Determination of water-soluble and insoluble compounds in size classified airborne particulate matter

Solidification of heavy metals in municipal solid waste incineration washed fly ash by asphalt mixture

Using asphalt mixture to solidify heavy metals in municipal solid waste incineration fly ash can reduce pollution and realize resource utilization. In this study, the physical and chemical properties of washed fly ash were analyzed, and washed fly ash was added to asphalt mixture as filler instead of mineral powder. The study involved analyzing the mechanical attributes of asphalt mixtures containing washed fly ash, along with examining the characteristics of asphalt binder that incorporates the washed fly ash. Subsequently, assess the potential leaching hazards associated with asphalt mixture incorporating washed fly ash. The test results showed that washed fly ash was a Si-Al-Ca system material, which had small particle size, large specific surface area and many pores. It increased the contact area with asphalt, which improved encapsulation of asphalt and aggregates. The optimal dosage of washed fly ash is 2.5%. At this dosage, the mixture attains optimal high-temperature performance, while both low-temperature performance and the characteristics of washed fly ash asphalt binder align with requirements. Asphalt mixture has solidification on heavy metals, with strongest solidification for Zn, followed by Cu, Cr. A prediction model of leaching amount versus time was constructed for Pb, Ba and Ni, which have weak solidified ability. The cumulative leaching amount of the road within 15 years of service life was calculated through the model, and it was obtained that the addition of washed fly ash will not cause pollution to environment. Overall, this study showed that asphalt mixtures can be used for stabilization/solidification of washed fly ash while saving natural mineral, providing a theoretical basis for the resource application of washed fly ash in asphalt road construction.

Determination of Water-Soluble Trace Elements in the PM10 and PM2.5 of Palermo Town (Italy)

This study contributes to the current knowledge on the solubility of trace elements in the atmospheric particulate matter of the urban area of Palermo. Daily sample filters of PM₁₀ and PM_2.5 were collected in monitoring stations within and outside the urban area, characterized by variable traffic density. The bulk of compositions in PM₁₀ and PM_2.5 were determined by ICP-MS. The water-soluble trace elements (WSTE) and major ion components of particulate matter were determined by ICP-MS and ion chromatography, respectively. A significant difference in the metals content was observed between the samples taken in urban areas and those from suburban areas. The calculated enrichment factor highlights the high values for Cu, Mo, Sb, V, and Zn, confirming the contribution of human activities. The leaching test was applied to PM₁₀ and PM_2.5 filters and showed different behaviors and transport of metals and metalloids. The calculated leaching coefficient highlights the metals typically produced by anthropic activities, compared to those of geogenic origin, are much more soluble in water and have greater mobility. The factor analysis was used to identify the sources of water-soluble ions. The main sources are anthropic, geogenic, and sea spray. The final objective of this study is to obtain, with the aid of leaching experiments on PM_2.5 and PM₁₀ filter samples, information about the bioavailability and mobility of the different metals and metalloids that could be used as the scientific basis for public health intervention and to raise the prevention and control of heavy metal pollution in the urban environment, especially in densely populated areas.

Chemical Fractionation in Environmental Studies of Potentially Toxic Particulate-Bound Elements in Urban Air: A Critical Review

In recent years, studies of heavy metal air pollution have increasingly gone beyond determining total concentrations of individual toxic metals. Chemical fractionation of potentially toxic elements in airborne particles is becoming an important part of these studies. This review covers the articles that have been published over the last three decades. Attention was paid to the issue of atmospheric aerosol sampling, sample pretreatment, sequential extraction schemes and conditions of individual extractions. Geochemical forms of metals occurring in the air in urban areas were considered in detail. Based on the data sets from chemical fractionation of particulate matter samples by three sequential extraction procedures (SEPs)—Fernández Espinosa, BCR and Chester’s—the compilation of the chemical distribution patterns of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn was prepared. The human health risk posed by these toxic and/or carcinogenic elements via inhalation of atmospheric particles was estimated for two categories of polluted urban areas: the commonly encountered pollution level and the high pollution level.

