Surface chemical characterization of 2.5-microm particulates (PM2.5) from air pollution in Salt Lake City using TOF-SIMS, XPS, and FTIR

Enhancing polyethylene degradation: a novel bioprocess approach using Acinetobacter nosocomialis pseudo-resting cells

Despite the discovery of several bacteria capable of interacting with polymers, the activity of the natural bacterial isolates is limited. Furthermore, there is a lack of knowledge regarding the development of bioprocesses for polyethylene (PE) degradation. Here, we report a bioprocess using pseudo-resting cells for efficient degradation of PE. The bacterial strain Acinetobacter nosocomialis was isolated from PE-containing landfills and characterized using low-density PE (LDPE) surface oxidation when incubated with LDPE. We optimized culture conditions to generate catalytic pseudo-resting cells of A. nosocomialis that are capable of degrading LDPE films in a bioreactor. After 28 days of bioreactor operation using pseudo-resting cells of A. nosocomialis, we observed the formation of holes on the PE film (39 holes per 217 cm2, a maximum diameter of 1440 μm). This study highlights the potential of bacteria as biocatalysts for the development of PE degradation processes. KEY POINTS: • New bioprocess has been proposed to degrade polyethylene (PE). • Process with pseudo-resting cells results in the formation of holes in PE film. • We demonstrated PE degradation using A. nosocomialis as a biocatalyst.

A comprehensive SERS, SEM and EDX study of individual atmospheric PM2.5 particles in Chengdu, China

Characterization of atmospheric fine particulate matter (PM_2.5) in large cities has important implications for the study of their sources and formation mechanisms, as well as in developing effective measures to control air pollution. Herein, we report a holistic physical and chemical characterization of PM_2.5 by combining surface-enhanced Raman scattering (SERS) with scanning electron microscopy (SEM) and electron-induced X-ray spectroscopy (EDX). PM_2.5 particles were collected in a suburban area of Chengdu, a large city in China with a population over 21 million. A special SERS chip composed of inverted hollow Au cone (IHAC) arrays was designed and fabricated to allow direct loading of PM_2.5 particles. SERS and EDX were used to reveal the chemical composition, and particle morphologies were analyzed from SEM images. SERS data of atmospheric PM_2.5 indicated qualitatively the presence of carbonaceous particulate matter, sulfate, nitrate, metal oxides and bioparticles. The EDX showed the presence of the elements C, N, O, Fe, Na, Mg, Al, Si, S, K, and Ca in the collected PM_2.5. Morphology analysis showed that the particulates were mainly in the form of flocculent clusters, spherical, regular crystal shaped or irregularly shaped particles. Our chemical and physical analyses also revealed that the main sources of PM_2.5 are automobile exhaust, secondary pollution caused by photochemical reactions in the air, dust, emission from nearby industrial exhaust, biological particles, other aggregated particles, and hygroscopic particles. SERS and SEM data collected during three different seasons showed that carbon-containing particles are the principal sources of PM_2.5. Our study demonstrates that the SERS based technique, when combined with standard physicochemical characterization methods, is a powerful analytical tool to determine the sources of ambient PM_2.5 pollution. Results obtained in this work may be valuable to the prevention and control of PM_2.5 pollution in air.

Roles of Amides on the Formation of Atmospheric HONO and the Nucleation of Nitric Acid Hydrates

Nitrous acid (HONO) is hazardous to the human respiratory system, and the hydrolysis of NO₂ is the source of HONO. Hence, the investigation on the removal and transformation of HONO is urgently established. The effects of amide on the mechanism and kinetics of the formation of HONO with acetamide, formamide, methylformamide, urea, and its clusters of the catalyst were studied theoretically. The results show that amide and its small clusters reduce the energy barrier, the substituent improves the catalytic efficiency, and the catalytic effect order is dimer > monohydrate > monomer. Meanwhile, the clusters composed of nitric acid (HNO₃), amides, and 1-6 water molecules were investigated in the amide-assisted nitrogen dioxide (NO₂) hydrolysis reaction after HONO decomposes by combining the system sampling technique and density functional theory. The study on thermodynamics, intermolecular forces, optics properties of the clusters, as well as the influence of humidity, temperature, atmospheric pressure, and altitude shows that amide molecules promote the clustering and enhance the optical properties. The substituent facilitates the clustering of amide and nitric acid hydrate and lowers the humidity sensitivity of the clusters. The findings will help to control the atmospheric aerosol particle and then reduce the harm of poisonous organic chemicals on human health.

Computational chemistry of cluster: Understanding the mechanism of atmospheric new particle formation at the molecular level

New particle formation (NPF), which exerts significant influence over human health and global climate, has been a hot topic and rapidly expands field of research in the environmental and atmospheric chemistry recent years. Generally, NPF contains two processes: formation of critical nucleus and further growth of the nucleus. However, due to the complexity of the atmospheric nucleation, which is a multicomponent process, formation of critical clusters as well as their growth is still connected to large uncertainties. Detection limits of instruments in measuring specific gaseous aerosol precursors and chemical compositions at the molecular level call for computational studies. Computational chemistry could effectively compensate the deficiency of laboratory experiments as well as observations and predict the nucleation mechanisms. We review the present theoretical literatures that discuss nucleation mechanism of atmospheric clusters. Focus of this review is on different nucleation systems involving sulfur-containing species, nitrogen-containing species and iodine-containing species. We hope this review will provide a deep insight for the molecular interaction of nucleation precursors and reveal nucleation mechanism at the molecular level.

