to the polluted aerosol component, and they represented 70% in weight of pollution. Coarse particles characterized the dust and salt components, and crustal oxides have been found to be the largest responsible for the aerosol concentration variations that occurred during the campaign. Nitrate has also been found in the coarse particles, representing ∼10% of mineral dust. The analysis of the transport mechanisms responsible for aerosol fluctuations permitted us to identify the origin of the major aerosol components: Pollution has been ascribed to regional transport driven by boundary layer meteorology, whereas mineral dust has been related to long‐range transport events originating in the Sahara and Sahel. A particularly significant Saharan episode has been identified on 10 August 2004 (PM10 daily concentration, 69.9 μg m−3). Average elemental ratios for the African dust events were as follows: Si/Al = 2.31, Fe/Ca = 0.94, Ca/Al = 0.90, K/Ca = 0.44, Ti/Ca = 0.11, and Ti/Fe = 0.12.

Subisokinetic sampling characteristics of high speed aircraft inlets: A new CFD-based correlation considering inlet geometries

Large spatial-scale atmospheric aerosol characterization is commonly accomplished from high-speed aircraft platforms using subisokinetic sampling. The aspiration efficiencies in these inlets are commonly determined from the empirical correlation of Belyaev and Levin [1974. Techniques for collection of representative aerosol samples. Journal of Aerosol Science, 5, 325–338] (B&L), though the correlation was obtained from experiments under conditions very different from those encountered during high-speed aircraft sampling. Aircraft inlets are generally thick-walled, often have a blunt-body downstream, operate at a large freestream to sampling velocity ratio, and under conditions of low ambient pressures. The dependence of sampling characteristics on these parameters is studied using computational fluid dynamics (CFD) modeling. The CFD calculations show that the anisokinetic inlet sampling characteristics are strongly influenced by the operating conditions and sampler geometry, especially the presence of an aft blunt body. It is observed that these dependencies are not accurately captured by the existing correlations. The presence of even a moderately sized blunt-body aft of a sampling inlet can greatly influence the sampling characteristics of a straight tube inlet. A new correlation is derived based on the CFD simulation results, and this correlation is seen to greatly improve prediction of inlet sampling characteristics considering their geometries.

Characterization of Atmospheric Aerosol in the Northern Foot of Mt. Fuji, Central Japan

The unique characteristics of atmospheric aerosol in the northern foot of Mt. Fuji, central Japan were first clarified. The Mt. Fuji (an altitute of 3776 m) is the largest basaltic stratovolcano in the quaternary period in Japan. The aerosol measurements were carried out at an altitute of 1100 m from June 2000 to April 2001. Ambient aerosol in the predominant area of a typical volcanic rock like basalt was referred to as a basaltic aerosol in this study. Fifteen elements (Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Ba, Pb) of major to trace in the aerosol samples were determined by X-ray fluorescence spectrometry. Total mass concentration (< 10 μm) of the basaltic aerosol showed the higher values in summer and spring rather than autumn to winter, and the seasonal variation pattern differed widely from that of general urban aerosol. The behavior of the basaltic aerosol was mainly controlled by mineral particles throughout the year, so that a typical anthropogenic-derived element like Pb was very rarely detected. Even V, Cr and Zn which have been generally considered to be typical anthropogenic-derived elements, showed crustal-like behaviors. A concentration ratio of Si/Al showed markedly a uniqueness of the basaltic aerosol. From a comparison with atmospheric aerosol Si/Al ratio in granitic region being an exact opposite geology, a correlation plot of Si/Al ratio against Si concentration was made. It showed a big regional difference available for source identification of atmospheric soil particles. The chemical and geological characteristics of the basaltic aerosol are very useful for the novel characterization of atmospheric soil particles.

