Anthropogenic influence on surface changes at the Olivares glaciers; Central Chile.

We have investigated the source and role of light-absorbing impurities (LAIs) deposited on the glaciers of the Olivares catchment, in Central Chile. LAIs can considerably darken (lowered albedo) the glacier surface, enhancing their melt. We combined chemical and mineralogical laboratory analyses of surface and ice core samples with field-based spectral reflectance measurements to investigate the nature and properties of such LAIs. Using remote sensing-based albedo maps, we upscaled local information to glacier-wide coverage. We then used a model to evaluate the sensitivity of surface mass balance to a change in ice and snow albedo. The across-scale surface observations in combination with ice core analysis revealed a history of over half a century of LAIs deposition. We found traces of mining residuals in glacier surface samples. The glaciers with highest mass loss in the catchment present enhanced concentrations of surface dust particles with low reflectance properties. Our results indicate that dust particles with strong light-absorbing capacity have been mobilized from mine tailings and deposited on the nearby glacier surfaces. Large-scale assessment from satellite-based observations revealed darkening (ice albedo lowering) at most investigated glacier tongues from 1989 to 2018. Glacier melt is sensitive to ice albedo. We believe that an accelerated winter and spring snow albedo decrease, partially triggered by surface impurities, might be responsible for the above-average mass loss encountered in this catchment.

Automated identification and quantification of tire wear particles (TWP) in airborne dust: SEM/EDX single particle analysis coupled to a machine learning classifier.

The share of non-exhaust particles, including tire wear particles (TWP), within the airborne dust and particularly within PM10 has increased in recent years due to a significant reduction of other particles including exhaust road traffic emissions. However, the quantification of TWP is a demanding task due to the non-specificity of tracers, and the fact that they are commonly contained in analytically challenging low concentrations (e.g. Zn, styrene, 1,3-butadiene, vinylcyclohexene). This difficulty is amplified by the chemical and morpho-textural heterogeneity of TWP resulting from the interaction between the tires and the road surface. In contrast to bulk techniques, automated single particle SEM/EDX analysis can benefit from the ubiquitous heterogeneity of environmental TWP as a diagnostic criterion for their identification and quantification. For this purpose, we follow a machine-learning (ML) approach that makes use of an extensive number (67) of morphological, textural (backscatter-signal based) and chemical descriptors to differentiate environmental particles into the following classes: TWP, metals, minerals and biogenic/organic. We present a ML-based model developed to classify airborne samples (trained by >100,000 environmental particles including 6841 TWP), and its application within a one-year monitoring campaign at two Swiss sites. In this study, the mass concentrations of TWP in the airborne fractions PM80-10, PM10-2.5 and PM2.5-1 were determined. Furthermore, the particle size distribution and shape characteristics of 5621 TWP were evaluated. A cut through a TWP by means of FIB-SEM evidences that the mineral and metal particles typically found in TWP are not only present on the particle surface but also throughout the complete TWP volume. At the urban background site, the annual average mass fraction of TWP and micro-rubber in PM10 was 1.8% (0.28 µg/m3) and 0.9%, respectively. At the urban kerbside site, the corresponding values were 6 times higher amounting to 10.5% (2.24 µg/m3) for TWP, and 5.0% for micro-rubber.

Transformation of TiO2 (nano)particles during sewage sludge incineration.

Titanium dioxide (TiO2) (nano)particles are produced in large quantities and their potential impacts on ecosystems warrants investigations into their fate after disposal. TiO2 particles released into wastewater are retained by wastewater treatment plants and accumulate in digested sludge, which is increasingly incinerated in industrialized countries. Therefore, we investigated the changes of the Ti-speciation during incineration of as-received sludge and of sludge spiked with anatase (d=20-50 nm) or rutile (d=200-400 nm) using X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM). In the as-received sludge, rutile and anatase were the dominant Ti bearing minerals and both remained unaffected by the anaerobic treatment. During incineration, Ti reacts with hematite to members of the hematite-ilmenite solid solution series (Hem-Ilm). Up to 80% of the Ti spiked as anatase transformed into Hem-Ilm, a distorted 6-fold coordinated Ti (Ti(IV)sulfate) and rutile during incineration. Up to 30% and 60% of rutile transformed into Hem-Ilm and Ti(IV)sulfate represented phases in fly and bottom ash, respectively. Fe and Ti were spatially correlated in ash derived from as-received and anatase spiked sludge, whereas only a thin layer of the spiked rutile reacted with Fe, in line with XAS data. This study highlights the transient nature of nano-Ti species during sewage sludge incineration.

