Mass-based Particle Size Distributions Research Articles

Characteristics of fine particle formation during combustion of high-alkali coal in a new full-scale circulating fluidized bed boiler

High-alkali coal generated an increased number of fine particles during the combustion process. Understanding the transformative characteristics of particulate matter (PM) in a full-scale boiler that burns 100 % Zhundong (ZD) coal is key for controlling pollutant emissions. This paper investigated PM formation in a novel full-scale Circulating Fluidized Bed (CFB) boiler. PM samples were collected from various points along the steam-cooled flue at 50 %, 67 %, and 100 % boiler load. Utilizing Low-pressure impactors and scanning electron microscopy coupled with energy disperse spectroscopy (SEM-EDS) were applied to analyze the mass-based particle size distribution(MPSD), elemental compositions, and morphology of PM. The results show that sub-micron particles produced under low boiler load consist primarily of AAEMs sulfates, whereas under high load, they consist primarily of alkali metal chlorides. Super-micron particles are predominantly sulfates and silicates. The concentrations of Na, K, and Cl in PM0.4 decreased as the flue gas cooled down in the steam-flue of the CFB. At 100 % boiler load, Na, K, Cl and S account for more than 90 % of the total elements in the sub-micron particles. However, these four elements demonstrated a 25 % decrease at a boiler load of 67 % compared to 100 % load. Interestingly, the compositions of super-micron particles seemed to be minimally affected by the boiler load.

Inhibiting the formation of PM0.4 by optimizing the distribution of excess air coefficient in preheating combustion of lignite

Preheating combustion can effectively reduce NOx concentration, but the formation characteristics of PM0.4 in preheating combustion is unclear. In this study, the emission of PM0.4 in preheating combustion was reduced by optimizing the distribution of excess air coefficient. The mass-based particle size distribution (MPSD) of PM10, mass yield of PM0.4, elemental compositions and morphologies of PM, and the number-based particle size distribution (NPSD) were analyzed to discuss the effect of αp on PM formation. The results showed that in preheating combustion, with an increase of αp, the mass yield of PM0.4 first decreased and then increased. The mass yield of PM0.4 is minimum when αp is 0.6. Preheating combustion can simultaneously reduce PM0.4 mass yield and NOx concentration. The relationship between NOx concentration and αp is similar to the relationship between the mass yield of PM0.4 and αp. The MPSD of PM0.4 is multimodal and unimodal when αp is less than 1 and larger than 1, respectively. Particle volume concentration of PM0.4 indicates that the multimodal and unimodal of PM0.4 is a result of evolution of particles with different characteristics of gas-to-particle transformation. The effect of αp on the transformation of inorganic element from coal particles to PM0.4 is S > Fe ≈ Ca ≈ Mg > Na > Si. αp affects the mass yield of PM0.4 by affecting the combustion intensity of coal/char particles in preheating furnace and combustion furnace. When αp is 0.6, the combustion intensity of coal particles in preheating furnace and combustion furnace minimize the vaporization of inorganic elements.

The effect of preheating temperature and combustion temperature on the formation characteristics of PM0.4 from preheating combustion of high-alkali lignite

Preheating combustion is getting popular because it can reduce NOx formation, but its effect on particulate matter (PM) formation is still unclear. This study focuses on the effect of preheating temperature (Tp) and combustion temperature (Tc) on the formation characteristics of fine mode particles (PM0.4) in preheating combustion. The mass-based particle size distribution, elemental compositions and morphologies of PM and number-based particle size distribution were analyzed to reveal the mechanisms of reducing PM0.4 formation during preheating combustion. The results showed that compared with conventional combustion, preheating combustion with optimized Tp and Tc can effectively decrease the mass yield of PM0.4 and NOx concentration by 77.9% − 82.2% and 70.9% − 77.8%, respectively. In preheating combustion, the mass yield of PM0.4 basically didn’t change with Tp. When Tc was lower than Tp, the mass yield of PM0.4 was basically unchanged with Tc. The precursors of PM0.4 mainly vaporized in the preheating furnace. The vaporization of inorganic elements, gas-to-particle transformation, and coagulation occurring in the combustion furnace had a negligible effect on the mass yield of PM0.4. When Tc was higher than Tp, increasing Tc can significantly increase the vaporization of inorganic elements from unburned char/coal particles in the combustion furnace. As a result, the mass yield of PM0.4 increased. To effectively reduce the formation of PM0.4 and NOx, a higher Tp and a lower Tc is suggested. The volatility of inorganic elements in preheating combustion has an order as S > Na > Mg > Fe≈Ca > Si. Refractory elements including Fe, Mg, and Ca contributed the most to decrease of PM0.4 in preheating combustion compared with conventional combustion. Preheating combustion has a stronger reductive atmosphere and a lower particle temperature. The vaporization of inorganic elements from coal particles in preheating combustion is probably determined by particle temperature rather than reductive atmosphere.