Size-segregated characterization of atmospheric aerosols in Taipei during Asian outflow episodes

To investigate the size resolved physico-chemical properties of aerosols transported from the eastern Asian Continent following the winter monsoons, an intensive field experiment was conducted in Taipei, Taiwan in January 2003. Mass concentration and the abundance of major functional groups in size-segregated aerosol samples were measured. The size distribution parameters of the aerosol mass and the associated functional groups were analyzed. The results of the infrared spectroscopic analysis showed that the contents of sulfate and ammonium in Taipei's sub-micron aerosols were significantly increased due to continental pollution. In addition, the Asian outflow aerosols contained higher levels of silicate and nitrate in the super-micron size range. The size-resolved functionalities of the aerosol samples collected during Asian outflow episodes were compared with those of local pollution samples. This comparison revealed that ammonium and sulfate generally coexisted in sub-micron aerosols, suggesting that there are substantial emissions of ammonia to neutralize the acidity of sulfate in the region from eastern China to northern Taiwan. The nitrate had a bimodal distribution over the size range between 0.1 and 10 μm. A significant enhancement was found in coarse nitrate during the Asian outflow episodes, implying heterogeneous reactions of nitric acid on the surface of dust and sea salt particles during the transport processes. High concentrations of sub-micron ammonium nitrate aerosols were observed prior to the frontal passage and served as an important indicator of local photochemical pollution. The aliphatic and carbonyl carbon in the aerosols were suggested as being mostly due to local pollution in Taipei. Nevertheless, our analysis found that the aerosols of Asian outflows had a higher infrared absorbance ratio of carbonyl to aliphatic carbon than those of the local pollution. The enrichment of carbonyl carbon in the Asian outflow aerosols is most likely due to the emissions of biomass burning aerosols in the eastern China.

Characterization of atmospheric aerosols from infrared measurements: simulations, testing, and applications

An inversion method for the characterization of atmospheric condensed phases from infrared (IR) spectra is described. The method is tested with both synthetic IR spectra and the spectra of particles that flow in a cryogenic flow tube. The method is applied to the IR spectra recorded by the Atmospheric Trace Molecule Spectroscopy instrument carried by the Space Shuttle during three missions in 1992, 1993, and 1994. The volume density and particle size distribution for sulfate aerosol are obtained as a function of altitude. The density and size distribution of ice particles in several cirrus clouds are also retrieved. The probable radius of the ice particles in the high-altitude (10-15-km) cirrus clouds is found to be approximately 6-7 microm.

A review of research on human activity induced climate change I. Greenhouse gases and aerosols

Extensive research on the sources and sinks of greenhouse gases, carbon cycle modeling, and the characterization of atmospheric aerosols has been carried out in China during the last 10 years or so. This paper presents the major achievements in the fields of emissions of greenhouse gases from agricultural lands, carbon cycle modeling, the characterization of Asian mineral dust, source identification of the precursors of the tropospheric ozone, and observations of the concentrations of atmospheric organic compounds. Special, more detailed information on the emissions of methane from rice fields and the physical and chemical characteristics of mineral aerosols are presented.

A compact multistage (cascade) impactor for the characterization of atmospheric aerosols

This paper presents the development, laboratory characterization, and field evaluation of a compact multistage cascade impactor (CCI). The CCI operates at a flow rate of 30 LPM and consists of eight impaction stages equipped with rectangular slit-shaped acceleration nozzles. A 47 mm backup Teflon membrane filter is used downstream of the eighth stage to collect particles smaller than 0.16 μm . In each stage, particles are retained by impaction onto the inert polyurethane foam (PUF) substrate. The major feature of this novel sampler is its ability to both fractionate by size and collect relatively large amounts of particles (mg quantities) onto an inert polyurethane foam impaction substrates. Even though the impaction substrates are not coated with adhesives such as grease or mineral oil, particle bounce and re-entrainment losses were found to be insignificant. Impaction characteristics (cutpoint and sharpness of collection efficiency curve) of the PUF substrates are maintained for mass loadings of at least 25 mg , which is much higher than for other commonly used rigid, flat impaction substrates. The system was calibrated in laboratory experiments using polydisperse aerosols. The 50% cutpoints of the eight stages were 9.9, 5.3, 3.3, 2.5, 1.7, 1.0, 0.47 and 0.16 μm (aerodynamic diameter), with pressure drops of 0.02, 0.02, 0.04, 0.06, 0.08, 0.27, 1.57 and 5.73 kPa . These pressure drops are considerably lower than those obtained using flat rigid impaction substrates with comparable cutpoints. Particle losses for each stage were less than 10% for particles smaller than 7 μm and less than 20% for particles larger than 7 μm . The CCI was also compared with the collocated micro-orifice impactor (MOI) in laboratory-controlled experiments using artificially generated polydisperse aerosol. These laboratory tests showed that the mass concentrations measured by the MOI are considerably lower than those measured by the CCI (the average ratio of total mass concentration of MOI to CCI was 0.86), with the size distribution measured by the CCI closer to that measured using the real time particle sizing instruments (SMPS, APS). A field comparison of CCI, the Harvard impactor (HI) and the federal reference method (FRM) for fine particles showed a good agreement between the CCI and the reference samplers for particles smaller than 2.5 μm .