Environmental risk assessment and factors influencing heavy metal concentrations in the soil of municipal solid waste landfills

The environmental risk assessment and the factors influencing heavy metals (HM) in the soil at the municipal solid waste landfill sites (MSWLs) were studied by literature review, field survey, and statistical methods. The results indicated that the dominant HM contamination in the soil at the MSWLs was caused by chromium (Cr) with the Nemero index values (PI) from 22.7 to 44.3 and zinc (Zn) with the PI from 0.7 to 9.8. There were significant differences in the Cr, mercury (Hg), lead (Pb), Zn, and arsenic (As) concentrations between soil samples from sanitary and non-sanitary landfills (NSLs) where HM contamination (PI = 10.9) was more obvious. As (CRA_As = 2.35 × 10^-4) and cadmium (Cd) (CRA_Cd = 1.45 × 10^-4) posed potential carcinogenic health effects. The soil Cd concentration had a significant negative correlation (r = -0.476^**) with the landfill age. The soil As concentration had a significant positive correlation (r = 0.472^**) with rainfall in NSLs. There were significant differences in the As (P = 0.042) and copper (Cu) (P = 0.042) concentrations between soil samples from the surrounding areas of MSWLs and the base where soil had higher HM concentrations. For the efficient prevention of HM ecological risk, a scientific site selection, undamaged coverage and anti-seepage systems, standardized management, and ongoing monitoring are required.

Indoor concentrations of PM2.5 and associated water-soluble and labile heavy metal fractions in workplaces: implications for inhalation health risk assessment

PM2.5 (i.e., particles with aerodynamic diameters less than 2.5 μm) and the associated water-soluble, dissolved, and labile fractions of heavy metals (Cu, Pb, Mn, Ni, Co, Zn, Cr, and Cd) were determined in indoor air of twenty workplaces in Alexandroupolis (Northeastern Greece). PM2.5 concentrations exhibited significant variance across the workplaces ranging from 11.5 μg m-3 up to 276 μg m-3. The water-soluble metal concentrations varied between 0.67 ± 2.52 ng m-3 for Co and 27.8 ± 19.1 ng m-3 for Ni exhibiting large variations among the different workplaces. The water-soluble metal fractions were further treated to obtain the labile metal fraction (by binding with Chelex 100-chelating resin) that might represent a higher potential for bioaccessibility than the total water-soluble fraction. The largest labile (chelexed) fractions (48-67% of the corresponding water-soluble concentrations) were found for Cd, Mn, Cu, and Ni, while the labile fractions of Pb, Cr, Co, and Zn were relatively lower (34-42% of the corresponding water-soluble concentrations). Water-soluble and labile concentrations of heavy metals were further used to calculate cancer and non-cancer risks via inhalation of the PM2.5-bound metals. To our knowledge, this is the first study estimating the health risks due to the inhalation of water-soluble and labile metal fractions bound to indoor PM.

Seasonal Evolution of the Chemical Composition of Atmospheric Aerosol in Terra Nova Bay (Antarctica)

Atmospheric aerosol samples were collected at Faraglione Camp, 3 km away from the Italian Mario Zucchelli Station (Terra Nova Bay, Ross Sea), from 1 December 2013 to 2 February 2014. A two-step extraction procedure was applied to characterize the soluble and insoluble components of PM10-bound metals. Samples were analyzed for Al, Fe, Cd, Cu, and Pb by square wave anodic stripping voltammetry (SWASV) and by graphite furnace atomic absorption spectrophotometer (GF-AAS). The mean atmospheric concentrations were (reported as means ± SD) Al 24 ± 3 ng m−3; Fe 23 ± 4 ng m−3; Cd 0.92 ± 0.53 pg m−3; Cu 43 ± 9 pg m−3, and Pb 16 ± 5 pg m−3. The fractionation pattern was metal-specific, with Al, Fe, and Pb mainly present in the insoluble fractions, Cd in the soluble one, and Cu equally distributed between the two fractions. The summer evolution showed overall constant behavior of both fractions for Al and Fe, while a bell-shaped trend was observed for the three trace metals. Cd and Cu showed a bell-shaped evolution involving both fractions. A seasonal increase in Pb occurred only for the insoluble fraction, while the soluble fraction remained almost constant. Sequential extraction and enrichment factors indicated a crustal origin for Al, Fe, and Pb, and additional (marine or anthropogenic) contributions for Cd and Cu. Back trajectory analysis showed a strong contribution of air masses derived from the Antarctic plateau. A potential low contribution from anthropized areas cannot be excluded. Further studies are necessary to better characterize the chemical composition of the aerosol, to discriminate between natural and anthropogenic sources, and to evaluate a quantitative source apportionment.

