Ultrafine Fraction Research Articles

Environmentally Relevant Iron Oxide Nanoparticles Produce Limited Acute Pulmonary Effects in Rats at Realistic Exposure Levels.

Iron is typically the dominant metal in the ultrafine fraction of airborne particulate matter. Various studies have investigated the toxicity of inhaled nano-sized iron oxide particles (FeOxNPs) but their results have been contradictory, with some indicating no or minor effects and others finding effects including oxidative stress and inflammation. Most studies, however, did not use materials reflecting the characteristics of FeOxNPs present in the environment. We, therefore, analysed the potential toxicity of FeOxNPs of different forms (Fe3O4, α-Fe2O3 and γ-Fe2O3) reflecting the characteristics of high iron content nano-sized particles sampled from the environment, both individually and in a mixture (FeOx-mix). A preliminary in vitro study indicated Fe3O4 and FeOx-mix were more cytotoxic than either form of Fe2O3 in human bronchial epithelial cells (BEAS-2B). Follow-up in vitro (0.003, 0.03, 0.3 µg/mL, 24 h) and in vivo (Sprague–Dawley rats, nose-only exposure, 50 µg/m3 and 500 µg/m3, 3 h/d × 3 d) studies therefore focused on these materials. Experiments in vitro explored responses at the molecular level via multi-omics analyses at concentrations below those at which significant cytotoxicity was evident to avoid detection of responses secondary to toxicity. Inhalation experiments used aerosol concentrations chosen to produce similar levels of particle deposition on the airway surface as were delivered in vitro. These were markedly higher than environmental concentrations. No clinical signs of toxicity were seen nor effects on BALF cell counts or LDH levels. There were also no significant changes in transcriptomic or metabolomic responses in lung or BEAS-2B cells to suggest adverse effects.

Urinary Oxidative Stress Biomarkers in Workers of a Titanium Dioxide Based Pigment Production Plant.

Titanium dioxide is produced or imported into the EU for over one million tons/year. The International Agency for Research on Cancer (IARC) classification is 2B, a possible inhalation carcinogen for humans. This study evaluates urinary biomarkers of oxidative stress in workers of a plant producing TiO2 pigment powder, having 0.25 µm average particle size and an ultrafine fraction, compared to unexposed subjects. Urine samples were collected from forty workers before and after the shift, from six employees of the same company and eighteen volunteers from the same geographical area. Titanium and other metals concentrations were measured by ICP-MS, while DNA, RNA, and protein oxidation products by HPLC/MS-MS. A statistically significant increase was found for the urinary concentration of Al, Cd, Cr, Cu, Fe, Mn, Pb, Ti, and Zr, and for all biomarkers of oxidative stress in post-shift workers’ urine samples. Urinary concentrations after the working shift were higher than for employees and volunteers pooled together for Cd, Mn, and Zr, and for the oxidative stress biomarkers 8-oxoGuo, 8-oxodGuo, and 3NO2Tyr. Biomonitoring studies on dose and effect biomarkers for TiO2 occupational exposure provide information useful for protecting workers’ health even in conditions that comply with health and safety standards, highlighting reversible effects of chronic exposure at very low doses.

Microstructural Changes and Strengthening of Austenitic Stainless Steels during Rolling at 473 K

The microstructural changes in 304L and 316L austenitic stainless steels during plate rolling with 95% rolling reduction at a temperature of 473 K and their effect on strengthening were studied. The microstructure evolution was associated with deformation twinning and microshear banding. The latter ones involved ultrafine crystallites, which rapidly evolved in strain-induced ultrafine austenite grains as a result of fast increase in misorientations between them. Besides the ultrafine austenite crystallite evolution, the microshear bands assisted local appearance of deformation martensite, which attained about 25 vol.% and 3 vol.% at total strain of 3 in 304L and 316L steels, respectively. Both the microshear banding and the martensitic transformation promoted the formation of ultrafine grains with a size of less than 1 µm. The strain dependence of the ultrafine grain fraction obeyed a modified Johnson-Mehl-Avrami-Kolmogorov function. The deformation grain size and dislocation density that develop during rolling could also be expressed by exponential functions of true strain. Incorporating the revealed relationships between the strain and the microstructural parameters into modified Hall–Petch-type equation, unique expression for the yield strength of processed steels was obtained. The dislocation strengthening was the largest contributor to the strength, especially at small to medium strains, although grain size strengthening increased during rolling approaching that from dislocations at large strains.

