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Atmospheric Environment (v.44, #6)
Fine particles and carbon monoxide from wood burning in 17th–19th century Danish kitchens: Measurements at two reconstructed farm houses at the Lejre Historical–Archaeological Experimental Center by Morten Ryhl-Svendsen; Geo Clausen; Zohir Chowdhury; Kirk R. Smith (pp. 735-744).
Carbon monoxide (CO) and particulate matter (PM2.5) were measured in two reconstructed Danish farmhouses (17–19th century) during two weeks of summer. During the first week intensive measurements were performed while test cooking fires were burned, during the second week the houses were monitored while occupied by guest families. A masonry hearth was located in the middle of each house for open cooking fires and with heating stoves. One house had a chimney leading to the outside over the hearth; in the other, a brickwork hood led the smoke into an attic and through holes in the roof. During the first week the concentration of PM2.5 averaged daily between 138 and 1650 μg m−3 inside the hearths and 21–160 μg m−3 in adjacent living rooms. CO averaged daily between 0.21 and 1.9 ppm in living areas, and up to 12 ppm in the hearths. Highest concentrations were measured when two fires were lit at the same time, which would cause high personal exposure for someone working in the kitchens. 15 min averages of up to 25 400 μg m−3 (PM2.5) and 260 ppm CO were recorded. WHO air quality guidelines were occasionally exceeded for CO and constantly for PM2.5. However, air exchange and air distribution measurements revealed a large draw in the chimney, which ensured a fast removal of wood smoke from the hearth area. The guest families were in average exposed to no more than 0.21 ppm CO during 48 h. Based on a hypothetical time-activity pattern, however, a woman living in this type of house during the 17–19th century would be exposed to daily averages of 1.1 ppm CO and 196 μg m−3 PM2.5, which exceeds WHO guideline for PM2.5, and is comparable to what is today observed for women in rural areas of developing countries.
Keywords: PM; 2.5; Wood smoke; Historic house; Personal exposures; Cooking fire
Soil water and particle size distribution influence laboratory-generated PM10 by Nicholaus M. Madden; Randal J. Southard; Jeffrey P. Mitchell (pp. 745-752).
Management of soils to reduce the amount of PM10 emitted during agricultural tillage operations is important for attainment of air quality standards in California's San Joaquin Valley (SJV). The purpose of this study was to improve and expand upon earlier work of predicting tillage-generated dust emissions based on soil properties. We focus on gravimetric soil water content (GWC) and soil texture. A mechanical laboratory dust generator was used to test 23 soils collected for this study. Averaged results showed PM10 concentrations (mg m−3) increased logarithmically as GWC decreased below soil water potentials of −1500 kPa. Soils with clay contents less than about 10% by weight began to emit PM10 at GWCs 1.5–4 times their GWC at −1500 kPa. Soils with clay contents greater than about 10% began to emit PM10 at GWC values closer to −1500 kPa. We found no correlation between maximum PM10 concentrations, measured at low GWC values, and the %sand, %silt, or %clay in a soil. However, there was a significant correlation between the %silt to %clay ratio and PM10 concentrations. This not only suggests the dependence of dust emission magnitudes on the supply of particles of PM10 size, but also the importance of clay in stabilizing aggregates and maintaining higher amounts of capillary water at lower water potentials. Based on modeled results of pooled data, PM10 concentrations increased linearly (slope = 564) for every unit increase in the %silt to %clay ratio. However, when soils were separated into groups based on clay content, the slopes for PM10 concentrations vs. %silt to %clay ratio were texture dependent. The slope for soils with <10% clay (slope = 727) was 3.3 times greater than for soils with >20% clay (slope = 221). Improved PM10 emission prediction based on soil properties should improve management decisions aimed at reducing tillage-generated PM10.
Keywords: PM; 10; Tillage; Emission estimates; Laboratory dust generation; Soil particle size distribution; Soil water content
A new Lagrangian particle model for the simulation of dense gas dispersion by D. Anfossi; G. Tinarelli; S. Trini Castelli; M. Nibart; C. Olry; J. Commanay (pp. 753-762).
