Low-pressure Cascade Impactor Research Articles

96 Optimization of the Preparation of Cascade Impactors Collection Media for Airborne Metallic Ultrafine Particles Sampling

Abstract For some years, the characterization of workers' exposure to airborne metallic ultrafine particles (UFP) has been an increasing issue. Many industrial processes may generate UFP, which are characterized by constituent particle diameter less than 100 nm, and refer to nanosized particles not intentionally produced (welding, thermal spraying, 3D-printing ...). Thus, determining the size distribution of such an aerosol together with its chemical composition provide a real contribution to the understanding of UFP exposures and associated health effects. In the framework of proposing characterization methods adapted to occupational situations, the optimization of metallic aerosol sampling using cascade impactors is studied in order to improve the reproducibility of these samplings. Cascade impactors represent a valuable help since both the size distribution of an aerosol and its chemical characterization can be obtained from the samples collected. A welding fume bench was used to generate a highly reproducible test aerosol of metallic UFP (mass median aerodynamic diameter MMAD = 430 nm, ρeff = 0.55 g.cm-3). Four different cascade impactors were involved (DLPI+, MARPLE, SIOUTAS and Minimoudi 135-8). Our investigations allowed the lubrificating procedure of the collection supports (membranes, filters) to be optimized by determining the nature and the quantity of grease, which is of significative influence in the collection efficiency. Furthermore, under optimized conditions, the Minimoudi 135-8 (intended for personal sampling) leads to results very close to those stemming from the reference low pressure cascade impactor, DLPI+, thanks to its high resolution in terms of number of stages (8) and lowest cutoff diameter (180 nm).

Size Distribution of Particulate Matter in Indoor Environment During Nanomaterial Paint Application

Due to the increasing production and development of nanoparticles, it has become necessary to control the exposure to ultrafineparticles (aerodynamic diameter < 0.1 μm) when handling nanopaints. The paper deals with the number and mass distributionof particulate matter (PM) in an indoor environment before, during and after the application of paint Protectam FN containingtitanium nanoparticles. The size distribution determination was performed by the electrical low-pressure cascade impactor (ELPI+)in the range from 0.006 μm to 9.93 μm. The highest number of particles was observed in the range from 0.006 to 0.0175 μm. Theparticulate mass concentration ranging from 0.0175 to 0.0307 μm did not represent more than 0.5% of the sum of PM10 during theindividual measurements. The particle mass concentration increased in the range of 0.0175 to 0.0307 μm, after application of thecoating nanopaint Protectam FN, but it was observed that the total number of particles has decreased. During the days followingthe application of the nanopaint, the mass concentration in this grain size class was significantly reduced.

Spatial mapping and size distribution of oxidative potential of particulate matter released by spatially disaggregated sources

The ability of particulate matter (PM) to induce oxidative stress is frequently estimated by acellular oxidative potential (OP) assays, such as ascorbic acid (AA) and 1,4-dithiothreitol (DTT), used as proxy of reactive oxygen species (ROS) generation in biological systems, and particle-bound ROS measurement, such as 2′,7′-dichlorodihydrofluorescein (DCFH) assay. In this study, we evaluated the spatial and size distribution of OP results obtained by three OP assays (OPAA, OPDCFH and OPDTT), to qualitative identify the relative relevance of single source contributions in building up OP values and to map the PM potential to induce oxidative stress in living organisms. To this aim, AA, DCFH and DTT assays were applied to size-segregated PM samples, collected by low-pressure cascade impactors, and to PM10 samples collected at 23 different sampling sites (about 1 km between each other) in Terni, an urban and industrial hot-spot of Central Italy, by using recently developed high spatial resolution samplers of PM, which worked in parallel during three monitoring periods (February, April and December 2017). The sampling sites were chosen for representing the main spatially disaggregated sources of PM (vehicular traffic, rail network, domestic heating, power plant for waste treatment, steel plant) present in the study area. The obtained results clearly showed a very different sensitivity of the three assays toward each local PM source. OPAA was particularly sensitive toward coarse particles released from the railway, OPDCFH was sensible to fine particles released from the steel plant and domestic biomass heating, and OPDTT was quite selectively sensitive toward the fine fraction of PM released by industrial and biomass burning sources.