Constraining the formation of authigenic carbonates in a seepage-affected cold-water coral mound by lipid biomarkers.

Cold-water coral (CWC) mounds are build-ups comprised of coral-dominated intervals alternating with a mixed carbonate-siliciclastic matrix. At some locations, CWC mounds are influenced by methane seepage, but the impact of methane on CWC mounds is poorly understood. To constrain the potential impact of methane on CWC mound growth, lipid biomarker investigations were combined with mineralogical and petrographic analyses to investigate the anaerobic oxidation of methane (AOM) and authigenic carbonate formation in sediment from a seep-affected CWC mound in the Gulf of Cadiz. The occurrence of AOM was confirmed by characteristic lipids found within a semi-lithified zone (SLZ) consisting of authigenic aragonite, high-magnesium calcite and calcium-excess dolomite. The formation of high-Mg calcite is attributed to AOM, acting as a lithifying agent. Aragonite is only a minor phase. Ca-excess dolomite in the SLZ and upper parts may be formed by organoclastic sulphate reduction, favouring precipitation by increased alkalinity. The AOM biomarkers in the SLZ include isoprenoid-based archaeal membrane lipids, such as abundant glycerol dibiphytanyl glycerol tetraethers (GDGTs) dominated by GDGT-2. The δ13 C values of GDGT-2, measured as ether-cleaved monocyclic biphytanes, are as low as -100‰ versus V-PDB. Further, bacterial dialkyl glycerol diethers with two anteiso-C15 alkyl chains and δ13 C values of -81‰ are interpreted as biomarkers of sulphate-reducing bacteria. The lipid biomarker signatures and mineralogical patterns suggest that anaerobic methane-oxidizing archaea of the ANME-1 group thrived in the subsurface at times of slow and diffusive methane seepage. Petrographic analyses revealed that the SLZ was exhumed at some point (e.g. signs of bioerosion of the semi-lithified sediment), providing a hard substrate for CWC larval settlement. In addition, this work reveals that AOM-induced semi-lithification likely played a role in mound stabilization. Lipid biomarker analysis proves to be a powerful tool to disentangle early diagenetic processes induced by microbial metabolisms.

Hybrid magnetic iron oxide nanoparticles with tunable field-directed self-assembly.

We describe the synthesis of hybrid magnetic ellipsoidal nanoparticles that consist of a mixture of two different iron oxide phases, hematite (α-Fe2O3) and maghemite (γ-Fe2O3), and characterize their magnetic field-driven self-assembly. We demonstrate that the relative amount of the two phases can be adjusted in a continuous way by varying the reaction time during the synthesis, leading to strongly varying magnetic properties of the particles. Not only does the saturation magnetization increase dramatically as the composition of the spindles changes from hematite to maghemite, but also the direction of the induced magnetic moment changes from being parallel to the short axis of the spindle to being perpendicular to it. The magnetic dipolar interaction between the particles can be further tuned by adding a screening silica shell. Small-angle X-ray scattering (SAXS) experiments reveal that at high magnetic field, magnetic dipole-dipole interaction forces the silica coated particles to self-assemble into a distorted hexagonal crystal structure at high maghemite content. However, in the case of uncoated maghemite particles, the crystal structure is not very prominent. We interpret this as a consequence of the strong dipolar interaction between uncoated spindles that then become arrested during field-induced self-assembly into a structure riddled with defects.

Electron transfer in peptides: on the formation of silver nanoparticles.

Some microorganisms perform anaerobic mineral respiration by reducing metal ions to metal nanoparticles, using peptide aggregates as medium for electron transfer (ET). Such a reaction type is investigated here with model peptides and silver as the metal. Surprisingly, Ag(+) ions bound by peptides with histidine as the Ag(+)-binding amino acid and tyrosine as photoinducible electron donor cannot be reduced to Ag nanoparticles (AgNPs) under ET conditions because the peptide prevents the aggregation of Ag atoms to form AgNPs. Only in the presence of chloride ions, which generate AgCl microcrystals in the peptide matrix, does the synthesis of AgNPs occur. The reaction starts with the formation of 100 nm Ag@AgCl/peptide nanocomposites which are cleaved into 15 nm AgNPs. This defined transformation from large nanoparticles into small ones is in contrast to the usually observed Ostwald ripening processes and can be followed in detail by studying time-resolved UV/Vis spectra which exhibit an isosbestic point.

