Particle Number Distribution Research Articles

Particle Fabrication Using Inkjet Printing onto Hydrophobic Surfaces for Optimization and Calibration of Trace Contraband Detection Sensors.

A method has been developed to fabricate patterned arrays of micrometer-sized monodisperse solid particles of ammonium nitrate on hydrophobic silicon surfaces using inkjet printing. The method relies on dispensing one or more microdrops of a concentrated aqueous ammonium nitrate solution from a drop-on-demand (DOD) inkjet printer at specific locations on a silicon substrate rendered hydrophobic by a perfluorodecytrichlorosilane monolayer coating. The deposited liquid droplets form into the shape of a spherical shaped cap; during the evaporation process, a deposited liquid droplet maintains this geometry until it forms a solid micrometer sized particle. Arrays of solid particles are obtained by sequential translation of the printer stage. The use of DOD inkjet printing for fabrication of discrete particle arrays allows for precise control of particle characteristics (mass, diameter and height), as well as the particle number and spatial distribution on the substrate. The final mass of an individual particle is precisely determined by using gravimetric measurement of the average mass of solution ejected per microdrop. The primary application of this method is fabrication of test materials for the evaluation of spatially-resolved optical and mass spectrometry based sensors used for detecting particle residues of contraband materials, such as explosives or narcotics.

Modeling particle nucleation and growth over northern California during the 2010 CARES campaign

Abstract. Accurate representation of the aerosol lifecycle requires adequate modeling of the particle number concentration and size distribution in addition to their mass, which is often the focus of aerosol modeling studies. This paper compares particle number concentrations and size distributions as predicted by three empirical nucleation parameterizations in the Weather Research and Forecast coupled with chemistry (WRF-Chem) regional model using 20 discrete size bins ranging from 1 nm to 10 μm. Two of the parameterizations are based on H2SO4, while one is based on both H2SO4 and organic vapors. Budget diagnostic terms for transport, dry deposition, emissions, condensational growth, nucleation, and coagulation of aerosol particles have been added to the model and are used to analyze the differences in how the new particle formation parameterizations influence the evolving aerosol size distribution. The simulations are evaluated using measurements collected at surface sites and from a research aircraft during the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted in the vicinity of Sacramento, California. While all three parameterizations captured the temporal variation of the size distribution during observed nucleation events as well as the spatial variability in aerosol number, all overestimated by up to a factor of 2.5 the total particle number concentration for particle diameters greater than 10 nm. Using the budget diagnostic terms, we demonstrate that the combined H2SO4 and low-volatility organic vapor parameterization leads to a different diurnal variability of new particle formation and growth to larger sizes compared to the parameterizations based on only H2SO4. At the CARES urban ground site, peak nucleation rates are predicted to occur around 12:00 Pacific (local) standard time (PST) for the H2SO4 parameterizations, whereas the highest rates were predicted at 08:00 and 16:00 PST when low-volatility organic gases are included in the parameterization. This can be explained by higher anthropogenic emissions of organic vapors at these times as well as lower boundary-layer heights that reduce vertical mixing. The higher nucleation rates in the H2SO4-organic parameterization at these times were largely offset by losses due to coagulation. Despite the different budget terms for ultrafine particles, the 10–40 nm diameter particle number concentrations from all three parameterizations increased from 10:00 to 14:00 PST and then decreased later in the afternoon, consistent with changes in the observed size and number distribution. We found that newly formed particles could explain up to 20–30 % of predicted cloud condensation nuclei at 0.5 % supersaturation, depending on location and the specific nucleation parameterization. A sensitivity simulation using 12 discrete size bins ranging from 1 nm to 10 μm diameter gave a reasonable estimate of particle number and size distribution compared to the 20 size bin simulation, while reducing the associated computational cost by ~ 36 %.

