Electrical Low Pressure Impactor Research Articles

Real-Time Measurements of Botanical Disinfectant Emissions, Transformations, and Multiphase Inhalation Exposures in Buildings

Thymol-based botanical disinfectants have emerged as natural alternatives to traditional chemical disinfectants given their effectiveness as antimicrobial pesticides and ability to inactivate SARS-CoV-2. This study investigates the impact of botanical disinfectants on indoor air chemistry and human exposure. Controlled surface disinfection experiments were conducted in a mechanically ventilated zero-energy tiny house laboratory. Volatile organic compounds (VOCs) and aerosol size distributions were measured in real-time (1 Hz) with a proton transfer reaction time-of-flight mass spectrometer and a high-resolution electrical low-pressure impactor, respectively. Botanical disinfectant spray and wipe products drove sudden changes in the chemical composition of indoor air. Mixing ratios of monoterpenes (C10H16) and monoterpenoids (C10H14O, C10H16O, C10H18O, and C10H20O) increased suddenly during the disinfection events (10-1 to 102 ppb) and exhibited volatility-dependent temporal emission profiles. VOC emission factors ranged from 100 to 104 μg g-1, and thymol intake fractions ranged from 6 to 7 × 103 ppm. Rapid new particle formation events were observed due to ozonolysis of monoterpenes and monoterpenoids, increasing sub-100 nm particle number concentrations by 104 to 105 cm-3. Botanical disinfectant sprays initiated multiphase inhalation exposure to VOCs, secondary organic aerosol, and sub-10 μm droplets, with large deposited doses in each respiratory tract region associated with the latter two. ©

Investigating the effect of flue gas temperature and excess air coefficient on the size distribution of condensable particulate matters

Primary particles emitted from fuel combustion mainly involve filterable particulate matter (FPM) and condensable particulate matter (CPM). Particularly, CPM has emerged as a subject for further emission control. This study investigated the effects of the sampling temperature and excess air coefficient (EAC) on the total mass, chemical speciation, and particle size distribution of CPM by integrating Electrical Low-Pressure Impactor+ (ELPI+) sampling devices with the EPA Method 202 (dry impinger method). The total mass of CPM increased with the sampling temperature and EAC. Specifically, the total concentration of CPM was 10.51–39.93 mg/m3, in which the mass fraction of organic species varied between 8.74 and 49.80%, and the organic components in CPM followed the ranking order of alkanes/alkenes (62.6–78.6%), oxygen-containing volatile organic compounds (OVOCs) (19.7–35.4%), and aromatics (5.6%). Compared with other inorganic species such as HCl and NOX, SO3 had a higher migration tendency from the flue gas to CPM. The particle size distribution suggested that heterogeneous condensation was responsible for the whole size range of particles in CPM, whereas the homogeneous condensation led to the increase of finer particles (smaller than 0.2 µm). Accordingly, adjusting the emission temperature and EAC could help to control the emission of CPM.

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.

Fuel supply system to DOC by nanopore-ceramic tube and measurement of fuel evaporation rate

When the deposited particles in DPF is oxidized, diesel fuel is injected to the diesel oxidation catalyst (DOC) for increasing the exhaust gas temperature. It is called a secondary fuel injection. However, it is difficult to form the uniform fuel mixture. If there is high fuel concentration region, hot spots and/or coking at the catalyst inlet face, leading to the potential damage of the catalyst. Also, the fuel must be completely evaporated to avoid the emission of harmful hydrocarbons in the outer atmosphere. Non-uniform fuel supply across the catalyst inlet face may cause incomplete fuel oxidation over the DOC. Thus, we may need an alternative approach for fuel supply system in the exhaust line. In this study, we have tested a fuel supply system to DOC using nanopore-ceramic tube. The fuel is uniformly vaporized on the surface of the tube filled with the diesel fuel, which automatically flows towards the DOC. Since we could not measure the vaporized gaseous component by an electrical low pressure impactor called ELPI+, the evaporation rate was evaluated in terms of the burning velocity of the premixed flame on a Bunsen burner. It was confirmed that most of water vaporized from the ceramic tube was gaseous water vapor. As the pore size of the tube was larger, the maximum evaporation rate increased. When the tube length or the tube outer diameter was larger, the fuel evaporation was enlarged due to the larger surface area of the fuel evaporation.

