Particle Mineralogy Research Articles

Environmental and health implications of Pb-bearing particles in settled urban dust from an arid city affected by Pb–Zn factory emissions

Metal-rich particles originating from non-ferrous metallurgical activities are the primary source of atmospheric metals in urban environments. These particles vary in size, morphology, and elemental compositions and they undergo weathering processes that alter their composition and affect their toxicity. This study focuses on lead (Pb)-rich particles in settled urban dust within an arid and dusty city, Torreón in North Mexico, affected by Met–Mex Peñoles complex, one of the world's largest Ag–Cd–Pb–Zn smelting and refining facilities in operating since 1901. Torreón is characterized by arid conditions, temperature fluctuations, and low humidity. Dry atmospheric particles were collected in 2015 and 2017 from Torreón's urban area within a 3 km radius of the Met–Mex Peñoles complex. We used various analytical techniques, including scanning electron microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray powder diffraction (XRD) to determine the size, morphology, elemental composition and mineralogy of Pb-bearing particles. Our analysis revealed a range of Pb-bearing particle sizes and morphologies with varying Pb (0.3 to 51–87.2%) and other element contents, such as As (0.04 to 1–3.4%), Cd (0.4 to 3.3–5.1%), Cu (0.51–14.1%), Hg (ND-0.6%), and Zn (1.7 to 79–90.3%). XRD analysis confirmed the presence of Pb and Zn sulfides, Pb carbonates, Pb sulfate, and Pb oxides in urban dust, both as individual particles and agglomerates. Primary Pb minerals were linked to fugitive feed concentrates and smelter flue gas at Met–Mex Peñoles, while secondary Pb minerals, like Pb carbonates, Pb sulfate, and Pb oxides, resulted from direct emissions and weathering processes. Compared to galena, secondary Pb minerals exhibit higher chemical availability in the environment, posing greater risks to the environment and human health. As the particles analyzed are presumed to be resuspended rather than freshly emitted by Met–Mex, the presence of secondary Pb minerals in settled urban dust is predominantly linked to weathering processes. The physical and chemical transformations in Pb-rich particles contribute to increased Pb bioavailability and toxicity in urban dust, with substantial implications for environmental and human health. These findings highlight the potential consequences of weathered Pb-rich particle in urban areas, particularly in the arid and dusty city of Torreón.

Mineralogy and mineral chemistry of detrital platinum-group minerals and gold particles from the Elbe, Germany

Mineralogy and mineral chemistry of detrital platinum-group minerals and gold particles from the Elbe, Germany

Mineralogy and phase transition mechanisms of atmospheric mineral particles: Migration paths, sources, and volatile organic compounds

Inorganic mineral particles play an important role in the formation of atmospheric aerosols in the Sichuan Basin. Atmospheric haze formation is accompanied by the phase transition of mineral particles under high humidity and stable climatic conditions. Backward trajectory analysis was used in this study to determine the migration trajectory of atmospheric mineral particles. Furthermore, Positive matrix factorization (PMF) was used to analyze the sources of atmospheric mineral particles. The phase transition mechanisms of atmospheric mineral particles were studied using ion chromatography, inductively coupled plasma emission spectrometry, total organic carbon analysis, X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy coupled with energy dispersive spectrometry, and grand canonical Monte Carlo methods. Three migration and phase transition paths were identified for the mineral particles. Sources of atmospheric mineral particles included combustion, vehicle emissions, industrial emissions, agricultural sources, and mineral dust. The main mineral phases in atmospheric particles, calcite and dolomite, were transformed into gypsum, and muscovite may be transformed into kaolinite. The phase transition of mineral particles seriously affects the formation of aerosols and worsens haze. Typically, along the Nanchong-Suining-Neijiang-Zigong-Yibin path, calcite is converted into gypsum under the influence of man-made inorganic pollution gases, which worsen the haze conditions and cause slight air pollution for 3–5 days. However, along the Guangyuan-Mianyang-Deyang-Chengdu-Meishan-Ya'an path, anthropogenic volatile organic compounds (VOCs) hindered gypsum formation from dolomite. Furthermore, dolomite and VOCs formed stable adsorption systems (system energies from −0.41 to −4.76 eV, long bonds from 0.20 to 0.24 nm). The adsorption system of dolomite and m/p-xylene, with low system energy (−1.46 eV/−1.33 eV) and significant correlation (r2 = 0.991, p < 0.01), was the main cause of haze formation. Consequently, calcite gypsification and dolomite–-VOC synergism exacerbated regional haze conditions. This study provides a theoretical reference for the mechanism of aerosol formation in basin climates.