A Lagrangian stochastic model (MicroSpray), able to simulate the airborne dispersion in complex terrain and in presence of obstacles, was modified to simulate the dispersion of dense gas clouds. This is accomplished by taking into account the following processes: negative buoyancy, gravity spreading and the particle's reflection at the bottom computational boundary. Elevated and ground level sources, continuous and instantaneous emissions, time varying sources, plumes with initial momentum (horizontal, vertical or oblique in any direction), plumes without initial momentum are considered. MicroSpray is part of the model system MSS, which also includes the diagnostic MicroSwift model for the reconstruction of the 3-D wind field in presence of obstacles and orography. To evaluate the MSS ability to simulate the dispersion of heavy gases, its simulation performances are compared in detail to two field experiments (Thorney Island and Kit Fox) and to a chlorine railway accident (Macdona). Then, a comprehensive analysis considering several experiments of the Modelers Data Archive is presented. The statistical analysis on the overall available data reveals that the performance of the new MicroSpray version for dense gas releases is generally reliable. For instance, the agreement between concentration predictions and observations is within a factor of two in the 72% up to 99% of the occurrences for the case studies considered. The values of other performance measures, such as correlation coefficient, geometric mean bias and geometric variance, mostly set in the ranges indicated as good-model performances in the specialized literature.
Keywords: Dense gas dispersion; Langevin equations; Gravity spreading; Field experiments; Accidental releases
On-road measurements of ultrafine particle concentration profiles and their size distributions inside the longest highway tunnel in Southeast Asia by Yu-Hsiang Cheng; Zhen-Shu Liu; Chih-Chieh Chen (pp. 763-772).
This study measured ultrafine particle (UFP) levels and their size distributions in the Hsuehshan tunnel from August 12 to 19, 2009, using a Fast Mobility Particle Sizer. Measurement results demonstrate that traffic volume, the slope of the tunnel (downhill or uphill) and the ventilation system affected UFP levels inside the tunnel. Average UFP levels were about 1.0 × 105–3.0 × 105 particles cm−3 at normal traffic volume. A traffic jam in the tunnel could raise UFP levels to over 1.0 × 106 particles cm−3. UFP levels at the uphill bore were significantly higher than those at the downhill bore due to high UFP levels exhausted from vehicles going uphill at high engine load conditions. UFP levels eventually diluted 10–50% with fresh air from tunnel air shafts. Gas-to-particle condensation conversion markedly produced nucleation mode particles at the tunnel entrance section. Observations also showed Aitken mode particles markedly formed by coagulation growth of nucleation mode particles in the tunnel middle section and exit section. That is, the particle size distributions changed significantly inside the tunnel. Measurement results suggest that particles in the Aitken mode in the long tunnel governed UFP levels.
Keywords: Ultrafine particle; Number concentration; Particle size distribution; Hsuehshan tunnel; Fast Mobility Particle Sizer
Alkyl nitrate photochemistry during the tropospheric organic chemistry experiment by David R. Worton; Claire E. Reeves; Stuart A. Penkett; William T. Sturges; Jana Slemr; David E. Oram; Brian J. Bandy; William J. Bloss; Nicola Carslaw; James Davey; Kathryn M. Emmerson; Thomas J. Gravestock; Jacqueline F. Hamilton; Dwayne E. Heard; James R. Hopkins; Anne Hulse; Trevor Ingram; Mark J. Jacob; James D. Lee; Roland J. Leigh; Alastair C. Lewis; Paul S. Monks; Shona C. Smith (pp. 773-785).
Alkyl nitrates (C1–C5) were measured at two sites (near urban and rural) in southeast England during the Tropospheric Organic Chemistry Experiment (TORCH). Methyl nitrate was the dominant species during both campaigns accounting for on average about one third of the total measured alkyl nitrates. High mixing ratios (>50 pptv) and variability of methyl nitrate were observed at the near urban site (TORCH1) that were not seen at the rural site (TORCH2) and which could not be explained by local photochemical production or direct emissions. The diurnal variation of methyl nitrate during TORCH1 showed a morning maximum that would be consistent with nighttime chemistry followed by transport to the surface by boundary layer dynamics. Similarly, elevated morning mixing ratios were also observed during TORCH2 although the magnitudes were much smaller. As a result, methyl nitrate could represent a tracer for nighttime chemistry seen at the ground the following day. At both campaigns, the dominant source of short chain alkyl nitrates and carbonyl precursor radicals (≤C4) were from decomposition of larger compounds. The magnitude of the source increased with decreasing carbon number consistent with increasing total precursor abundance. Non-photochemical emissions of acetaldehyde and acetone could not be accounted for by automobile exhaust emissions alone and indicated that other direct sources are likely important in this environment.