Fe and Mn oxidation states by TEM-EELS in fine-particle emissions from a Fe-Mn alloy making plant.

Fine particles were sampled both inside the chimneys and in the near-field of an Fe-Mn-alloy manufacturing plant. The transfer from one point to another point in the environment, as well as the bioavailability and toxicity of these two metals, depend above all on their speciation. The oxidation states of iron and manganese in the collected particles were determined by using transmission electron microscopy coupled with electron energy-loss spectroscopy (TEM-EELS). The mineralogical identity of these metal-rich particles was determined by selected area electron diffraction (SAED) coupled with energy-dispersive X-ray spectroscopy (EDX). This study shows that both iron and manganese in metallic particles are prone to oxidation reactions via gas/particle conversion mechanisms, which take place in the flue gases within the smoke stacks. This phenomenon is more pronounced for the smallest Fe-rich particles. However, no further change of oxidation state of the two elements was observed in the near-field of the plant, after emission into the atmosphere (within <2000 m of the smoke stacks). The oxidation states of iron and manganese remain mainly between +II and +III, which is probably due to short residence time of these particles in the pollution plume.

Debinding mechanisms in thermoplastic processing of a Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ)- stearic acid-polystyrene mixture.

In the present study, we address the interaction between a thermoplastic binder system and Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) (BSCF) during thermal treatment of the thermoplastic feedstock. BSCF powder was coated with different amounts of stearic acid (SA) acting as a surfactant. Oxygen release from the uncoated BSCF surface changes the decomposition of polystyrene (PS) in inert atmospheres from a pyrolytic to a thermoxidative mechanism, thereby decreasing the break-down temperature and the activation energy. In mixtures with coated BSCF powder, the decomposition products of SA carbonatize the BSCF surface, which inhibits oxygen release. Mass spectrometry of the breakdown products indicates that the decomposition of SA in the presence of BSCF also modifies the decomposition pathway of PS. The influence of BSCF on the polymer decomposition reaction in air is not as strong. Oxygen diffusion seems to be responsible for the differences to pure PS in reaction rates and the activation energies.

Cellular uptake and toxic effects of fine and ultrafine metal-sulfate particles in human A549 lung epithelial cells.

Ambient airborne particulate matter is known to cause various adverse health effects in humans. In a recent study on the environmental impacts of coal and tire combustion in a thermal power station, fine crystals of PbSO(4) (anglesite), ZnSO(4)·H(2)O (gunningite), and CaSO(4) (anhydrite) were identified in the stack emissions. Here, we have studied the toxic potential of these sulfate phases as particulates and their uptake in human alveolar epithelial cells (A549). Both PbSO(4) and CaSO(4) yielded no loss of cell viability, as determined by the WST-1 and NR assays. In contrast, a concentration-dependent increase in cytotoxicity was observed for Zn sulfate. For all analyzed sulfates, an increase in the production of reactive oxygen species (ROS), assessed by the DCFH-DA assay and EPR, was observed, although to a varying extent. Again, Zn sulfate was the most active compound. Genotoxicity assays revealed concentration-dependent DNA damage and induction of micronuclei for Zn sulfate and, to a lower extent, for CaSO(4), whereas only slight effects could be found for PbSO(4). Moreover, changes of the cell cycle were observed for Zn sulfate and PbSO(4). It could be shown further that Zn sulfate increased the nuclear factor kappa-B (NF-κB) DNA binding activity and activated JNK. During our TEM investigations, no effect on the appearance of the A549 cells exposed to CaSO(4) compared to the nonexposed cells was observed, and in our experiments, only one CaSO(4) particle was detected in the cytoplasm. In the case of exposure to Zn sulfate, no particles were found in the cytoplasm of A549 cells, but we observed a concentration-dependent increase in the number and size of dark vesicles (presumably zincosomes). After exposure to PbSO(4), the A549 cells contained isolated particles as well as agglomerates both in vesicles and in the cytoplasm. Since these metal-sulfate particles are emitted into the atmosphere via the flue gas of coal-fired power stations, they may be globally abundant. Therefore, our study is of direct relevance to populations living near such power plants.

