The Mass Distribution of Large Atmospheric Particles

This paper describes the results of a study to determine the total mass and the mass distribution of atmospheric aerosols, especially that mass associated with particles greater than 10 μm diameter. This study also determined what fraction of the total aerosol mass a standard high-volume air sampler collects and what fraction and size interval settle out on a dust fall plate. A special aerosol sampling system was designed for this study to obtain representative samples of large airborne particles. A suburban sampling site was selected because no local point sources of aerosols existed nearby. Samples were collected under various conditions of wind velocity and direction to obtain measurements on different types of aerosols.

Study measurements show that atmospheric particulate matter has a bimodal mass distribution. Mass associated with large particles mainly ranged from 5 to 100 μm in size, while mass associated with small particles ranged from an estimated 0.03 to 5 μm in size. Combined, these two distributions produced a bimodal mass distribution with a minimum around 5 μm diameter. The high-volume air sampler was found to collect most of the total aerosol mass, not just that fraction normally considered suspended particulate. Dust fall plates did not provide a good or very useful measure of total aerosol mass. The two fundamental processes of aerosol formation, condensation and dispersion appear to account for the formation of a bimodal mass distribution in both natural and anthropogenic aerosols. Particle size distribution measurements frequently are in error because representative samples of large airborne particles are not obtained. Considering this descrepancy, air pollution regulations should specify or be based upon an upper particle size limit.     

Indoor/outdoor connections exemplified by processes that depend on an organic compound's saturation vapor pressure

Outdoor and indoor environments are profitably viewed as parts of a whole connected through various physical and chemical interactions. This paper examines four phenomena that share a dependence on vapor pressure—the extent to which an organic compound in the gas phase sorbs on airborne particles, sorbs on surfaces, sorbs on particles collected on a filter or activates trigeminal nerve receptors. It also defines a new equilibrium coefficient for the partitioning of organic compounds between an airstream and particles collected by a filter in that airstream. Gas/particle partitioning has been studied extensively outdoors, but sparingly indoors. Gas/surface partitioning occurs primarily indoors while gas/filter partitioning occurs at the interface between outdoors and indoors. Activation of trigeminal nerve receptors occurs at the human interface. The logarithm of an organic compound's saturation vapor pressure correlates in a linear fashion with the logarithms of equilibrium coefficients characteristic of each of these four phenomena. Since, to a rough approximation, the log of an organic compound's vapor pressure scales with its molecular weight, molecular weight can be used to make first estimates of the above processes. For typical indoor conditions, only larger compounds with lower-saturation vapor pressures (e.g., tetracosane, pentacosane, or di-2-ethylhexyl phthalate) have airborne particle concentrations comparable to or larger than gas phase concentrations. Regardless of a compound's vapor pressure, the total mass sorbed on indoor airborne particles is quite small compared to the total sorbed on indoor surfaces, reflecting the large difference in surface areas between particles within a room and surfaces within a room. If the actual surface areas are considered, accounting for roughness and porosity, the surface concentration of organics sorbed on typical airborne particles appears to be comparable to the surface concentration of organics sorbed on indoor carpets, walls and other materials (based on data from several studies in the literature). Mirroring the importance of phase distributions outdoors, an organic compound's indoor lifetime, fate and even health impacts depend on its distribution between phases and among surfaces.     

Effects of a constructional intervention on airborne and deposited particulate matter in the Portuguese National Tile Museum, Lisbon

In the 1970s, a large ambulatory of the National Tile Museum, Lisbon, was closed with glass panes on both ground and first floor. Although this design was meant to protect the museum collection from ambient air pollutants, small openings between the glass panes remain, creating a semi-enclosed corridor. The effects of the glass panes on the indoor air quality were evaluated in a comparative study by monitoring the airborne particle concentration and the extent of particle deposition at the enclosed corridor as well as inside the museum building. Comparison of the indoor/outdoor ratio of airborne particle concentration demonstrated a high natural ventilation rate in the enclosed corridor as well as inside the museum building. PM₁₀ deposition velocities on vertical surfaces were estimated in the order of 3?×?10^?4 m s^?1 for both indoor locations. Also, the deposition rates of dark-coloured and black particles in specific were very similar at both indoor locations, causing visual degradation. The effectiveness of the glass panes in protecting the museum collection is discussed.     