The Effect of Soil Mineralogy and Particle Breakage on the Impulse Generated from Shallow Buried Charges

Historically, most testing with shallow buried charges has focussed on soils which are predominantly quartz (silica)-based. Particle size, moisture content and density have previously been investigated to ascertain their importance, along with other geotechnical parameters, in governing the magnitude of an impulsive output. This has shown that, in order of importance, moisture content, density and particle size drive the total impulse imparted. The work in this paper presents the results of blast testing carried out with carbonate sands to investigate the difference that particle mineralogy (and hence, propensity for breakage) has on both the localised loading and the total impulse using an array of 17 Hopkinson pressure bars known as the Characterisation of Blast Loading (CoBL) apparatus. Carbonate sands are thought to have more friable particles due to their plate-like morphology, as opposed to the rounded morphology of quartz-based sands. Testing was conducted with low moisture content samples and compared with the well-established Leighton Buzzard uniform sand to isolate the effect of particle mineralogy/morphology on the loadings measured. The results show that, despite attaining a 23% lower bulk density, carbonate soils deliver almost identical total impulses (0.7–3.0% higher) when compared with quartz soils for nominally identical moisture contents.

Pathogenic Potential of Respirable Spodumene Cleavage Fragments following Application of Regulatory Counting Criteria for Asbestiform Fibres

Health risks from exposure to lithium-bearing spodumene cleavage fragments are unknown. While asbestiform fibres can lead to fibrosis, mesothelioma and lung cancer, controversy remains whether non-asbestiform cleavage fragments, having equivalent dimensions, elicit similar pathologic responses. The mineralogy of respirable particles from two alpha (α)-spodumene concentrate grades (chemical and technical) were characterised using semi-quantitative X-ray diffraction (XRD). Particles were measured using scanning electron microscopy (SEM) and the dimensions (length [L], diameter [D], aspect ratio [AR]) applied to regulatory counting criteria for asbestiform fibres. Application of the current World Health Organization (WHO) and National Occupational Health and Safety Commission (NOHSC) counting criteria, L ˃ 5 µm, D ˂ 3 µm, AR ˃ 3:1, to 10 SEM images of each grade identified 47 countable particles in the chemical and 37 in the technical concentrate test samples. Of these particles, 17 and 16 in the chemical and technical test samples, respectively, satisfied the more rigorous, previously used Mines Safety and Inspection Regulations 1995 (Western Australia [WA]) criteria, L ˃ 5 µm and D ≤ 1 µm. The majority of the countable particles were consistent with α-spodumene cleavage fragments. These results suggest elongated α-spodumene particles may pose a health risk. It is recommended the precautionary principle be applied to respirable α-spodumene particles and the identification and control of dust hazards in spodumene extraction, handling and processing industries be implemented.

Relationship between the physicochemical and electrostatic charge characteristics of filler materials on the morphological and adhesive Pull-Off tensile strength of asphalt mastics