Internal Combustion Engines as the Main Source of Ultrafine Particles in Residential Neighborhoods: Field Measurements in the Czech Republic

Ultrafine particles (UFP, diameter < 100 nm) exposure has already been associated with adverse effects on human health. Spatial distribution of UFP is non-uniform; they concentrate in the vicinity of the source, e.g. traffic, because of their short lifespan. This work investigates spatial distribution of UFP in three areas in the Czech Republic with different traffic load: High traffic (Prague neighborhood—Sporilov), commuter road vicinity (Libeznice), and a small city with only local traffic (Celakovice). Size-resolved measurements of particles in the 5–500 nm range were taken with a particle classifier mounted, along with batteries, GPS and other accessories, on a handcart and pushed around the areas, making one-minute or longer stops at places of interest. Concentrations along main roads were elevated in comparison with places farther from the road; this pattern was observed in all sites, while particle number distributions both close and away from main roads had similar patterns. The absence of larger particles, the relative absence of higher concentrations of particles away from the main roads, and similar number distributions suggest that high particle number concentrations cannot be readily attributed to sources other than internal combustion engines in vehicles and mobile machinery (i.e., mowers and construction machines).

Characterization of the Ultrafine and Nano Particle Emissions on Modified Indian Driving Cycle for Passenger Cars Operating on CNG Phase Wise Analysis

The ultrafine and nano particles compared to larger particles are gaining high importance because of their vulnerable effects to environment and human health causing respiratory problems, cardiovascular disease, and various types of cancers leading to premature death [1]. WHO report points out that approximately, two thirds of the global burden of disease due to urban outdoor air pollution is mostly from the developing countries in Asia (Cohen et al. 2004)[2]. By number, nearly all of the particles emitted by a diesel engine are nanoparticles which are also true for gasoline engines [3]. This is addressed by new UN Regulations by introducing the emission norms for diesel and GDI vehicles for particle number and PM2.5 as 6 x 10 11 and 4.5 mg/km respectively [4]. However, other S.I. engines like CNG, even though they look clean as there is no visible smoke but emitting large number of particles is necessary to investigate. This research paper focuses on characterization of ultrafine and nano particle emissions from CNG vehicle on Indian driving cycle and it covers experimental Investigation to identify the significance of different operating phases viz. idling, acceleration, deceleration and cruising for their contributions to particle number and size distribution pattern over urban as well as on extra urban part of the cycle. CNG passenger car shows large peak of PN emissions during cold starting phase at the beginning of the test cycle which is almost twice that of diesel vehicle. However, this concentration peak will decrease near to 25% on light operating loads during urban part of the cycle, but during acceleration and cruising operation on extra urban cycle under heavy load the PN emissions from CNG car are higher in magnitude. The particles emitted from CNG buses are too small to contribute to PM10 as they are of ultrafine and nano size range.

Comparative Study of Characterization of the Ultrafine and Nanoparticle Emissions on Modified Indian Driving Cycle for Passenger Cars Operating on Diesel and CNG – Phase Wise Analysis

