Physicochemical characterization of particulate matter in a cement production plant.

Employees working in cement production plants are exposed to airborne particulate matter (PM) which may lead to lung function impairments and airway symptoms. The PM consists of raw materials, clinker and additives which vary depending on cement blend. The aim of this work was to characterize the thoracic fraction of PM with regard to size, phase composition and mixing state. Both stationary and personal impactors were used to collect size-fractionated samples in a cement production plant in Norway. Stationary samples were measured with aerosol particle counters and collected with a 13-stage cascade impactor, which were stationed at three locations of the cement production plant: at the raw meal mill, clinker conveyor belt and cement mill. Sioutas cascade impactors, and thoracic and respirable dust samplers were used in parallel for personal sampling. Additionally, particles for electron microscopy were collected with the stationary cascade impactor for size-fractionated single particle characterization. Gravimetric measurements and element compositions of the samples from the stationary impactors show that the PM mass is dominated by calcium-rich particles of size >1 µm. The size distribution results of stationary and personal impactors were similar. Characterization of single particles reveals that limestone is the dominating material in the raw meal mill, whereas clinker and limestone dominate at the clinker conveyor belt and at the cement mill. The element composition of clinker PM did not change with particle size. The PM collected on impactor stages with aerodynamic diameter cut-offs below 0.56 µm was dominated by soot and volatile secondary particles at the three locations. The number of ultrafine particles of the cement related compounds was low. Air concentrations of PM in personal respirable and thoracic samples ranged from 0.14-10 mg m-3 to 0.37-9.5 mg m-3, respectively. Considerable local variations exist, both in composition and air concentration of the PM.

Particle characterisation and bioaccessibility of manganese in particulate matter in silico- and ferromanganese smelters.

The aim of this study was to characterise particulate matter (PM) collected in the furnace area during SiMn and high carbon (HC)-FeMn production in terms of single particle analysis and to determine the bioaccessibility of Mn in the PM in a simulated lung fluid. Airborne PM was collected with Sioutas cascade impactors and respirable cyclones in the breathing zone of tappers and crane operators. Stationary samples were collected from the furnace area with a nanoMOUDI cascade impactor and an ESPnano electrostatic particle collector. Individual particles were characterised by scanning and transmission electron microscopy. Bioaccessibility of Mn was studied in terms of the dissolution of Mn in Gamble solution (24 hours leaching at 37 °C) relative to total Mn. Slag particles, alloy fragments, Mn and Fe oxides as well as carbonaceous particles were observed in the size fraction > 1 µm aerodynamic diameter (dae). Thermally generated condensation particles dominated the dae size range of 0.18-1 µm collected from the tapping fumes, while carbonaceous particles dominated the fraction below 0.18 µm. Condensation generated particles from the furnace area of HC-FeMn production were coated with an amorphous Si-O rich surface layer which seemed to hold primary particles together as aggregates. In the same size range, the particles from the furnace area of SiMn production were dominated by spherical condensation particles rich in Si, Mn and O, but without a Si-O rich surface layer. Instead, the Mn oxides were enclosed in an amorphous Si-O rich matrix. The bioaccessibility of Mn was low to moderate (<30%), but higher for SiMn furnace workers (highest median = 23%) than HC-FeMn furnace workers (highest median = 12%). This difference in bioaccessibility was significant for PM with dae up to 2.5 µm, and most pronounced in the dae size range between 0.25 and 1.0 µm. Also, a significantly higher bioaccessibility of Mn was found for PM larger than dae of 0.5 µm collected among crane operators compared to tappers in the HC-FeMn smelter.

Size distribution and single particle characterization of airborne particulate matter collected in a silicon carbide plant.

The global SiC market is projected to grow in the coming years, and research on potential health effects as well as epidemiological studies is therefore of importance. A detailed characterization in terms of the phase composition, morphology and mixing state of airborne PM is still missing, though highly necessary to identify sources and to understand the risk factors in this industry. Particles in the size range of 10 nm to 10 µm were collected with a 13-stage NanoMOUDI impactor in the Acheson Furnace Hall as well as in processing departments during two sampling campaigns. Particle mass concentrations, including the fraction of ultrafine particles (UFPs), were lower in the processing departments in comparison to those in the Acheson Furnace Hall. The particle number size distribution measured with a scanning mobility particle sizer confirmed the low amount of UFPs in the processing departments compared to the furnace hall. Significant differences in the particle mass concentration and distribution were observed in the Acheson Furnace Hall during the two sampling campaigns. The PM size distribution depends upon the sampling location, on the cycle of the nearby furnaces and on special incidents occurring during a furnace run. Scanning and transmission electron microscopy (SEM and TEM) showed that the size range of 0.32-10 µm (aerodynamic diameter) is dominated by carbon (C)-rich particles, which were identified as petroleum coke, graphite, soot and amorphous spherical C-rich particles. Soot was further classified into three types based on the primary particle size, morphology and composition. Diesel-powered vehicles, pyrolysis of petroleum coke and incomplete combustion of volatile components from this pyrolysis are suggested as sources of different soot particle types. Amorphous spherical C-rich particles were also sub-classified based on their morphology and composition as tar balls (TBs) and C-spherical type 2. The amount of SiC fibers and crystalline SiO2 was found to be low. In the size fraction below 0.32 µm (aerodynamic diameter), sulphur (S)-rich particles dominate. This knowledge of the particle size distribution, and chemical and physical properties of the PM occurring in the SiC production is fundamental for an appropriate risk assessment, and these findings should have implications for future epidemiological studies and for the mitigation of worker exposure.