Applicability of a modified MCE filter method with Button Inhalable Sampler for monitoring personal bioaerosol inhalation exposure

In this study, a “modified” mixed cellulose ester (MCE) filter culturing method (directly placing filter on agar plate for culturing without extraction) was investigated in enumerating airborne culturable bacterial and fungal aerosol concentration and diversity both in different environments. A Button Inhalable Sampler loaded with a MCE filter was operated at a flow rate of 5 L/min to collect indoor and outdoor air samples using different sampling times: 10, 20, and 30 min in three different time periods of the day. As a comparison, a BioStage impactor, regarded as the gold standard, was operated in parallel at a flow rate of 28.3 L/min for all tests. The air samples collected by the Button Inhalable Sampler were directly placed on agar plates for culturing, and those collected by the BioStage impactor were incubated directly at 26 °C. The colony forming units (CFUs) were manually counted and the culturable concentrations were calculated both for bacterial and fungal aerosols. The bacterial CFUs developed were further washed off and subjected to polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) for diversity analysis. For fungal CFUs, microscopy method was applied to studying the culturable fungal diversity obtained using different methods. Experimental results showed that the performance of two investigated methods varied with sampling environments and microbial types (culturable bacterial and fungal aerosols). For bacterial aerosol sampling, both methods were shown to perform equally well, and in contrast the “modified” MCE filter method was demonstrated to enumerate more culturable fungal aerosols than the BioStage impactor. In general, the microbial species richness (number of gel bands) was observed to increase with increasing collection time. For both methods, the DGGE gel patterns were observed to vary with sampling time and environment despite of similar number of gel bands. In addition, an increase in sampling time from 20 to 30 min was found not to substantially alter the species richness. Regardless of the sampling methods, more species richness was observed in the outdoor environment than the indoor environment. This study described a new personal bioaerosol exposure assessment protocol, and it was demonstrated applicable in monitoring the personal bioaerosol exposure in replace of an Andersen-type impactor.     

Pesticide dispersion by spraying under tropical conditions

Pesticide air pollution by spraying was evaluated under different temperature, humidity and wind climatic conditions in Brazil. Field experiments were performed with application towards the soil and in guava orchards, where spray dispersion was monitored by adding p-aminobenzoic acid (PABA), a fluorescent substance, as a tracer to the water contained in the spray tanks. Samples were collected with filter membranes (Whatman 180025), and the PABA was extracted from the filters by shaking with water in a Petri dish and measured in a spectrofluorometer. A spray aimed towards the soil with filters positioned on the ground and hung at different heights did not show different upward dispersion as observed when lateral pulverization was conducted. In this case, a tractor with a sprayer moved through a 3 m high and 6 m wide frame with filter membranes mounted at 60 cm intervals. Spray dispersion patterns were modified by guava leaf resistance. No influence of temperature and humidity was observed in this short-lived spraying process. Nevertheless, wind drift can occur during airborne dispersion and is an important pesticide pollution source which requires control. Droplets with PABA powered by assisted spraying upwards returned to the ground by gravity and, therefore, did not constitute a vertical source of atmospheric pollution.     

Optimization of a wet scrubber with electrolyzed water spray—Part II: Airborne culturable bacteria removal