Keywords: Alkyl nitrates; Methyl nitrate; Acetone; Acetaldehyde; Photochemistry; Nighttime chemistry
Evaluation of non-enteric sources of non-methane volatile organic compound (NMVOC) emissions from dairies by Myeong Y. Chung; Matt Beene; Shawn Ashkan; Charles Krauter; Alam S. Hasson (pp. 786-794).
Dairies are believed to be a major source of volatile organic compounds (VOC) in Central California, but few studies have characterized VOC emissions from these facilities. In this work, samples were collected from six sources of VOCs (Silage, Total Mixed Rations, Lagoons, Flushing Lanes, Open Lots and Bedding) at six dairies in Central California during 2006–2007 using emission isolation flux chambers and polished stainless steel canisters. Samples were analyzed by gas chromatography/mass spectrometry and gas chromatography/flame ionization detection. Forty-eight VOCs were identified and quantified in the samples, including alcohols, carbonyls, alkanes and aromatics. Silage and Total Mixed Rations are the dominant sources of VOCs tested, with ethanol as the major VOC present. Emissions from the remaining sources are two to three orders of magnitude smaller, with carbonyls and aromatics as the main components. The data suggest that animal feed rather than animal waste are the main source of non-enteric VOC emissions from dairies.
Keywords: Cattle; Flux measurements; Ozone precursors; California
Development of a variable configuration cascade impactor for aerosol size distribution measurement by Sanjay Singh; B.K. Sapra; Arshad Khan; P.K. Kothalkar; Y.S. Mayya (pp. 795-802).
In atmospheric aerosol studies, it is often required to use two different impactors, namely, the normal pressure and the low-pressure impactor, to measure the mass-size distribution over a wide size range. From the perspective of rendering the system compact for such measurements, it may be more advantageous to combine the two features in a single instrument. In an effort towards exploring this option, a variable configuration cascade impactor (VCCI) comprising of 7 normal pressure and 4 low-pressure stages has been designed and developed. In configuration-1, it operates as a low-pressure impactor, with a sampling flow rate of 10 L min−1 and classifies the particles from 0.1 to 21 μm in eleven size classes. In configuration-2, it operates as a normal pressure impactor, with a sampling flow rate of 45 L min−1, and classifies the particles from 0.53 to 10 μm in seven size classes. As part of performance evaluation of the system, the deposit patterns and the integral performance have been studied. For integral performance, a comparative mass-size distribution measurement between VCCI and standard Andersen impactor was carried out. Its performance was also evaluated against the GRIMM Scanning Mobility Particle Sizer (SMPS) in the common size range of both these instruments and against GRIMM Optical Particle Counter (OPC). In addition to this, VCCI was evaluated for its performance in the PMx configuration obtained by removing a few of the impactor stages sequentially and measuring corresponding size distribution for every stage removed. Changes in the distribution parameters due to spillover of the deposits of previous stage to remaining stages were within 10%. This variation is well within the generally accepted value for all environmental measurement related applications.
Keywords: Aerosol; Size distribution; Impactor; Variable configuration
Modelling pollutants dispersion and plume rise from large hydrocarbon tank fires in neutrally stratified atmosphere by C.D. Argyropoulos; G.M. Sideris; M.N. Christolis; Z. Nivolianitou; N.C. Markatos (pp. 803-813).
Petrochemical industries normally use storage tanks containing large amounts of flammable and hazardous substances. Therefore, the occurrence of a tank fire, such as the large industrial accident on 11th December 2005 at Buncefield Oil Storage Depots, is possible and usually leads to fire and explosions. Experience has shown that the continuous production of black smoke from these fires due to the toxic gases from the combustion process, presents a potential environmental and health problem that is difficult to assess. The goals of the present effort are to estimate the height of the smoke plume, the ground-level concentrations of the toxic pollutants (smoke, SO2, CO, PAHs, VOCs) and to characterize risk zones by comparing the ground-level concentrations with existing safety limits. For the application of the numerical procedure developed, an external floating-roof tank has been selected with dimensions of 85 m diameter and 20 m height. Results are presented and discussed. It is concluded that for all scenarios considered, the ground-level concentrations of smoke, SO2, CO, PAHs and VOCs do not exceed the safety limit of IDLH and there are no “death zones” due to the pollutant concentrations.