SIZE DISTRIBUTION AND CONTRIBUTION OF PARTICLES FROM RICE STRAW OPEN BURNING TO THE ATMOSPHERE IN HANOI

Atmospheric ultrafine, accumulation mode and coarse fractions collected at representative rice straw open burning areas in Hanoi were investigated to identify characteristics of size distribution and contribution of particles emitted from rice straw (RS) burning season to the atmosphere. The sampling was conducted in two episodes: RS burning episode and RS non-burning episode at Dong Anh and Quoc Oai, in seven consecutive days for each sampling campaign from 2018 to 2019. In the RS burning episode, PM1-2.5 showed the highest fraction among all collected particles in both sampling sites, while PM2.5-10 was the most abundant in RS non-burning season. The average mass concentration of PM2.5 in RS burning period and RS non-burning period were 79.7  46.5 g m-3 and 65.2  21.9 g m-3, respectively at Dong Anh sampling site. Those values were 90.9  33.2 g m-3 in the QO_RS burning site and 71.9  29.3 g m-3 in the TM_RS non-burning site. The proportion of fine particle (PM2.5) at both sites were considerable higher in RS burning period as compared to non-burning period, while the concentration of ultrafineparticle (PM0.1) and coarse particle (PM>10m) were similar between two episodes. This result provides better understanding on size distribution and contribution of fine particles from open RS burning to the atmosphere in Hanoi, which is an useful information for the environmental managers to control RS open burning in Hanoi as well as in Vietnam.

Biotransformation of Food-Grade and Nanometric TiO2 in the Oral-Gastro-Intestinal Tract: Driving Forces and Effect on the Toxicity toward Intestinal Epithelial Cells.

Background: Oral exposure to titanium dioxide (TiO2) is common since it is widely used in food and pharmaceutical products. Concern on the safety of this substance has been recently raised, due to the presence of an ultrafine fraction in food-grade TiO2. Discrepancy exists among data reported in in vitro and in vivo studies on intestinal acute/chronic toxicity of TiO2. This might be due to the different biological identity of TiO2 in traditional in vitro test by respect in vivo conditions. Methods: One food-grade TiO2 and two nanometric TiO2 samples were treated with a simulated human digestive dystem (SHDS) in order to investigate the bio-transformation occurring to the particles once ingested in term of size distribution (Dynamic Light Scattering—DLS-, Flow Particle Imaging, Asymmetric Flow Field Flow Fractionation-AF4-) and surface modification (Electrophoretic Light Scattering—ELS-, Electron Paramagnetic Resonance Spectroscopy—EPR-). The effect of SHDS on the cyto-, genotoxicity and potential to induce oxidative stress towards human colorectal carcinoma HCT116 cells was also assessed. Results: Aggregation as a consequence of the high ionic strength of the gastric and intestinal simulated fluids was observed, together with the formation of a partially irreversible bio-corona containing phosphate ions and proteins. Such bio-corona led to a partial masking of the TiO2 particles surface and reactivity. Pristine and treated TiO2 nanoparticles showed comparable acute toxicity and genotoxicity toward HCT116 cells, whereas a small decrease of the induction of oxidative stress after treatment was observed. Conclusions: Overall the results underline the importance of SHDS as a tool to improve the predictive power of in vitro tests towards intestinal nanomaterial toxicity.