Airborne microorganisms, especially the pathogenic microorganisms, emitted from animal feeding operations (AFOs) may harm the environment and public health and threaten the biosecurity of the farm and surrounding environment. Electrolyzed water (EW), which was considered to be an environmentally friendly disinfectant, may be a potential spraying medium of wet scrubber for airborne microorganism emission reduction. A laboratory test was conducted to investigate the airborne bacteria (CB) removal efficiency of the wet scrubber by EW spray with different designs and operating parameters. Both the available choline (AC) initial loss rate and AC traveling loss rate of acidic electrolyzed water (AEW; pH = 1.35) were much higher than those of slightly acidic electrolyzed water (SAEW; pH = 5.50). Using one spraying stage with 4 m sec^?1 air speed in the duct, the no detect lines (NDLs) of SAEW (pH = 5.50) for airborne Escherichia coli, Staphylococcus aureus, and Salmonella enteritidis removal were all 50 mg L^?1, whereas the NDLs of AEW (pH = 1.35) for airborne E. coli, S. aureus, and S. enteritidis removal increased to 70, 90, and 90 mg L^?1, respectively. The NDLs of SAEW (pH = 5.50) for airborne E. coli, S. aureus, and S. enteritidis were lower than those of AEW (pH = 1.35) at single spraying stage. Increase in the number of stages lowered the NDLs of both SAEW (pH = 5.50) and AEW (pH = 1.35) for airborne E. coli, S. aureus, and S. enteritidis. EW with a higher available chlorine concentration (ACC) was needed at air speed of 6 m sec^?1 to reach the same airborne CB removal efficiency as that at air speed of 4 m sec^?1. The results of this study demonstrated that EW spray wet scrubbers could be a very effective and feasible airborne CB mitigation technology for AFOs.

Implications: It is difficult to effectively reduce airborne bacteria emitted from animal feeding operations (AFOs). Electrolyzed water (EW) with disinfection effect and acidity is a potential absorbent for spray in wet scrubber to remove microorganisms and ammonia. Based on the field test results, a laboratory experiment we conducted this time was to optimize the design and operation parameters to improve the airborne bacteria removal efficiency. A better understanding of the EW application in the wet scrubber can contribute to the mitigation of airborne bacteria from animal houses and improve the atmosphere air quality.     

Closing Comments

Fine particles are those which penetrate into the respiratory system where they may act as a carcinogen, may contribute to blockage of the alveoli, or may accommodate pulmonary pathogens . Mr. Harrington observed that fine particles are not a single pollutant but a large category of pollutants. It is therefore difficult to agree on a general definition of fine particles as a pollutant. However, it has been shown that particles with diameters smaller than 5 µm do penetrate past the nasal cavity and nasopharynx into the lungs and that particles with diameters as small as 0.01 µm are deposited in the lungs. Other problems associated with submicron particles are that they are slow in settling out of the atmosphere and they create haze and adverse weather modification.     

Potential sources and meteorological factors affecting PM<Subscript>2.5</Subscript>-bound polycyclic aromatic hydrocarbon levels in six main cities of northeastern Italy: an assessment of the related carcinogenic and mutagenic risks

A yearlong sampling campaign (2012–2013) was conducted in six major cities of the Veneto region to investigate the spatial-temporal trends and the factors affecting the polycyclic aromatic hydrocarbon (PAHs) variations and identify the local sources. Sixty samples per city were collected for analyses in every alternate month (April, June, August, October, December, and February): 10 samples per sampling site in 10 consecutive days of the months selected. Samples were ultrasonically extracted with acetonitrile and processed through high-performance liquid chromatography. Total Σ-PAH concentrations ranged from 0.19 to 70.4 ng m^?3 with a mean concentration of 11.5 ng m^?3. The mean benzo[a]pyrene (BaP) concentration reached 2.0 ng m^?3, which is two-times higher than the limit set by the European Union. BaP contributed for 17.4% to the total concentration of PAHs, which showed the same pattern across the region with maxima during cold months and minima in the warm period. In this study, PAHs showed an inverse relationship with temperature, solar radiation, wind speed, and ozone. According to this study, biomass burning for household heating and cooking, followed by gaseous PAHs absorption on particles due to low atmospheric temperature, were the main reasons for increasing PAHs concentration in winter. Health risk, evaluated as lifetime lung cancer risk (LCR), showed a potential carcinogenic risk from the airborne BaP_TEQ six-fold higher in the cold season than in the warm one. Diagnostic ratios and conditional probability functions were used to locate the sources, and results confirmed that local emission, overall domestic heating, and road transport exhausts were responsible for higher concentration rates of PAHs as well as of PM_2.5.     