Size distribution and chemical characteristics of particles from crop residue open burning in North China

Crop residue open burning is an important emission source of ambient particles in China. This study analyzed the particle emission characteristics of crop residue open burning through combustion experiments with a novel open combustion simulation device using three typical crop straws in north China (corn, wheat, and rice). Particle samples size ranging from 0.006–9.890 µm were collected by an Electrical Low Pressure Impactor plus, a high size-resolution instrument capable of dividing particles into 14 size stages. The size distributions of organic carbon (OC), elemental carbon (EC), water-soluble ions, and elements were analyzed, and source chemical profiles were constructed for PM0.1, PM1, PM2.5, and PM10. The number concentration of particles was concentrated in the Aiken nuclei mode (0.006–0.054 µm), accounting for 75% of the total number, whereas the mass concentration was concentrated in the accumulation mode (0.054–0.949 µm), accounting for 85.43% of the mass loading. OC, EC, Cl−, and K(include total K and water-soluble K) were the major chemical components of the particles, whose mass percentage distributions differed from those of other components. These five main components exhibited a bell-shaped size distribution in the 0.006–9.890 µm range, whereas the other components exhibited a U-shaped distribution. Among the chemical profiles for PM0.1–PM10, OC was the most important component at 10–30%, followed by EC at 2%–8%. The proportions of K+, Cl−, and K varied substantially in different experimental groups, ranging from 0–15%, and K+ and Cl− were significantly correlated (r = 0.878, α = 0.000).

Primary Carbonaceous Particle Emission from Four Power Plants with Ultralow Emission in China.

Particulate matters (PMs) were collected in stacks from two types of ultralow emission coal-fired power plants by a heated electrical low-pressure impactor (HT-ELPI+), including ultralow emission pulverized combustion technology boilers (ULPCBs) and ultralow emission circulating fluidized bed boilers (ULCFBs). The characteristics of organic carbon (OC) and elemental carbon (EC) in size-resolved particles were analyzed. The ultralow emission technologies significantly decreased the mass concentrations of the carbonaceous content, and the emission concentrations of OC and EC ranged from 5.64 to 17.9 μg/m3 for ULPCBs and from 0.57 to 1.85 μg/m3 for ULCFBs. However, the number concentration of particles was not significantly decreased in the four ultralow emission power plants. The OC in the particle emission of ULPCBs presents a bimodal size distribution with the particle size, while three successive unimodal distributions were observed in the ULCFB emission. Compared to ULPCBs, much more char-EC and soot-EC condensed in the particles, which were collected from ULCFBs. Furthermore, the char-EC/soot-EC in the particle fractions of ULPCBs characterized by the “V” type with the sequence of PM1.0 > PM2.5–10 > PM1.0–2.5, differing from the PM1.0 > PM1.0–2.5 > PM2.5–10 of ULCFBs. The ratios of OC/EC in the stacks from two types of boilers did not show obvious variations in particle size distributions, and the mean OC/EC was far higher than those for non-ultralow emission power plants. Considering the impact of OC1, OC4, and EC1, the ratio of high-temperature organic carbon (HTOC, defined as OC2 + OC3) and soot-EC was studied. The HTOC/soot-EC increased with the increase of RH in the stack, and the highest HTOC/soot-EC values were obtained from ULPCBs (33.0% (PM1.0), 11.4% (PM1.0–2.5), and 23.9% (PM2.5–10)). Meanwhile, strong correlations (0.69–0.85, p < 0.001) between HTOC and soot-EC were obtained, implying that HTOC and soot-EC probably simultaneously condensed in the purification equipment.