Characterization and washability of Pakistani bituminous coal from Punjab

ABSTRACT Pre-combustion cleaning techniques are used to remove unwanted impurities and environmentally harmful constituents in coal. In this study, gross samples collected from seven zones of Punjab coalfield were separately subjected to sizing into coarse (+25 mm), intermediate (–25 + 1.168 mm), fine (–1.168 + 0.147 mm), and ultrafine (–0.147 mm) fractions. Proximate and ultimate components, forms of sulfur and gross calorific value of all size fractions and the composite sample of each zone coal were determined. Float-sink tests were conducted on coarse, intermediate and fine fractions. The results show that Punjab coal contains moisture, ash, volatile matter, and fixed carbon in the range of 2.28–4.61%, 34.13–51.59%, 26.72–34.25%, and 18.17–28.92%, respectively, belonging to high volatile bituminous B and C categories. The large proportion of mass lies in the intermediate size range for Chambel (63.10%), Dandot (60.27%), Trans-Indus (54.83%), Dalwal (52.20%), and Ara-Basharat (47.22%) coals whereas coarse particles constitute the major proportion of Padhrar (47.92%) and Jhelum (45.83%) coals. At 16% target ash content, the overall clean coal yield achievable for Jhelum, Ara-Basharat, Dandot, Dalwal, Padhrar, Chambel, and Trans-Indus zone coals were found as 16.32%, 20.76%, 37.20%, 48.59%, 46.29%, 70.43%, and 67.40% with sulfur contents of 2.89%, 2.80%, 2.90%, 3.57%, 4.28%, 3.89%, and 4.21%, respectively. The extent of coal cleaning was found higher for the Central Salt Range (Padhrar and Chambel zone) and Western Punjab (Trans-Indus zone) coals than the Eastern Salt Range (Jhelum, Ara-Basharat, Dandot and Dalwal zone) coals based on their degrees of washing and S-values. Padhrar coal exhibits the best washing characteristics as revealed by its highest S-value of 78.5.

A closer look at mineral aerosol emissions from the Makgadikgadi Pans, Botswana, using automated SEM-EDS (QEMSCAN®)

ABSTRACT This paper demonstrates the use of Quantitative Evaluation of Minerals by SCANning electron microscopy (QEMSCAN®), an automated scanning microscopy technique, which combines scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), providing ultra-fast analysis of particle grains at a micron-scale resolution. We evaluate its application in aerosol studies by comparing surface and airborne samples from the Makgadikgadi Pan in Botswana. The playa is a major global dust emitter and its aerosols have a widespread effect on atmospheric, biological and terrestrial processes. Sampling was conducted at a carefully selected surface location and associated BSNE dust trap stack at 0.25, 0.5, 0.85 1.65 meters. The dominant minerals identified here are quartz, halite, thernadite, mica, calcite and feldspar. Surface sample results from QEMSCAN are in line with other forms of elemental and mineralogical analyses. When comparing surface samples with elevated trap samples, we noted a fining and fractionation during grain entrainment, resulting in a compositional shift with height. We also observed some ultra-fine fraction losses from the BSNE traps. Overall, the single location here establishes the link between fluvial playa basin inputs, sediment storage, evaporation products and aeolian losses and outputs from a dry lake surface, not unlike semi-arid evaporative dust sources elsewhere.

Toxicity of iron nanoparticles towards primary cultures of human bronchial epithelial cells.