Today, in the automotive emissions ultrafine and nanoparticles emissions are of very high importance because of their vulnerable effects to environment and human health causing respiratory problems like bronchitis, asthma, cardiovascular disease, and various types of cancers spreading in all age groups in the society leading to premature death [1]. Therefore, characterization of ultrafine and nanoparticles in terms of their size distribution and number concentration for the automobiles operating on various fuels and traffic conditions is of great importance in understanding the phenomenon and the adverse effects. Various research studies carried out at international level show the adverse health effects due to ultrafine particles from C.I. and S.I. engines and hence, there is definite need to examine for the particulate mass, size and number concentration considering social needs [2].Even after very stringent emission norms which were tightened over the years and today down to more than 97% from it’s baseline norms couldn’t show proportionate improvement in the ambient air quality. Climate effects inevitably lead to health effects leading to premature death due to ultrafine particles from the automotive exhaust [1]. Recent WHO report confirmed the vulnerable effect of diesel particles in terms of carcinogenicity and severe health effects of diesel fuel used in automotive sector [3]. European regulations has taken the steps to address this concern by introducing new norms for particle number and PM2.5 as 6 x 1011 and 4.5 mg/km respectively [4]. Investigations carried out on GDI vehicles show substantial ultrafine and nanosize particle emissions and by number, nearly all of the particles emitted by a diesel engine are nanoparticles which are also true for gasoline engines [5]. Like gasoline engines other S.I. engines, even though they look very clean as there is no visible smoke and large particles emitted in their exhaust, it is necessary to investigate them. Very limited research work has been carried out particularly, on CNG engines/ vehicles for their PM and PN levels at national and international level. Characterization of ultrafine and nanoparticles in terms of their size distribution and number concentration for the automobiles operating on various fuels and traffic conditions is of great importance in understanding the phenomenon and their significance.In this context and understanding the social need this research work was carried out to investigate experimentally the significance of CNG and diesel passenger car for it’s contribution to particle number (PN) and PM2.5. This work includes comparative investigation of CNG and diesel passenger cars to characterize the ultrafine and nanoparticle emissions on modified Indian driving cycle. CNG passenger car show large peak of PN emissions during cold starting phase at the beginning of the test cycle which is almost twice that of diesel vehicle but it settles down to lower level as the vehicle gets warmed up. During acceleration and cruising operation on extra urban cycle under heavy load the PN emissions from CNG car are higher in magnitude. For diesel car, urban part of cycle contributes approximately 53% compared to 25% for CNG vehicle and rest 47% and 75% is contributed by extra urban part towards PN emissions.This research paper covers experimental Investigation carried out to compare the behavior of diesel and CNG passenger cars to characterize the particle emissions and to identify the significance of different operating phases viz. idling, acceleration, deceleration and cruising for their contributions to Particle number and size distribution pattern on urban and on extra urban part of the driving cycle.

Atmospheric particle number concentration and size distribution in a traffic–impacted area

This study measured ambient particle number concentrations (PNC) and the particle number distributions (PND) in the urban area of Porto Alegre, Rio Grande do Sul, Brazil. The samples were analyzed using a NanoScan model 3910 from TSI (diameters between 10 and 420 nm) and were taken from sites with high density of vehicular traffic, including two roadsides, two traffic intersections, one street canyon and one urban background. Association of meteorological variables (temperature, relative humidity, solar radiation, wind direction, and wind speed) on nanoparticle concentrations was examined. The results indicated PNC averages between 4.85×104 cm–3 and 1.80×105 cm–3 for locations affected by vehicular traffic, wherein highest concentrations were observed at sites corresponding to traffic intersections. In addition, all sites studied showed a trimodal average PND, with the modes centered at ~14 nm, ~30 nm, and ~105 nm. PND was dominated by nucleation (44.9%) and Aitken (42.0%) modes being representative at the studied sites of the pollution originating from urban traffic, except at the urban background. Meteorological parameters and synoptic meteorological conditions contributed to the variation in the results between the sampled days in the same location.

Impact of intermediate ethanol blends on particulate matter emission from a spark ignition direct injection (SIDI) engine

The purpose of this study was to investigate particle emission characteristics from a spark ignition direct injection (SIDI) engine fueled with ethanol–gasoline blends. Particulate matter (PM) from internal combustion engine is a complex mixture of substances deemed harmful for the human body. Consequently, they are regulated by stringent legislation. According to the Euro-6 regulation, the standard for particle number (PN) emissions of SIDI vehicles is 6.0×1011N/km. Recent studies have reported that SIDI engines, renowned for their feasibility in reducing CO2 emissions, could produce excessive amounts of PM due to its structural characteristics. For this reason, there have been many studies on reducing PM emissions from SIDI engines to satisfy strict emission standards. Because ethanol contains an oxygen atom in each molecule, it has a significant influence on combustion performance and characteristics of vehicular discharge, including PM. This study focused on the effect of intermediate ethanol blends from E0 (pure gasoline fuel) to E20 (gasoline fuel with 20% volume of ethanol) on engine performance, size-resolved particle emissions, and engine startability. Particle emission characteristics including particle number and size distribution at part-load test and start performance were investigated with operation points, fuel pressure and injection timing.