Concentrations and Size Distributions of Particle Lung-deposited Surface Area (LDSA) in an Underground Mine

ABSTRACT Ultrafine particles produced by diesel-powered vehicles in underground mines are largely unaccounted for in mass-based air quality metrics. The Lung Deposited Surface Area concentration (LDSA) is an alternative to describe the harmfulness of particles. We aim to study concentrations and size distributions of LDSA at various locations in an underground mine as well as to evaluate the applicability of sensor-type measurement of LDSA. This study was conducted in an underground mine in Kemi, Finland, in 2017. Our main instrument was an electrical low-pressure impactor (ELPI+) inside a mobile laboratory. Additionally, five diffusion-charging based sensors were tested. The environment was challenging for the sensors as the particle size distribution was often outside the optimum range (20–300 nm) and dust accumulated inside the instruments. Despite this, the correlations with the ELPI+ were decent (R2 from 0.53 to 0.59). With the ELPI+ we determined that the maintenance area had the lowest mean LDSA concentration (79 ± 38 µm2 cm–3) of the measured locations. At the other locations, concentrations ranged from 137 to 405 µm2 cm–3. The mode particle size for the LDSA distribution was around 100 nm at most locations, with the blasting site as a notable exception (mode size closer to 700 nm). Diffusion-charging based sensors—perhaps aided by optical sensors—are potential solutions for long-term monitoring of LDSA if dust accumulation is taken care of. Our research indicates worker exposure could be reduced with the implementation of a sensor network to show which locations need either protective gear or increased ventilation.

Characteristics of Chemical Composition and Particle Size Distribution from Real Coal-fired Circulating Fluidised Bed (CFB) Boiler

ABSTRACT The chemical component (element, ion, and carbonaceous aerosols) behaviour in particle size distributions (PSDs) was studied by determining the particulate matter (PM) emitted from the circulating fluidised-bed (CFB) combustion flue gas. Four CFB coal-fired boilers were employed in power plants. The actual particle mass percentages and PSDs were measured using an electrical low-pressure impactor (ELPI). Ion concentrations (SO42–, Cl–, NO3–, Na+, NH4+, Mg2+, K+ and Ca2+) were determined by ion chromatography (IC), elements (Al, Ca, Cr, Cu, Fe, K, Mg, Na, Ni, Pb, S, Si, Ti and Zn) were determined by inductively coupled plasma-mass spectrometry (ICP-AES), and the carbonaceous content (OC1, OC2, OC3, OC4, EC1, EC2 and EC3) was measured by thermal optical analysis. Significant differences were observed in the four boilers for PSD. Chemical species in particulate matter mainly concentrated in sizes 0.1–2.5 µm in aerodynamic diameter. In this work, the mass percentage of Ca, Ca2+, SO42–, NH4+ and OC were significantly high in different particle size regions. The mass concentrations of elements, ions, and carbonaceous aerosols in various sizes displayed trimodal or bimodal distributions; however, the peaks of mass concentrations of chemical species in different particle sizes varied greatly. Furthermore, the size distribution of chemical species was influenced by the pollution control device employed, and the same chemical species showed a marked difference among coal-fired boiler equipped with different pollution control devices. In addition, it was observed that the ratio of OC to EC was related to dust-cleaning method.

Analysis of wear induced particle emissions from brake pads during the worldwide harmonized light vehicles test procedure (WLTP)

Brake emissions generated from brake systems were investigated to elucidate the mechanism of airborne particle generation using commercial brake pads. Brake emission tests were performed using a 1/5 scale brake dynamometer enclosed in a chamber, and the particles were counted using an electrical low-pressure impactor (ELPI+) as a particle counter. The results revealed that the emission factor of low-steel brake pads was approximately five times greater than that of non-steel brake pads on average. In comparison, brake emissions in the number concentration were about two times greater in the case of using low-steel pads. Considerable amounts of off-brake emissions were also found after brake applications. Although multiple concentration peaks were observed in the particle size distribution, there was no correlation among chemical composition, size distribution, and particle morphology. On the other hand, the amount of brake emissions and the size distribution were strongly influenced by the pad surface topography, which comprised contact plateaus and lowlands, regardless of the type of pad.