Interactions of model airborne particulate matter with dipalmitoyl phosphatidylcholine and a clinical surfactant Calsurf

HYPOTHESIS

Lung surfactant protects lung tissue and reduces the surface tension in the alveoli during respiration. Particulate matter with an aerodynamic diameter of less than 2.5 μm (PM_2.5), which invades primely through inhalation, can deposit on and interact with the surfactant layer, leading to changes in the biophysical and morphological properties of the lung surfactant.

EXPERIMENTS

Langmuir monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and clinical surfactant Calsurf were investigated with a PM_2.5 model injected into the water subphase, which were characterized by surface pressure-area isotherms, Brewster angle microscopy, atomic force microscopy, fluorescent microscopy, and x-ray photoelectron spectroscopy. The binding between DPPC/Calsurf and PM_2.5 was studied using isothermal titration calorimetry.

FINDINGS

PM_2.5 induced the expansion of the monolayers at low surface pressure (п) and film condensation at high п. Aggregation of PM_2.5 mainly occurred at the interface of liquid expanded/liquid condensed (LE/LC) phases. PM_2.5 led to slimmer and ramified LC domains on DPPC and the reduction of nano-sized condensed domains on Calsurf. Both DPPC and Calsurf showed fast binding with PM_2.5 through complex binding modes attributed to the heterogeneity and amphiphilic property of PM_2.5. This study improves the fundamental understanding of PM_2.5-lung surfactant interaction and shows useful implications of the toxicity of PM_2.5 through respiration process.

Time-of-flight secondary ion mass spectrometry fragment regularity in gallium-doped zinc oxide thin films

Time-of-flight secondary ion mass spectrometry fragment analysis remains a challenging task. The fragment appearance regularity (FAR) rule is particularly useful for two-element compounds such as ZnO. Ion fragments appearing in the form of ZnxOy obey the rule [Formula: see text] in the positive secondary ion spectrum and [Formula: see text] in the negative spectrum where the valence of Zn is + 2 and that of O is - 2. Fragment analysis in gallium-doped ZnO (GZO) films can give insights into the bonding of the elements in this important semiconductor. Fragment analysis of 1 and 7 wt% GZO films shows that only the negative ion fragments obey the FAR rule where ZnO‒, 66ZnO‒, 68ZnO‒ and ZnO2‒ ion fragments appear. In the positive polarity, subdued peaks from out-of-the-rule ZnO+, 66ZnO+ and 68ZnO+ ion fragments are observed. The Ga ion peaks are present in both the positive and negative spectra. The secondary ion spectra of undoped ZnO also shows consistency with the FAR rule. This implies that Ga doping even in amounts that exceed the ZnO lattice limit of solubility does not affect the compliance with the FAR rule.

Photochemical aging of Beijing urban PM2.5: Production of oxygenated volatile organic compounds

PM_2.5 has become the dominant atmospheric pollutant in many countries. Many components of PM_2.5 are highly photoactive. However, the photochemical aging of PM_2.5 remains poorly understood. In this study, the photoaging of real PM_2.5 samples collected from 2017 to 2018 in Beijing under simulated solar radiation (λ ~ 340-850 nm) was investigated. Our study showed that large amounts of oxygenated volatile organic compounds (OVOCs), such as acetaldehyde, formic acid, acetone and acetic acid, were released during the photochemical aging of PM_2.5. Furthermore, although a positive correlation between the OVOCs yield and the organic matter (OM) in PM_2.5 was observed, the product distribution from the photoaging of PM_2.5 was different from that in the direct photolysis of artificially synthesized SOA. Because of the release of OVOCs, the PM_2.5 mass loss was evaluated to be ~1.80% per day under typical atmospheric conditions. The OVOCs released during the photoaging of PM_2.5 may contribute substantially to the OVOCs sources omitted from troposphere chemistry models and may have a significant effect on the OVOCs distribution and oxidation capacity of the atmosphere.

Carbon fractionation and stable carbon isotopic fingerprint of road dusts near coal power plant with emphases on coal-related source apportionment

Road dust from coal utilization is a significant source contributing to the generation of pollutants that can affect the health of people residing within close proximity to roadways. In this study, road dust samples were collected from different directions centered around a coal-fired power plant in Huainan. Black carbon (BC), soot, char, organic carbon (OC) and total carbon (TC), as well as the δ¹³C of samples, were determined. Compared to the reference locations which were distant from the power plant, the research areas surrounding the power plant were featured by significantly higher OC/BC ratio and TC concentration. The OC/BC showed significant difference in urban vs. rural areas, and at different distances from the central power plant, which implied that the source and spread of carbonaceous species was dominantly affected by wind direction and urban/rural area differences. Surface morphology analysis showed that the road dust was mixed with spherical particles similar to fly ash. High-resolution XPS C1s spectrum revealed the existence of metal carbide, metal carbonate, and CF₃ in the road dust samples. The speciation of carbon in road dusts was found correlated with sampling directions and urban functional areas. Based on the δ¹³C and OC/BC, it could be inferred that coal-related substances might be important sources of road dusts.