Aerosol optical depth and ozone variations during the total solar eclipse of 24 October 1995

The total solar eclipse of 24 October 1995 has provided an important opportunity to investigate a variety of eclipse-related atmospheric phenomena. The path of totality of the eclipse passed through a few stations in India. Field campaign experiments have been carried out with an objective to investigate the effects of solar eclipse phenomenon on atmospheric aerosol characterization and columnar ozone over Robertsgunj (24°42′N, 83°04′E, 312 m AMSL), Uttar Pradesh, India during 23–25 October 1995 using a multi-channel radiometer. The solar irradiance measured in the ultra-violet (UV) to near-infrared (NIR) wavelength region has been utilized to study the spectral–temporal variations of height-integrated aerosol optical depth and corresponding aerosol size distribution, and total column ozone during the pre- and post-eclipse period (control days) and on the total solar eclipse day. The study has revealed that aerosol optical characteristics and ozone variations observed on the eclipse day, especially during the period of totality, differ significantly from those noticed on the control days. These deviations are explained on the basis of changes in meteorological parameters induced by the eclipse phenomenon.

Characterization of Atmospheric Aerosol over XiAn in the South Margin of the Loess Plateau, China

The mass concentrations of TSP, PM-10, several secondary aerosol species, and up to 20 elements were determined for bulk aerosol samples collected from four ground-based monitoring sites in XiAn, China. The samples were collected during four seasons from September 1996 to August 1997; and in July 1998. Daily concentrations of TSP, SO 2 and NO x from 1995 to 1997 were also obtained from the same sampling sites. Representative concentrations (annual averages) of TSP, SO 2 and NO x were 410, 39, 43 μg m −3, respectively. PM-10 accounted for about 60–70% of TSP in summer 1998. The most abundant elements in the samples were Si, Ca, Al, Fe, Cl, P, K and S. A fraction of the Ca, which in typically associated with dust, was from non-crustal sources, especially in coarse particles. In winter, the element with the highest concentration was S, and it was primarily in the form of sulfate. The seasonal mean sulfate concentrations, averaged over all sites, were 100, 340, 59 and 27 μg SO 2− 4 m −3 for autumn, winter, spring and summer, respectively. The corresponding loadings of ammonium ion were 49, 140, 40 and 17 μg NH 4 + m −3 for the same seasons and those for nitrate were 22, 65, 33, 16 μg NO 3 − m −3. Dispersed sources of coal-combustion (most likely residential heating), as opposed to stationary point sources, evidently play an important role in the large increases in TSP and three-fold increases in sulfate, nitrate and ammonium loading during XiAn's space-heating season.

SEM-EDS Quantitative Analysis of Aerosols ≥ 80nm: Impacts on Atmospheric Aerosol Characterization Campaigns

Journal Article SEM-EDS Quantitative Analysis of Aerosols ≥ 80nm: Impacts on Atmospheric Aerosol Characterization Campaigns Get access Michael A Carpenter, Michael A Carpenter University at Albany, School of Nanosciences and Nanoengineering, Albany, NY 12203 Search for other works by this author on: Oxford Academic Google Scholar Eric Lifshin, Eric Lifshin University at Albany, School of Nanosciences and Nanoengineering, Albany, NY 12203 Search for other works by this author on: Oxford Academic Google Scholar Raynald Gauvin Raynald Gauvin Mcgill University, Depart. of Mining, Metals and Materials Engineering, Montreal, QC H3A 2B2 Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 8, Issue S02, 1 August 2002, Pages 1482–1483, https://doi.org/10.1017/S1431927602104041 Published: 01 August 2002