Lung cancer risk of airborne particles for Italian population

Airborne particles, including both ultrafine and supermicrometric particles, contain various carcinogens. Exposure and risk-assessment studies regularly use particle mass concentration as dosimetry parameter, therefore neglecting the potential impact of ultrafine particles due to their negligible mass compared to supermicrometric particles. The main purpose of this study was the characterization of lung cancer risk due to exposure to polycyclic aromatic hydrocarbons and some heavy metals associated with particle inhalation by Italian non-smoking people. A risk-assessment scheme, modified from an existing risk model, was applied to estimate the cancer risk contribution from both ultrafine and supermicrometric particles. Exposure assessment was carried out on the basis of particle number distributions measured in 25 smoke-free microenvironments in Italy. The predicted lung cancer risk was then compared to the cancer incidence rate in Italy to assess the number of lung cancer cases attributed to airborne particle inhalation, which represents one of the main causes of lung cancer, apart from smoking. Ultrafine particles are associated with a much higher risk than supermicrometric particles, and the modified risk-assessment scheme provided a more accurate estimate than the conventional scheme. Great attention has to be paid to indoor microenvironments and, in particular, to cooking and eating times, which represent the major contributors to lung cancer incidence in the Italian population. The modified risk assessment scheme can serve as a tool for assessing environmental quality, as well as setting up exposure standards for particulate matter.

Combustion and emission behavior of linear C8-oxygenates

Alternative fuels have become of great importance in order to secure a sustainable mobility within the next decades. Within the Cluster of Excellence, “Tailor-Made Fuels from Biomass” at RWTH Aachen University, several possible fuel candidates could be derived from (hemi-)cellulose by selective catalytic conversion. The proposed fuel candidates include furans, ethers, alcohols, and ketones. Experiments with the isomers di-n-butyl ether and 1-octanol have proven their suitability for diesel-type combustion. With di-n-butyl ether being prone to auto-ignition, overall hydrocarbon, carbon monoxide, and soot emissions are reduced compared to diesel. In contrast, the prolonged ignition delay with 1-octanol causes an increase in HC and CO emissions particularly at low engine loads. However, soot emissions are even below those of di-n-butyl ether. With regard to particulate matter, an Exhaust Emissions Particulate Sizer Spectrometer (EEPS™) has been utilized to investigate the particle size or number distribution. Compared to diesel, a reduction of the total particle number up to 80% was seen with the oxygenates next to a shift toward reduced particle mobility diameter. The HC emissions of both di-n-butyl ether and 1-octanol have been studied in detail by means of gas chromatography–mass spectrometry. As a main result, not only the general emission reduction potential of the biofuel alternatives 1-octanol and di-n-butyl ether can be shown with this work. Gas chromatography–mass spectrometry revealed that the composition of hydrocarbons emitted with the C8-oxygenates is almost equal to those with diesel, except for the unburned fuel that is present in the exhaust gas. Quantification showed that the carcinogenic component 1,3-butadiene increased with the alternative fuel candidates, whereas particularly benzene and ethyl benzene reduced. Since both di-n-butyl ether and 1-octanol are found in high proportions in the exhaust gas, the effects on the aftertreatment system have to be investigated in a subsequent campaign.

Effects of Particle Filters and Selective Catalytic Reduction on Heavy-Duty Diesel Drayage Truck Emissions at the Port of Oakland.

Effects of fleet modernization and use of diesel particle filters (DPF) and selective catalytic reduction (SCR) on heavy-duty diesel truck emissions were studied at the Port of Oakland in California. Nitrogen oxides (NOx), black carbon (BC), particle number (PN), and size distributions were measured in the exhaust plumes of ∼1400 drayage trucks. Average NOx, BC, and PN emission factors for newer engines (2010-2013 model years) equipped with both DPF and SCR were 69 ± 15%, 92 ± 32%, and 66 ± 35% lower, respectively, than 2004-2006 engines without these technologies. Intentional oxidation of NO to NO2 for DPF regeneration increased tailpipe NO2 emissions, especially from older (1994-2006) engines with retrofit DPFs. Increased deployment of advanced controls has further skewed emission factor distributions; a small number of trucks emit a disproportionately large fraction of total BC and NOx. The fraction of DPF-equipped drayage trucks increased from 2 to 99% and the median engine age decreased from 11 to 6 years between 2009 and 2013. Over this period, fleet-average BC and NOx emission factors decreased by 76 ± 22% and 53 ± 8%, respectively. Emission changes occurred rapidly compared to what would have been observed due to natural (i.e., unforced) turnover of the Port truck fleet. These results provide a preview of more widespread emission changes expected statewide and nationally in the coming years.