Keywords: Tank fire; Pollutant dispersion; Safety limits; Smoke plume; Turbulence; CFD
Ground-level ozone in the Pearl River Delta region: Analysis of data from a recently established regional air quality monitoring network by Junyu Zheng; Liuju Zhong; Tao Wang; Peter K.K. Louie; Zhicheng Li (pp. 814-823).
The ambient air quality monitoring data of 2006 and 2007 from a recently established Pearl River Delta (PRD) regional air quality monitoring network are analyzed to investigate the characteristics of ground-level ozone in the region. Four sites covering urban, suburban, rural and coastal areas are selected as representatives for detailed analysis in this paper. The results show that there are distinct seasonal and diurnal cycles in ground-level ozone across the PRD region. Low ozone concentrations are generally observed in summer, while high O3 levels are typically found in autumn. The O3 diurnal variations in the urban areas are larger than those at the rural sites. The O3 concentrations showed no statistically significant difference between weekend and weekdays in contrast to the findings in many other urban areas in the world. The average ozone concentrations are lower in urban areas compared to the sites outside urban centers. Back trajectories are used to show the major air-mass transport patterns and to examine the changes in ozone from the respective upwind sites to a site in the center of the PRD (Wanqingsha). The results show higher average ozone concentrations at the upwind sites in the continental and coastal air masses, but higher 1 h-max O3 concentrations (by 8–16 ppbv) at the center PRD site under each of air-mass category, suggesting that the ozone pollution in the PRD region exhibits both regional and super-regional characteristics.
Keywords: Ground-level ozone; Temporal; Spatial characteristics; HYSPLIT model
Canopy influence on trace metal atmospheric inputs on forest ecosystems: Speciation in throughfall by L. Gandois; E. Tipping; C. Dumat; A. Probst (pp. 824-833).
Atmospheric inputs of selected Trace Metals (TM: Cd, Cu, Ni, Pb, Sb, Zn, as well as Al, Fe and Mn) were studied on six forested sites in France. In order to evaluate canopy interaction with atmospheric inputs, TM were measured in both Open Field Bulk Deposition (BD) and Throughfall (TF). Anthropogenic contribution to BD composition is high for Zn, Cd and Sb, reflecting actual TM emissions trends. Canopy greatly influences precipitation composition, through different processes, including assimilation and leaching by canopy, complexation as well as accumulation/dissolution of dry deposition. TM and Dissolved Organic Carbon (DOC) physical fractionation between colloidal and truly dissolved phases was performed with ultrafiltration. Al, Fe, Pb and Cu are found in the colloidal fraction whereas Cd, Ni, Zn and Sb are mostly in the truly dissolved fraction. Chemical speciation predicted with WHAM-VI shows that in throughfall, Al, Fe, Pb and Cu are almost entirely complexed by DOC, whereas Ni, Cd and Zn are present in average 30% in the free metal ion form. TM present in labile forms (Cd, Ni, Zn) interact with the canopy, are cycled in the ecosystem, and their concentration is either slightly increased or even decreased in throughfall. Sb, Pb and Cu concentration are increased through canopy, as a consequence of dry deposition accumulation.
Keywords: Trace metal; Throughfall; Speciation; WHAM-VI; Ultrafiltration; DOC
Atmospheric deposition of phthalate esters in a subtropical city by Feng Zeng; Yujun Lin; Kunyan Cui; Jiaxin Wen; Yongqin Ma; Hongli Chen; Fang Zhu; Zhiling Ma; Zunxiang Zeng (pp. 834-840).