Characterization of atmospheric aerosols across Canada from a ground‐based sunphotometer network: AEROCAN

Ground‐based sunphotometry measurements acquired under clear sky conditions can be used to investigate atmospheric aerosol optical properties. Such measurements are not only important in their own right as a technique for monitoring generic aerosol dynamics, but also represent a direct means of evaluating the contribution of aerosol induced radiative forcing in the modelling of climate change. In this paper we analyze derived aerosol optical properties using datasets from the Canadian AEROCAN (AERosol CANada) sunphotometer network. The AEROCAN network currently includes eight sunphotometers distributed across Canada at sites chosen in order to obtain a diverse sampling of continental, maritime and arctic aerosols. Some of these sites have been operational since 1993 as part of the Boreal Ecosystem‐Atmosphere Study (BOREAS). These instruments permit standard and automatic multi‐wavelength measurements of solar extinction radiance centred on the solar disk as well as sky radiance scans off the solar disk. These data yields aerosol optical depth, the Ångström exponent, aerosol particle volume size distribution, refractive index, column‐averaged single scattering albedo, and precipitable water vapour content. Spatial and temporal trends of these parameters as well as observed inter‐correlations are discussed. The results demonstrate the utility and significance of these types of measurements and illustrate the potential applications of networked sunphotometry data.

Characterization of visibility and atmospheric aerosols in urban, suburban, and remote areas

Visibility data from over the past four decades accumulated from urban areas of central Taiwan indicated that air pollutants have significantly degraded visibility in recent years. Currently, the annual average visibility in urban areas of the same region is approximately 8–10 km, while the visibility in remote areas is approximately 25–30 km. To understand how aerosols affect the visibility in this region, here we selected three sites in central Taiwan to measure the soluble ionic and carbonaceous species of PM 2.5 and PM 2.5–10 during 1997–1998. A MOUDI cascade impactor was used to measure the size distributions of atmospheric sulfate, nitrate, and carbonaceous particles. The aerosol data were then analyzed together with meteorological and air quality data. Comparing the results obtained from urban, coastal suburban and remote sites revealed that sulfate, carbonaceous species and local wind speed significantly affected the visibility in the urban area. However, sulfate concentration and humidity influenced visibility in the coastal area of central Taiwan. The particulate concentration at the remote station was roughly one-fifth of that in the city. Regression analysis results indicated that humidity is a dominant factor affecting remote visibility.

Size and chemical characterization of atmospheric aerosol and savanna fire samples in Southern Africa

Size and chemical characterization of atmospheric aerosol and savanna fire samples in Southern Africa

Biomass Burning in Southern Africa: Individual Particle Characterization of Atmospheric Aerosols and Savanna Fire Samples

Ambient atmospheric aerosols and savanna fireparticulate emission samples from southern Africa werecharacterised in terms of particle classes and theirnumber abundance by electron probe X-ray microanalysis(EPXMA). About ten particle classes were identifiedfor each sample. The major classes werealuminosilicates and sea salts for ambient coarse(2–10 μm equivalent aerodynamic diameter (EAD))samples, and K-S and S-only particles for ambient fine(<2 μm EAD) samples. The K-S particles are oneof the major products of biomass burning. The EPXMAresults were found to be consistent with the resultsfrom bulk analyses on a sample by sample basis. Forsavanna fire fine samples, quantitative EPXMA revealedthat many particles had a composition of simple saltssuch as KCl. Some particles had a deviatingcomposition in the sense that more ionic species wereinvolved in sustaining the balance between cations andanions, and they were composite or mixed salts.Because of extensive processing during the atmospherictransport, the composition of the K-S particles in theambient samples was different from K2SO4,and such particles were enriched with S. The finepyrogenic KCl particles and the fine sea-saltparticles were much depleted in chlorine.