Nanoparticle exposure due to pyrotechnics during a football match

Abstract Use of pyrotechnic articles is a common, though forbidden practice at football matches. While the fans, especially the members of the ultras groups, view pyrotechnic displays as a part of their culture, these devices can be dangerous for the public. In addition to the risks of burning, hand flares and similar items release toxic combustion by-products, including particulate matter – inhaling of which is harmful both for the spectators and players. In order to assess the amounts and composition of the aerosol particles released at a typical event, we performed a study using both a scanning mobility particle sizer and a low-pressure cascade impactor. The number concentration of nanoparticles was clearly correlated with the burning events. Several elements were identified in the collected samples, including heavy metals, while the majority of the sample consisted of amorphous carbon. The nanoparticle number concentration increased up to 12-fold immediately after the beginning of the flares burning, with the largest contribution of particles 155 nm in diameter. The cumulative dose the players inhaled during the match was around 7 × 108 particles/kg, which is 300% higher than the dose one would get in a low-pollution environment. We discuss the results in view of similar pyrotechnical events, especially fireworks.

Influence of the type and output of domestic hot-water boilers and wood moisture on the production of fine and ultrafine particulate matter

Abstract The Ministry of the Environment of the Czech Republic within the Operational Programme Environment of the European Union (EU) has supported a ‘grant to replace old boilers’ from 2015 to 2020. The aim was to replace outdated, non-ecological, solid-fuel boilers with modern low-emission boilers (for the combustion of biomass, coal, or a combination), heat pumps, gas boilers, or solar systems. All heat sources must comply with the Ecodesign Directive of the EU. According to the Air Protection Act in the Czech Republic, commencing in 2022, outdated boilers of the 1st and 2nd emission classes will no longer be operable in households. The grant also aimed to reduce particulate matter (PM), organic gaseous compounds, and CO and NOx emissions. Our goal was to compare the PM emissions of four boilers: an outdated overfire boiler (B1), an outdated boiler with down-draft combustion (B2), a new gasification boiler (B3), and a new automatic boiler (B4). A Dekati low-pressure cascade impactor was used to determine the mass concentration of individual dust fractions; a scanning mobility particle sizer SMPS 3936 was utilized to determine the particle size distributions of the dust particles. Dry and wet spruce wood and wood pellets were combusted. Regarding the mass concentration of the PM and specific emissions (SE) of individual size fractions, they were much higher in boilers of older types (B1 and B2), while the reduction in SE of PM was very significant in boilers of newer types (B3 and B4). However, the SE of ultrafine particles (PM0.1) from the newer boilers remained in a range similar to that of B1 at a reduced output (Pmin) and B2.

Particle formation during pressurized entrained flow gasification of wood powder: Effects of process conditions on chemical composition, nanostructure, and reactivity

The influence of operating condition on particle formation during pressurized, oxygen blown gasification of wood powder with an ash content of 0.4 wt% was investigated. The investigation was performed with a pilot scale gasifier operated at 7 bar(a). Two loads, 400 and 600 kW were tested, with the oxygen equivalence ratio (λ) varied between 0.25 and 0.50. Particle concentration and mass size distribution was analyzed with a low pressure cascade impactor and the collected particles were characterized for morphology, elemental composition, nanostructure, and reactivity using scanning electron microscopy/high resolution transmission electron microscopy/energy dispersive spectroscopy, and thermogravimetric analysis. In order to quantify the nanostructure of the particles and identify prevalent sub-structures, a novel image analysis framework was used. It was found that the process temperature, affected both by λ and the load of the gasifier, had a significant influence on the particle formation processes. At low temperature (1060 °C), the formed soot particles seemed to be resistant to the oxidation process; however, when the oxidation process started at 1119 °C, the internal burning of the more reactive particle core began. A further increase in temperature ( > 1313 °C) lead to the oxidation of the less reactive particle shell. When the shell finally collapsed due to severe oxidation, the original soot particle shape and nanostructure also disappeared and the resulting particle could not be considered as a soot anymore. Instead, the particle shape and nanostructure at the highest temperatures ( > 1430 °C) were a function of the inorganic content and of the inorganic elements the individual particle consisted of. All of these effects together lead to the soot particles in the real gasifier environment having less and less ordered nanostructure and higher and higher reactivity as the temperature increased; i.e., they followed the opposite trend of what is observed during laboratory-scale studies with fuels not containing any ash-forming elements and where the temperature was not controlled by λ.