Experimental study on PM10 formation characteristics of co-combustion with pulverized coal and sludge

At present, the output of municipal sludge in China is increasing year by year, and co-combustion of sludge and pulverized coal for power generation is a means to treat sludge in large quantities. However, the co-combustion of sludge and pulverized coal will generate a lot of particulate matter (PM). In this paper, the formation characteristics of particulate matter (PM10) produced by the co-combustion of sludge and pulverized coal were studied. The effect of the furnace temperature and the sludge mixing ratio on the mass-based particle size distribution and elemental composition of PM10 in sludge, coal combustion and co-combustion was discussed. The experiment results show that the mass-based particle size distribution of PM10 produced by pulverized coal and sludge combustion are both bimodal, while the elemental composition and particle size distribution of PM10 are different. Whether burning alone or co-firing, increasing the furnace temperature will increase the mass yield of PM10. Increasing the temperature promotes particle fragmentation more than the melting aggregation of particulate minerals, increasing PM0.4–10 yield. The mass yield of PM10 produced by coal combustion is higher than that of sludge. In the sludge addition ratio range ≤ 30%, increasing the sludge addition ratio will reduce the mass yield of PM10. The synergistic effect exists between sludge and pulverized coal co-combustion. Compared to the weighted calculation results, the content of main elements Si, Ca, Fe and S in PM0.4 decreases, while in PM0.4–10 the content of Si decreases and the content of Ca, Fe, Al, and P increases. At a low sludge addition ratio of 10%, the elemental composition of PM10 with the particle size distribution trend is consistent with that of pulverized coal, and sludge co-firing takes negligible effect on PM10 formation.

Effect of calcined kaolin on PM0.4 formation from combustion of Zhundong lignite

Kaolin is a widely used additive to alleviate slagging and to control particulate matter (PM) during coal combustion. Calcination is a widely used method of physical modification of kaolin. However, the effect of calcined kaolin on PM during Zhundong lignite combustion is not fully studied. In this research, Zhundong lignite blended with calcined kaolin was combusted in a drop-tube furnace. The performance of calcined kaolin on PM0.4 reduction was analyzed by means of mass-based particle size distribution of PM10, elemental composition of PM0.4, and number-based particle size distribution of PM0.4. Aerosol dynamic modeling was adopted to compare the contribution of chemical adsorption and coagulation to PM0.4 reduction by calcined kaolin. The effect of the addition ratio and the furnace temperature on PM0.4 reduction was systematically investigated. The results showed that the reduction efficiency of PM0.4 by calcined kaolin for Zhundong lignite lacking Si-Al compounds was higher than that for Zhundong lignite rich in Si-Al compounds. Aerosol dynamic modeling indicated that chemical adsorption contributed the most to PM0.4 reduction by calcined kaolin. During Zhundong lignite combustion, the order of the reactivities for the inorganic elements with calcined kaolin was Na > Mg > Fe > Ca. Due to the formation of more reaction sites by calcination, PM0.4 reduction efficiency was proportional to the furnace temperature in range from 900 °C to 1300 °C. By considering the PM0.4 reduction, the increase in SO2 and NOx emissions, and the variation of ash fusion temperatures, the optimized addition ratio of calcined kaolin for Zhundong lignite is approximately 6%.