Air pollution is a public health issue and the toxicity of ambient particulate matter (PM) is well-recognized. Although it does not mostly contribute to the total mass of PM, increasing evidence indicates that the ultrafine fraction has generally a greater toxicity than the others do. A better knowledge of the underlying mechanisms involved in the pathological disorders related to nanoparticles (NPs) remains essential. Hence, the goal of this study was to determine better whether the exposure to a relatively low dose of well-characterized iron-rich NPs (Fe-NPs) might alter some critical toxicological endpoints in a relevant primary culture model of human bronchial epithelial cells (HBECs). We sought to use Fe-NPs representative of those frequently found in the industrial smokes of metallurgical industries. After having noticed the effective internalization of Fe-NPs, oxidative, inflammatory, DNA repair, and apoptotic endpoints were investigated within HBECs, mainly through transcriptional screening. Taken together, these results revealed that, despite it only produced relatively low levels of reactive oxygen species without any significant oxidative damage, low-dose Fe-NPs quickly significantly deregulated the transcription of some target genes closely involved in the proinflammatory response. Although this inflammatory process seemed to stay under control over time in case of this acute scenario of exposure, the future study of its evolution after a scenario of repeated exposure could be very interesting to evaluate the toxicity of Fe-NPs better.

Ultrafine particles in scanning sprays: a standardized examination of five powders used for dental reconstruction

BackgroundIntraoral matting sprays for chairside systems can release fine or ultrafine particles or nanoparticles at dentists’ workplaces and cause work-related health problems by inhalation exposure. Until now, little is known about the magnitude of the ultrafine fraction, when using these scanning sprays. Hence, more information is needed for workplace risk assessments in dental practices.MethodsFive commonly used dental spray-powders were examined under standardized conditions. Ingredients were taken from the respective safety data sheet. Particle number-size distributions and total number concentrations were analyzed with a fast mobility particle sizer, and reported graphically as well as mean particle fractions smaller than 100 nm. Based on these measurements, risk assessments were conducted, and particle depositions in the lung were modelled.ResultsThe mean fraction of particles smaller than 100 nm varied between 9 and 93% depending on the matting agent and mode of application of the intraoral scanning spray. Propellants can represent a large fraction of these particles. Titanium dioxide, pigment-suspensions, talcum and others particles, which can pose relevant health risks, were listed as ingredients of scanning sprays in safety data sheets. Nevertheless, the deposited fraction of hazardous particles in the lung of employees in dental practices seems to be small (15%) during this dental procedure.ConclusionsOur results suggest that dentists’ personnel can be exposed to hazardous fine and ultrafine particles. Though extensive standardized measurements and systematic evaluation of safety data sheets were used for this study, they cannot sufficiently assess and categorize potential workplace-related health risks.

Mitochondrial alterations triggered by repeated exposure to fine (PM2.5-0.18) and quasi-ultrafine (PM0.18) fractions of ambient particulate matter

Nowadays ambient particulate matter (PM) levels still regularly exceed the guideline values established by World Health Organization in most urban areas. Numerous experimental studies have already demonstrated the airway toxicity of the fine fraction of PM (FP), mainly triggered by oxidative stress-induced airway inflammation. However, only few studies have actually paid close attention to the ultrafine fraction of PM (UFP), which is likely to be more easily internalized in cells and more biologically reactive. Mitochondria are major endogenous sources of reactive oxygen species (ROS) through oxidative metabolism, and coordinate many critical cellular signaling processes. Mitochondria have been often studied in the context of PM toxicity and generally associated with apoptosis activation. However, little is known about the underlying adaptation mechanisms that could occur following exposure at sub-apoptotic doses of ambient PM. Here, normal human bronchial epithelial BEAS-2B cells were acutely or repeatedly exposed to relatively low doses (5 µg.cm−2) of FP (PM2.5-0.18) or quasi-UFP (Q-UFP; PM0.18) to better access the critical changes in mitochondrial morphology, functions, and dynamics. No significant cytotoxicity nor increase of apoptotic events were reported for any exposure. Mitochondrial membrane potential (ΔΨm) and intracellular ATP content were also not significantly impaired. After cell exposure to sub-apoptotic doses of FP and notably Q-UFP, oxidative phosphorylation was increased as well as mitochondrial mass, resulting in increased production of mitochondrial superoxide anion. Given this oxidative boost, the NRF2-ARE signaling pathway was significantly activated. However, mitochondrial dynamic alterations in favor of accentuated fission process were observed, in particular after Q-UFP vs FP, and repeated vs acute exposure. Taken together, these results supported mitochondrial quality control and metabolism dysfunction as an early lung underlying mechanism of toxicity, thereby leading to accumulation of defective mitochondria and enhanced endogenous ROS generation. Therefore, these features might play a key role in maintaining PM-induced oxidative stress and inflammation within lung cells, which could dramatically contribute to the exacerbation of inflammatory chronic lung diseases. The prospective findings of this work could also offer new insights into the physiopathology of lung toxicity, arguably initiate and/or exacerbate by acutely and rather repeated exposure to ambient FP and mostly Q-UFP.