Influence of sulfur dioxide-related interactions on PM2.5 formation in iron ore sintering

ABSTRACTThe formation of PM2.5 (aerosol particulate matter less than 2.5 µm in aerodynamic diameter) in association with SO2 emission during sintering process has been studied by dividing the whole sintering process into six typical sampling stages. A low-pressure cascade impactor was used to collect PM2.5 by automatically segregating particulates into six sizes. It was found that strong correlation existed between the emission properties of PM2.5 and SO2. Wet mixture layer (overwetted layer and raw mixture layer) had the function to simultaneously capture SO2 and PM2.5 during the early sintering stages, and released them back into flue gas mainly in the flue gas temperature-rising period. CaSO4 crystals constituted the main SO2-related PM2.5 during the disappearing process of overwetted layer, which was able to form perfect individual crystals or to form particles with complex chemical compositions. Besides the existence of individual CaSO4 crystals, mixed crystals of K2SO4-CaSO4 in PM2.5 were also found during the first half of the temperature-rising period of flue gas. The interaction between fine-grained Ca-based fluxes, potassium vapors, and SO2 was the potential source of SO2-related PM2.5.Implications: The emission property of PM2.5 and SO2 throughout the sintering process exhibited well similarity. This phenomenon tightened the relationship between the formation of PM2.5 and the emission of SO2. Through revealing the properties of SO2-related PM2.5 during sintering process, the potential interaction between fine-grained Ca-based fluxes, potassium vapors, and SO2 was found to be the source of SO2-related PM2.5. This information can serve as the guidance to develop efficient techniques to control the formation and emission of PM2.5 in practical sintering plants.

Towards the ranking of airborne particle emissions from car brakes – a system approach

Airborne particulate matter emitted from motor vehicle brakes is a contributor to urban air quality. Therefore, a method to rank brake pairs (pads and rotors) with respect to their particle emission factors in a reliable way is needed to develop a low-emission disc brake. A novel inertial disc brake dynamometer designed for brake particle emission studies, a modified SAE J 2707 cycle, an electrical low-pressure cascade impactor and a filter are used to test five different pad materials against cast-iron rotors. By changing only the pad materials, it is shown that the differences between the mass emission factor and the number emission factor of the the worst brake pair and those of the best brake pair decreases by more than four times and 19 times respectively. Furthermore, the results show that the material combination ranked the best in terms of the mass emission factor is ranked the worst in terms of the number emission factor. The results reveal that this combination of a test stand, a test cycle and particle instruments can discriminate between different brake pair materials in a reliable way in the case of the mass emission factors while more research has to be carried out in the case of the number emission factors.

A New Method to Measure Aerosol Particle Bounce Using a Cascade Electrical Low Pressure Impactor

The phase state of secondary organic aerosol (SOA) in the atmosphere is of scientific interest as it can impact SOA growth and reactivity. For this purpose, a simplified method is described herein to estimate SOA bounce factor to gain an improved understanding of the phase state of atmospheric aerosols. This new method involves the use of a multistage electrical low pressure cascade impactor operating with either smooth or sintered impaction plates. Measurement of the raw current on smooth and sintered plates allows one to calculate the bounce factor, eliminating the need for a scanning mobility particle sizer to independently measure the SOA aerodynamic size distribution. The proposed method provides the temporal resolution necessary to measure phase changes in a continuously evolving SOA parcel.We validate our method by measuring the bounce factor of solid and liquid aerosols, namely ammonium sulfate (AS), dioctyl sebacate (DOS), oleic acid (OA) and ozonized OA, and also present bounce factor evolution ...