Cytotoxicity of the soluble and insoluble fractions of atmospheric fine particulate matter

Inhaled atmospheric fine particulate matter (PM_2.5) includes soluble and insoluble fractions, and each fraction can interact with cells and cause adverse effects. PM_2.5 samples were collected in Jinan, China, and the soluble and insoluble fractions were separated. According to physiochemical characterization, the soluble fraction mainly contains water-soluble ions and organic acids, and the insoluble fraction mainly contains kaolinite, calcium carbonate and some organic carbon. The interaction between PM_2.5 and model cell membranes was examined with a quartz crystal microbalance with dissipation (QCM-D) to quantify PM_2.5 attachment on membranes and membrane disruption. The cytotoxicity of the total PM_2.5 and the soluble and insoluble fractions, was investigated. Negatively charged PM_2.5 can adhere to the positively charged membranes and disrupt them. PM_2.5 also adheres to negatively charged membranes but does not cause membrane rupture. Therefore, electrostatic repulsion does not prevent PM_2.5 attachment, but electrostatic attraction induces remarkable membrane rupture. The human lung epithelial cell line A549 was used for cytotoxicity assessment. The detected membrane leakage, cellular swelling and blebbing indicated a cell necrosis process. Moreover, the insoluble PM_2.5 fraction caused a higher cell mortality and more serious cell membrane damage than the soluble fraction. The levels of reactive oxygen species (ROS) enhanced by the two fractions were not significantly different. The findings provide more information to better understand the mechanism of PM_2.5 cytotoxicity and the effect of PM_2.5 solubility on cytotoxicity.

Spatial varying profiling of air PM constituents using paper-based microfluidics

Accurate and quantitative profiling of air particulate matter (PM) compositions is essential for assessing local pollution information. The method combining mobile aerial sampling using unmanned aerial vehicles (UAVs) and prompt analysis excels in this regard as it allows spatiotemporal mapping of air pollution, especially in the vertical direction. However, applications of the method are still scarce as it is limited by a lack of sampling reliability due to insufficient aerial sampling time and a lack of accurate, portable quantification techniques. In this work, by integrating mobile aerial sampling with in-flight tethered charging and smartphone-based colorimetric analysis in a cost-effective paper microfluidic device, we present a method for quantitative, reliable profiling of spatiotemporal variation in air PM compositions. The method extends aerial sampling time to 12-15 flight hours per deployment, thereby significantly improving sampling reliability while maintaining the maneuverability of the UAVs. Also, smartphone-based colorimetric analysis combined with paper-based microfluidics enables portable, economically efficient analysis and is well-suited for using in low-resource settings. We demonstrated the utility of the method by carrying out a spatiotemporal variation study of air PM trace metal components (Fe, Ni, and Mn) at 4 geographical locations in Fuzhou, China, for a period of 21 days, and the results were in good agreement with results obtained from using a commercial instrument. Beside air PM composition study, this method is universally applicable and holds great potential to be extended to multipollutant analysis, such as prompt detection of airborne viruses, bacteria, and others.

Comparison of operator- and computer-controlled scanning electron microscopy of particles from different atmospheric aerosol types

Individual aerosol particles from an urban background site in Mainz (Germany), a traffic hotspot site in Essen (Germany), the free troposphere in the Swiss Alps (high altitude research station Jungfraujoch), a rural background/marine site on Cyprus (Cyprus Atmospheric Observatory) and a rural background site in the forested area of Odenwald (Germany) were characterised with two different scanning electron microscopy techniques, operator controlled (opSEM) and computer controlled (ccSEM). For all samples, about 500 particles were investigated by opSEM, and between 1103 and 6940 particles by ccSEM. Large systematic differences (in some cases a factor up to ~ 20) in the abundance of the various particle groups are observed in the results of the two techniques. These differences are dependent on particle type and size. With ccSEM, information on the mixing state of particles (e.g., presence of heterogeneous inclusions, surface coatings or gradients in chemical composition) cannot be obtained, and particle groups which are recognised by their complex morphology (e.g., soot and fly ash particles) are classified into other particle groups. In addition, highly volatile particles (i.e., particles which evaporate under electron bombardment within seconds) will be overlooked by ccSEM. If these limitations of ccSEM are not considered, normalising the particle group abundances to 100% (a popular practise in many publications) may lead to drastic misinterpretation of the real aerosol composition. OpSEM is indispensable when detailed information of particle composition is required, although it suffers from a much higher expenditure of time. In conclusion, both techniques might be used for single particle characterisation as long as drawbacks of each are considered.

A density functional theory study of the molecular interactions between a series of amides and sulfuric acid

Amides, a class of nitrogen-containing organic pollutants in the atmosphere, may affect the formation of atmospheric aerosols by the interactions with sulfuric acid. Here, the molecular interactions of sulfuric acid with formamide, methylformamide, dimethylformamide, acetamide, methylacetamide and dimethylacetamide was investigated by density functional theory. Geometry optimization and Gibbs free energy calculation were carried out at M06-2X/6-311++G(3df,3pd) level. The results indicate that the addition of amides to H₂SO₄ might have a promoting effect on atmospheric new particle formation at 298.15 K and 1 atm. In the initial stage of new particle formation, the binding capacity of amides and sulfuric acid is stronger than ammonia, but weaker than methylamine. It is worth noting that the trans-methylacetamide could have similar capabilities of stabilizing sulfuric acid as dimethylamine. In the presence of water, amides are found to only have a weak enhancement capability on new particle formation. In addition, we can infer from evaporation rate that the small molecule clusters of formamide and sulfuric acid may be more energetically favorable than macromolecule clusters.