Dust build-up on surfaces in the indoor environment

The concentration and the composition of dust in the indoor environment has been associated with reported symptoms of the sick building syndrome. Levels of airborne concentrations of dust particles are well known. However, the relation to dust on surfaces for office environments are not well described. In this study, 662 measurements were performed of surface dust concentrations on hard surfaces in 19 buildings within Harvard University based on a sticking gelatine foil method. The measure is the dust covered area of the surface as a percentage. In three offices, the build-up of dust on surfaces was measured for a period of five days. Close to these surfaces the airborne PM_2.5 and PM₁₀ particle mass concentrations were measured simultanously. A significant correlation between the dust build-up and the difference between the PM₁₀ and the PM_2.5 was established. The particle size distribution was measured by means of an Aerodynamic Particle Sizer. The mean dust build-up normalized with the measured PM₁₀ was approximately four times higher than the equivalent calculated by a deposition model. This may in part be due to the effect of preferred orientation when particles settle to a surface. Different data for dust on surfaces and airborne particles in offices were compared. The levels of airborne particles in offices in Europe seem to be higher than the levels in the US.     

The Identification and Determination of Airborne Particulates By Means of the Ring Oven Technique

The ring oven technique was first introduced as a means for conducting separations and concentrations on filter paper for final spot test analysis. By means of the technique, a complete qualitative scheme of separation and analysis can be made on a single drop of unknown. Recently, the effectiveness of the ring oven as a tool for quantitative analysis has been recognized. The method is particularly attractive for studies of airborne particulates. Samples of airborne particulates can be collected by high volume samplers, tape samplers, electrostatic precipitators, or by other appropriate means. The samples may be put into solution and an aliquot added to filter paper on a ring oven and washed to the ring zone for final identification and estimation. Any necessary separations can normally be carried out during the ring oven operations. A convenient approach for most studies is to collect the samples on tapes and carry out the necessary dissolution, separation, identification, and estimation steps directly on the tape itself. The ring oven methods are usually selective or even specific. The method applies to the microgram to nanogram range and the accuracies are comparable with those obtained by emission spectroscopy, polarography, fluorimetry, and spectrophotometry.     

Concentration and size distribution of particulate matter in a new aviary system for laying hens in China

ABSTRACT

Particulate matter (PM) from poultry production facilities may strongly affect the health of animals and workers in the houses, and PM emitted to the ambient air is an important pollution source to the surrounding areas. Aviary system is considered as a welfare friendly production system for laying hens. However, its air quality is typically worse as compared with conventional cage systems, because of the higher PM concentration of indoor air and other airborne contaminants. Furthermore, PM’s physical property, which has a direct impact on the penetration depth into the lungs of the birds and humans, is largely unknown for the aviary system. Therefore, a systematic method was utilized to investigate the characteristics of particles in the aviary house with large cage aviary unit system (LCAU) in Beijing, China. For the field measurements, three measuring locations were selected with two inside and one outside the house with LCAU to continuously monitor PM concentrations and collect the samples for particle size distribution (PSD) analysis. Results showed that PM_2.5, PM₁₀, and total suspended particulate (TSP) concentrations averaged at 0.037 ± 0.025 mg/m³, 0.42 ± 0.10 mg/m³, and 1.92 ± 1.91 mg/m³, respectively. Particle concentrations increased from October to December due to less ventilation as the weather got colder, and were generally affected by stocking density, ventilation rate, birds’ activities, and housing system. Meanwhile, indoor PM_2.5 concentration was easily impacted by the ambient air quality. Mass median diameter (MMD) and mass geometric standard deviation (MGSD) of the TSP during the measurement were 18.92 ± 7.08 μm and 3.11 ± 0.31, respectively. Count median diameter (CMD) and count geometric standard deviation (CGSD) were 1.94 ± 0.14 μm and 1.48 ± 0.08, respectively. Results indicated that the aviary system can attain a good indoor condition by suitable system design and environment control strategy.

Implications: Indoor PM_2.5 concentration of the layer house can be significantly affected by ambient air quality when the air quality index (AQI) was larger than 100. PM_2.5 and PM₁₀ concentrations of the layer house with a LCAU system were comparable to the cage system. TSP concentration was higher, and PM size was larger than most of the cage system. System design, larger space volume, and higher ventilation rate were the main influence factors. Good indoor environment of the aviary system can be achieved through the reasonable design of the production system and appropriate environment control strategy.     