Germinated Rhynchosia nulubilis Fermented with Lactobacillus pentosus SC65 Reduces Particulate Matter Induced Type II Alveolar Epithelial Apoptotic Cell Death

Particulate matter (PM) is a significant environmental pollutant that promotes respiratory diseases, including lung injury and inflammation, by inducing oxidative stress. Rhynchosia nulubilis (black soybean) is traditionally used to prevent chronic respiratory disease via inducing antioxidant and anti-inflammatory effects. To investigate the effects of Lactobacillus pentosus SC65 fermented GR (GR-SC65) and Pediococcus pentosaceus ON81A (GR-ON81A) against PM-induced oxidative stress and cell death in A549 cells, we performed the 2-7-dichlorodihydrofluorescein diacetate and cell counting kit-8 assays, as well as Hoechst 33342 and propidium iodide staining and western blotting. GR-SC65 showed the highest total polyphenolic contents and 1,1-diphenyl-2-picrylidrazil radical scavenging activity among lactic acid bacteria-fermented GRs (p < 0.001 vs. GR). Four soy peptides, β-conglycinin breakdowns (INAENNQRNF, ISSEDKPFN, LAFPGSAQAVEK, and LAFPGSAKDIEN), were detected in GR-SC65, but not in GR. In GR-SC65, PM-induced A549 cell death was less than that observed in GR-ON81A and GR (p < 0.001 vs. PM-treated group). GR-SC65 significantly decreased intracellular reactive oxidative species (ROS) when compared with PM (*** p < 0.001 vs. PM). GR-SC65 decreased the levels of BAX, active caspase-9, -3, and poly ADP-ribose polymerase (PARP) proteins (#p < 0.01, ###p < 0.001 vs. PM), while increasing the level of BCL-2 protein, a mitochondrial anti-apoptotic protein (###p < 0.001 vs. PM). Our findings indicate that GR-SC65 inhibited PM-induced cell death by suppressing the levels of ROS, active caspase-9 and -3, and PARP proteins, while enhancing the level of BCL-2 protein in type II alveolar epithelial A549 cells. Therefore, GR-SC65 might be a potential therapeutic and preventive agent against PM-induced lung injury.

Bioaccessibilities of metal(loid)s and organic contaminants in particulates measured in simulated human lung fluids: A critical review

Particle-bound pollutants can pose a health risk to humans. Inhalation exposure evaluated by total contaminant concentrations significantly overestimates the potential risk. To assess the risk more accurately, bioavailability, which is the fraction that enters into the systemic circulation, should be considered. Researchers have replaced bioavailability by bioaccessibility due to the rapid and cost-efficient measurement for the latter, especially for assessment by oral ingestion. However, contaminants in particulates have different behavior when inhaled than when orally ingested. Some of the contaminants are exhaled along with exhalation, and others are deposited in the lung with the particulates. In addition, a fraction of the contaminants is released into the lung fluid and absorbed by the lung, and another fraction enters systemic circulation under the action of cell phagocytosis on particulates. Even if the release fraction, i.e., release bioaccessibility, is considered, the measurement faces many challenges. The present study highlights the factors influencing release bioaccessibility and the incorporation of inhalation bioaccessibility into the risk assessment of inhaled contaminants. Currently, there are three types of extraction techniques for simulated human lung fluids, including simple chemical solutions, sequential extraction techniques, and physiologically based techniques. The last technique generally uses three kinds of solution: Gamble's solution, Hatch's solution, and artificial lysosomal fluid, which are the most widely used physiologically based simulated human lung fluids. External factors such as simulated lung fluid composition, pH, extraction time, and sorption sinks can affect release bioaccessibility, whereas particle size and contaminant properties are important internal factors. Overall, release bioaccessibility is less used than bioaccessibility considering the deposition fraction when assessing the risk of contaminants in inhaled particulates. The release bioaccessibility measurement poses two main challenges: developing a unified, accurate, stable, simple, and systematic biologically based method, and validating the method through in-vivo assays.