Airborne Wear Particle Emissions Produced during the Dyno Bench Tests with a Slag Containing Semi-Metallic Brake Pads

The aim of the present paper is to investigate the level of airborne wear particles released during the dyno-bench tests with the brake pads consisting of alkali-activated slag as an abrasive. Airborne wear particles are generated with a full-scale dyno-bench adapted for airborne wear particles emission studies. The tested disc brake is equipped with two semi-metallic brake pads and a grey cast iron brake disc. A reduced Los Angeles City Traffic (LACT) driving cycle, developed within the LOWBRASYS project (European Union’s Horizon 2020 research and innovation programme), is used to mimic city driving. The same friction pair is used six times with reduced LACT cycle. The weight loss and thickness of the pads and disc are registered after each test cycle ends. The amount of the airborne wear particles emissions released during each test cycle are characterized using a PM10 impactor and electric low-pressure impactor. The obtained data of wear particle emissions are correlated with the parameters of the brake stops. The maximum disc temperature was indicated as the parameter having the largest influence on the production of particle emissions together with the duration of the brake event

Effect of disc material on particulate matter emissions during high-temperature braking

Brake emissions during high-temperature brake applications were investigated using four different brake discs—FC170 and FC250 Gy iron discs, oxynitride-coated gray iron discs, and ceramic discs. The brake emission tests were performed with a low-steel brake pad using a 1/5 scale brake dynamometer with a high resolution electrical low-pressure impactor. The highest number concentration was observed using ceramic discs, whereas the gray iron discs produced higher mass concentrations than others. The effect of the disc material on brake emissions at elevated temperatures was primarily determined by the thermal conductivity of the disc and the time- and temperature-dependent variations of contact plateaus on the pad surface.

Size and chemical characteristics of particles emitted from typical rural biomass cookstoves in North China

The emission characteristics of biomass combustion in rural household stoves were measured in northern China. The Electrical Low-Pressure Impactor plus (ELPI+) was used to collect the emitted particles in the size range of 0.006–9.890 μm. The particle number concentration (PNC), particle mass concentration (PMC), and size distribution characteristics of organic carbon (OC), elemental carbon (EC), and water-soluble ions were analyzed. The experimental results showed that the PNC peaked at 0.006–0.030 μm, and the PMC peaked at 0.257–0.603 μm. The mass concentration of OC and EC exhibited a “bell-shaped” size distribution in the 0–10 μm range. The OC content of particles reached its peak at 0.006–0.016 μm and ranged from 25% to 38%. The mass concentration and percentage of K+ and Cl− showed “bell-shaped” size distribution characteristics and the contents of K+ and Cl− in each particle size group were significantly correlated. The chemical source profiles of PM0.1, PM1, PM2.5, and PM10 were constructed, whose main components were OC, EC, K+, and Cl−. PM2.5 profile included 8.39–20.27% OC, 1.94–20.96% EC, 0.25–13.36% K+, and 0.36–16.97% Cl−.

Density enhancement of nano-sized and submicron-sized water droplets induced by charges released from corona discharge

Corona discharge is widely used as an ionization source in field experiments of weather modification induced by charged particles due to its high efficiency and economy. However, deficient research efforts have been devoted to the effects of corona discharge on the size distribution and evolution of droplets in the humid air. In this paper, the characteristic of water droplets spectrum evolution in humid air with unipolar corona discharge is studied by an electrical low pressure impactor (ELPI) experiment in a 96 m3 cloud chamber. Results show that nano-sized water droplets with diameters from 9 nm to 25 nm grow rapidly because of the inducement of charges released from corona discharge. Additionally, an increase in the concentration of submicron droplets appears at 20 min. To reveal the potential mechanism of the phenomena, the average charge values of charged droplets measured by ELPI are further analyzed. Meanwhile, the relationship between saturated vapor pressure over charged droplet’s surface and its radius is discussed by the modified Kelvin–Thomson equation. Results show that, for the density enhancement of nano-sized droplets, condensational growth induced by charges released from corona discharge dominates significantly. The subsequent increase in the density of submicron-sized droplets is regarded as the break-up of the micron-sized droplets, with the process of evaporation when droplets are approaching the Rayleigh limit in the sub-saturated environment. This research may bring some new perspectives to further study of weather modification and cloud-seeding induced by charged particles, such as by increasing condensed nuclei density, broadening cloud droplets spectrum, and suppressing the evaporation of cloud droplets, etc.