• This paper assesses the viability of using mineral fillers from industrial by-products. • Lime kiln dust and dolomite powder were studied and compared to cement powder. • Changes in asphalt binder phases occur as a result of asphalt-filler interactions. • The pH conditions dictate mastics adhesive tendencies due to electrostatic ionic exchange. • Thus, impacting pull-off strengths within asphalt-aggregate interfaces. The influence of filler particle mineralogy, pH and electrostatic charge on the adhesive tensile strength and morphological structure of asphalt mastic composites were assessed in this study. Three different fillers i.e., dolomite powder (DP), lime kiln dust (LKD), and ordinary Portland cement (OPC) together with a conventional PEN 60/70 binder were used for the asphalt mastic preparation. The mastics were mixed at dosages of (0.4, 0.8, and 1.2) filler to binder concentration (F/B) by volume as per the dust to binder specifications of Superpave mix designs. OPC mastic was utilised as the control mastic sample for all conducted tests, while the DP and LKD mastics were tested as sustainable alternatives to the OPC. The impact of filler inclusions in asphalt liquid phases was investigated via optical microscope assessments. Similarly, physicochemical tests of the elemental and mineralogical composition of each filler were accounted for using x-ray diffraction tests. The surface charge characteristics of each test filler was analysed relative to its mastic pH conditions through the application of zeta potential tests. Adhesive pull-off tensile strengths of the mastics on granite and limestone interfaces were also assessed for both dry and moisture conditions. The incorporation of fillers in asphalt binders highlighted the effect of filler reactivity and inert tendency on binders’ morphological phase modification wherein the OPC and LKD were reactive with the asphaltene while the DP was less reactive and inert. Results obtained from both the x-ray diffraction and zeta potential tests also infer the calcium based OPC and LKD to exhibit better surface ionic attraction compatibility with the PEN 60/70 binder than the DP at high F/B. Meanwhile, the relationship between the filler surface charge and mastic pH condition was observed to be significant and reliant upon the mastics adhesive pull-off tensile characteristics.

Identification and particle sizing of submicron mineral dust by using complex forward-scattering amplitude data

An accurate observational dataset of the size-resolved concentration of mineral dust particles in the atmosphere, hydrosphere, and cryosphere is needed for investigating the effect of mineral dust on the climate with earth system models. However, automated measurements of dust particles remain challenging due to the complexities of the physicochemical properties (e.g., shape and mineralogy) of individual dust particles and the difficulties in discriminating dust from other particulate components (e.g., black carbon). Here, we suggest the use of complex forward-scattering amplitude data obtained by the single particle extinction and scattering (SPES) method as a low-cost optical approach for identification and quantification of silicate (aluminosilicates + quartz) particles, the major particulate component of desert dust. We focus here on the submicron particle-size range to challenge the robust identification of wavelength or smaller scale dust solely according to the principle of elastic light scattering. The two-dimensional nature of the complex scattering amplitude data allows us to identify silicate-dominant particles in waterborne dust samples and discriminate them from light-absorbing particulate components (e.g., hematite). We demonstrate that the two-dimensional dataspace of the complex amplitude allows an accurate retrieval of the particle-size distribution of silicate particles thanks to the simultaneous retrieval of the particle’s effective refractive index. We discuss some notable differences in our results from those retrieved from conventional elastic light scattering approaches.Copyright © 2022 American Association for Aerosol Research

Impact of Particle Sizes, Mineralogy and Pore Fluid Chemistry on the Plasticity of Clayey Soils

The current classification of clayey soils does not entail information of pore fluid chemistry and particle size less than 75 µm. However, the pore fluid chemistry and particle size (at given mineralogy) are critical in the plasticity of clayey soils because of their impact on negative charge density. Therefore, this study extensively discusses the description of clay with respect to mineralogy, particle sizes, and pore fluid chemistry based on liquid and plastic limits of kaolinite, illite, and bentonite, and estimates undrained shear strength from the observed liquid limits. The liquid limits and undrained shear strength estimated from the observed liquid limits as a function of mineralogy (clay type), particle size, and ionic concentration reveal the need of incorporating pore fluid chemistry and particle size into the fines classification system. Furthermore, multiple linear regression models developed in this study demonstrate the importance of particle size and ionic concentration in predicting the liquid limit of clayey soils. This study also discusses the need for a comprehensive understanding of fines classification for proper interpretation of natural phenomena and engineering applications for fine-grained sediments.

Influence of particle mineralogy and size on the morphological characteristics of mineral fillers

The morphological characteristics of mineral filler particles, such as contour shape, angularity and surface texture, are closely related to their mineralogy and size and the crushing process used. In the present study, the importance and effects of particle mineralogy and size on the morphology of different mineral fillers were examined. A total of 12 mineral filler fractions were prepared using the same grinding process and sieving method, and analyzed by digital imaging. Six parameters were used to describe the 2-dimensional characteristics of mineral filler particles based on digital image processing. The sensitivity of these parameters was analyzed by correlation and analysis of variance methods. The results show that for mineral fillers of the same particle mineralogy, as the particle size decreases, the contour shape becomes more regular and the angularity and surface texture becomes less abundant. For mineral fillers of the same particle size, the granite filler particles have a more regular contour shape and richer angularity and surface texture than the limestone and basalt filler particles. The form factor, angularity parameter AI1 and fractal dimension can best reflect the sensitivity of contour shape, angularity and surface texture characteristics of mineral filler particles to particle mineralogy and size.