Assessment of the effect of alkali chemistry on post-flame aerosol formation during oxy-combustion of biomass

The oxy-combustion of biomass enables negative CO2 emissions by combining subsequent CO2 capture technology. The potassium sulfation process significantly affects deposition and corrosion in heat transfer surfaces during biomass combustion. In the present work, a detailed aerosol dynamics model coupling with the detailed gas-reaction chemistry of K-S-Cl is proposed to investigate the effect of alkali chemistry on the evolution of post-flame aerosol during oxy-combustion of biomass. According to the modelling results, the mass-based particle size distributions are generally unimodal. Changing the environment from the air (N2 as a balance gas) to oxy (CO2 as balance gas) has a slight effect on the particle size distribution; yet, a slight left-shift particle size distribution was observed. The difference is mainly explained by the more substantial diffusion capacity of KCl(g) and K2SO4(g) in N2 than that in CO2, indicating a bit higher heterogeneous condensation of KCl(g) and K2SO4(g) in a CO2-based atmosphere. Further, the modelling results revealed that oxy-combustion significantly affects the evolution of aerosol and sulfation of KCl regardless of flue gas recirculation strategy. The wet oxy-combustion case has the largest particle size of PM1.0, that is due to the higher concentration of water and SO2, which increased KCl sulfation with value of ∼ 92%. The increased K2SO4 concentration in the flue gas causes earlier onset nucleation and prolonged the residence time for particle growth. Further ROP analysis results indicate that the reaction pathway for the sulfation of KCl via SO3 and K2SO4 condensation significantly influences the overall sulfation.

The role of H2O(g) in the formation of ultrafine PMs under O2/N2/H2O atmosphere

To explore the effect of water vapor (H2O(g)) on the formation characteristics of ultrafine particulate matter (PMs), Huangling coal char reacted in a high-temperature drop tube furnace (DTF) at 1800 K under various O2/N2/H2O atmospheres, with the content of H2O(g) varied at 0, 5%, 10%, 20% and 30% respectively. The results showed that both the number-based and mass-based particle size distributions (PSDs), the bimodal distribution of ultrafine PMs remained almost unchanged with increasing H2O(g) content, while the peak of ultrafine PMs shifted and the magnitude of the main peak fluctuated. H2O(g) elevated the mass fraction of ultrafine PMs with a larger particle size (D50 = 0.2134 μm) and the number fraction of ultrafine PMs with a smaller particle size (D50 = 0.0093 μm and D50 = 0.0167 μm) significantly. With the increase of H2O(g) content, both the number and mass of ultrafine PMs decreased first and then increased with the inflection point at 5% H2O(g) content, indicating that lower H2O(g) content inhibited the formation of ultrafine PMs while higher H2O(g) content promoted its formation. Meanwhile, with the increase of H2O(g) content, the average mass of single ultrafine particle, being higher in wet combustion atmospheres than that in dry combustion atmosphere, increased first and then decreased with the inflection point at the content of 5%. In addition, when the H2O(g) content was 5%, the average particle size of ultrafine particle was the largest, which increased by 9.07% compared with that under dry combustion atmosphere. Finally, the influence mechanism of H2O(g) on the formation of ultrafine PMs during char combustion was clarified.

Evolution of particulate matter in the post-combustion zone of Zhundong lignite

Understanding the conversion of particulate matter (PM) in the post-combustion zone is important for controlling the emissions and ash deposition from coal combustion. In this study, the evolution of PM in the post-combustion zone of coal was investigated experimentally and numerically. The air combustion of three Zhundong lignite was performed in a drop tube furnace. PM was sampled at different flue gas temperature from 473K to 1273K. Low pressure impactor, X-ray fluorescence, scanning electron microscope, and scanning mobility particle sizer were applied to analyze mass-based particle size distribution (MPSD), elemental compositions, morphology, and number-based particle size distribution (NPSD) of PM. The results show that when the flue gas temperature decreases from 1273K to 473K, the MPSD and compositions of PM0.4-10 remain stable, while PM0.4 moves towards larger particle size. The reduction of NaCl concentration in the flue gas between 1073K and 1273K may be due to the sulfation of NaCl. The critical condensation temperature of NaCl in flue gas is between 843K and 902K. When the flue gas was sampled beyond the critical condensation temperature, NaCl vapors is converted to PM0.4 through nucleation and condensation during the cooling of the sampling system. The particle size distribution of submicron particles in the post-combustion zone is well described by an aerosol dynamics model with moment method. In the post-combustion zone of Zhundong lignite, coagulation is the dominate mechanism controlling the evolution of PM0.4 from 1273K to 473K.