Physico-chemical characterisation of atmospheric aerosols in a rural area affected by the aznalcollar toxic spill, south-west Spain during the soil reclamation activities

High levels of atmospheric contamination due to the re-suspension of pyrite particles from the mining waste slurry were recorded in the Guadiamar valley (the Guadiamar is a tributary of the Guadalquivir river) after the toxic spill of Aznalcóllar, north of the Doñana Natural Park (SW Spain). Major high-particulate events occurred during the extraction of the pyrite-rich mud layer, which covered an extensive area of the valley downstream of the confluence of the Agrio and Guadiamar rivers. This study deals with the monitoring of the ambient air quality at two stations near the village of Aznalcázar in the central part of the flooded area. Although the Spanish legal limit for atmospheric particles and lead in environmental air were not exceeded, high daily levels of total suspended particles (TSP) and of some elements with an environmental significance (As, Cd, Cu, Mn, Ni, Pb, Sn, Tl and Zn) were recorded at Aznalcázar and in the Guadiamar valley during soil reclamation (July–August 1998). Despite a progressive decrease in TSP levels through September–October 1998, background was higher than the levels for the May–June period. Evolution of levels for most of the elements studied showed a similar trend. The exceptions were copper, which was partially increased by other emission sources such as fumigation activities, and sodium, which remained at relatively constant levels during the study period because of its marine origin. The physico-chemical characterisation of the atmospheric particulates allowed us to determine the major grain size modes of the pyrite related elements and the solubility of the potentially toxic elements, and to identify the major particulate types present in the atmosphere in the area. Secondary and tertiary aromatic amines (i.e. alkyldiphenylamines and phenylcarbazoles, respectively) were identified in the suspended particles and in the vapour phase collected at the same station as the TSP samples. As some of these aromatic amines had been previously identified in the pyrite sludge, it is assumed that fine sludge particles containing aromatic amines were re-suspended in the atmosphere. The highest concentrations of aromatic amines in the particulate phase were recorded in August 1998 during the pyrite slurry extraction in the proximity of the Aznalcazár sampling site. Despite a sharp drop in the suspended particles of the aromatic amine concentrations, a significant concentration was detected in the vapour phase (<1.2 mm) during autumn, probably because of longer residence time in the atmosphere. Although health hazards associated with the presence of these aromatic amines are unknown, their acute toxicity exceeded that of urban aerosols.

Physical and Chemical Characterization of Atmospheric Aerosols by Atomic Force Microscopy

A new approach to the measurement of the size distribution of atmospheric particles as a function of chemical reactivity is demonstrated. In this method, particles are collected on an atomically flat mica substrate and imaged using atomic force microscopy. The particle size distribution is obtained from analysis of the image. The sample is then repeatedly exposed to a reactive gas such as ozone or oxygen atoms and reimaged. The dimensions of organic and graphitic (soot) particles are found to shrink at different rates due to formation of volatile products, while inorganic particles remain unchanged. Using this approach, it is possible to classify particles as organic, graphitic, or inorganic and to obtain the size distribution for each chemical class.

PIXE, PIGE and ion chromatography of aerosol particles from northeast Amazon Basin

Characterization of atmospheric aerosols collected in the northeast part of the Amazon Basin is presented. The main aerosol source in that region is the forest natural biogenic emission. The aerosol samples were collected using stacked filter units, and were analyzed applying several analytical techniques: Particle Induced X-ray Emission (PIXE) for the quantitative analysis of trace elements with Z > 11; Particle Induced Gamma-ray Emission (PIGE) for the quantitative analysis of Na; Ion Chromatography (IC) was used to quantify ionic contents of aerosols from the fine mode particulate samples. A reflectance technique was used in order to measure black carbon concentrations; Gravimetric analysis was used in order to determine the total atmospheric aerosol mass concentration. The comparison from PIXE and IC concentration measurements for S, K and Ca techniques were in an excellent agreement. A good agreement was also obtained for Na concentrations measured by PIGE and IC techniques. Multivariate statistical analysis was used in order to identify and characterize the sources of the atmospheric aerosol present in the sampled region. The Serra do Navio aerosol is characterized by biogenic emissions, responsible for the majority of the total fine mass concentration. A strong marine influence was also noted. Soil dust is also an important aerosol source in that region.