A comprehensive evaluation of the treatment of lead in MSWI fly ash by the combined cement solidification and phosphate stabilization process

Fly ash is a hazardous material that is produced from municipal solid waste incineration. It contains heavy metals and should be properly treated to meet landfill entry requirements. In this study, under the precondition that the leachable concentration of lead (Pb) exceeded the limit value for landfill disposal, the effects of cement solidification, chemical stabilization, and their combination on the leachable Pb concentration and the chemical state of Pb were systematically investigated. In addition, the reaction conditions were optimized by response surface methodology (RSM) in terms of leachable Pb concentration, volume change ratio, and treatment cost. The results indicated that the leachable Pb concentration decreased at lower cement or sodium dihydrogen phosphate (NaH₂PO₄) dosages in cement solidification or NaH₂PO₄ stabilization, and the liquid-to-solid ratio had a significant influence on cement solidification. The leachable Pb concentration met the limit value for landfill disposal in the individual processes with 20% cement or 5% NaH₂PO₄, and in the combined process with 10% cement + 2% NaH₂PO₄. The combined process achieved the best treatment efficiency by enabling Pb to transform to a stable residual state. According to the RSM, a combined cement content of 11.64%, NaH₂PO₄ content of 2.79%, and liquid-to-solid ratio of 0.48 were the optimal parameters, resulting in substantial decreases in the volume change ratio and treatment costs, while satisfying the preconditions for landfill disposal. In conclusion, the combined process can reduce the pollution risk to the environment, and is an efficient and cost-effective pre-treatment method for incinerator fly ash.

Chemical Composition of PM10 in 16 Urban, Industrial and Background Sites in Italy

Italy is characterized by a very variable configuration in terms of altitude, proximity to the sea, latitude and the presence of industrial plants. This paper summarizes the chemical characterization of PM10 obtained from 38 sampling campaigns carried out in 16 sites in Italy during the years 2008–2018. Chemical determinations include all macro-components (six macro-elements, eight ions, elemental carbon and organic carbon). The sum of the individual components agrees well with the PM10 mass. The chemical composition of the atmospheric aerosol clearly reflects the variety in the Italian territory and the pronounced seasonal variations in the meteoclimatic conditions that characterize the country. Macro-sources reconstruction allowed us to identify and evaluate the strength of the main PM10 sources in different areas. On 10 sampling sites, the soluble and insoluble fractions of 23 minor and trace elements were also determined. Principal Component Analysis was applied to these data to highlight the relationship between the elemental composition of PM10 and the characteristics of the sampling sites.

Speciation and bioaccessibility of heavy metals in PM2.5 in Baoding city, China

The health risks and toxicity of heavy metals (HMs) in PM_2.5 are not only associated with their total amounts, but also with their species and bioaccessibility. In this study, the speciation (fractions) and bioaccessibility of HMs (Pb, Cd, Cr, Cu and Zn) as well as their correlations in fine particulate matter (PM_2.5) samples from four seasons were studied. A sequential extraction procedure was applied to divide the studied HMs into four fractions: acid-soluble fraction (F1), reducible fraction (F2), oxidative fraction (F3) and residual fraction (F4). The simulated body fluids (gastrointestinal and lung phases) were used for in vitro tests in order to evaluate the bioaccessibility of HMs. The distribution of HMs in PM_2.5 was season and element dependent. It was found that Zn was the most abundant element among the five measured metals and followed by Pb, Cu, Cr and Cd. The total contents of each HM in different seasons were in the following order: winter > autumn > spring > summer. The studied HMs were mainly concentrated in acid-soluble fraction (F1) with high bioaccessibility (p < 0.05) except for Cr. Zn, Pb and Cu possessed the highest bioaccessibility in summer while Cd and Cr were the highest in winter. In vitro tests indicated that HMs in PM_2.5 were much more accessible to gastrointestinal fluids rather than lung phase (Gamble's solution). A significant correlation was found between the results from the optimized BCR sequential extraction and solubility bioaccessibility research consortium (SBRC). The fractions extracted by SBRC were consistent with the first two fractions extracted by the sequential extraction method.

Evaluation of chemical speciation and environmental risk levels of heavy metals during varied acid corrosion conditions for raw and solidified/stabilized MSWI fly ash