Intra-laboratory assessment of a method for the detection of TiO2 nanoparticles present in sunscreens based on multi-detector asymmetrical flow field-flow fractionation

In this study, an intra-laboratory assessment was carried out to establish the effectiveness of a method for the detection of TiO2 engineered nanoparticles (ENPs) present in sunscreen containing nano-scale TiO2 and a higher nanometer-range (approx. 200–500 nm) TiO2, as well as iron oxide particles. Three replicate measurements were performed on five separate days to generate the measurement uncertainties associated with the quantitative asymmetrical flow field-flow fractionation (AF4) measurement of the hydrodynamic radius rh,mode1 (MALS), rh,mode1 (ICP-MS), rh,mode2 (ICP-MS), and calculated mass-based particle size distribution (d10, d50, d90). The validation study demonstrates that the analysis of TiO2 ENPs present in sunscreen by AF4 separation-multi detection produces quantitative data (mass-based particle size distribution) after applying the sample preparation method developed within the NanoDefine project with uncertainties based on the precision (uIP) of 3.9–8.8%. This method can, therefore, be considered as the method with a good precision. Finally, the bias data shows that the trueness of the method (ut = 5.5–52%) can only be taken as a proxy due to the lack of a sunscreen standard containing certified TiO2 ENPs.

Experimental study on the formation of ultrafine particulate matters (PMs) during pulverized coal (PC) char combustion in O2/N2 and O2/CO2 atmospheres

Under the force of increasingly strict emission standard of particulate matters (PMs) and serious haze in China, further understanding of the formation of ultrafine PMs during coal combustion is crucial. In this work, the formation characteristics of ultrafine PMs during pulverized coal (PC) char combustion in O2/N2 and O2/CO2 atmospheres were investigated through a high-temperature drop tube furnace (DTF) with a two-stage dilution sampling system and a 14-stage electrical low pressure impactor (ELPI+). Results showed that in both number-based and mass-based particle size distribution (PSD) the peaks of ultrafine PMs located nearby 0.2 μm under all experimental atmospheres including O221%/N279%, O221%/CO279%, O227%/CO273% and O233%/CO267% (O21N79, O21C79, O27C73 and O33C67). And the peak values increased with the increase of O2 concentration in O2/CO2 atmospheres because of the high char combustion temperature at elevated O2 level. However, the mass and number concentration of ultrafine PMs in O2/CO2 atmospheres reduced significantly compared with these in O2/N2 atmosphere. When O21N79 atmosphere switched to O21C79, O27C73, O33C67 atmosphere, the mass concentration of ultrafine PMs reduced by 80.90%, 76.58% and 14.31%, and the number concentration reduced by 74.16%, 63.17% and 10.50%, respectively. Furthermore, the total mass of the ultrafine PMs was determined by the mass of the ultrafine PMs with larger particle size, whereas the total number of ultrafine PMs was determined by the number of the ultrafine PMs with smaller particle size. In this work, the ultrafine PMs with the aerodynamic size smaller than 0.3 μm were collected on the 1st to 7th impactor surfaces of the ELPI+. Among the ultrafine PMs, the particles on the 7th impactor (PMs with the superior limit of ultrafine PMs size) accounted for more than 94.8% of the total ultrafine PMs by mass, but less than 2.3% of the total ultrafine PMs by number; The particles deposited on the 1st impactor (PMs with the detectable minimum size of ultrafine PMs) accounted for more than 79.6% of the total ultrafine PMs by number, but less than 0.4% of the total ultrafine PMs by mass. In addition, PM0.1 which accounted for 96% of the total number of the ultrafine PMs was analyzed for chemical composition by Inductively Coupled Plasma Mass Spectrometer (ICP-MS). Results showed that the prominent components of PM0.1 were Ca, Na, and Si in both O2/N2 and O2/CO2 atmospheres. However, compared with O2/N2 atmosphere, Na, Si, Al, and Fe were more enriched in PM0.1 in O2/CO2 atmospheres.