How to Cope With Heavy Metal Ions: Cellular and Proteome-Level Stress Response to Divalent Copper and Nickel in Halobacterium salinarum R1 Planktonic and Biofilm Cells.

Halobacterium salinarum R1 is an extremely halophilic archaeon capable of adhesion and forming biofilms, allowing it to adjust to a range of growth conditions. We have recently shown that living in biofilms facilitates its survival under Cu2+ and Ni2+ stress, with specific rearrangements of the biofilm architecture observed following exposition. In this study, quantitative analyses were performed by SWATH mass spectrometry to determine the respective proteomes of planktonic and biofilm cells after exposition to Cu2+ and Ni2+.Quantitative data for 1180 proteins were obtained, corresponding to 46% of the predicted proteome. In planktonic cells, 234 of 1180 proteins showed significant abundance changes after metal ion treatment, of which 47% occurred in Cu2+ and Ni2+ treated samples. In biofilms, significant changes were detected for 52 proteins. Only three proteins changed under both conditions, suggesting metal-specific stress responses in biofilms. Deletion strains were generated to assess the potential role of selected target genes. Strongest effects were observed for ΔOE5245F and ΔOE2816F strains which exhibited increased and decreased biofilm mass after Ni2+ exposure, respectively. Moreover, EPS obviously plays a crucial role in H. salinarum metal ion resistance. Further efforts are required to elucidate the molecular basis and interplay of additional resistance mechanisms.

Phase identification of individual crystalline particles by combining EDX and EBSD: application to workplace aerosols.

This paper discusses the combined use of electron backscatter diffraction (EBSD) and energy dispersive X-ray microanalysis (EDX) to identify unknown phases in particulate matter from different workplace aerosols. Particles of α-silicon carbide (α-SiC), manganese oxide (MnO) and α-quartz (α-SiO2) were used to test the method. Phase identification of spherical manganese oxide particles from ferromanganese production, with diameter less than 200 nm, was unambiguous, and phases of both MnO and Mn3O4 were identified in the same agglomerate. The same phases were identified by selected area electron diffraction (SAED) in transmission electron microscopy (TEM). The method was also used to identify the phases of different SiC fibres, and both ß-SiC and α-SiC fibres were found. Our results clearly demonstrate that EBSD combined with EDX can be successfully applied to the characterisation of workplace aerosols. Graphical abstract Secondary electron image of an agglomerate of manganese oxide particles collected at a ferromanganese smelter (a). EDX spectrum of the particle highlighted by an arrow (b). Indexed patterns after dynamic background subtraction from three particles shown with numbers in a

Morphology, chemical composition and nanostructure of single carbon-rich particles studied by transmission electron microscopy: source apportionment in workroom air of aluminium smelters.

Sources of C-rich particles at work places in two aluminium smelters in Norway were studied by transmission electron microscopy and energy-dispersive X-ray microanalysis. Based on morphology, nanostructure and chemistry, three different types of C-rich particles are distinguished: (a) chain-like agglomerates (70-100% by number, relative to the sum of C-rich particles) consisting of primary particles with typical onion-shell structure of graphene layers, (b) multi-walled carbon nanotube particles (≈3%) and (c) spheres or agglomerates of amorphous C-rich particles (0-30%). Chain-like agglomerates are interpreted as diesel soot in accordance with literature data on primary particle diameter, chemical composition and nanostructure of primary particles. The source of the observed multi-walled carbon nanotubes is not known. The amorphous C-rich particles most likely consist of organic carbon species which cannot be characterized further by X-ray microanalysis. Unaltered graphitic electrode material was not found among the C-rich particles. The high fraction of diesel soot particles indicates that elemental carbon is generally suited as proxy for diesel soot in aluminium smelters. However, due to the presence of carbon nanotubes and amorphous C-rich particles, detailed characterization of sources of carbon-rich particles by electron microscopy is recommended for accurate assessment of adverse health effects.

Electron microscopy of particles deposited in the lungs of nickel refinery workers.