Airborne particulate matter around the Cathedral of Burgos (Castilla y León,Spain)

A methodology to collect and analyse atmospheric particulate matter has been developed at the Cathedral of Burgos (Spain). Particles were collected in a portable particle sampler on carbon layers and stone surfaces. The analyses were undertaken under SEM-EDX by means X-ray mapping and Featurescan (a program for the automated characterisation of particles). To determine their possible sources, particles collected in the sampler and on carbon layers were classified according to their composition, mainly by cluster analysis. Then, they were compared with those deposited on stone surfaces. This classification is useful when a plan of preventive conservation for monuments is to be undertaken. In general, no important differences are observed between the chemical composition of particles directly collected from the atmosphere and those deposited on different substrates. Fine particles present the highest sulphur contents (almost 100%), while calcium is the major element in the medium and coarse particles. Other abundant elements are silicon, chlorine and phosphorus. The number of iron-rich particles is small. The study of the material deposited on carbon layers and stone substrates has confirmed the presence of gypsum in all cases.     

The influence of aerosol dynamics on indoor exposure to airborne DEHP

A mass-balance model was extended to investigate the influence of aerosol particles on the accumulation of indoor airborne DEHP, which allows the consideration of a variable particle concentration. The calculated gas-phase di-2-ethylhexyl phthalate (DEHP) concentration is consistent with those measured within residences in both the United States and Europe. Model predictions suggest that there are differences of more than 10% of particle-phase DEHP concentrations between the variable-particle-concentration case and the constant one for over half (578 days) within the calculation time of 1000 days. Airborne DEHP consists primarily of a particle phase. The exposure data indicate that the influence of particle dynamics remains significant throughout the calculation period, and the size fraction of 0–0.5 μm contributes the most, at 39.1%, to the total exposure to particle-phase DEHP as a result of a strong “source” effect which brings particles into the indoor air and a weak “sink” effect which removes particles from the indoor air. The sensitivity analysis indicates that deposition exhibits the most apparent influence, and particle emission from cooking is a significant factor, as cooking is the main source of particles in the size fraction of 0–0.5 μm. The sensitivity analysis also shows that particle penetration has a less obvious influence on the exposure to airborne DEHP because air exchange rate caused penetration introduces and removes particles simultaneously, thus having a limited influence on the airborne DEHP; while resuspension exhibits the weakest influence because it contributes little to the small particles which are the main component of aerosol particles indoors. Strategies for enhancing deposition and reducing particle emissions from cooking and penetration may be helpful to reduce residents’ exposure to airborne SVOCs.     

Sampling and analysis of biological aerosols

The extreme particle size range and enormous heterogeneity of airborne biological particles make sampling a significant challenge. Three major sampler types available include gravity devices, impactors and suction samplers. Gravity methods, while most commonly used, are neither qualitatively or quantitatively accurate and of very limited use. Impaction samplers (rotating, centrifugal) accelerate air by rotating the collecting surface or with a fan. Particles are collected from measured volumes of air but these devices preferentially sample particles larger than 10 μm. Suction samplers, which efficiently collect particles of a wide size range from measured volumes of air, include slit samplers, cascade impactors, filtration devices and liquid impingers. Suction samplers can retrieve viable particles by direct impaction on culture media, or by subsequent culture of impinger fluid or filter eluates. Nonviable particles can often be identified by microscopic examination of slides, filters or filtrates of impinger fluids. Immunoassays and biochemical assays can be used with impinger fluid and filter eluates to assess antigen and toxin levels in measured air samples.     