Conversion of particle size distribution data from mass to number-based and its application to biomass processing

Standard sieving analysis is a simple and common method for determining the mass-based particle size distributions of systems with high polydispersity. Conversion of mass-based particle size distributions to finite number of particles having different sizes (number-based particle size distribution) is required in order to predict the physical characteristics of a polydisperse system or to investigate the behaviour of such a system with computational models that consider the impact of individual particles during large-scale processing. A general method for this conversion from size distribution to number of particles is developed here, that determines the minimal total number of particles that is required for capturing a broad particle size distribution, and identifies the factors that impact the generated mass-based size distribution. As an example, this algorithm is utilised for semi-crystalline biomass particles to demonstrate the effect of different algorithm parameters on the dissolution behaviour of this highly polydisperse system. Both the upper and lower limits of the particle size have an important impact on the physical characteristics of the generated polydisperse system. Considering a low value for the lower limit (minimum particle diameter) causes coarser particles not to be captured well, while considering a very high value for the upper limit results in fine particles not being present in the system. The proposed method and the obtained insights are useful in the numerical non-continuum (discrete) population modelling of polydisperse systems undergoing changes that are physical (e.g., dissolution, drying), chemical (e.g., combustion, gasification), or biological (e.g., enzymatic hydrolysis).

Characteristics of Particulate Matter Emitted from Agricultural Biomass Combustion

In this work, the emission of particulate matter (PM) from combustion of agricultural biomass was investigated in comparison to woody biomass. The mechanism of PM emission was studied by means of mass-based particle size distributions (PSDs), inorganic elemental component analysis and morphology at variant combustion temperatures, and different biomass feedstocks. The mass-based PSDs of PM10 of cotton stalk, rice husk, and camphor wood exhibit a bimodal distribution, while that of corn stalk exhibits a unimodal distribution. The emission of PM10 of agricultural biomass is much higher than that of woody biomass, and it is mainly composed of PM1, in which Na and K are enriched as alkali metal chloride and sulfide. On the other hand, Mg and Ca are enriched as the main inorganic compounds in PM1–10 for woody biomass. A higher combustion temperature is favorable for the formation of fine PM particles against a reduction of PM10. PM1 and PM1–10 formation mechanisms are different for different biomass feedstocks...

Sedimentation field flow fractionation and optical absorption spectroscopy for a quantitative size characterization of silver nanoparticles

Many advanced industrial and biomedical applications that use silver nanoparticles (AgNPs), require that particles are not only nano-sized, but also well dispersed, not aggregated and not agglomerated. This study presents two methods able to give rapidly sizes of monodispersed AgNPs suspensions in the dimensional range of 20–100nm.The first method, based on the application of Mie’s theory, determines the particle sizes from the values of the surface plasmon resonance wavelength (SPRMAX), read from the optical absorption spectra, recorded between 190nm and 800nm. The computed sizes were compared with those determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS) and resulted in agreement with the nominal values in a range between 13% (for 20nm NPs) and 1% (for 100nm NPs),The second method is based on the masterly combination of the Sedimentation Field Flow Fractionation (SdFFF − now sold as Centrifugal FFF-CFFF) and the Optical Absorption Spectroscopy (OAS) techniques to accomplish sizes and quantitative particle size distributions for monodispersed, non-aggregated AgNPs suspensions. The SdFFF separation abilities, well exploited to size NPs, greatly benefits from the application of Mie’s theory to the UV–vis signal elaboration, producing quantitative mass-based particle size distributions, from which trusted number-sized particle size distributions can be derived. The silver mass distributions were verified and supported by detecting off-line the Ag concentration with the graphite furnace atomic absorption spectrometry (GF-AAS).

Analytical approaches for the characterization and quantification of nanoparticles in food and beverages.