Submicron Particles during Macro- and Micro-Weldings Procedures in Industrial Indoor Environments and Health Implications for Welding Operators

One of the emerging risks in the engineering and electronic industries is the exposure of workers to ultrafine particles during (micro-)welding operations, i.e., processes used for joining two metal parts heated locally, which constitute the base metal, with or without addition of another metal which is the filler metal, melted between the edges to be joined. The process is accompanied by formation of metallic fumes arising from the molten metal as well as by the emission of metal fumes of variable composition depending on the alloys welded and fused. The aim of this paper is to investigate the number, concentration and size distribution of submicron particles produced by (micro-)welding processes. Particle number size distribution is continuously measured during (micro-)welding operations by means of two instruments, i.e., Fast Mobility Particle Sizer and Nanoparticle Surface Area Monitor. The temporal variation of the particle number size distribution across the peaks evidences the strong and fast-evolving contribution of nucleation mode particles: peak values are maintained for less than 10 s. The implication of such contribution on human health is linked to the high deposition efficiency of submicronic particles in the alveolar interstitial region of the human respiratory system, where gas exchange occurs.

A Flow-Cytometry-Based Approach to Facilitate Quantification, Size Estimation and Characterization of Sub-visible Particles in Protein Solutions.

Sub-visible particles were shown to facilitate unwanted immunogenicity of protein therapeutics. To understand the root cause of this phenomenon, a comprehensive analysis of these particles is required. We aimed at establishing a flow-cytometry-based technology to analyze the amount, size distribution and nature of sub-visible particles in protein solutions. We adjusted the settings of a BD FACS Canto II by tuning the forward scatter and the side scatter detectors and by using size calibration beads to facilitate the analysis of particles with sizes below 1 μM. We applied a combination of Bis-ANS (4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid dipotassium salt) and DCVJ (9-(2,2-dicyanovinyl)julolidine) to identify specific characteristics of sub-visible particles. The FACS technology allows the analysis of particles between 0.75 and 10 μm in size, requiring relatively small sample volumes. Protein containing particles can be distinguished from non-protein particles and cross-β-sheet structures contained in protein particles can be identified. The FACS technology provides robust and reproducible results with respect to number, size distribution and specific characteristics of sub-visible particles between 0.75 and 10 μm in size. Our data for number and size distribution of particles is in good agreement with results obtained with the state-of-the-art technology micro-flow imaging.

Sulfuric acid nucleation: An experimental study of the effect of seven bases

AbstractNucleation of particles with sulfuric acid, water, and nitrogeneous bases was studied in a flow reactor. Sulfuric acid and water levels were set by flows over sulfuric acid and water reservoirs, respectively, and the base concentrations were determined from measured permeation rates and flow dilution ratios. Particle number distributions were measured with a nano‐differential‐mobility‐analyzer system. Results indicate that the nucleation capability of NH3, methylamine, dimethylamine, and trimethylamine with sulfuric acid increases from NH3 as the weakest, methylamine next, and dimethylamine and trimethylamine the strongest. Three other bases were studied, and experiments with triethylamine showed that it is less effective than methylamine, and experiments with urea and acetamide showed that their capabilities are much lower than the amines with acetamide having basically no effect. When both NH3 and an amine were present, nucleation was more strongly enhanced than with just the amine present. Comparisons of nucleation rates to predictions and previous experimental work are discussed, and the sulfuric acid‐base nucleation rates measured here are extrapolated to atmospheric conditions. The measurements suggest that atmospheric nucleation rates are significantly affected by synergistic interactions between ammonia and amines.

Source apportionment of airborne nanoparticles in a Middle Eastern city using positive matrix factorization.