In this work, the leaching pattern, chemical speciation, and environmental risks of various heavy metals (Pb, Zn, Cu, Cd, Cr, and Ni) were investigated synchronously under different acid corrosion conditions through end-point pH leaching experiments. The heavy metals were present in raw, stabilized (phosphoric acid; chelating agent), and solidified (Portland cement) municipal solid waste incineration (MSWI) fly ash. The results showed that the stabilization and solidification pre-treatment could effectively decrease the leaching of most heavy metals. However, phosphoric acid stabilization and Portland cement solidification increased the solubility of Ni and Pb/Cu/Cd under low end-point pH conditions, while that of Cr and Pb increased under high end-point pH conditions. Overall, the leaching pattern of heavy metals was not affected by the addition of binders/additives. The results from speciation analysis showed that the bioavailable fractions (exchangeable and carbonate-bound) were leached out from initial raw or solidified/stabilized fly ash after distilled water leaching. However, with the decrease in end-point pH levels, the bioavailable fractions increased again due to the increase in acid corrosion on metal-bearing mineral matrixes. The risk assessment results indicated that, after exposing the raw or solidified/stabilized fly ash to highly acidic conditions, not only the high-content Pb/Zn/Cu, but also some low-content Cd posed potential risks to the environment. During the leaching process, under extremely acidic conditions, the increased environmental risks posed by Pb/Zn/Cu/Cd in residual fly ash solids were greatly ascribed to the increase in bioavailable fractions, which might result in the re-leaching of some heavy metals to the environment.

Characterization of Urban Particulate Matter by Diffusive Gradients in Thin Film Technique

A diffusive gradient in thin films (DGT) technique was employed in characterization of the particulate matter related to the urban area suffering from heavy traffic. Kinetics of mobilization metals fluxes from the metal-contaminated particulate matter was investigated. To monitor responses of the particulate matter sample, DGT probes of various thickness of diffusion layer were deployed in aqueous model suspensions of the particulate matter for different time periods. Particulate matter samples and exposed DGT resin gels were decomposed in a mixture of nitric and hydrochloric acid in a microwave pressurized PTFE-lined system. Total content of some traffic-related elements (Cd, Co, Cu, Mo, Ni, Pb, Pd, Pt, Rh, Sb, and V) was determined by inductively coupled plasma mass spectrometry. DGT measurements revealed that two metals pools associated with particles could be recognized, which can be characterized as high soluble fraction and almost insoluble fraction. DGT-measured metal fluxes from the labile pool showed significant difference in mobilization and resupply fluxes of individual selected elements, which might reflect the origin of selected metals and their speciation in particulate matter. The DGT technique can be applied as a useful tool for characterization of metals mobilization from the particulate matter.

In vitro bioaccessibility and health risk assessment of heavy metals in atmospheric particulate matters from three different functional areas of Shanghai, China

The bioaccessibility and human health risks of heavy metals in PM_2.5 and PM₁₀ samples from three functional areas of Shanghai, China including a commercial area (CA), a residential area (RA), and an industrial area (IA), were investigated. Gamble's solution and physiologically based extraction test were employed to simulate human respiratory and digestive system, respectively. Both PM_2.5 and PM₁₀ concentration in the three areas exceeded the guideline of WHO, and followed the order of IA>CA≈RA. Zinc and Pb were the most abundant metals with a concentration range of 0.19-0.44 and 0.05-0.42μgm^-3, respectively. In respiratory system, heavy metal bioaccessibility for PM_2.5 and PM₁₀ varied within the range of 5.3%-71.4% and 4.8%-51.5%, respectively. Heavy metals in RA showed higher bioaccessibility than those in CA and IA in the respiratory system. In digestive system, heavy metal bioaccessibility for PM_2.5 and PM₁₀ reached 24.6%-90.9% and 28.5%-88.9% in the gastric phase and was reduced to 8.7%-85.5% and 8.5%-81.8% in the intestinal phase, respectively. The bioaccessibility of heavy metals in CA was highest among three areas in the digestive system. Based on the bioaccessibility analysis, the hazard quotient values of heavy metals in PMs via inhalation exposure were far below 1, the safe level, for both adults and children. However, potential risks via ingestion exposure resulted from Pb existed for children of three areas and for adults of RA as their hazard quotient values could reach up to 11. The obtained results indicated that the air quality in Shanghai need to be improved and the health risks to humans via ingestion exposure to atmospheric Pb must be considered.

Particulate metal bioaccessibility in physiological fluids and cell culture media: Toxicological perspectives