Estimating consumer exposure to nanomaterials (NMs) in food products and predicting their toxicological properties are necessary steps in the assessment of the risks of this technology. To this end, analytical methods have to be available to detect, characterize and quantify NMs in food and materials related to food, e.g. food packaging and biological samples following metabolization of food. The challenge for the analytical sciences is that the characterization of NMs requires chemical as well as physical information. This article offers a comprehensive analysis of methods available for the detection and characterization of NMs in food and related products. Special attention was paid to the crucial role of sample preparation methods since these have been partially neglected in the scientific literature so far. The currently available instrumental methods are grouped as fractionation, counting and ensemble methods, and their advantages and limitations are discussed. We conclude that much progress has been made over the last 5years but that many challenges still exist. Future perspectives and priority research needs are pointed out. Graphical Abstract Two possible analytical strategies for the sizing and quantification of Nanoparticles: Asymmetric Flow Field-Flow Fractionation with multiple detectors (allows the determination of true size and mass-based particle size distribution); Single Particle Inductively Coupled Plasma Mass Spectrometry (allows the determination of a spherical equivalent diameter of the particle and a number-based particle size distribution).

Quantitative analysis of dendron-conjugated cisplatin-complexed gold nanoparticles using scanning particle mobility mass spectrometry

We report a high-resolution and traceable method to quantify the drug loading on nanoparticle-based cancer therapeutics, and demonstrate this method using a model cisplatin functionalized dendron-gold nanoparticle (AuNP) conjugate. Electrospray differential mobility analysis (ES-DMA) provides upstream size classification based on the electrical mobility of AuNP conjugates in aerosol form following electrospray conversion from the aqueous suspension. A condensation particle counter (CPC) and inductively coupled plasma mass spectrometer (ICP-MS) provide the principal downstream quantification. CPC and ICP-MS yield complementary number-based and elemental mass-based particle size distributions, respectively. Conjugation using three different dendron formulations was differentiated based on changes in the mean mobility particle size. The subsequent cisplatin complexation to the dendron conjugates was quantified by coupling ES-DMA with ICP-MS. Discrete AuNP clusters (e.g., dimers, trimers) could be resolved from the relative quantity of atoms (i.e., Au and Pt) per particle after separation by ES-DMA. Surface density of cisplatin on Au was shown to be proportional to the density of carboxylic groups present and was independent of the state of AuNP clustering. Additionally, we found that colloidal stability of the conjugate is inversely proportional to the surface loading of cisplatin. This study demonstrates a prototype methodology to provide traceable quantification and to determine other important formulation factors relevant to therapeutic performance.

Combustion of Volatiles Produced in Situ from the Fast Pyrolysis of Woody Biomass: Direct Evidence on Its Substantial Contribution to Submicrometer Particle (PM1) Emission

Using a novel two-stage pyrolysis/combustion system, volatiles produced in situ from the fast pyrolysis of a woody biomass at 800–1000 °C were combusted in a drop-tube furnace (DTF) at 1300 °C to investigate its contribution to submicrometer particle (PM1) emission. During pyrolysis, the majority of Na, K, and Cl (43.5–97.2%) was volatilized and the consequent combustion of Na-, K-, and Cl-containing volatiles contributed substantially to PM1 emission (77.4–89.3% of total PM1 collected from the combustion of volatiles and char). Oppositely, the majority (83.9–97.5%) of Mg and Ca was retained in chars, and as a result, 97.5–99.7% of the yield of total PM1–10 is from char combustion. An increase in the pyrolysis temperature leads to an increase in the PM0.1 yields and the mass of Na, K, and Cl in PM0.1 from volatiles combustion, as a result of enhanced volatilization of Na, K, and Cl during pyrolysis. The mass-based particle size distributions (PSDs) of PM10 and elemental-mass-based PSDs of Na, K, and Cl (which are dominantly contained in PM1) from volatiles combustion generally show a unimodal distribution with a fine mode range from ∼0.022 to ∼0.043 μm. The mass-based PSDs of PM10 and elemental-mass-based PSDs of Mg and Ca (which are dominantly contained in PM1–10) from char combustion also generally show a unimodal distribution but with a coarse mode of ∼6.8 μm. The results clearly demonstrate that the combustion of volatiles (therefore Na, K, and Cl included) produced in situ from the fast pyrolysis of woody biomass is a key mechanism responsible for PM1 emission. There are strong correlations between the PM1 yields and the contents of (Na + K + Cl), (Na + K), and Cl in the volatiles during combustion.