Assessment of Air Quality in School Environments in Hanoi, Vietnam: A Focus on Mass-Size Distribution and Elemental Composition of Indoor-Outdoor Ultrafine/Fine/Coarse Particles

Indoor and outdoor ultrafine, accumulation mode, and coarse fractions collected at two preschools (S1 and S2) in Hanoi capital, Vietnam were characterized in terms of mass-size distribution and elemental composition to identify major emission sources. The sampling campaigns were performed simultaneously indoors and outdoors over four consecutive weeks at each school. Indoor average concentrations of CO2 and CO at both schools were below the limit values recommended by American Society of Heating, Refrigerating and Air-Conditioning Engineers (1000 ppm for CO2) and World Health Organization (7 mg/m3 for CO). Indoor concentrations of PM2.5 and PM10 at S1 and S2 were strongly influenced by the presence of children and their activities indoors. The indoor average concentrations of PM2.5 and PM10 were 49.4 µg/m3 and 59.7 µg/m3 at S1, while those values at S2 were 7.9 and 10.8 µg/m3, respectively. Mass-size distribution of indoor and outdoor particles presented similar patterns, in which ultrafine particles accounted for around 15–20% wt/wt while fine particles (PM2.5) made up almost 80% wt/wt of PM10. PM2.5–10 did not display regular shapes while smaller factions tended to aggregate to form clusters with fine structures. Oxygen (O) was the most abundant element in all fractions, followed by carbon (C) for indoor and outdoor particles. O accounted for 36.2% (PM0.5–1) to 42.4% wt/wt (PM0.1) of indoor particles, while those figures for C were in the range of 14.5% (for PM0.1) to 18.1% (for PM1–2.5). Apart from O and C, mass proportion of other major and minor elements (Al, Ca, Cr, Fe , K, Mg, Si, Ti) could make up to 50%, whereas trace elements (As, Bi, Cd, Co, Cr, Cu, La, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, and Zn) accounted for less than 0.5% of indoor and outdoor airborne particles. There were no significant indoor emission sources of trace and minor elements. Traffic significantly contributed to major and trace elements at S1 and S2.

Possible morphological similarities between lunar dust particles and interplanetary dust particles collected from earth's atmosphere

This paper shows morphological similarity between aggregates separated from the lunar regolith ultra-fine size fraction and interplanetary dust particles (IDPs) collected in Earth’s stratosphere. It also demonstrates morphological difference between mentioned above and cometary particles from comet Wild 2 collected in the “Stardust” project. Given the number of lunar meteorites found on Earth, the Moon’s proximity to Earth, and its large surface area subject to high energy meteoroid impacts, makes it highly likely that all size spectrum of material ejected from lunar surface may have been grazed by Earth.

Upregulation of epithelial metallothioneins by metal-rich ultrafine particulate matter from an underground railway.