Screening Coarse Airborne Dust for Lead-Rich Phase Occurrence during Characterisation of Particle Mineralogy, Chemistry and Provenance: Application to Deposits in the Vicinity of an Integrated Steelworks

A method has been developed to screen large numbers (~103–104 per sample) of coarse airborne dust particles for the occurrence of Pb-rich phases, together with quantification of the particles’ mineralogy, chemistry, and inferred provenance. Using SEM-EDS spectral imaging (SI) at 15 kV, and processing with the custom software PARC, screening of individual SI pixels is performed for Pb at the concentration level of ~10% at a length-scale of ~1 µm. The issue of overlapping Pb-Mα and S-Kα signal is resolved by exploiting peak shape criteria. The general efficacy of the method is demonstrated on a set of NIST particulate dust standard reference materials (SRMs 1649b, 2580, 2584 and 2587) with variable total Pb concentrations, and applied to a set of 31 dust samples taken in the municipalities surrounding the integrated steelworks of Tata Steel in IJmuiden, the Netherlands. The total abundances of Pb-rich pixels in the samples range from none to 0.094 area % of the (total) particle surfaces. Overall, out of ca. 92k screened particles, Pb was found in six discrete Pb-phase dominated particles and, more commonly, as superficial sub-particles (sub-micron to 10 µm) adhering to coarser particles of diverse and Pb-unrelated provenance. No relationship is apparent between the samples’ Pb-rich pixel abundance and their overall composition in terms of particle provenance.

Mechanical behavior of hydrate-bearing sands with fine particles under isotropic and triaxial compression

The presence of fine particles has a significant impact on the mechanical behavior of hydrate-bearing sediments. In this study, a series of isotropic compression and triaxial tests were conducted using a customized testing system for the hydrate-bearing sediment. Carbon dioxide hydrate was formed in the host sediments, which were mixtures of sand and silty-sized quartzitic or illite fine particles. The isotropic and triaxial compression tests offered valuable datasets of the compression and the swelling indices, yielding stress, strength, stiffness, and dilatancy for hydrate-bearing sediments. The results highlighted that the addition of illite particles enhances compressibility but restricts stiffness and dilatancy. The strength is highly increased by hydrate saturation and less dependent on the mineralogy of fine particles. The cohesion is significantly enhanced by the hydrate saturation due to cementation. With the increasing hydrate saturation, the angle of internal friction increases slightly at lower hydrate saturation but it decreases slightly at higher hydrate saturation. The experimental results and mechanism analysis can be used to assess the stability of the hydrate reservoir under methane-carbon dioxide replacement and provide a reference to estimate the mechanical properties of the methane hydrate reservoir.

Bursera fagaroides bark as a bioindicator for air particle pollution using magnetic properties

Shrub barks can accumulate airborne particles and seem to be suitable biological monitors for assessing air pollution. We studied the bark of the species Bursera fagaroides as a biomonitor of air pollution in an urban area of Mexico. Samples were collected in dry and rainy seasons during 2011 and 2012, in 28 sites which are exposed to magnetic pollutants emitted by different human activities (industrial point-sources and vehicular emissions). Environmental magnetism studies allow determining mineralogy, concentration and grain size of magnetic particles accumulated in barks, providing information on the sources and characteristics of their emitted particles. Magnetic properties of all samples were determined by environmental magnetism method. The highest values of magnetic concentration dependent parameters were observed in industrial and vehicular traffic sites. The mean values of saturation of isothermal remanent magnetization SIRM for dry seasons are two to threefold (SIRM = 0.8–1.2 × 10−3Am2kg−1) the mean value for rainy season (SIRM = 0.4 × 10−3Am2kg−1). The integrated magnetic analysis indicates the presence of ferrimagnetic minerals, mostly magnetite-like (remanent coercivity Hcr = 31.6–38.7 mT) particles of small sizes (1 – < 0.1 μm). Selected samples were observed by scanning electron microscopy, revealing the presence of such iron-rich particles hosted in species’ lenticels. These results demonstrate the usefulness of the species' cortex as a biomonitor of air pollution, with an affordable and immediate application, and raise new questions about what type of physiological mechanism is involved for trapping magnetic particles.