In Chinese cities, air pollution has become a serious and aggravating environmental problem undermining the sustainability of urban ecosystems and the quality of urban life. Bulk atmospheric deposition samples were collected two-weekly, from February 2007 to January 2008, at three representative areas, one suburban and two urbanized, in the subtropical city, Guangzhou, China, to assess the deposition fluxes and seasonal variations of phthalate esters (PAEs). Sixteen PAE congeners in bulk deposition samples were measured and the depositional fluxes of ∑16PAEs ranged from 3.41 to 190 μg m−2 day−1, and were highly affected by local anthropogenic activities. The significant relationship between PAEs and particulate depositional fluxes (correlation coefficient R2 = 0.72, P < 0.001) showed PAEs are associated primarily with particles. Temporal flux variations of PAEs were influenced by seasonal changes in meteorological parameters, and the deposition fluxes of PAEs were obviously higher in wet season than in dry season. Diisobutyl phthalate (D iBP), Di- n-butyl phthalate (D nBP), and Di(2-ethylhexyl) phthalate (DEHP) dominated the PAE pattern in bulk depositions, which is consistent with a high consumption of the plasticizer market in China. PAE profiles in bulk deposition showed similarities exhibited in both time and space, and a weak increase of high molecular weight PAE (HMW PAE) contribution in the wet season compared to those in the dry season. Average atmospheric deposition fluxes of PAEs in the present study were significantly higher than those from other studies, reflecting strong anthropogenic inputs as a consequence of rapid industrial and urban development in the region.
Keywords: Phthalate esters; Depositional flux; Seasonal variation; Guangzhou; South China
Source apportionment of fine particles at urban background and rural sites in the UK atmosphere by Jianxin Yin; Roy M. Harrison; Qiang Chen; Andrew Rutter; James J. Schauer (pp. 841-851).
Airborne fine particulate matter (PM2.5) has been collected at two sites in the West Midlands conurbation, UK, representing urban background and rural locations. Chemical analyses have been carried out for major anions, trace metals, total OC and EC, and for individual organic marker species including n-alkanes, hopanes, PAHs, organic acids and sterols. Source apportionment has been conducted using both a pragmatic mass closure model and the US EPA chemical mass balance (CMB) model. The pragmatic mass closure model is well able to account for the measured PM2.5 mass in terms of chemical/source components, and the chemical mass balance model has been used to apportion the carbonaceous component of the aerosol. The dominant components of PM2.5 at both sites are secondary inorganic (sulphate and nitrate) and carbonaceous particles. The CMB model shows the latter to arise mainly from road traffic sources, with smaller contributions from vegetative detritus, wood smoke, natural gas, coal, and dust/soil. The CMB model also identifies an important component of the organic aerosol not associated with these primary sources, which correlates very strongly with secondary organic aerosol estimated from the OC/EC ratio. The split between different automotive source types does not relate well to UK emission inventories, and may indicate that CMB source profiles from North American studies and different carbon analysis protocols may lead to erroneous conclusions.
Keywords: PM; 2.5; Source apportionment; Chemical mass balance; Mass closure; Chemical composition
Determination of aerosol yields from 3-methylcatechol and 4-methylcatechol ozonolysis in a simulation chamber by Cécile Coeur-Tourneur; Valentine Foulon; Michel Laréal (pp. 852-857).
Secondary Organic Aerosol (SOA) formation during the ozonolysis of 3-methylcatechol (3-methyl-1,2-dihydroxybenzene) and 4-methylcatechol (3-methyl-1,2-dihydroxybenzene) was investigated using a simulation chamber (8 m3) at atmospheric pressure, room temperature (294 ± 2 K) and low relative humidity (5–10%). The initial mixing ratios were as follows (in ppb): 3-methylcatechol (194–1059), 4-methylcatechol (204–1188) and ozone (93–531). The ozone and methylcatechol concentrations were followed by UV photometry and GC–FID (Gas chromatography–Flame ionization detector), respectively and the aerosol production was monitored using a SMPS (Scanning Mobility Particle Sizer). The SOA yields (Y) were determined as the ratio of the suspended aerosol mass corrected for wall losses (Mo) to the total reacted methylcatechol concentrations assuming a particle density of 1.4 g cm−3. The aerosol formation yield increases as the initial methylcatechol concentration increases, and leads to aerosol yields ranging from 32% to 67% and from 30% to 64% for 3-methylcatechol and 4-methylcatechol, respectively. Y is a strong function of Mo and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. These data are comparable to those published in a recent study on secondary organic aerosol formation from catechol ozonolysis. To our knowledge, this work represents the first investigation of SOA formation from the ozone reaction with methylcatechols.
Keywords: Simulation chamber; Methylcatechols; Secondary organic aerosol yields
Two extreme types of mixing of dust with urban aerosols observed in Kosa particles: ‘After’ mixing and ‘on-the-way’ mixing by Issei Suzuki; Yasuhito Igarashi; Yukiko Dokiya; Tasuku Akagi (pp. 858-866).