Airborne particulate matter (PM) is a leading cause of mortality and morbidity. However, understanding of the range and mechanisms of effects of PM components is poor. PM generated in underground railways is rich in metals, especially iron. In the ultrafine (UFPM; <0.1 μm diameter) fraction, the combination of small size and metal enrichment poses an unknown health risk. This study aimed to analyse transcriptomic responses to underground UFPM in primary bronchial epithelial cells (PBECs), a key site of PM deposition. The oxidation state of iron in UFPM from an underground station was determined by X-ray absorption near edge structure (XANES) spectroscopy. Antioxidant response was assayed using a reporter cell line transfected with an antioxidant response element (ARE)-luciferase construct. Differentiated PBECs were exposed to UFPM for 6 h or 24 h for RNA-Seq and RT-qPCR analysis. XANES showed predominance of redox-active Fe3O4, with ROS generation confirmed by induction of ARE-luciferase expression. 6 h exposure of PBECs to UFPM identified 52 differentially expressed genes (DEGs), especially associated with epithelial maintenance, whereas 24 h exposure yielded 23 DEGs, particularly involved with redox homeostasis and metal binding. At both timepoints, there was upregulation of members of the metallothionein family, low molecular weight proteins with antioxidant activity whose main function is binding and homeostasis of zinc and copper ions, but not iron ions. This upregulation was partially inhibited by metal chelation or ROS scavenging. These data suggest differential regulation of responses to metal-rich UFPM depending on exposure period, and highlight novel pathways and markers of PM exposure, with the role of metallothioneins warranting further investigation.

Experimental evaluation of the in-the-field capabilities of total-reflection X-ray fluorescence analysis to trace fine and ultrafine aerosol particles in populated areas

European countries have made progress in reducing particulate air pollution in recent decades being concerned about their heath and climate effect. In addition to determining particulate number size distributions, it is crucial to have a methodology to determine size distribution of elemental concentrations down to the ultrafine size fraction. The present study shows capabilities for combination of May-type cascade impactor sampling and laboratory total-reflection X-ray fluorescence analysis on ambient aerosol samples taken in urban areas of Budapest (Hungary) and Cassino (Italy). In addition, results for a sample collected in Budapest during the fireworks provided for the Hungarian National Day are discussed.The combined novel method is suitable for determining size distributions for major and trace elemental concentrations form ultrafine to coarse particles (70 nm up to 10 μm) in seven size fractions. Moreover, short sampling times (1–4 h) are sufficient for reaching detection limits in the range of 100 pg/m3 for transition metals. The size and time resolution were found to be optimal for identifying pollution episodes with elevated elemental concentrations. The in-the-field analytical applicability of the proposed method for major and trace elements is demonstrated by comparison to elemental size distributions resulted from destructive analytical techniques.

Unacknowledged Potential Factors in Catastrophic Bat Die-off Arising from Coal Fly Ash Geoengineering

Bats have great economic and environmental importance, including nocturnal insect control, pollination, seed dispersal and forest regeneration. Bats, however, like insects and birds are suffering a precipitous global decline due to anthropogenic causes. Deliberate air pollution in the form of undisclosed tropospheric aerosol geoengineering (TAG) has extremely damaging effects throughout the biosphere. Forensic scientific evidence implicates coal fly ash (CFA), the toxic waste product of coal-burning, as the main constituent of the jet-sprayed particulate trails seen around the world. Coal fly ash is a primary source of the ultrafine and nano-sized particulate fraction of air pollution that adversely impacts human and environmental health. Recently, countless exogenous magnetic pollution particles from combustion sources were found in human brains and heart tissue. Previous studies reveal that aerosolized CFA is a significant factor in the catastrophic global decline of birds and insects. Insects can accumulate aerosolized CFA on their body surfaces and/or ingest CFA particulates that insectivorous bats then consume. Bats are excellent mammalian bioindicators of environmental contaminants and it is known that their tissue contains high levels of metals and persistent organic pollutants. From a review of the literature, we show that the pollutant element ratios in bat tissue and bat guano are consistent with an origin in CFA-type air pollution. These findings suggest that CFA, including its use in covert climate engineering operations, is an unacknowledged factor in the morbidity and mortality of bats. Bats, therefore, are an important "canary in the coal mine" pointing to the urgency of halting covert climate engineering and greatly reducing ultrafine particulate air pollution.