According to the literature, tiny amounts of transition metals in airborne fine particles (PM_2.5) may induce proinflammatory cell response through reactive oxygen species production. The solubility of particle-bound metals in physiological fluids, i.e. the metal bioaccessibility is driven by factors such as the solution chemical composition, the contact time with the particles, and the solid-to-liquid phase ratio (S/L). In this work, PM_2.5-bound metal bioaccessibility was assessed in various physiological-like solutions including cell culture media in order to evidence the potential impact on normal human bronchial epithelial cells (NHBE) when studying the cytotoxicity and inflammatory responses of PM_2.5 towards the target bronchial compartment. Different fluids (H₂O, PBS, LHC-9 culture medium, Gamble and human respiratory mucus collected from COPD patients), various S/L conditions (from 1/6000 to 1/100,000) and exposure times (6, 24 and 72h) were tested on urban PM_2.5 samples. In addition, metals' total, soluble and insoluble fractions from PM_2.5 in LHC-9 were deposited on NHBE cells (BEAS-2B) to measure their cytotoxicity and inflammatory potential (i.e., G6PDH activity, secretion of IL-6 and IL-8). The bioaccessibility is solution-dependent. A higher salinity or organic content may increase or inhibit the bioaccessibiliy according to the element, as observed in the complex mucus matrix. Decreasing the S/L ratio also affect the bioaccessibility depending on the solution tested while the exposure time appears less critical. The LHC-9 culture medium appears to be a good physiological proxy as it induces metal bioaccessibilities close to the mucus values and is little affected by S/L ratios or exposure time. Only the insoluble fraction can be linked to the PM_2.5-induced cytotoxicity. By contrast, both soluble and insoluble fractions can be related to the secretion of cytokines. The metal bioaccessibility in LHC-9 of the total, soluble, and insoluble fractions of the PM_2.5 under study did not explain alone, the cytotoxicity nor the inflammatory response observed in BEAS-2B cells. These findings confirm the urgent need to perform further toxicological studies to better evaluate the synergistic effect of both bioaccessible particle-bound metals and organic species.

In Vitro Investigations of Human Bioaccessibility from Reference Materials Using Simulated Lung Fluids

An investigation for assessing pulmonary bioaccessibility of metals from reference materials is presented using simulated lung fluids. The objective of this paper was to contribute to an enhanced understanding of airborne particulate matter and its toxic potential following inhalation. A large set of metallic elements (Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, and Zn) was investigated using three lung fluids (phosphate-buffered saline, Gamble's solution and artificial lysosomal fluid) on three standard reference materials representing different types of particle sources. Composition of the leaching solution and four solid-to-liquid (S/L) ratios were tested. The results showed that bioaccessibility was speciation- (i.e., distribution) and element-dependent, with percentages varying from 0.04% for Pb to 86.0% for Cd. The higher extraction of metallic elements was obtained with the artificial lysosomal fluid, in which a relative stability of bioaccessibility was observed in a large range of S/L ratios from 1/1000 to 1/10,000. For further investigations, it is suggested that this method be used to assess lung bioaccessibility of metals from smelter-impacted dusts.

A critical review of approaches and limitations of inhalation bioavailability and bioaccessibility of metal(loid)s from ambient particulate matter or dust

Inhalation of metal(loid)s in ambient particulate matter (APM) represents a significant exposure pathway to humans. Although exposure assessment associated with this pathway is currently based on total metal(loid) content, a bioavailability (i.e. absorption in the systemic circulation) and/or bioaccessibility (i.e. solubility in simulated lung fluid) based approach may more accurately quantify exposure. Metal(loid) bioavailability-bioaccessibility assessment from APM is inherently complex and lacks consensus. This paper reviews the discrepancies that impede the adoption of a universal protocol for the assessment of inhalation bioaccessibility. Exposure assessment approaches for in-vivo bioavailability, in-vitro cell culture and in-vitro bioaccessibility (composition of simulated lungs fluid, physico-chemical and methodological considerations) are critiqued in the context of inhalation exposure refinement. An important limitation of bioavailability and bioaccessibility studies is the use of considerably higher than environmental metal(loid) concentration, which diminishing their relevance to human exposure scenarios. Similarly, individual metal(loid) studies have been criticised due to complexities of APM metal(loid) mixtures which may impart synergistic or antagonistic effects compared to single metal(loid) exposure. Although a number of different simulated lung fluid (SLF) compositions have been used in metal(loid) bioaccessibility studies, information regarding the comparative leaching efficiency among these different SLF and comparisons to in-vivo bioavailability data is lacking. In addition, the particle size utilised is often not representative of what is deposited in the lungs while assay parameters (extraction time, solid to liquid ratio, temperature and agitation) are often not biologically relevant. Research needs are identified in order to develop robust in-vitro bioaccessibility protocols for the assessment or prediction of metal(loid) bioavailability in APM for the refinement of inhalation exposure.