Provenance of Fe in Chinese Deserts: Evidence from the geochemistry and mineralogy of soil particles

Determining the categories and content of Fe containing silicate minerals in the desert soils and sediments of northern China is important for understanding the Fe cycle and for correctly interpreting the paleoenvironmental signals from the Loess Plateau downwind. Using a mineral liberation analyzer (MLA), we established the modal mineral abundances of a complete set of Fe containing mineral species in the fine sand to silt fractions of surface samples from Chinese deserts. Results show that the most common discrete particles containing Fe are the silicate phases (~15 wt%), while the weathering product (i.e., Fe oxides) phases are minor and their abundances vary greatly (0.38–4.15 wt%). The degree of weathering has a substantial particle size dependence. The fine fraction (5–20 µm) generally has a relatively low Fe/Si ratio, possibly due to weathering, while the Fe/Si ratio of the coarse fractions (20–45 µm, 45–63 µm, 63–75 µm, and >75 µm) are relatively invariant. Abundant Fe is contained within the coarse fractions, which are associated with the local geology. The strong relationship between the Fe and Mg bound within the silicate phases further supports the conclusion that the correlated deviations in the Fe/Si and Mg/Si ratios originate from the provenance bedrock (i.e., siliciclastic, low-grade metamorphic, and possibly high-grade metamorphic, rocks). Since Mg tends to be easily removed during weathering, the Fe/Mg ratios of silicate species largely reflect the weathering intensity. We used the regression equation for the relationship between the local precipitation amount and the Fe/Mg ratios of the soils to produce a novel precipitation proxy. Compared with classical provenance studies conducted using coarse sand and larger rock fragments, the MLA methodology is more applicable to the fine sand and silt fractions; thus, it contributes to the development of weathering and provenance indices based on geochemistry and mineralogy.

Downhole nuclear magnetic resonance logging in glaciomarine sediments near Ottawa, Ontario, Canada

ABSTRACTDownhole nuclear magnetic resonance technology was applied in four boreholes intersecting glaciomarine sediments of the Ottawa Valley, Ontario. The study evaluated the ability of slim‐hole nuclear magnetic resonance tools to measure in situ volumetric water contents (porosities in saturated sediments) for geohazard and hydrogeological applications. The sediments are composed of clay‐ and silt‐sized grains of glacially eroded rock flour derived from the Precambrian Shield containing trace amounts of magnetic minerals, and porosities ranging from 40 to 74 porosity units (PU, 1% porosity = 1 PU). Two nuclear magnetic resonance instruments were deployed with echo times of 0.5 and 1.0 ms, and diameters of investigation ranging from 14.0 to 30.5 cm. Quantitative nuclear magnetic resonance porosities in the sediments were typically within ±5 PU (95% within ±10 PU) of core calibration data sets in the silty clays where threshold bulk magnetic susceptibility values were &lt;30 × 10−4 SI. This was found to deviate, however, where the concentration and mineralogy of magnetic particles changed, interpreted to be shortening relaxation times which led to underestimation of true water contents. This effect is correlated with a change in depth from magnetite to superparamagnetic nanoparticles of greigite (low‐temperature iron monosulphide) magnetism, interpreted to occur at the sulphate‐methane interface. Clay mineralogy and pore water chemistry were also examined as contributing factors, but were not found to significantly shorten nuclear magnetic resonance relaxation responses. Very short T2 times (&lt;2 ms) are typical in these particular silty clays, requiring a tool with an echo spacing of &lt;1.0 ms. Due to increased potential for sediment disturbance around a well caused by the geotechnical sensitivity of the sediments, a nuclear magnetic resonance instrument with multiple frequencies provided signal penetration out to various diameters around the tool, giving needed information about the size of the disturbed zone surrounding the casing.