Urban Aerosol Particle Size Characterization in Eastern Mediterranean Conditions

Characterization of urban particle number size distribution (PNSD) has been rarely reported/performed in the Middle East. Therefore, we aimed at characterizing the PNSD (0.01–10 µm) in Amman as an example for an urban Middle Eastern environment. The daily mean submicron particle number concentration (PNSub) was 6.5 × 103–7.7 × 104 cm−3 and the monthly mean coarse mode particle number concentration (PNCoarse) was 0.9–3.8 cm−3 and both had distinguished seasonal variation. The PNSub also had a clear diurnal and weekly cycle with higher concentrations on workdays (Sunday–Thursday; over 3.3 × 104 cm−3) than on weekends (below 2.7 × 104 cm−3). The PNSub constitute of 93% ultrafine fraction (diameter &lt; 100 nm). The mean particle number size distributions was characterized with four well-separated submicron modes (Dpg,I, Ni): nucleation (22 nm, 9.4 103 cm−3), Aitken (62 nm, 3.9 103 cm−3), accumulation (225 nm, 158 cm−3), and coarse (2.23 µm, 1.2 cm−3) in addition to a mode with small geometric mean diameter (GMD) that represented the early stage of new particle formation (NPF) events. The wind speed and temperature had major impacts on the concentrations. The PNCoarse had a U-shape with respect to wind speed and PNSub decreased with wind speed. The effect of temperature and relative humidity was complex and require further investigations.

Flotation of coarse coal particles in a fluidized bed: The effect of clusters

This paper is concerned with the separation of coarse particles from siliceous gangue, in a fluidized bed froth flotation column, the NovaCell. Coarse particles are allowed to settle in the base of a column, and are fluidized by an upward-flowing stream of liquid. Air bubbles are introduced with the stream, which collide with hydrophobic particles in the bed, carrying them to the top of the vessel as flotation product.The paper describes the use of bubble clusters as a means of recovering particles in a flotation machine. Clusters are buoyant aggregates of bubbles and particles. Copious quantities were observed to form in the fluidized bed, rising to the top of the flotation column. They were present in such volumes that the froth was unable to absorb them all, and a thick cluster layer developed beneath the froth. This layer was drawn off and separated on a screen as a secondary flotation product, in addition to the conventional froth product.Here we describe the flotation of coal particles from different sources with a top size of 2 mm, in a NovaCell fluidized bed contactor. High combustibles recoveries were achieved, at acceptable ash contents, over the whole size range. The froth phase contributed approximately 65% of the total, the balance appearing on the screen. Particles of all sizes from 0 to 2 mm were represented in the froth discharge.The NovaCell gave two flotation products and two tailings streams. It was possible to control the tails from the fluidized bed so that the solids fraction was as high as 60–70%, in the size range 300 µm–2 mm. The results highlight the value of coarse particle froth flotation from a product de-watering perspective, when compared with flotation in conventional cells that are restricted to a top size of 500 µm. The ultrafine fraction less than 74 µm in diameter in the product was reduced by a third when the top size was increased to 2 mm from the normal top size of 500 µm for coal.The fact that low-buoyancy clusters can form beneath the froth, provides an alternative explanation for the phenomenon known as froth dropback.