Seasonal behavior of radon decay products in indoor air and resulting radiation dose to human respiratory tract

Most of radiation hazard of indoor radon is largely due to the radon progenies, which are inhaled and deposited in the human respiratory tract. It is essential to evaluate aerodynamic characteristics of the radon progenies, which are either attached or unattached to aerosol particles, because the dose is strongly dependent on the location of deposition in respiratory tract and hence on the aerodynamic characteristics of the aerosol particles. This paper presents the seasonal behavior of radon decay products in indoor air under domestic conditions at Nagoya University, Japan. A low pressure cascade impactor as an instrument for classifying aerosol sizes and imaging plate as a radiation detector have been employed to characterize the activity size distribution of short-lived radon decay products. In parallel, radon and its progenies concentrations were measured. Taking into account the progeny characteristics, the inhalation dose in the different seasons was also estimated based on a lung dose model with the structure that is related to the ICRP66 respiratory tract model. The result evident that, the highest dose 0.22 mSvy−1 was observed during the winter where the highest value of equilibrium equivalent concentration of radon (EEC) and lowest value of the activity median aerodynamic diameter (AMAD) were found in this season; whereas, the dose in spring appeared to be lowest 0.02 mSvy−1.

Emissions of Nanoparticles from Small Combustion Equipment with Regard to the Combustion Mode and Wood Humidity

Contamination of air by solid particles is serious problem for human health and also environment, especially in certain regions of the Czech Republic and Poland. Small particles in nano-sizes are more dangerous than same weight of larger size. Negative effect namely of the solid particles depends on number, specific surface area, respirability and bonding of others substances (e.g. PAH, As, Cd, Zn, Cu etc.) which are higher for smaller (nano-sizes) particles compared to larger one. With the approaching winter, yearly problems with distribution of particles from small combustion equipments arise. The annual emission balance indicate that the proportion of small sources to total air pollution (PAH, dust) is surprisingly expressive [1]. For this reason mentioned above this contribution deals with measuring of amount, and distribution of nanoparticles produced form combustion of wood in small combustion unit. <br />For combustion test in grave-free stoves were used three samples of wood (wet spruce, dry spruce and raw spruce) and two combustion modes. Nanoparticles from flue gas were characterized by the aperture low-pressure cascade impactor DLPI (separation and weighing of particles in sizes 30 ηm ÷ 10 µm). Wood were combusted in the form of ¼ logs.

High-resolution low-pressure cascade impactor

This study introduces the calibration and performance evaluation of a new high-resolution low-pressure cascade impactor (HRLPI). It is a 10-stage cascade impactor designed to be used with the electrical detection of aerosol particles. The particle size range with the filter stage is approximately from 5nm to 200nm, and the flow rate is 1.2lpm. The cutpoint of the first stage is 7.7nm, which is so far the lowest cutpoint introduced for cascade impactors. The HRLPI stages have sharp cut-curves, which improve the performance significantly when the cutpoints are brought as close to each other as in the HRLPI. The HRLPI was calibrated with monodisperse dioctylsebacate particles. The average cut-curve steepness parameter was 9.9, and for the ELPI+ the corresponding value was 3.5. The HRLPI was tested in laboratory measurements together with five other commercial instruments. The HRLPI could resolve the location of the size distribution mode down to 10nm, whereas for the ELPI with an additional low cutpoint stage, the minimum size was around 24nm. Measurements also showed that the HRLPI and SMPSs were the only instruments of the tested five size-distribution measurement instruments that could resolve a bimodal distribution in which the geometric mean diameters of the modes were around 15nm and 30nm.