Mechanism of Goethite Precipitation on Magnetite and Maghemite Nanoparticles Studied by Surface Complexation/Precipitation Modeling

Precipitation of goethite on magnetic nanoparticles (MNPs) has been proposed as an effective means to separate goethite from calcium sulfate in the iron removal process of zinc hydrometallurgy, which allows reuse of the hazardous residues. This study focuses on investigating the underlying mechanisms of goethite precipitation on magnetite and maghemite MNPs, providing insights on Fe(III)_aq adsorption and nucleation of goethite on MNPs. A predictive surface complexation/precipitation model of the system was developed based on the results from two different types of experiments: the potentiometric titration of MNPs to calculate proton binding constants ( K_a) of discrete MNP surface functional groups and the corresponding site concentrations; and adsorption of Fe(III)_aq onto MNP surfaces to determine metal binding constants ( K_f). The composition of the surface complexes on MNPs was determined by time-of-flight secondary ion mass spectrometry. The results indicated the formation of polynuclear surface complexes. The content of polynuclear surface complexes was found to be significantly higher on maghemite MNPs than on magnetite MNPs. This trend is consistent with our experimental results of a greater goethite precipitation on maghemite than on magnetite. Overall, the formation of Fe(III) polynuclear surface complexes correlates directly to the nucleation and precipitation of goethite on the surfaces of both types of MNPs.

TOF-SIMS surface analysis of chemical components of size-fractioned urban aerosols in a typical heavy air pollution event in Beijing

Size-fractioned atmospheric aerosol particles were collected during a typical heavy air pollution event in Beijing. The organic and inorganic components on the surfaces of the samples were analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The variation characteristics of the surface chemical composition and influencing factors were studied, and the possible sources of these chemical compositions were identified through principal component analysis. The results showed that inorganic components such as crustal elements and sulfate, and organic components such as aliphatic hydrocarbons and oxygen-containing organic groups were present. Some surface components, such as polycyclic aromatic hydrocarbons, heavy metals and fluorides may exert adverse effects on human health. The species and relative percentages of the chemical components varied with particle size, diurnal and pollution progress. During a heavy pollution event, the species and relative percentages of secondary components such as oxygen-containing organic groups and sulfurous compounds increased, indicating that particles aged during this event. The surface chemical composition of the aerosol particles was affected mainly by emissions from coal combustion and motor vehicles. In addition, air pollution, meteorological factors, and air mass transport also exerted a significant effect on the surface chemical composition of aerosol particles.

Nanoscale spectroscopic and mechanical characterization of individual aerosol particles using peak force infrared microscopy

Atmospheric aerosol particles of sizes less than 2.5 microns affect public health in cities. Understanding the fine structures of aerosol particles is important to decipher their source. Here, we use a novel spectroscopic and mechanical microscopy technique of 10 nm spatial resolution to reveal the nanoscale structures of individual aerosol particles.

Sampling and single particle analysis for the chemical characterisation of fine atmospheric particulates: A review

To better understand the potential environmental and human health impacts of fine airborne particulate matter (APM), detailed physical and chemical characterisation is required. The only means to accurately distinguish between the multiple compositions in APM is by single particle analysis. A variety of methods and instruments are available, which range from filter-based sample collection for off-line laboratory analysis to on-line instruments that detect the airborne particles and generate size distribution and chemical data in real time. There are many reasons for sampling particulates in the ambient atmosphere and as a consequence, different measurement strategies and sampling devices are used depending on the scientific objectives and subsequent analytical techniques. This review is designed as a guide to some of the techniques available for the sampling and subsequent chemical analysis of individual inorganic particles.

Secondary ion mass spectrometry: The application in the analysis of atmospheric particulate matter

Currently, considerable attention has been paid to atmospheric particulate matter (PM) investigation due to its importance in human health and global climate change. Surface characterization, single particle analysis and depth profiling of PM is important for a better understanding of its formation processes and predicting its impact on the environment and human being. Secondary ion mass spectrometry (SIMS) is a surface technique with high surface sensitivity, high spatial resolution chemical imaging and unique depth profiling capabilities. Recent research shows that SIMS has great potential in analyzing both surface and bulk chemical information of PM. In this review, we give a brief introduction of SIMS working principle and survey recent applications of SIMS in PM characterization. Particularly, analyses from different types of PM sources by various SIMS techniques were discussed concerning their advantages and limitations. The future development and needs of SIMS in atmospheric aerosol measurement are proposed with a perspective in broader environmental sciences.

A preliminary analysis of the surface chemistry of atmospheric aerosol particles in a typical urban area of Beijing

Atmospheric aerosol particle samples were collected using an Ambient Eight Stage (Non-Viable) Cascade Impactor Sampler in a typical urban area of Beijing from 27th Sep. to 5th Oct., 2009. The surface chemistry of these aerosol particles was analyzed using Static Time of Flight-Secondary Ion Mass Spectrometry (Static TOF-SIMS). The factors influencing surface compositions were evaluated in conjunction with the air pollution levels, meteorological factors, and air mass transport for the sampling period. The results show that a variety of organic ion groups and inorganic ions/ion groups were accumulated on the surfaces of aerosol particles in urban areas of Beijing; and hydrophobic organic compounds with short- or middle-chain alkyl as well as hydrophilic secondary inorganic compounds were observed. All these compounds have the potential to affect the atmospheric behavior of urban aerosol particles. PM1.1-2.1 and PM3.3-4.7 had similar elements on their surfaces, but some molecules and ionic groups demonstrated differences in Time of Flight-Secondary Ion Mass Spectrometry spectra. This suggests that the quantities of elements varied between PM1.1-2.1 and PM3.3-4.7. In particular, more intense research efforts into fluoride pollution are required, because the fluorides on aerosol surfaces have the potential to harm human health. The levels of air pollution had the most significant influence on the surface compositions of aerosol particles in our study. Hence, heavier air pollution was associated with more complex surface compositions on aerosol particles. In addition, wind, rainfall, and air masses from the south also greatly influenced the surface compositions of these urban aerosol particles.