Bioaccessibility of trace elements in fine and ultrafine atmospheric particles in an industrial environment

The lung bioaccessibility, i.e., the solubility in alveolar lung fluid of metals in particulate matter, has been recognized as an important parameter for health risk assessment, associated with the inhalation of airborne particles. The purpose of this study is to use an in vitro method to estimate the pulmonary bioaccessibility of toxic metals in different particle sizes, from a multi-influenced industrial emission area. The fine and ultrafine particles collected with cascade impactors in the chimneys and at different distances from a Fe-Mn smelter were extracted with a simulated alveolar fluid (Gamble solution). In addition, a four-step sequential extraction procedure was employed to approach the metal speciation. The bioaccessibility of metals ranged from almost insoluble for Fe (<1%) to extremely soluble for Rb (>80%). In terms of particle size, the trace element bioaccessibility is generally higher for the finer size fractions (submicron and ultrafine particles) than for the coarse one (>1 µm). These submicron particles have a very high number concentration and specific surface area, which confer them an important contact surface with the alveolar fluid, i.e., a higher bioaccessibility. Interestingly, the bioaccessibility of most metals clearly increases between the chimney stacks and the close environment of the studied Fe-Mn smelter, over a very short distance (800 m), possibly due to a mix with surrounding steelworks emissions. This increase is not observed over a greater distance from the smelter (2000 m), when industrial particles were mixed with urban aerosols, except for Fe, under more soluble forms in combustion particles.

Determination of water-soluble and insoluble elements in PM2.5 by ICP-MS

The elemental composition of water-soluble and acid-soluble fractions of PM2.5 samples from two different Greek cities (Patras and Megalopolis) was investigated. Patras and Megalopolis represent different environments. Specifically, Patras is an urban environment with proximity to a large port, while Megalopolis is a small city located close to lignite power plants. Both cities can serve as a representative example of European cities with similar characteristics. The concentration of 14 elements (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Fe, Sr, Ti, V and Zn) was determined in each fraction by ICP-MS. Microwave assisted digestion was used to digest the samples using a mixture of HNO3 and HF. For the determination of the water soluble fraction, water was chosen as the simplest and most universal extraction solvent. For the validation of the extraction procedure, the recoveries were tested on two certified reference materials (NIST SRM 1648 Urban Particulate Matter and NIST 1649a Urban Dust). Results showed that Zn has the highest total concentration (273 and 186 ng/m(3)) and Co the lowest (0.48 and 0.23 ng/m(3)) for Patras and Megalopolis samples, respectively. Nickel with 65% for Patras and As with 49% for Megalopolis displayed the highest solubility, whereas Fe (10%) and Ti (2%) the lowest ones, respectively.

Development and application of an inhalation bioaccessibility method (IBM) for lead in the PM10 size fraction of soil

An approach for assessing the inhalation bioaccessibility of Pb in the PM10 size fraction is presented, using an in vitro simulated epithelial lung fluid to represent the extracellular environment of the lung. The developed inhalation bioaccessibility method (IBM) is applied to a range of urban surface soils and mining wastes obtained from Mitrovica, Kosovo, a site where impacts upon human health following exposure to Pb have been internationally publicised. All Pb determinations were undertaken by inductively coupled plasma mass spectrometry (ICP-MS). The pseudo-total concentration of Pb (microwave acid digestion using aqua-regia) varied between matrices: smelter (20,900-72,800mgkg(-1)), topsoil (274-13,700mgkg(-1)), and tailings (2990mgkg(-1)-25,300mgkg(-1)). The in vitro inhalation bioaccessibility was typically several orders of magnitude lower: smelter (7.0-965mgkg(-1)), topsoil (9.8-1060mgkg(-1)), and tailings (0.7mgkg(-1)-49.2mgkg(-1)). The % inhalation bioaccessibility ranged from 0.02 to 11.0%, with the higher inhalation bioaccessible Pb concentrations being observed for samples from the Bosniak Mahalla area of Mitrovica (an area proposed for the relocation of internally displaced peoples). The estimated inhalation dose (for adults) calculated from the PM10 pseudo-total Pb concentration ranged from 0.369 to 1.284μgkg(-1)BWday(-1) (smelter), 0.005-0.242μgkg(-1)BWday(-1) (topsoil), and 0.053-0.446μgkg(-1)BWday(-1) (tailings). When daily inhalation doses were calculated using the bioaccessible Pb concentration the modelled exposure doses were much lower: smelter (0.0001-0.0170μgkg(-1)BWday(-1)), topsoil (0.0002-0.0187μgkg(-1)BWday(-1)) and tailings (0.0001-0.0009μgkg(-1)BWday(-1)). Modelled for the neutral pH conditions of the interstitial lung environment, the results indicate a low potential inhalation bioaccessibility for Pb in these samples. Given the already elevated environmental Pb burden experienced by the local population, where significant prolonged dust or particulate generating activities are taking place, or where the inhaled particles are phagocytized, then inhalation exposure has the potential to significantly add to the overall Pb burden. Such data are important for local policy makers to better enable them to assess risk, especially in areas where soils/dusts have elevated levels of contamination.