Driving the paradigm shift of near surface exploration geochemistry using ultrafine soils

SummarySoils are widely used as a geochemical sample medium. These samples are sieved to <250 μm or <180 μm to remove larger gravels and coarse sand and later pulverized for analysis, but no other refinement is commonly used. Why is this the case? In transported cover, the soils that host/adsorb the mobile element signature are the smallest size fractions, so we should consider concentrating the clay size fraction (<2 μm) as an improved sample medium. Industry is unlikely to fully adopt these changes without proof of the benefit of refining the size fraction so a series of experiments were conducted to demonstrate the value of using <2 μm fractions for exploration geochemistry. Twenty-seven composite reference soils were collected in the vicinity of known mineral deposits (including background areas) that reflect the common soil types of Western Australia. These soils were used in replicate testing to assess differences in particle size, sample weight, dispersants and how this relates to the geochemistry with intent to optimise the extraction and speed of ultra-fine fraction recovery. Following the refinement of the technique, we commercialised and then applied the new UltraFine+ workflow to numerous orientation site studies, including reprocessed archived regional soil samples from the Geological Survey of Western Australia. Orientation results were promising. Analysing fine fractions (<2 μm) generated reproducible, reliable results, with bigger concentrations. Key benefits were the removal of nugget effects (for Au) and the challenges with detection limits in materials that are dominantly quartz sand. Importantly, the study revealed a marked decrease in censored results for Au (63% to 10% below detection limit) and less variation with sampling depth in soil profiles. The UltraFine+ workflow demonstrates the additional value from (re-) assaying regional soil and sediment samples to generate new targets and improve regional geochemical maps.

Atmospheric contaminations and bad conservation effects in Roman mosaics and mortars of Italica

The advanced microscopic (AM) analyses of mosaics and mortars from ancient construction have been studied for millennia in several Roman buildings in Europe. The geochemical characteristics of mosaics and mortars in Italica, Spain, were composed of amorphous and crystalline raw materials. Applied AM and X-ray diffraction (XRD) studies of different mosaics and mortars were carried out to observe the occurrence of natural and anthropogenic phases with organic and inorganic hazardous compounds. The results revealed a broad range of particles (micro-to nano-scale) including coarse (2.5–10 μm), fine (0.1–2.5 μm), and ultrafine ones (<0.1 μm), down to a few nanometers, as measured on electron microscope images. The particles occur typically in the form of aggregates, even in the ultrafine scale. Single, i.e., non-agglomerated particles are more common in the ultrafine fraction than at larger sizes. Geochemical studies of the samples showed that high proportions of aluminum, calcium, iron, potassium, silicon, and titanium yielded high standards of cementation manifestations. In addition, it was confirmed in this study that many of the mosaics blanketed by land remained unchanged; however, when the soil was removed, such mosaics began to undergo changes, mainly by weathering and atmospheric contamination. Several materials identified by XRD can also be detected using a high-resolution transmission electron microscopy (H-TEM)/field emission scanning electron microscope (FE-SEM) and vice versa. The occurrence of minerals containing potential hazardous elements (PHEs) and several associated organic compounds due to the modification caused by moisture and pollution was also demonstrated. The results offered important information about the building materials that were used to meet the mechanical requirements of the buildings.

A systematic approach for the comparison of PM10, PM2.5, and PM1 mass concentrations of characteristic environmental sites.

This study explores the use of a systematic approach in the comparison of simultaneous measurements of PM10, PM2.5, and PM1 mass concentrations using Aitchison geometry. Three case studies in three different Asian cities where the PM coarse, fine, and ultrafine size fraction prevail were investigated and the data was displayed using a dedicated triangular diagram. Simultaneous size-segregated PM measurements, for each case study, were assessed in terms of PM ratios and PM10 levels and were compared to similar measurements reported in literature. Non-central chi-squared distribution quantiles, for each case study, were evaluated and used to investigate the degree of similarity between simultaneous size-segregated PM ratios. Likewise, a comparative number k was used to show the proportion between PM10 levels. The issues relating to the location of the simultaneous size-segregated PM ratios on the triangular diagram were examined and the effects of the non-centrality parameter λ on PM comparison were indicated. The results show that the proposed systematic approach can estimate an explorative quantile (i.e., 2.5%) within which the simultaneous size-segregated PM measurements from one site can be compared with simultaneous size-segregated PM measurements from other sites reported in literature highlighting the existence of possible similarities or correspondences in the kind of sources influencing the PM.