Mercury in compact fluorescent lamps (CFLs): European legislation introduces an avoidable analytical bias

European legislation has set a limit of 5 mg Hg per compact fluorescent lamp (CFL). Compliance with this regulation is tested with a method given in a European law from 2002 (“EU method”). According to the EU method, the arc tube has to be placed inside a fume cupboard and cut into segments. These pieces are collected and washed with HNO₃, which is finally analyzed for Hg. In this study, we investigated the losses of Hg via the gas phase, which are ignored by the EU method, using a semiquantitative radiochemical neutron activation analysis (RNAA) technique developed at the TRIGA Mark II reactor in Vienna (Austria). Depending on the product, the losses range as high as approximately 2 % at 20 °C. At higher ambient temperatures (hot summer days), the losses may increase by a factor of 4. Quality products generally suffer lower emission via the gas phase than cheap products, which is probably due to amalgam or other techniques that retain the Hg from broken CFLs. In any case, the EU method introduces a small but avoidable systematic error into the analysis and, in contrast to recommended practices, underestimates the Hg content of the CFL in question. Having technical alternatives at hand, we urge European lawmakers to adjust the law accordingly.     

Evaluating the capabilities of Aerosol-to-Liquid Particle Extraction System (ALPXS)/ICP-MS for monitoring trace metals in indoor air

This study investigates the application of the Aerosol-to-Liquid Particle Extraction System (ALPXS), which uses wet electrostatic precipitation to collect airborne particles, for multi-element indoor stationary monitoring. Optimum conditions are determined for capturing airborne particles for metal determination by inductively coupled plasma–mass spectrometry (ICP-MS), for measuring field blanks, and for calculating limits of detection (LOD) and quantification (LOQ). Due to the relatively high flow rate (300 L min^?1), a sampling duration of 1 hr to 2 hr was adequate to capture airborne particle-bound metals under the investigated experimental conditions. The performance of the ALPXS during a building renovation demonstrated signal-to-noise ratios appropriate for sampling airborne particles in environments with elevated metal concentrations, such as workplace settings. The ALPXS shows promise as a research tool for providing useful information on short-term variations (transient signals) and for trapping particles into aqueous solutions where needed for subsequent characterization. As the ALPXS does not provide size-specific samples, and its efficiency at different flow rates has yet to be quantified, the ALPXS would not replace standard filter-based protocols accepted for regulatory applications (e.g., exposure measurements), but rather would provide additional information if used in conjunction with filter based methods.

ImplicationsThis study investigates the capability of the Aerosol-to-Liquid Particle Extraction System (ALPXS) for stationary sampling of airborne metals in indoor workplace environments, with subsequent analysis by ICP-MS. The high flow rate (300 L/min) permits a short sampling duration (< 2 hr). Results indicated that the ALPXS was capable of monitoring short-term changes in metal emissions during a renovation activity. This portable instrument may prove to be advantageous in occupational settings as a qualitative indicator of elevated concentrations of airborne metals at short time scales.     

Effect of temperature and particle size on the thermal desorption of PCBs from contaminated soil

Thermal desorption is widely used for remediation of soil contaminated with volatiles, such as solvents and distillates. In this study, a soil contaminated with semivolatile polychlorinated biphenyls (PCBs) was sampled at an interim storage point for waste PCB transformers and heated to temperatures from 300 to 600 °C in a flow of nitrogen to investigate the effect of temperature and particle size on thermal desorption. Two size fractions were tested: coarse soil of 420–841 μm and fine soil with particles <250 μm. A PCB removal efficiency of 98.0 % was attained after 1 h of thermal treatment at 600 °C. The residual amount of PCBs in this soil decreased with rising thermal treatment temperature while the amount transferred to the gas phase increased up to 550 °C; at 600 °C, destruction of PCBs became more obvious. At low temperature, the thermally treated soil still had a similar PCB homologue distribution as raw soil, indicating thermal desorption as a main mechanism in removal. Dechlorination and decomposition increasingly occurred at high temperature, since shifts in average chlorination level were observed, from 3.34 in the raw soil to 2.75 in soil treated at 600 °C. Fine soil particles showed higher removal efficiency and destruction efficiency than coarse particles, suggesting that desorption from coarse particles is influenced by mass transfer.     