Water soluble and insoluble components of urban PM2.5 and their cytotoxic effects on epithelial cells (A549) in vitro

When PM2.5 enters human bodies, the water soluble (WS-PM2.5) and insoluble components (WIS-PM2.5) of PM2.5 would interact with cells and cause adverse effects. However, the knowledge about the individual toxicity contribution of these two components is limited. In this study, the physiochemical properties of PM2.5 were well characterized. The toxic effects of WS-PM2.5 and WIS-PM2.5, which include the cell viability, cell membrane damage, reactive oxygen species (ROS) generation and morphological changes, were examined with human lung epithelial A549 cells in vitro. The results indicated that WS-PM2.5 could induce the early response of ROS generation, multiplied mitochondria and multi-lamellar bodies in A549 cells, which might cause cell damage through oxidative stress. Meanwhile, WIS-PM2.5 was predominantly associated with the cell membrane disruption, which might lead to the cell damage through cell-particle interactions. Moreover, the synergistic cytotoxic effects of WS-PM2.5 and WIS-PM2.5 were observed at longer exposure time. These findings demonstrate the different cytotoxicity mechanisms of WS-PM2.5 and WIS-PM2.5, which suggest that not only the size and dosage of PM2.5 but also the solubility of PM2.5 should be taken into consideration when evaluating the toxicity of PM2.5.

Fabrication of Nanometer- and Micrometer-Scale Protein Structures by Site-Specific Immobilization of Histidine-Tagged Proteins to Aminosiloxane Films with Photoremovable Protein-Resistant Protecting Groups

The site-specific immobilization of histidine-tagged proteins to patterns formed by far-field and near-field exposure of films of aminosilanes with protein-resistant photolabile protecting groups is demonstrated. After deprotection of the aminosilane, either through a mask or using a scanning near-field optical microscope, the amine terminal groups are derivatized first with glutaraldehyde and then with N-(5-amino-1-carboxypentyl)iminodiacetic acid to yield a nitrilo-triacetic-acid-terminated surface. After complexation with Ni(2+), this surface binds histidine-tagged GFP and CpcA-PEB in a site-specific fashion. The chemistry is simple and reliable and leads to extensive surface functionalization. Bright fluorescence is observed in fluorescence microscopy images of micrometer- and nanometer-scale patterns. X-ray photoelectron spectroscopy is used to study quantitatively the efficiency of photodeprotection and the reactivity of the modified surfaces. The efficiency of the protein binding process is investigated quantitatively by ellipsometry and by fluorescence microscopy. We find that regions of the surface not exposed to UV light bind negligible amounts of His-tagged proteins, indicating that the oligo(ethylene glycol) adduct on the nitrophenyl protecting group confers excellent protein resistance; in contrast, exposed regions bind His-GFP very effectively, yielding strong fluorescence that is almost completely removed on treatment of the surface with imidazole, confirming a degree of site-specific binding in excess of 90%. This simple strategy offers a versatile generic route to the spatially selective site-specific immobilization of proteins at surfaces.

Comparison of physicochemical properties between fine (PM2.5) and coarse airborne particles at cold season in Korea

Although it has been well-known that atmospheric aerosols affect negatively the local air quality, human health, and climate changes, the chemical and physical properties of atmospheric aerosols are not fully understood yet. This study experimentally measured the physiochemical characteristics of fine and coarse aerosol particles at the suburban area to evaluate relative contribution to environmental pollution in consecutive seasons of autumn and winter, 2014-2015, using XRD, SEM-EDX, XNI, ICP-MS, and TOF-SIMS. For these experimental works, the fine and coarse aerosols were collected by the high volume air sampler for 7 days each season. The fine particles contain approximately 10 μg m(-3) of carbonaceous aerosols consisting of 90% organic and 10% elemental carbon. The spherical-shape carbonaceous particles were observed for the coarse samples as well. Interestingly, the coarse particles in winter showed the increased frequency of carbon-rich particles with high contents of heavy metals. These results suggest that, for the cold season, the coarse particles could contribute relatively more to the conveyance of toxic contaminants compared to the fine particles in the study area. However, the fine particles showed acidic properties so that their deposition to surface may cause facilitate the increase of mobility for toxic heavy metals in soil and groundwater environments. The fine and coarse particulate matters, therefore, should be monitored separately with temporal variation to evaluate the impact of atmospheric aerosols to environmental pollution and human health.