Airborne nanoparticles have been studied worldwide, but little is known about their sources in the Middle East region, where hot, arid and dusty climatic conditions generally prevail. For the first time in Kuwait, we carried out size-resolved measurements of particle number distributions (PNDs) and concentrations (PNCs) in the 5-1000 nm size range. Measurements were made continuously for 31 days during the summer months of May and June 2013 using a fast-response differential mobility spectrometer (Cambustion DMS500) at a sampling rate of 10 Hz. Sources and their contributions were identified using the positive matrix factorization (PMF) approach that was applied to the PND data. Simultaneous measurements of gaseous pollutants (i.e., O3, NO, NOx, SO2 and CO), PM10, wind speed and direction were also carried out to aid the interpretation of the PMF results through the conditional probability function plots and Pearson product-moment correlations. Six major sources of PNCs were identified, contributing ∼46% (fresh traffic emissions), 27% (aged traffic emissions), 9% (industrial emissions), 9% (regional background), 6% (miscellaneous sources) and 3% (Arabian dust transport) of the total PNCs. The sources of nanoparticles and their PND profiles identified could serve as reference data to design more detailed field studies in the future and treat these sources in dispersion modelling and health impact assessment studies.

Synthesis and Characterization of Nanocrystalline Zinc Oxide Thin Films for Ethanol Vapor Sensor

ZnO nanoparticles as gas sensors have a property of changing the electrical conductivity of the sensing element on exposure to gas atmospheres. The number, density and size distribution of particles plays a key role in gas sensing applications. The gas sensing mechanism mainly depends upon the morphology, ion occupancy and the operating temperature, which helps in adsorbing the OH- groups on the surface of oxide materials. The ethanol vapor sensing measurements have been carried out on the ZnO pellet with silver pasted electrodes on both the ends. The change in electrical resistance was used as the measure of ethanol vapor response at different temperatures in the range of 25°C to 45°C at an interval of 5°C under an ethanol concentration of 25.02, 50.05, 75.08, 100.11 and 150.17 ppm. These results showed that the indium zinc oxide film based ethanol sensor has high response quick recovery time and selectivity to the ethanol vapor.

Influence of phosphorus on the development of nickel alloy/h-BN-based self-lubricating composites processed by powder metallurgy

The purpose of this work was to evaluate the influence of phosphorus quantity of the matrix of a nickel alloy on microstructure and hardness of nickel composite with hexagonal boron nitride – h-BN. The work was carried out using two nickel alloys with varying quantities of phosphorus (0.3 and 0.75 wt.%). The quantity of particles of solid lubricant added to the alloy was 10 vol.% of h-BN. The samples were compacted at 600 MPa and sintered at 1150 °C for 60 min in plasma. The results showed that the composite with 0.3 wt.% of phosphorus had hardness of 236 HV 0.025 (±34,25) and the composite with 0.75 wt.% of phosphorus had hardness of 326 HV 0.025 (±38,90), and formation of pellets of h-BN with a size between 50 and 100 μm and low porosity due to the formation of liquid phase of phosphide during sintering which carries the lubricant fine particles of approximately 10 μm dispersed in the microstructure during pore coalescence. As a result, the quantity of phosphorus present may influence the microstructural properties (pore number and size and distribution of particles of solid lubricant) and hardness which are so important for the development of self-lubricating composites, particularly, the nickel alloy/h-BN composites.

Statistical Power Law due to Reservoir Fluctuations and the Universal Thermostat Independence Principle

Certain fluctuations in particle number, \(n\), at fixed total energy, \(E\), lead exactly to a cut-power law distribution in the one-particle energy, \(\omega\), via the induced fluctuations in the phase-space volume ratio, \(\Omega_n(E-\omega)/\Omega_n(E)=(1-\omega/E)^n\). The only parameters are \(1/T=\langle \beta \rangle=\langle n \rangle/E\) and \(q=1-1/\langle n \rangle + \Delta n^2/\langle n \rangle^2\). For the binomial distribution of \(n\) one obtains \(q=1-1/k\), for the negative binomial \(q=1+1/(k+1)\). These results also represent an approximation for general particle number distributions in the reservoir up to second order in the canonical expansion \(\omega \ll E\). For general systems the average phase-space volume ratio \(\langle e^{S(E-\omega)}/e^{S(E)}\rangle\) to second order delivers \(q=1-1/C+\Delta \beta^2/\langle \beta \rangle^2\) with \(\beta=S^{\prime}(E)\) and \(C=dE/dT\) heat capacity. However, \(q \ne 1\) leads to non-additivity of the Boltzmann–Gibbs entropy, \(S\). We demonstrate that a deformed entropy, \(K(S)\), can be constructed and used for demanding additivity, i.e., \(q_K=1\). This requirement leads to a second order differential equation for \(K(S)\). Finally, the generalized \(q\)-entropy formula, \(K(S)=\sum p_i K(-\ln p_i)\), contains the Tsallis, Rényi and Boltzmann–Gibbs–Shannon expressions as particular cases. For diverging variance, \(\Delta\beta^2\) we obtain a novel entropy formula.