COMBUSTION AEROSOLS FROM MUNICIPAL WASTE INCINERATION—EFFECT OF FUEL FEEDSTOCK AND PLANT OPERATION

Combustion aerosols were measured in a 22 MW (thermal energy) municipal waste incinerator. Different types of waste fractions were added to a base-load waste and the effect on aerosol formation was measured. The waste fractions applied were: PVC plastic, pressure-impregnated wood, shoes, salt (NaCl), batteries, and automotive shredder waste. Also, runs with different changes in the operational conditions of the incinerator were made. Mass-based particle size distributions were measured using a cascade impactor and the number-based size distributions were measured using a Scanning Mobility Particle Sizer. The plant is equipped with flue gas cleaning and the penetration through this was determined. The particle morphology was investigated by Transmission Electron Microscopy (TEM) and chemical analysis of the aerosol particles was made by Energy Dispersive X-ray Spectroscopy (EDS). The mass-based particle size distribution was bimodal with a fine mode peak around 0.4 µm and a coarse mode peak around 100 µm. The addition of NaCl, shredder waste, and impregnated wood increased the mass concentration of fine particles (aerodynamic diameter below 2.5 µm). In general the mass concentration was stable and close to the reference PM2.5-value of 252 ± 21 mg/m3 (std.T,P). The total number concentration deviated during runs and between runs spanning from 43 · 106 to 87 · 106 #/cm3(std.T,P). The aerosols formed were mixtures of dense and aggregated particles in all tests. The fine particles are mainly composed by alkali salts, zinc, and lead. The heavy metals Cu, Cd, Hg, and Pb are significantly enriched in the fine particles.

Size-based speciation of iron in clay mineral particles by gravitational field-flow fractionation with electrothermal atomic absorption spectrometry

Gravitational field-flow fractionation (FFF) coupled to UV and ETAAS detectors has been tested for micron-size particles in the range of 5–20 μm using three Fe-rich clay samples. The iron content estimated after aqua regia extraction was about 20–40 mg kg −1. The ETAAS analysis was performed both off-line from collected fractions and in an online continuous sampling mode using a specially designed flow through vial placed in the autosampler of the ETAAS. Comparison of the direct injection method with total analysis after aqua regia digestion shows that slurry injection of the dilute samples in the gravitational field-flow fractionation (GrFFF) effluent is quite efficient in these samples. In the majority of cases, more than 90% recovery was obtained for the slurry injection method. Fe mass-based particle size distributions and Fe concentration versus particle diameter plots can be generated using certain assumptions. This provides detailed information on size-based speciation of particulate samples. Generally, the Fe concentrations in the particles decreased slightly with an increase in particle size as is often found for soil and sediment samples.

Fractionation and composition of colloidal and suspended particulate materials in rivers

The association of pollutants (nutrients, heavy metals and organic compounds) with colloidal and suspended particle matter (SPM) plays a dominant role in determining their transport, fate, biogeochemistry, bioavailability and toxicity in natural waters. A scheme for the fractionation and composition of colloidal and SPM from river waters has been tested. All four separation methods, i.e. sieving, continuous flow centrifugation, tangential flow filtration, sedimentation field-flow fractionation, were for the first time used to separate five size particulate fractions from river. Significant (gram) amounts of colloidal material (<1 μm) in three size ranges, nominally 1–0.2, 0.2–0.006 and 0.006–0.003 μm were obtained. The separation scheme was able to process large samples (100 l), within reasonable times (1 day) and the apparatus was portable. The aquatic colloid size was also characterized with high resolution by using sedimentation field-flow fractionation technique. The mass-based particle size distribution for the water sample showed a broad size distribution between 0.05 and 0.4 μm with the maximum around 0.14 μm. There was a systematic increase in the content of organic carbon (estimated by loss on ignition), Mg, Ca, Na, Cu and Zn with decreasing particle size, highlighting the importance of the colloidal (<1 μm) fraction. It was concluded that the colloidal Cu and Zn concentrations in rivers might be much higher than those reported before.