Secondary ion mass spectrometry signatures for verifying declarations of fissile-material production

Direct analysis of uranium enrichment facility components were performed using secondary ion mass spectrometry (SIMS). A standard protocol was developed to enable preparation of SIMS samples from a corroded pipe piece without disturbing the corrosion layer. Unique uranium, oxygen and fluorine containing signatures were discovered in the corrosion layer by performing a mass scan of the region of interest from 230 to 280amu. These signatures identified the source of the corrosion layer as uranium hexafluoride (UF6) or an associated hydrolysis product. Isotopic analysis of the corrosion layer determined enrichment of (235)U to a value of 0.0116±0.0019 for the (235)U/(238)U isotopic ratio as compared to the NIST traceable standard (CRM 112-A) with a natural (235)U/(238)U isotopic ratio of 0.007254±0.000004. SIMS depth analysis revealed that the corrosion layer was isotopically homogenous to a depth of ~23.5µm. Optical profilometry measurements prior to and following SIMS depth analysis were used to determine a sputter rate of 0.48nm/s for 18.5keV O(-) ion bombardment of the corrosion layer. The data presented is conclusive evidence that SIMS depth analysis can be used to identify novel nuclear archeology signatures from uranium enrichment components and perform meaningful isotopic analysis of these signatures.

Parameters influencing sulfur speciation in environmental samples using sulfur k-edge x-ray absorption near-edge structure

This paper aims to enhance the credibility of applying the sulfur K-edge XANES spectroscopy as an innovative "fingerprint" for characterizing environmental samples. The sensitivities of sulfur K-edge XANES spectra of ten sulfur compound standards detected by two different detectors, namely, Lytle detector (LyD) and Germanium detector (GeD), were studied and compared. Further investigation on "self-absorption" effect revealed that the maximum sensitivities of sulfur K-edge XANES spectra were achieved when diluting sulfur compound standards with boron nitride (BN) at the mixing ratio of 0.1%. The "particle-size" effect on sulfur K-edge XANES spectrum sensitivities was examined by comparing signal-to-noise ratios of total suspended particles (TSP) and particulate matter of less than 10 millionths of a meter (PM(10)) collected at three major cities of Thailand. The analytical results have demonstrated that the signal-to-noise ratios of sulfur K-edge XANES spectra were positively correlated with sulfate content in aerosols and negatively connected with particle sizes. The combination of hierarchical cluster analysis (HCA) and principal component analysis (PCA) has proved that sulfur K-edge XANES spectrum can be used to characterize German terrestrial soils and Andaman coastal sediments. In addition, this study highlighted the capability of sulfur K-edge XANES spectra as an innovative "fingerprint" to distinguish tsunami backwash deposits (TBD) from typical marine sediments (TMS).

Mass size distribution and chemical composition of the surface layer of summer and winter airborne particles in Zabrze, Poland

Mass size distributions of ambient aerosol were measured in Zabrze, a heavily industrialized city of Poland, during a summer and a winter season. The chemical analyses of the surface layer of PM(10), PM(2.5) and PM(1) in this area were also performed by X-ray photoelectron spectroscopy (XPS). Results suggested that the influence of an atmospheric aerosol on the health condition of Zabrze residents can be distinctly stronger in winter than in summer because of both: higher concentration level of particulate matter (PM) and higher contribution of fine particles in winter season compared to summer. In Zabrze in June (summer) PM(10) and PM(2.5) reached about 20 and 14 μg/m(3), respectively, while in December (winter) 57 and 51 μg/m(3), respectively. The XPS analysis showed that elemental carbon is the major surface component of studied airborne particles representing about 78%-80% (atomic mass) of all detected elements.

Characterization of lead-recycling facility emissions at various workplaces: major insights for sanitary risks assessment

Most available studies on lead smelter emissions deal with the environmental impact of outdoor particles, but only a few focus on air quality at workplaces. The objective of this study is to physically and chemically characterize the Pb-rich particles emitted at different workplaces in a lead recycling plant. A multi-scale characterization was conducted from bulk analysis to the level of individual particles, to assess the particles properties in relation with Pb speciation and availability. Process PM from various origins were sampled and then compared; namely Furnace and Refining PM respectively present in the smelter and at refinery workplaces, Emissions PM present in channeled emissions. These particles first differed by their morphology and size distribution, with finer particles found in emissions. Differences observed in chemical composition could be explained by the industrial processes. All PM contained the same major phases (Pb, PbS, PbO, PbSO(4) and PbO·PbSO(4)) but differed on the nature and amount of minor phases. Due to high content in PM, Pb concentrations in the CaCl(2) extractant reached relatively high values (40 mg L(-1)). However, the ratios (soluble/total) of CaCl(2) exchangeable Pb were relatively low (<0.02%) in comparison with Cd (up to 18%). These results highlight the interest to assess the soluble fractions of all metals (minor and major) and discuss both total metal concentrations and ratios for risk evaluations. In most cases metal extractability increased with decreasing size of particles, in particular, lead exchangeability was highest for channeled emissions. Such type of study could help in the choice of targeted sanitary protection procedures and for further toxicological investigations. In the present context, particular attention is given to Emissions and Furnace PM. Moreover, exposure to other metals than Pb should be considered.