Cytotoxicity and genotoxicity of size-fractionated iron oxide (magnetite) in A549 human lung epithelial cells: role of ROS, JNK, and NF-κB.

Airborne particulate matter (PM) of varying size and composition is known to cause health problems in humans. The iron oxide Fe(3)O(4) (magnetite) may be a major anthropogenic component in ambient PM and is derived mainly from industrial sources. In the present study, we have investigated the effects of four different size fractions of magnetite on signaling pathways, free radical generation, cytotoxicity, and genotoxicity in human alveolar epithelial-like type-II cells (A549). The magnetite particles used in the exposure experiments were characterized by mineralogical and chemical techniques. Four size fractions were investigated: bulk magnetite (0.2-10 µm), respirable fraction (2-3 µm), alveolar fraction (0.5-1.0 µm), and nanoparticles (20-60 nm). After 24 h of exposure, the A549 cells were investigated by transmission electron microscopy (TEM) to study particle uptake. TEM images showed an incorporation of magnetite particles in A549 cells by endocytosis. Particles were found as agglomerates in cytoplasm-bound vesicles, and few particles were detected in the cytoplasm but none in the nucleus. Increased production of reactive oxygen species (ROS), as determined by the 2',7'-dichlorfluorescein-diacetate assay (DCFH-DA), as well as genotoxic effects, as measured by the cytokinesis block-micronucleus test and the Comet assay, were observed for all of the studied fractions after 24 h of exposure. Moreover, activation of c-Jun N-terminal kinases (JNK) without increased nuclear factor kappa-B (NF-κB)-binding activity but delayed IκB-degradation was observed. Interestingly, pretreatment of cells with magnetite and subsequent stimulation with the pro-inflammatory cytokine tumor necrosis factor-alpha (TNFα) led to a reduction of NF-κB DNA binding compared to that in stimulation with TNFα alone. Altogether, these experiments suggest that ROS formation may play an important role in the genotoxicity of magnetite in A549 cells but that activation of JNK seems to be ROS-independent.

Genotoxic effects of three selected black toner powders and their dimethyl sulfoxide extracts in cultured human epithelial A549 lung cells in vitro.

Until now, the adverse effects of toner powders on humans have been considered to be minimal. However, several recent reports have suggested possible significant adverse health effects from toner dust inhalation. The aim of this study was to evaluate the genotoxic potential of black toner powders in vitro. For the study of DNA damage, A549 cells were exposed to toner-powder suspensions and to their DMSO extracts, and then subjected to the comet assay and to the in-vitro cytokinesis block micronucleus test (CB-MNvit). Cytotoxic effects of the toner samples were assessed by the erythrosin B assay. Furthermore, size, shape, and composition of the toner powders were investigated. None of the three toner powders or their DMSO extracts reduced cell viability; however, they did induce DNA damage and formed micronuclei at concentrations from 80 to 400 µg cm(-2) , although to a varying extent. All toner powders contain considerable amounts of the pigments carbon black and magnetite (Fe(3) O(4) ) as well as small amounts of polycyclic aromatic hydrocarbons (PAHs). The overall results of our in-vitro study suggest that the investigated toner-powder samples are not cytotoxic but genotoxic. From the results of the physical and chemical characterization, we conclude that metals and metalloids as components of magnetite, or PAHs as components of the carbon-bearing material, are responsible for the genotoxic effects. Further research is necessary to determine the relevance of these in-vitro observations for private and occupational toner powder exposure.

In situ ESEM observation of melting silver and Inconel on an Al(2)O(3) powder bed.

A hot stage in an environmental scanning electron microscope (ESEM) was used for in situ infiltration experiments. Pressureless infiltration of a porous Ti-activated Al(2)O(3) preform has been investigated at temperatures up to 1530 degrees C under two atmospheres (He and H(2)O((g))). A brief description of the operating and the experimental set-up is given. Silver and Inconel (Ni superalloy) infiltration experiments demonstrate the in situ potential of the ESEM at temperatures up to 1500 degrees C.