The sources and seasonal fluxes of particulate organic carbon in the Yellow River

AbstractThe Yellow River transports a large amount of sediment and particulate organic carbon (POC), which is thought to mainly derive from erosion of the Chinese Loess Plateau (CLP). However, the compositions, sources and erosional fluxes of POC in the Yellow River remain poorly constrained. Here we combined measurements of mineralogy, total organic carbon content (OCtotal), stable organic carbon isotopes (δ13Corg), radiocarbon (14C) activity of organic matter in bulk suspended sediments collected seasonally from the upper and middle Yellow River, to quantify the compositions and fluxes of the POC and to assess its sources (biospheric and petrogenic POC, i.e. POCbio and POCpetro, respectively). The results showed that the POC loading of sediments was controlled by mineralogy, grain size and specific surface area of loess particles. The Fmod of POC (0.71 to 0.31) can be explained by mixing of POCpetro with modern and aged POCbio. A binary mixing model based on the hyperbolic relationship of the Fmod and OCtotal revealed a wide range of ages of POCbio from 1300 to 11100 14C years.Relative to the upstream station, the annual POCbio and POCpetro fluxes in the Yellow River are more than doubled after it flows crossing the CLP within 35% drainage area gain, resulting in POCbio and POCpetro yields of the CLP at 3.50 ± 0.59 and 0.48 ± 0.49 tC/km2/yr, respectively. POC flux seasonal variation revealed that monsoon rainfall exerts a first‐order control on the export of both POCbio and POCpetro from the CLP to the Yellow River, resulting in more than 90% of the annual POC exported during the monsoon season. Around one third of annual POC erosional flux was transported during a storm event period, highlighting the important role of extreme events in POC export in this large river. © 2020 John Wiley &amp; Sons, Ltd.

Investigation on the morphological and mineralogical properties of coarse aggregates under VSI crushing operation

ABSTRACT In this paper, the role of crushing operation on the cubical controlling features of coarse aggregates, and its influence on the shape distribution characteristics of aggregates (i.e. angularity, sphericity, and flatness & elongation ratio) were investigated through the second version of Aggregate Image Measuring System (AIMS II). Three types of aggregate from different origins were chosen and crushed by the vertical shaft impactor (VSI) with fixed rotational speed. The results indicate that the rotation speed of VSI is influenced by the input power of the machine to the particle sizes, and higher speed leads to more cracks on aggregates during the crushing process. By using X-ray diffraction (XRD), the aggregate samples from different origins and mineral compositions were analysed under the same working operation of crusher. Besides that, the correlation between particle shape characteristics influenced by the mineralogical composition, and their collision behaviours have been discussed according to the tested results. A recommendation for optimal operation of VSI on crushing granite aggregates is given based on this study. Whereas, the cubical condition of aggregates and energy saving factors were taken into account. Furthermore, petrographic analyses were imposed to correlate particle mineralogy to its collision behaviour during crushing.

On the intrinsic behaviour of decomposed volcanic rocks

The intrinsic behaviour of soils is very essential and the mechanical behaviour of reconstituted soils depends mainly on its intrinsic properties. The separate role played by particle shape, particle mineralogy and grading on the mechanical behaviour of soils resulting from weathered igneous rocks have not been extensively studied. The effects of particle shape, particle mineralogy and grading on the mechanics of decomposed volcanics have been systematically investigated through one-dimensional compression and triaxial tests. This was achieved by using samples of different weathering degrees. The results indicate that the influence of particle mineralogy on the one-dimensional compression behaviour is relatively small compared to grading. There is effect of grading on the shearing behaviour, and it is less pronounced than in compression. There is slight effect of grading at a small strain level. Generally, grading has a notable influence on the mechanical behaviour of volcanic saprolites, and it is more important than particle mineralogy for volcanic saprolites.