The size, morphology, and chemical composition of particles deposited in the lungs of two nickel refinery workers were studied by scanning and transmission electron microscopy. The particles were extracted from the lung tissue by low-temperature ashing or by dissolution in tetramethylammonium hydroxide. The suitability of both sample preparation techniques was checked with reference materials. Both approaches lead to Fe-rich artifact particles. Low-temperature ashing leads to oxidation of small (diameter < 2 µm) metallic Ni and Ni sulfide particles, dissolution in tetramethylammonium hydroxide to removal of sulfate surface layers. Silicates and alumosilicates are the most abundant particle groups in the lungs of both subjects. From the various metal-dominated particle groups, Ni-rich particles are most abundant followed by Fe-rich and Ti-rich particles. Ni appears to be present predominantly as an oxide. Pure Ni metal and Ni sulfides were not observed. The presence of soluble Ni phases was not investigated as they will not be preserved during sample preparation. Based on their spherical morphology, it is estimated that a large fraction of Ni-rich particles (50-60 % by number) as well as Fe-rich and Cu-rich particles (27-45 %) originate from high-temperature processes (smelting, welding). This fraction is much lower for silicates (3-5 %), alumosilicates (1-2 %), and Ti-rich particles (9-11 %). The absence of metallic Ni particles most likely results from low exposure to this species. The absence of Ni sulfides may be either ascribed to low exposure or to fast clearance.

Involvement of IL-1 genes in the cellular responses to carbon nanotube exposure.

The interleukin-1 (IL-1) family has been implicated in cellular responses to nanoparticles including carbon nanotubes (CNTs). IL-1α and ß are key proinflammatory cytokines important in inflammatory and oxidative stress responses. The aim of this study was to characterize the role of IL-1 in cellular responses of CNTs in cells from IL-1α/ß wild type (IL1-WT) mice and cells with reduced inflammatory potential from IL-1α/ß deficient (IL1-KO) mice. Two multi-walled CNTs, CNT-1 containing long and thick fibers and CNT-2 containing short and thin fibers, were compared to UICC crocidolite asbestos fibers. Upon CNT exposure toxicity and apoptosis were affected differently in IL1-WT and IL1-KO cells. Upregulation of TNFα and IL-1α mRNA expression in IL1-WT cells was dependent on the type of CNT. On the contrary precursor IL-1α protein was downregulated after 24h. The mitogen-activated protein kinase (MAPK) c-Jun N-terminal kinase (JNK) was activated in IL1-KO cells and regulated by CNTs, whereas no significant changes of extracellular regulated kinase (ERK) were observed when comparing IL1-WT and IL1-KO cells. In summary, the results presented here indicate that IL-1 contributes to the cellular and molecular effects of CNT exposure and that the type of CNT has an important effect on the cellular response.

Source apportionment of aerosol particles near a steel plant by electron microscopy.

The size, morphology and chemical composition of 37,715 individual particles collected over 22 sampling days in the vicinity of a large integrated steel production were studied by scanning and transmission electron microscopy. Based on the morphology, chemistry and beam stability the particles were classified into the following fourteen groups: silicates, sea salt, calcium sulfates, calcium carbonates, carbonate-silicate mixtures, sulfate-silicate mixtures, iron oxides, iron mixtures, metal oxide-metals, complex secondary particles, soot, Cl-rich particles, P-rich particles, and other particles. The majority of iron oxide (≈85%) and metal oxide-metal (≈70%) particles as well as ≈20% of the silicate particles are fly ashes from high temperature processes. The emissions from the steel work are dominated by iron oxide particles. For source apportionment, seven source categories and two sectors of local wind direction (industrial and urban background) were distinguished. In both sectors PM10 consists of four major source categories: 35% secondary, 20% industrial, 17% soil and 16% soot in the urban background sector compared to 45% industrial, 20% secondary, 13% soil, and 9% soot in the industrial sector. As the secondary and the soot components are higher in the urban background sector than in the industrial sector, it is concluded that both components predominantly originate from urban background sources (traffic, coal burning, and domestic heating). Abatement measures should not only focus on the steel work but should also include the urban background aerosol.

Determination of O[H] and CO coverage and adsorption sites on PtRu electrodes in an operating PEM fuel cell.

A special in situ PEM fuel cell has been developed to allow X-ray absorption measurements during real fuel cell operation. Variations in both the coverage of O[H] (O[H] indicates O and/or OH) and CO (applying a novel Deltamu(L3) = mu(L3)(V) - mu(L3)(ref) difference technique), as well as in the geometric (EXAFS) and electronic (atomic XAFS) structure of the anode catalyst, are monitored as a function of the current. In hydrogen, the N(Pt)(-)(Ru) coordination number increases much slower than the N(Pt)(-)(Pt) with increasing current, indicating a more reluctant reduction of the surface Pt atoms near the hydrous Ru oxide islands. In methanol, both O[H] and CO adsorption are separately visible with the Deltamu technique and reveal a drop in CO and an increase in OH coverage in the range of 65-90 mA/cm(2). With increasing OH coverage, the Pt-O coordination number and the AXAFS intensity increase. The data allow the direct observation of the preignition and ignition regions for OH formation and CO oxidation, during the methanol fuel cell operation. It can be concluded that both a bifunctional mechanism and an electronic ligand effect are active in CO oxidation from a PtRu surface in a PEM fuel cell.