Thoron concentration, aerosol characteristics of 212Pb and estimation of equivalent dose

The thoron gas (220Rn) activity concentration as well as activity size distribution of unattached and attached 212Pb to aerosol particles was measured in the open air of Jeddah City, Kingdom of Saudi Arabia. An electroprecipitation method was applied for measuring the 220Rn concentration. A mean activity concentration of 220Rn was determined to be 1.80±0.47Bqm−3. The unattached activities of 212Pb were collected using the wire screen diffusion battery technique while a low-pressure cascade impactor collected the attached activities. The mean activity median thermodynamic diameter (AMTD) of unattached 212Pb was determined to be 1.32nm with a relative mean geometric standard deviation (σg) of 1.45. A mean concentration of unattached activity of 212Pb was found to be 9.48±1.12mBqm−3. A mean unattached fraction (fp) of 0.028±0.002 was obtained at a mean aerosol particle concentration of 29×103cm−3. Sometimes, the fp values were less than the detection limit of 0.009. A mean activity median aerodynamic diameter (AMAD) of the accumulation mode of attached 212Pb was determined to be 352nm with a mean (σg) of 2.6. The mean value of specific air activity concentration of 212Pb associated with that mode was determined to be 310±12mBqm−3. With a dosimetric model calculation (ICRP, 1994) the total and regional deposition fractions, total and regional equivalent doses could be evaluated considering the obtained parameters of the activity size distributions. At a total deposition fraction of about 97% of unattached activities the total equivalent dose to the human lung was determined to be 0.16µSv while a total equivalent dose of 0.44µSv was determined at a total deposition fraction of about 23% for the attached activities. It was found that an unattached fraction of fP≈3% yields to about 27% of the total equivalent dose.

Characterisation of submicron particles produced during oxygen blown entrained flow gasification of biomass

In this paper submicron particles sampled after the quench during 200kW, 2bar(a) pressurised, oxygen blown gasification of three biomass fuels, pure stem wood of pine and spruce, bark from spruce and a bark mixture, have been characterised with respect to particle size distribution with a low pressure cascade impactor. The particles were also characterised for morphology and elemental composition by a combination of scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and high resolution transmission electron microscopy/energy dispersive spectroscopy/selected area electron diffraction pattern (HRTEM/EDS/SAED) techniques. The resulting particle concentration in the syngas after the quench varied between 46 and 289mg/Nm3 consisting of both carbon and easily volatile ash forming element significantly depending on the fuel ash content. Several different types of particles could be identified from classic soot particles to pure metallic zinc particles depending on the individual particle relation of carbon and ash forming elements. The results also indicate that ash forming elements and especially zinc interacts in the soot formation process creating a particle with shape and microstructure significantly different from a classical soot particle.

Comprehensive characterization of ambient nanoparticles collected near an industrial science park: Particle size distributions and relationships with environmental factors

We investigated the characteristics of ambient particles and their relationships with various environmental factors, including gaseous pollutants (CH 4, non-methane hydrocarbons (NMHC), total hydrocarbons (THC), NO x, CO, SO 2), meteorological parameters (humidity, temperature), and time (day/night, workday/weekend). We used an electrical low-pressure cascade impactor to measure the number and size distributions of ambient particles (0.007–10 μm) that were collected approximately 1 km northwest of Hsinchu Science Park in Taiwan between February and May 2007. The number concentrations of particles were enhanced through photochemical reactions during the day. In addition, high traffic flow during workdays increased the formation of particulates. Except for SO 2, all of the gaseous pollutants we studied (CH 4, NMHC, THC, NO x, CO) correlated positively with the total number concentrations of ambient particles during daytime, indicating that they might contribute to the particulate burden. The poorer relationship between the SO 2 level and the total number concentration of particles suggests that SO 2 might participate indirectly in the nucleation process during particle formation, The high enrichment factors for Zn, Pb, Cu, and Mn, which mostly comprised the ultrafine particles (diameter: < 0.1 μm) and fine particles (diameter: 0.1–1 μm), presumably arose from emissions from traffic and high technology factories. Heterogeneous reactions on solid particles might play a role in the removal of SOx and NO x from the atmosphere. Sulfides and nitrides can further react with these local pollutants, forming specific Cu-containing compounds: CuO (39%), CuSO 4 (34%), and Cu(NO 3) 2 (27%), within the ambient particles in this industrial area.