Mineralogy and mixing state of north African mineral dust by online single-particle mass spectrometry

Abstract. The mineralogy and mixing state of dust particles originating from the African continent influences climate and marine ecosystems in the North Atlantic due to its effect on radiation, cloud properties and biogeochemical cycling. However, these processes are difficult to constrain because of large temporal and spatial variability, and the lack of in situ measurements of dust properties at all stages of the dust cycle. This lack of measurements is in part due to the remoteness of potential source areas (PSAs) and transport pathways but also because of the lack of an efficient method to report the mineralogy and mixing state of single particles with a time resolution comparable to atmospheric processes, which may last a few hours or less. Measurements are equally challenging in laboratory simulations where dust particles need to be isolated and characterised in low numbers whilst conditions are dynamically controlled and monitored in real time. This is particularly important in controlled expansion cloud chambers (CECCs) where ice-nucleating properties of suspended dust samples are studied in cold and mixed phase cloud conditions. In this work, the mineralogy and mixing state of the fine fraction (&lt;2.5 µm) in laboratory-suspended dust from PSAs in north Africa were made using novel techniques with online single-particle mass spectrometry (SPMS) and traditional offline scanning electron microscopy (SEM). A regional difference in mineralogy was detected, with material sourced from Morocco containing a high number fraction of illite-like particles in contrast to Sahelian material which contains potassium- and sodium-depleted clay minerals like kaolinite. Single-particle mixing state had a much greater local variation than mineralogy, particularly with respect to organic–biological content. Applying the same methods to ambient measurement of transported dust in the marine boundary layer at Cabo Verde in the remote North Atlantic enabled the number fractions of illite/smectite clay mineral (ISCM), non-ISCM and calcium-containing particles to be reported at a 1 h time resolution over a 20-day period. Internal mixing of silicate particles with nitrate, chlorine and organic–biological material was also measured and compared to that in the suspended soils. The results show SPMS and SEM techniques are complementary and demonstrate that SPMS can provide a meaningful high-resolution measurement of single-particle mineralogy and mixing state in laboratory and ambient conditions. In most cases, the differences in the mineralogical composition between particles within a soil sample were small. Thus, particles were not composed of discrete mineral phases. In ambient measurements, the ISCM and nitrate content was found to change significantly between distinct dust events, indicating a shift in source and transport pathways which may not be captured in offline composition analysis or remote sensing techniques.

Magnetic measurement system of sandy gravel specimens shape during tests in a large triaxial apparatus

As well known, rockfill behaviour is strongly influenced by both intrinsic (mineralogy and size of particles, grain shapes, soil grading etc.) and state parameters (relative density, stress state, relative humidity). To investigate their mechanical response to stresses and relative humidity (RH) loadings, a large size triaxial device (H = 410 mm, D = 200 mm) has been developed at the University of Naples Federico II (Italy), including modifications required to impose partially saturated conditions in the specimen by means of the vapour equilibrium technique. In order to evaluate local axial and radial strains and global volumetric strains in partially saturated conditions, a magnetic shape detector device has been designed and installed. The accuracy of this system has been evaluated in some isotropic compression triaxial tests on compacted sandy-gravel specimens. The experimental data clearly show the effectiveness of the magnetic system in the measurement of axial displacements while the measurement in radial direction appear to be strongly affected by the non-linearity of the complex magnetic field generated during the test and requires further checking tests.

Single particle mineralogy of microparticles from Himalayan ice-cores using SEM/EDX and ATR-FTIR imaging techniques for identification of volcanic ash signatures

In this study, insoluble microparticles from four discrete layers of ice-cores drilled out from the East Rongbuk glacier of the Himalayas were characterized on a single particle basis by scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM/EDX) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) imaging. The combined application of the two single particle analytical techniques for the analysis of the same individual particles provided complementary information, i.e., their elemental compositions and morphology by SEM/EDX and their molecular species, functional groups, and crystallinity by ATR-FTIR imaging, which is crucial for the definite identification of the mineral species including their polymorphs. The results showed that the integrated signatures of volcanic ash (VA), involving their mineralogical characteristics for silica polymorphs, vitreous nature of silica and silicate particles, chemical heterogeneity within the micrometer sized particles, and unique morphology, can be used to clearly differentiate micrometer sized VA from the mineral dust of a soil origin on a single-particle basis. The different mineralogical characteristics among the volcanic samples would be due to their association with different volcanic eruptions.