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.

Complex Aerosol Characterization by Scanning Electron Microscopy Coupled with Energy Dispersive X-ray Spectroscopy

Particulate matter (PM) air pollution is a central concern for public health. Current legislation relies on a mass concentration basis, despite broad acceptance that mass alone is insufficient to capture the complexity and toxicity of airborne PM, calling for additional and more comprehensive measurement techniques. We study to what extent scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) can be applied for physicochemical characterization of complex aerosols, and investigate its potential for separating particle properties on a single particle basis, even for nanosized particles. SEM/EDS analysis is performed on impactor samples of laboratory generated aerosols, consisting of either NaCl, Halloysite fibers, soot-like Printex90 agglomerates, or their combination. The analysis is automated and performed as EDS maps, covering a statistically relevant number of particles, with analysis times of approximately one hour/sample. Derived size distributions are compared to scanning mobility particle sizer (SMPS) and electric low-pressure impactor (ELPI) results. A method is presented to estimate airborne number concentrations and size distributions directly from SEM results, within a factor 10 of SMPS and ELPI outcomes. A classification scheme is developed based on elemental composition, providing class-specific information with individual particle statistics on shape, size, and mixing state. This can identify primary particles for source apportionment and enables easy distinction between fibrous and dense particle classes, e.g. for targeted risk assessments. Overall, the SEM/EDS analysis provides a more detailed physicochemical characterization of PM than online measurements, e.g. SMPS and ELPI. The method has the potential to improve assessments of PM exposure and risk, and facilitates source identification, even without prior knowledge at sampling.

Nanoparticle Emission and Characterization from Pre-Dried Lignite and Bituminous Coal Co-Combustion

Nowadays, the high share of electricity production from renewables drives coal-fired power plants to adopt a more flexible operation scheme and, at the same time, maintain flue gas emissions within respective standards. A 500 kWth pulverized coal furnace was used to study pre-dried lignite combustion or co-combustion as an available option for these plants. Bituminous coal from Czech Republic and pre-dried lignite from Greece were blended for the experiments. Particle emissions measurements with a heated Electrical Low Pressure Impactor (ELPI+) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS) analyses were performed. The effect of the pre-dried lignite proportions in the fuel feed and the combustion conditions regarding the combustion air staging were the two parameters selected for this study. Skeletal density values were measured from the cyclone prior to the impactor. Results are depicted with respect to the aerodynamic and Stokes diameter for impactor stages. The presence of pre-dried lignite in the fuel blend lowers the particle matter (PM) PM2.5, PM1 and PM0.1 emissions, thus having a positive impact on ESP’s fractional and overall efficiency. The staged combustion air feed reduces the particle emissions in all cases. Sulfur content follows a pattern of higher concentration values for finer particles.

Size-segregated carbonaceous aerosols emission from typical vehicles and potential depositions in the human respiratory system

Particles emitted from five typical types of vehicles (including light-duty gasoline vehicles, LDG; heavy-duty gasoline vehicles, HDG; diesel buses, BUS; light-duty diesel vehicles, LDD and heavy-duty diesel vehicles, HDD) were collected with a dilution sampling system and an electrical low-pressure impactor (ELPI+, with particle sizes covering fourteen stages from 6 nm to 10 μm) on dynamometer benches. The mass concentrations and emission factors (EF) for organic carbon (OC) and elemental carbon (EC) were obtained with a DRI Model 2001 thermal/optical carbon analyzer. A respiratory deposition model was used to calculate the deposition fluxes of size-segregated carbonaceous aerosols in human respiratory system. Results indicated that the OC produced from LDG mainly existed in the size range of 2.5–10 μm, while EC from HDG enriched in 0.94–2.5 μm. For diesel vehicles, both OC and EC concentrations peaked at 0.094–0.25 μm. The OC/EC ratios for PM2.5 varied from different types of vehicles, from 0.61 to 8.35. The primary emissions from LDD and HDD exhibited high OC/EC ratios (>3), suggesting that using OC/EC higher than 2 to indicate the formation of secondary organic aerosol (SOA) was not universal. The emission factors for OC and EC of LDG (HDG) in PM10 were 1.78 (3.14) mg km−1 and 0.88 (4.32) mg km−1, respectively. The OC2 and OC3 were the main section (over 60%) of OC emitted from all the five types of vehicles. EC1 was the most abundant EC fraction of LDG (76.9%), while EC2 dominated for other types of vehicles (more than 62%). About 60% of the OC in ultrafine particles could be deposited in the alveoli. Diesel EC mainly could be deposited in the alveolar region. It is necessary to control the emission of ultrafine particles and diesel EC.