Besides well-known episodic Kosa during spring, high concentrations of Ca2+ in aerosols were observed early in summer as well as in the semi-continuous data of the aerosols at the summit of Mt. Fuji. We further analysed the data to study the chemical characteristics of the high calcium event during early summer. The back trajectory analyses of the event indicated that Ca was transported from arid and semi-arid regions (e.g. the Taklamakan desert) through the westerly-dominated troposphere higher than the height of the summit of Fuji. The amount of SO42− was always equivalent to that of NH4+ unlike the case of the normal Kosa period where SO42− is in excess with respect to NH4+. This shows the ‘after’ mixing of unreacted CaCO3 of Kosa origin with (NH4)2SO4, which was only realized by the downward injection of Kosa particles from higher altitudes to the air masses of different origin. In the case of normal Kosa, the air bearing Kosa particles passed through the polluted area to absorb unneutralized acids (‘on-the-way’ mixing), whereas in the case of the Kosa-like phenomena in summer, the acids from the polluted area have been neutralized by NH4+ and become inactive before mixing with CaCO3 (“after” mixing). We have simplified the chemistry of aerosols using their three major components, Ca2+, SO42− and NH4+, and introduced a new triangle diagram with the three assumed end-members of CaCO3, CaSO4 and (NH4)2SO4 to quantify the contribution of the ‘after’ mixing to the aerosols (AMI; ‘after’ mixing index). Based on the back trajectories of some high AMI cases, CaCO3 in Kosa particles was transported through the middle troposphere (5000–7000 m) and descended to meet another air mass where SO42− had been already neutralized by NH3.
Keywords: Asian dust; Ca; 2+; Background Kosa; SO; 4; 2−; NH; 4; +
Experimental evidence for a significant contribution of cellulose to indoor aerosol mass concentration by Mário Cerqueira; Daniel Marques; Alexandre Caseiro; Casimiro Pio (pp. 867-871).
An apartment bedroom located in a residential area of Aveiro (Portugal) was selected with the aim of characterizing the cellulose content of indoor aerosol particles. Two sets of samples were taken: (1) PM10 collected simultaneously in indoor and outdoor air; (2) PM10 and PM2.5 collected simultaneously in indoor air. The aerosol particles were concentrated on quartz fibre filters with low-volume samplers equipped with size selective inlets. The filters were weighed and then extracted for cellulose analysis by an enzymatic method. The average indoor cellulose concentration was 1.01 ± 0.24 μg m−3, whereas the average outdoor cellulose concentration was 0.078 ± 0.047 μg m−3, accounting for 4.0% and 0.4%, respectively, of the PM10 mass. The corresponding average ratio between indoor and outdoor cellulose concentrations was 11.1 ± 4.9, indicating that cellulose particles were generated indoors, most likely due to the handling of cotton-made textiles as a result of routine daily activities in the bedroom. Indoor cellulose concentrations averaged 1.22 ± 0.53 μg m−3 in the aerosol coarse fraction (determined from the difference between PM10 and PM2.5 concentrations) and averaged 0.38 ± 0.13 μg m−3 in the aerosol fine fraction. The average ratio between the coarse and fine fractions of cellulose concentrations in the indoor air was 3.6 ± 2.1. This ratio is in line with the primary origin of this biopolymer. Results from this study provide the first experimental evidence in support of a significant contribution of cellulose to the mass of suspended particles in indoor air.
Keywords: Cellulose; Indoor air; Particulate matter; Aerosol size distribution
Collection efficiency of a midget impinger for nanoparticles in the range of 3–100 nm by Zhicheng Wei; Robert C. Rosario; Lupita D. Montoya (pp. 872-876).
Impingers have been employed for collection of biological particles for a long time and the collection efficiency for submicron particles has been well studied for a few impinger models, like the SKC Biosampler and the AGI 30. These efficiency studies have been limited to particles larger than about 15 nm. The aim of this research is to determine the collection efficiency of ultrafine particles (from 3 to 100 nm) of a 25 ml midget impinger. The effect of different collection parameters (particle type, collection fluid volume and type and flow rate) was studied and results are presented here. All results showed minimum collection efficiencies from 3 to 10% at approximately 40–57 nm. Increasing the volume of the collection liquid and flow rate improved the collection efficiency of the impinger.
Keywords: Midget impinger; Nanoparticles; Ultrafines; Aerosol sampling; Collection efficiency