Evaluation of asphaltene degradation on highly ordered TiO2 nanotubular arrays via variations in wettability

Photocatalytic degradation of both aquatic and atmospheric organic pollutants on titanium dioxide has been extensively investigated in the past decades, but research on direct photocatalytic degradation of solid-phase organic pollutants is rather limited. In this work, photocatalytic degradation of n-C(7) asphaltene, which is composed of solid-phase organic substances found in crude oil, on highly ordered TiO(2) nanotubular arrays (TNAs) was studied using the wettability as an indicator. It was observed that the water contact angle rose linearly with increasing the concentration of n-C(7) asphaltene solution up to 0.02 g mL(-1). Further increasing the concentration of n-C(7) asphaltene only caused small augment in the contact angle, which eventually became stable around 98°. It is demonstrated that the water contact angle can be used as an indicator to reflect the residual solid-phase organic pollutants within a certain range of pollutant concentration. As observed, n-C(7) asphaltene film degraded on TNAs under UV illumination for 60 min, showing complete mineralization of ∼80% of n-C(7) asphaltene that was released into air finally. The remaining 20% of asphaltene was partially decomposed into smaller organic molecules, e.g., -C(═O)- and -C(═O)-OH, confirmed by high-resolution X-ray photoelectron spectra analysis. TNAs can be reused to degrade the solid-phase n-C(7) asphaltene for a number of cycles without further treatment.

Simulataneous pentachlorophenol decomposition and granular activated carbon regeneration assisted by dielectric barrier discharge plasma

An integrated granular activated carbon (GAC) adsorption/dielectric barrier discharge (DBD) process was applied to the treatment of high concentration pentachlorophenol (PCP) wastewater. The PCP in water firstly was adsorbed onto GAC, and then the degradation of PCP and regeneration of exhausted GAC were simultaneously carried out by DBD. The degradation mechanisms and products of PCP loaded on GAC were analyzed by EDX, FT-IR and GC-MS. The results suggested that the C-Cl bonds in PCP adsorbed by GAC were cleaved by DBD plasma, and some dechlorination and dehydroxylation products were identified. The adsorption capacity of adsorption/DBD treated GAC could maintain relatively high level, which confirmed that DBD treatment regenerated the GAC for subsequent reuse. The adsorption of N2, Boehm titration and XPS were used to investigate detailed surface characterizations of GAC. It could be found that DBD plasma not only increased the BET surface area and pore volume in micropore regions, but also had remarkably impact on the distribution of the oxygen-containing functional groups of GAC.

Urban PM2.5Surface Chemistry and Interactions with Bronchoalveolar Lavage Fluid

This study investigated the surface chemistry of urban fine particles (PM(2.5)), and quantified the adsorbed and desorbed species after exposure to bronchoalveolar lavage fluid (BALF). Urban background and roadside PM(2.5) samples of different mass concentration and total weight were collected in triplicate in the South Bronx region of New York City. Simultaneously, the concentrations of other atmospheric pollutants (CO, NO(x), SO(2), O(3), elemental carbon) were measured, and weather conditions were recorded. The collected PM(2.5) samples underwent one of three treatments: no treatment, treatment in vitro with BALF, or treatment in a saline solution (control). The surfaces of untreated, saline-treated, and BALF-treated PM(2.5) samples were analyzed using x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). These results were then compared with ambient air pollutant concentrations, weather variables, selected BALF characteristics, and results from a previous London study conducted using identical preparation methods by XPS analysis only. Both XPS and ToF-SIMS detected PM(2.5) surface species and observed changes in surface concentrations after treatment. XPS analysis showed the surface of untreated urban PM(2.5) consisted of 79 to 87% carbon and 10 to 16% oxygen with smaller contributions of N, S, Si, and P in the samples from both background and roadside locations. A wider variety of other inorganic and organic species (including metals, aliphatic and aromatic hydrocarbons, and nitrogen-containing molecules) was detected with ToF-SIMS. Surface characteristics of particles from the roadside and background sites were very similar, except for higher (p <.05) nitrate concentrations at the roadside, which were attributable to higher roadside NO(x) concentrations. Comparable species and quantities were identified in a previous study of London PM(2.5), where PM(2.5) surface chemistry differed considerably depending on the source, particularly in surface concentrations of oxygen and trace species. After treatment with BALF the N-C signal detected by XPS analysis increased in the average by 372 +/- 203%, indicating significant surface adsorption of protein or other N-containing biomolecules. Lower (nonsignificant) N-C signals were observed for smoker BALF, compared to nonsmoker BALF. ToF-SIMS data confirmed protein adsorption after BALF treatment--smoker BALF resulted in lower levels of adsorbed proteins compared to nonsmoker BALF. ToF-SIMS also indicated an adsorption of phospholipid on the treated PM(2.5) surfaces. The primary phospholipid in BALF is dipalmitoylphospatidylcholine (DPPC), although positive identification was not possible due to low concentrations at the PM(2.5) surface. Oxygen content of PM(2.5) surfaces was the most significant determinant of both N-C and phospholipid adsorption. The XPS signal of the soluble species NH(+)(4), NO(2-)(3), Si, and S decreased in both saline- and BALF-treated samples, showing that these species may be bioavailable in the lung. Similarly, ToF-SIMS analysis suggests the bioavailability of Na(+) and Al(+) as well as NH(+)(4) and Si(+).