Seasonal variations in the chemical composition of particulate matter: a case study in the Po Valley. Part II: concentration and solubility of micro- and trace-elements

Size distribution (fine and coarse fraction) and solubility distribution (extracted and residual fraction) of 20 elements (As, Ba, Be, Cd, Co, Cu, Fe, Li, Mn, Pb, Ni, Rb, S, Sb, Se, Sn, Sr, Ti, Tl, V) in atmospheric particulate matter (PM) were determined during a 5-year field study carried out in the Po Valley (peri-urban area of Ferrara, in Northern Italy). By studying the contribution of the two size fractions and the two solubility fractions to the atmospheric concentration of each element, it was possible to obtain interesting information about the variability of PM sources, to assess the role played by atmospheric stability in determining pollution episodes, and to obtain an estimate of the bio-accessible fraction. Atmospheric stability is confirmed to be one of the main causes of atmospheric pollution in this area and is to be responsible for the pronounced winter increase in both PM and elemental concentration. Long-range transport of natural and polluted air masses caused temporary increases in PM and elemental concentration, while local industrial emission seemed to play a secondary role. Regulated elements were well below their concentration limit, but many toxic elements were in the form of fine particles and soluble chemical species, more accessible to the environment, and the human body.

Chemical characteristics and risk assessment of typical municipal solid waste incineration (MSWI) fly ash in China

The release of heavy metals in municipal solid waste incineration (MSWI) fly ash has become a worrying issue while fly ash is utilized or landfilled. This work investigated the potential mobility of heavy metals in the fly ashes from 15 typical MSWI plants in Chinese mainland by the characterization of distribution, chemical speciation and leaching behavior of heavy metals. The results showed that total content of heavy metals decreased in the order Zn>Pb>Cu>Cr>Ni>Cd in samples. The toxicity characteristics leaching procedure (TCLP) of fly ash indicated that the amount of leached Cd in 67% of samples exceeded the regulated limit. Also, the excess amount of leached Zn and Pb was observed in 40% and 53% of samples, respectively. The chemical speciation analysis revealed that this excess of heavy metal leached in TCLP was contributed to the high content of acid soluble fraction (F1) and reducible fraction (F2) of heavy metal. Moreover, the great positive relevance between leaching behavior of heavy metals and F1 fraction was supported by principal component analysis (PCA). Risk assessment code (RAC) results suggested that Cd and Pb showed a very high risk class to the environment.

Development of an in vitro method to estimate lung bioaccessibility of metals from atmospheric particles

The research presented here was initiated to improve the current knowledge on easily released metals from atmospheric particles. The objectives of this paper were to develop an in vitro method to estimate lung bioaccessibility and to provide quantitative data on metals bioaccessibility. A large set of metals has been investigated (Ba, Cd, Ce, Co, Cu, La, Mn, Mo, Ni, Pb, Rb, Sb and Zn) using two distinct fluids (water and Gamble solution) on four reference materials representing different types of particle sources. Through this study, different parameters such as extraction-time, composition of the leaching solution and solid-to-liquid (S/L) ratios were investigated. The findings obtained for four SRMs suggest that the bioaccessibility is maximized after a 24 h extraction for a range of S/L ratios varying from 1/500 to 1/50,000. We clearly demonstrate that the higher bioaccessibility of metals is obtained with the Gamble solution. Moreover, our results imply that bioaccessibility is speciation and element dependent with percentages varying from 3.3% for Pb to 92.5% for Zn. An estimation of uncertainties of 11% to 30% was obtained for metals bioaccessibility in the four reference materials. In addition, the extraction procedure was validated by performing a mass balance on both soluble and insoluble fractions. This developed method may be used to evaluate the pulmonary bioaccessibility of trace elements present in the atmospheric particles without major artefacts.