Effects of aerosol dynamics and gas–particle conversion on dry deposition of inorganic reactive nitrogen in a temperate forest

Abstract. Dry deposition has an impact on nitrogen status in forest environments. However, the mechanism for the high dry-deposition rates of fine nitrate particles (NO3-) observed in forests remains unknown and is thus a potential source of error in chemical transport models (CTMs). Here, we modified and applied a multilayer land surface model coupled with dry-deposition and aerosol dynamic processes for a temperate mixed forest in Japan. This represents the first application of such a model to ammonium nitrate (NH4NO3) gas–particle conversion (gpc) and the aerosol water uptake of reactive nitrogen compounds. Thermodynamics, kinetics, and dry deposition for mixed inorganic particles are modeled by a triple-moment modal method. Data for inorganic mass and size-resolved total number concentrations measured by a filter pack and electrical low-pressure impactor in autumn were used for model inputs and subsequent numerical analysis. The model successfully reproduces turbulent fluxes observed above the canopy and vertical micrometeorological profiles noted in our previous studies. The sensitivity tests with and without gpc demonstrated clear changes in the inorganic mass and size-resolved total number concentrations within the canopy. The results also revealed that within-canopy evaporation of NH4NO3 under dry conditions significantly enhances the deposition flux of fine-NO3- and fine-NH4+ particles, while reducing the deposition flux of nitric acid gas (HNO3). As a result of the evaporation of particulate NH4NO3, the calculated daytime mass flux of fine NO3- over the canopy was 15 times higher in the scenario of “gpc” than in the scenario of “no gpc”. This increase caused high contributions from particle deposition flux (NO3- and NH4+) to total nitrogen flux over the forest ecosystem (∼39 %), although the contribution of NH3 was still considerable. A dry-deposition scheme coupled with aerosol dynamics may be required to improve the predictive accuracy of chemical transport models for the surface concentration of inorganic reactive nitrogen.

Measurement of the human respiratory tract deposited surface area of particles with an electrical low pressure impactor

Particle deposition in the human respiratory tract is considered to have negative effects on human health. The lung deposited surface area (LDSA) is an important metric developed to assess the nega...

Changes in the elemental composition of particulate matter in a speleotherapeutic cave

Atmosphere inside caves used for speleotherapy are microenvironments influenced by ventilation and human activities inside. In this context, particulate matter with an aerodynamic diameter from 15 nm to 10 μm was collected with an electrical low-pressure impactor ELPI+ in the Císařská Cave in the northern part of the Moravian Karst (Czech Republic) and 33 elements were determined with inductively coupled plasma tandem mass spectrometry (ICPMS/MS). To see the effect of ventilation, samples were collected with closed and opened entrances.Nucleation mode particles (particles with aerodynamic diameter less than 10 nm) were dominant in particle number concentrations at both cave ventilation regimes. Aitken mode particles (10–100 nm) differed in the content of sulphur, calcium, iron, chromium, magnesium and nickel for different ventilation regimes. Accumulation mode particles (100–1000 nm) consisted predominantly of sulphur and calcium, also chromium, copper, arsenic, molybdenum, selenium, cadmium and lead were mainly present in this particle size range. Coarse mode particles (larger than 1000 nm) contained predominantly calcium, in addition to common earth crust elements, originating by mechanical abrasion of cave floor.It is suggested that ventilation as well as children activities in the cave influence the elemental composition of particulate matter, which might have an impact on speleotherapy.