Relation between sources of particulate air pollution and biological effect parameters in samples from four European cities: an exploratory study

Given that there are widely different prevalence rates of respiratory allergies and asthma between the countries of Europe and that exposure to ambient particulate matter (PM) is substantial in urban environments throughout Europe, an EU project entitled "Respiratory Allergy and Inflammation Due to Ambient Particles" (RAIAP) was set up. The project focused on the role of physical and chemical composition of PM on release of cytokines of cells in vitro, on respiratory inflammation in vivo, and on adjuvant potency in allergy animal models. Coarse (2.5-10 microm) and fine (0.15-2.5 microm) particles were collected during the spring, summer and winter in Rome (I), Oslo (N), Lodz (PL), and Amsterdam (NL). Markers within the same model were often well correlated. Markers of inflammation in the in vitro and in vivo models also showed a high degree of correlation. In contrast, correlation between parameters in the different allergy models and between allergy and inflammation markers was generally poor. This suggests that various bioassays are needed to assess the potential hazard of PM. The present study also showed that by clustering chemical constituents of PM based on the overall response pattern in the bioassays, five distinct groups could be identified. The clusters of traffic, industrial combustion and/or incinerators (TICI), and combustion of black and brown coal/wood smoke (BBCW) were associated primarily with adjuvant activity for respiratory allergy, whereas clusters of crustal of material (CM) and sea spray (SS) are predominantly associated with measures for inflammation and acute toxicity. The cluster of secondary inorganic aerosol and long-range transport aerosol (SIALT) was exclusive associated with systemic allergy. The present study has shown that biological effect of PM can be linked to one or more PM emission sources and that this linkage requires a wide range of bioassays.

3-Nitrobenzanthrone, a potential human cancer hazard in diesel exhaust and urban air pollution: a review of the evidence

Epidemiological studies have shown that exposure to diesel exhaust and urban air pollution is associated with an increased risk of lung cancer. 3-Nitrobenzanthrone [3-nitro-7H-benz[de]anthracen-7-one (3-NBA)] is an extremely potent mutagen and suspected human carcinogen identified in diesel exhaust and ambient air particulate matter. The main metabolite of 3-NBA, 3-aminobenzanthrone (3-ABA), was found in the urine of salt mine workers occupationally exposed to diesel emissions, indicating that human exposure to 3-NBA due to diesel emissions can be significant and is detectable. There is clear evidence that 3-NBA is a genotoxic mutagen forming DNA adducts after metabolic activation through simple reduction of the nitro group. Several human enzymes have been shown to activate 3-NBA and its metabolites in vitro and in cells to form electrophilic arylnitrenium and rearranged carbenium ions, leading to the formation of purine adducts at the C8 and N2 position of guanine and at the C8 and N6 position of adenine. The predominant DNA adducts in vivo, 2-(2'-deoxyguanosin-N2-yl)-3-aminobenzanthrone and N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone are also the most persistent adducts in target tissue in rodents, and are most probably responsible for the induction of GC-->TA transversion mutations observed in vivo. It is concluded that these adducts not only represent premutagenic lesions in DNA but are of primary importance for the initiation of the carcinogenic process and subsequent tumour formation in target tissue. Indeed, 3-NBA is carcinogenic in rats after intratracheal instillation, inducing mainly squamous cell carcinoma in lung. The intention of this article is to provide a critical review on the potential genotoxic effects of 3-NBA on human health. However, in general, there is a need for more mechanistic studies that relate 3-NBA to all processes that are considered to orchestrate tumour development and of studies on the ability of particles to promote 3-NBA genotoxicity. Because of its widespread environmental presence, 3-NBA may represent not only an occupational health hazard but also a hazard for larger sections of the general population. For an accurate risk assessment more epidemiological studies on 3-NBA-exposed individuals and a broader monitoring of environmental levels of 3-NBA are required.

Photocatalytic degradation of polystyrene plastic under fluorescent light

Plastic is used widely all over the world, due to the fact that it is low cost, is easily processable, and has lightweight properties. However, the hazard of discarding waste plastic, so-called "white pollution", is becoming more and more severe. In this paper, solid-phase photocatalytic degradation of polystyrene (PS) plastic, one of the most common commercial plastics, over copper phthalocyanine (CuPc) sensitized TiO2 photocatalyst (TiO2/CuPc) has been investigated under fluorescent light irradiation in the air. UV-vis spectra show that TiO2/CuPc extends its photoresponse range to visible light, contrasting to only UV light absorption of pure TiO2. The PS photodegradation experiments exhibit that higher PS weight loss rate, lower PS average molecular weight, less amount of volatile organic compounds, and more CO2 can be obtained in the system of PS-(TiO2/CuPc), in comparison with the PS-TiO2 system. Therefore, PS photodegradation over TiO2 CuPc composite is more complete and efficient than over pure TiO2, suggesting the potential application of dye-sensitized TiO2 catalyst in the thorough photodegradation of PS plastic under fluorescent light. During the photodegradation of PS plastic, the reactive oxygen species generated on TiO2 or TiO2/CuPc particle surfaces play important roles in chain scission. The present study demonstrates that the combination of polymer plastic with dye-sensitized TiO2 catalyst in the form of thin film is a practical and useful way to photodegrade plastic contaminants in the sunlight.

Surface-analytical studies on environmental and geochemical surface processes

The surface chemical compositions of solid samples from environmental and geological sources can differ from the bulk or average compositions, because of changes caused by adsorption, dissolution, oxidation, etc. Accordingly, analytical information on surface layers is important for a better understanding of the environmental chemistry involving solid surfaces. The rapid development of surface-analytical techniques has enabled us to probe the surface chemistry of environmental and geological solid samples of complex composition. This article demonstrates some examples of important items of information that can be obtained by applying surface-analytical techniques, such as X-ray photoelectron spectroscopy and secondary ion mass spectrometry, to environmental and geological samples. The surface analysis of fly ashes, soils, sediments and weathered silicate minerals is reviewed.