Influence of beam intensity profile on the aerodynamic particle size distributions generated by femtosecond laser ablation

AbstractThe dependence of nanoparticle size distributions on laser intensity profile was determined during infrared femtosecond laser ablation of silver targets in air. Laser parameters were adjusted to ablate at the same peak fluence with spatially homogeneous (flat-top) and inhomogeneous (Gaussian) intensity distributions formed by diffractive optical elements. Aerodynamic particle size was measured online by an electric low-pressure cascade impactor. Narrower size distributions were detected for the flat-top intensity profile in the fluence range from 0.6 to 4.4 J/cm2, while the Gaussian beam produced broad and bimodal distributions. The aerodynamic number frequency of the primary nanoparticulate fraction (40 nm) was equal to the number frequency of the submicron agglomerate fraction (200 nm) at laser fluence of 1 J/cm2. The Feret diameter of primary particles was 80 nm. Geometrical interpretation of the irradiated spots at the corresponding laser fluence regimes explains the formation of bimodal (submicron and nanoparticulate) size distribution in the case of Gaussian beams. The bimodality is attributed to different thermalization pathways during laser ablation.

Size-partitioning of an urban aerosol to identify particle determinants involved in the proinflammatory response induced in airway epithelial cells

BackgroundThe contribution of air particles in human cardio-respiratory diseases has been enlightened by several epidemiological studies. However the respective involvement of coarse, fine and ultrafine particles in health effects is still unclear. The aim of the present study is to determine which size fraction from a chemically characterized background aerosol has the most important short term biological effect and to decipher the determinants of such a behaviour.ResultsAmbient aerosols were collected at an urban background site in Paris using four 13-stage low pressure cascade impactors running in parallel (winter and summer 2005) in order to separate four size-classes (PM0.03–0.17 (defined here as ultrafine particles), PM0.17–1 (fine), PM1–2.5(intermediate) and PM2.5–10 (coarse)). Accordingly, their chemical composition and their pro-inflammatory potential on human airway epithelial cells were investigated. Considering isomass exposures (same particle concentrations for each size fractions) the pro-inflammatory response characterized by Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) release was found to decrease with aerosol size with no seasonal dependency. When cells were exposed to isovolume of particle suspensions in order to respect the particle proportions observed in ambient air, the GM-CSF release was maximal with the fine fraction. In presence of a recombinant endotoxin neutralizing protein, the GM-CSF release induced by particles is reduced for all size-fractions, with exception of the ultra-fine fraction which response is not modified. The different aerosol size-fractions were found to display important chemical differences related to the various contributing primary and secondary sources and aerosol age. The GM-CSF release was correlated to the organic component of the aerosols and especially its water soluble fraction. Finally, Cytochrome P450 1A1 activity that reflects PAH bioavailability varied as a function of the season: it was maximal for the fine fraction in winter and for the ultrafine fraction in summer.ConclusionIn the frame of future regulations, a particular attention should thus be paid to the ultrafine/fine (here referred to as PM1) fraction due to their overwhelming anthropogenic origin and predominance in the urban aerosol and their pro-inflammatory potential.

Apply appropriate models in the study of dry deposition fluxes of particulate matter and polycyclic aromatic hydrocarbons (PAHs) in Tsukuba, Japan

In this study, plates for downward flux and upward flux were used to measure atmospheric dry deposition fluxes for particulate mass and polycyclic aromatic hydrocarbons (PAHs) in TERC (Tsukuba), Japan. Ambient particles concentrations were also collected using a high-volume air sampler, and ambient particle size distributions between 0.01 μm and 13.1 μm were measured using a low-pressure cascade impactor to characterise the PAHs levels and dry deposition. The results indicated that the average cumulative fraction of dry deposition flux for particles and PAHs which attached with them was caused by the particle size of greater than 1.2-6.3 μm (97%).