Emission of carbon monoxide, total hydrocarbons and particulate matter during wood combustion in a stove operating under distinct conditions

Wood combustion experiments were carried out to determine the effect of ignition technique, biomass load and cleavage, as well as secondary air supply, on carbon monoxide (CO), total hydrocarbon (THC), particulate matter (PM10) and particle number emissions from a woodstove. Wood from two typical tree species in the Iberian Peninsula was selected: pine (Pinus pinaster) and beech (Fagus sylvatica). The highest CO and total hydrocarbon emission factors (EFs) were observed, respectively, for pine and beech, for high and low fuel loads. The highest PM10 EF was recorded for the operation with low loads for both woods. Secondary air supply produced the lowest PM10 emission factors. The top ignition can decrease the PM10 EF to less than half when compared with the common technique of lighting from the bottom. The lowest particle number emission factors were observed when operating with high loads of split beech logs and when using secondary air supply during the combustion of pine. Regarding particle number distributions, the highest geometric mean diameter (Dg), for both woods, were observed when operating with high loads (with split and non-split wood).

Number and size distribution of airborne nanoparticles during summertime in Kuwait: first observations from the Middle East.

We made fast response measurements of size-resolved particle number concentrations (PNCs) and distributions (PNDs) in the 5-1000 nm range close to a busy roadside, continuously for 31 days, in Kuwait. The aims were to understand their dispersion characteristics during summertime and dust events, and association with trace pollutants (NOx, O3, CO, SO2, and PM10) and meteorological parameters. PNCs were found up to ∼19-times higher (5.98 × 10(5) cm(-3)) than those typically found in European roadside environments. Size distributions exhibited over 90% of PNCs in ultrafine size range (<100 nm) and a negligible fraction over 300 nm. Peak PNDs appeared at ∼12 nm, showing an unusually large peak in nucleation mode. Diurnal variations of PNCs coincided with the cyclic variations in CO, NOx, and traffic volume during morning and evening rush hours. Despite high traffic volume, PNC peaks were missing during noon hours due to high ambient temperature (∼48 °C) that showed an inverse relationship with the PNCs. Principal Component Analysis revealed three probable sources in the area--local road traffic, fugitive dust, and refineries. Dust events, categorized by PM10 with over 1000 μg m(-3), decreased PNCs by ∼25% and increased their geometric mean diameters (GMDs) by ∼66% compared with nondust periods.

Size-resolved effective density of urban aerosols in Shanghai

Size-resolved effective density of 50–400 nm urban particles was determined by a TDMA–APM system in Shanghai during wintertime. The average effective density ranged from 1.36 to 1.55 g cm−3, increasing with the particle diameter. The size dependent increase of density was consistent with previous hygroscopic measurements. We attributed the increase in density to the condensation of hygroscopic secondary aerosols and large massive organics. The diurnal variation of effective density was pronounced for smaller particles. A similar diurnal pattern was observed between particle density and the contribution of secondary NH4NO3 and (NH4)2SO4 to PM1.0, suggesting that density change in response to particle compositions. The effective density of Aitken mode particles had a considerable increase during the NPF event, in agreement with the contribution of sulfate. Particle mass distribution was derived from particle number distribution in combination with effective density. PM0.6 was highly correlated with PM1.0, revealing that secondary aerosols tend to condense on smaller particles.