Zn isotope study of atmospheric emissions and dry depositions within a 5 km radius of a Pb–Zn refinery

The present paper examines the use of zinc isotopes as tracers of atmospheric sources and focuses on the potential fractionation of Zn isotopes through anthropogenic processes. In order to do so, Zn isotopic ratios are measured in enriched ores and airborne particles associated with pyrometallurgical activities of one of the major Pb–Zn refineries in France. Supporting the isotopic investigation, this paper also compares morphological and chemical characteristics of Zn particles collected on dry deposition plates (“environmental samples”) placed within a 5 km radius of the smelter, with those of Zn particles collected inside the plant (“process samples”), i.e. dust collected from the main exhaust system of the plant. To ensure a constant isotopic “supply”, the refinery processed a specific set of ores during the sampling campaigns, as agreed with the executive staff of the plant. Enriched ores and dust produced by the successive Zn extraction steps show strong isotope fractionation (from ?0.66 to +0.22‰) mainly related to evaporation processes within the blast furnaces. Dust from the main chimney displays a δ⁶⁶Zn value of ?0.67‰. Application of the Rayleigh equation to evaluate the fractionation factor associated with the Zn vapor produced after a free evaporation gives a range of α_ore/vapor from 1.0004 to 1.0008. The dry deposits, collected on plates downwind of the refinery, display δ⁶⁶Zn variations of up to +0.7‰. However, it is to be noted that between 190 and 1250 m from the main chimney of the refinery, the dry deposits show a high level of large (>10 μm) Zn, S, Fe and O bearing aggregates characterized by positive δ⁶⁶Zn values (+0.02 to +0.19‰). These airborne particles probably derive from the re-suspension of slag heaps and local emissions from the working-units. In contrast, from 1720 to 4560 m, the dry deposits are comprised of small (PM10) particles, including spherical Zn-bearing aggregates, showing negative δ⁶⁶Zn values (?0.52 to ?0.02‰). Our results suggest that the source of the distal dry fallouts is the main chimney plume, whose light Zn isotopic signature they preserve. Based on Zn isotopic analysis in combination with morphological and chemical characteristics of airborne particles, the present study suggests the traceability of smelter dusts by Zn isotopes.     

The assessment of particulate matter emitted from stone-crushing industry by correlating rock textures with particles generated after comminution and dispersed in air environment

The generation and emission of particulate matter from abrasion industry are subjects of the pollution monitoring by multidisciplinary study involving earth sciences and engineering disciplines. This work investigates the correlation between textural properties of in situ rock with class size distribution and morphology of particles generated after rock comminution and particles emitted in the air. A special comminution-dust sampling architecture was realised. The combined use of scanning electron microscopy and particle size analyser was considered in performing digital image analysis on both crushed products and airborne particles collected onto membrane filters. The results show that the size and morphology of crushed particles are linked to the petrographic rock properties. In particular, particles with fibrous morphology are prominent in rocks showing foliated textures where elongated minerals occurred, with implication for asbestos-bearing rocks. For what concerns the airborne particles, the results show that their aerodynamic diameters are independent of the crusher operating conditions. External parameters probably intervene in the distribution of the airborne particles emission, including the dynamic air fluxes, or environmental conditions. By applying mathematical models, the morphology and size range of airborne particles following the comminution processes can be predicted, and results has implication for pollutants contamination due to particulate matters emitted by crush stone industry.     

Covariations in the concentrations of organic compounds associated with springtime atmospheric aerosols

Organic compounds that can be thermally desorbed from airborne particles change cohesively with time, providing information about sources, photochemical transformations and transport of aerosols. In the spring of 1985, 138 airborne particulate samples were collected at an urban site in Boulder, Colorado. Samples were collected by drawing approximately 300 ℓ of air, for 58 min, through a small glass tube containing a quartz fiber filter. Particles were subsequently analyzed by direct thermal desorption of volatile organic compounds into a gas Chromatographic column followed by separation and detection of compounds with flame ionization or mass spectrometry. Factor analysis on the concentrations of 42 organic compounds in 138 1-h samples with time and meteorology revealed characteristic chromatograms for photochemical activity, biological sources and motor vehicle sources. Organic compounds desorbed from particles include terpenoids from biogenic sources, alkanes from vehicular and biological sources and aldehydes, ketones, carboxylic acids, lactones and furans from photochemical transformations and other sources. Concentrations of oxygenated species increased on sunny days relative to cloudy days or nights. Terpenoid concentrations increased when the wind direction was from a forested region west of the sampling site. Odd carbon number n-alkanes increased as temperature increased with the progression of springtime.