Influence of reaction products of K-getter fuel additives on commercial vanadia-based SCR catalysts: Part I. Potassium phosphate

Commercial vanadia-based full-length monoliths have been exposed to aerosols formed by injection of K3PO4 (dissolved in water) in a hot flue gas (T>850°C) from a natural gas burner. Such aerosols may form when burning fuels with high K- and P-content, or when P-compounds are mixed with biomass as a K-getter additive. The formed aerosols have been characterized by using both a SMPS system and a low pressure cascade impactor, showing a dual-mode volume-based size distribution with a first peak at around 30nm and a second one at diameters >1μm. The different peaks have been associated with different species. In particular, the particles related to the 30nm peak are associated to condensed phosphates, whereas the larger particles are associated to potassium phosphates. Two monoliths have been exposed during addition of 100 and 200mg/Nm3 K3PO4 for 720 and 189h, respectively. Overall, deactivation rates up to 3%/day have been measured. The spent catalysts have been characterized by bulk chemical analysis, Hg-porosimetry and SEM-EDX. NH3-chemisorption tests on the spent elements and activity tests on catalyst powders obtained by crushing the monoliths have also been carried out. The catalyst characterization has shown that poisoning by K is the main deactivation mechanism. The results show that binding K in K–P salts will not reduce the rate of catalyst deactivation.

Influence of reaction products of K-getter fuel additives on commercial vanadia-based SCR catalysts: Part II. Simultaneous addition of KCl, Ca(OH)2, H3PO4 and H2SO4 in a hot flue gas at a SCR pilot-scale setup

A commercial V2O5–WO3–TiO2 corrugated-type SCR monolith has been exposed for 1000h in a pilot-scale setup to a flue gas doped with KCl, Ca(OH)2, H3PO4 and H2SO4 by spraying a water solution of the components into the hot flue gas. The mixture composition has been adjusted in order to have P/K and P/Ca ratios equal to 2 and 0.8, respectively. At these conditions, it is suggested that all the K released during biomass combustion gets captured in P–K–Ca particles and the Cl is released in the gas phase as HCl, thus limiting deposition and corrosion problems at the superheater exchangers during biomass combustion. Aerosol measurements carried out by using a SMPS and a low pressure cascade impactor have shown two distinct particle populations with volume-based mean diameters equal to 12 and 300nm, respectively. The small particles have been associated to polyphosphoric acids formed by condensation of H3PO4, whereas the larger particles are due to P–K–Ca salts formed during evaporation of the water solution. No Cl has been found in the collected particles. During the initial 240h of exposure, the catalyst element lost about 20% of its original activity. The deactivation then proceeded at slower rates, and after 1000h the relative activity loss had increased to 25%. Different samples of the spent catalyst have been characterized after 453h and at the end of the experiment by bulk chemical analysis, Hg-porosimetry and SEM-EDX. NH3-chemisorption tests on the spent elements and activity tests on catalyst powders obtained by crushing the monolith have also been carried out. From the characterization, it was found that neither K nor Ca were able to penetrate the catalyst walls, but only accumulated on the outer surface. Poisoning by K has then been limited to the most outer catalyst surface and did not proceed at the fast rates known for KCl. This fact indicates that binding K in P–K–Ca compounds is an effective way to reduce the negative influence of alkali metals on the lifetime of the vanadia-based SCR catalysts. On the other hand, P-deposition was favoured by the formation of the polyphosphoric acids, and up to 1.8wt% P was accumulated in the catalyst walls. Deactivation by polyphosphoric acids proceeded at about 0.2%day−1. About 6–7% of the initial activity was lost due to the accumulation of these species. However, the measured relative activity reached a steady-state level during the last 240h of exposure indicating that the P-concentration in the bulk reached a steady-state level due to the simultaneous hydrolysis of the polyphosphoric acids.