Fractionation of eleven elements by chemical bonding from airborne particulate matter collected in an industrial city in Argentina

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.

Size-resolved measurements of PM2.5 water-soluble elements in Iasi, north-eastern Romania: Seasonality, source apportionment and potential implications for human health

The present paper reports the first size-resolved element measurements in the PM_2.5 fraction collected throughout 2016 in the Iasi urban area in north-eastern Romania. Concentrations of water-soluble elements (Ag, Al, As, B, Ba, Be, Bi, Cd, Co, Cu, Cr, Fe, Ga, Mg, Mn, Mo, Ni, Pb, Rb, Se, Sr, Te, Ti, U, V, Zn) were determined using inductively coupled plasma mass spectrometry. Several water-soluble heavy metals (Al, Fe, Zn, As, Cr, Pb) exhibit clear seasonal patterns with maxima over the cold season and minima over the warm season. Elements as Al, Fe, Mg, Zn, Ni, Mn, and Cu present the highest levels in the PM_2.5 fraction, indicating significant contributions from soil-dust resuspension or brake lining and tires. Clear fine mode size-dependent distributions were observed for anthropogenic source-origin elements (Pb, Zn, Cd, V, etc.) due to an acidity-driven metals dissolution process. Positive matrix factorization, concentration weighted trajectory and bivariate polar plot analyses were applied to the entire PM_2.5 database. Based on relative concentrations of various elements, five factors associated with specific sources were identified. The most important contributions to the total PM_2.5 mass concentration (during the total period) come from secondary formation of the ammonium sulfate form (~44%) and from nitrate (~37%). Resuspended dust accounts for a contribution of about 16%, while biomass burning mixed with NaCl salt/sea-salt sources contribute as much as ~3%. Traffic and industrial sources seem to yield little contribution (<0.05%). An assessment investigation of non-carcinogenic and carcinogenic health risks revealed water-soluble arsenic and chromium (VI) as elements with the largest incremental carcinogenic risks. Both metals have traffic and industrial related sources and therefore it is believed that in the future, at the local/regional level, these sources should receive attention by implementing appropriate emission control measures.

Chemical fractionation, bioavailability, and health risks of heavy metals in fine particulate matter at a site in the Indo-Gangetic Plain, India

In the present study, the distribution and chemical fractionation of heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in PM_2.5 collected at Sikandarpur in Agra from September 2015 to February 2016 were carried out to evaluate their mobility potential, environmental, and human health risk through inhalation. Sequential extraction procedure was applied to partition the heavy metals into four fractions (soluble and exchangeable fraction (F1); carbonates, oxides, and reducible fraction (F2); bound to organic matter, oxidizable, and sulphidic fraction (F3); and residual fraction (F4)) in PM_2.5 samples. The metals in each fraction were analyzed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Daily PM_2.5 concentration ranged between 13 and 238 μg m^-3 during the study period. For more than 92% of the days, the mass concentrations were greater than the National Ambient Air Quality Standard (NAAQS) set at 60 μg m^-3. The total mass concentration of the eight metals was 3.3 μg m^-3 that accounted for 2.5% of the PM_2.5 mass concentration and followed the order Fe > Zn > Cu > Mn > Pb > Ni > Cd > Cr in dominance. The carcinogenic metals (Cd, Cr, Ni, and Pb) comprised 10% of the total metal determined. Almost all the metals had the highest proportion in the residual fraction (F4) except Ni, which had the highest proportion in the reducible fraction (F2). Chemical fractionation and contamination factor (CF) showed that Pb and Ni are readily mobilized and more bioavailable. Risk assessment code (RAC) showed that Cd, Cu, Mn, Ni, Pb, and Zn had medium environmental risk, while Cr and Fe had low risk. When the bioavailable (F1 + F2) concentrations were applied to calculate non-carcinogenic and carcinogenic risk, the results showed that the value of hazard index (HI) for toxic metals was 1.7 for both children and adults through inhalation. The integrated carcinogenic risk was 1.8 × 10^-6 for children and 7.3 × 10^-6 for adults, with both values being higher than the precautionary criterion (1 × 10^-6). Enrichment factor (EF) calculations showed that Cd, Pb, Zn, and Ni were enriched being contributed by anthropogenic activities carried out in the industrial sectors of the city.

Analytical methods for assessing metal bioaccessibility in airborne particulate matter: A scoping review

In contrast to the existence of standardized methods to assess metal bioaccessibility via the gastrointestinal route, there are no widely-accepted, established in vitro testing protocols to measure elemental solubility in the human lung. This may be attributed, in part, to the difficulty associated with simulating the lung's complex in vivo conditions. The purpose of this review is two-fold: (1) to determine how the bioaccessibility of metals associated with ambient particulate matter (PM) in the human lung has been assessed in the literature, and (2) examine the suitability and biological relevance of applied methods for the measurement of metal bioaccessibility employed to date. The review revealed that limited attention has been paid to the development and application of biologically-relevant in vitro methods to measure elemental solubility in ambient PM as a proxy for bioaccessibility in the human lung. Few studies (n=14) used synthetic lung fluids to simulate in vivo conditions, with only half extracting samples at a biologically-relevant temperature of 37°C. There was limited evidence suggesting that the use of water is less effective as a leaching agent compared to simulated lung fluids. In sum, this scoping review highlights a critical need to develop standardized methods for the systematic assessment of elemental bioaccessibility via the respiratory route. Priority should be placed on the validation of biologically-relevant methods, including the use of leaching agents and extraction parameters used, which allow for testing to be conducted in a reliable, yet cost efficient, manner.

Use of tree bark for comparing environmental pollution in different sites from Buenos Aires and Montevideo

Multi-elemental profiles in bark of green ash trees collected in three representative areas of Buenos Aires, Argentina and Montevideo, Uruguay, were assessed as potential air pollution indicators. Ten elements: Al, Ba, Cr, Cu, Fe, Mg, Mn, Ni, Pb, and Zn, were measured using inductively coupled plasma optical emissions spectrometry from 70 samples collected in different environments: central, residential and rural (reference site), in order to compare spatial patterns of metal concentration. The samples used as a control were collected from a nature reserve situated far away from any significant influences, not even a nearby road. The reference site (RF) exhibited the lowest concentrations of Al, Cr, Fe, Ni, Pb, and Zn. However, Ba and Mn showed similar concentrations in all measured sites. Magnesium is the only element that had a greater concentration in RF than at the other sites. Copper did not show any clear pattern. The Centre of Montevideo (MVD) showed higher concentrations of Al, Ba, Cr, Fe, Pb and Zn than the Centre of Buenos Aires (BA). In the A sectors, Montevideo (SAMVD) showed higher concentrations of Al, Cu, Mg, Ni, and Zn and lower concentrations of Ba, Cr, Fe, Mn, and Pb than Buenos Aires (SABA). In the B sectors, Montevideo (SBMVD) showed higher concentrations of Al, Ba, Cu, Fe, Pb, and Zn and lower concentrations of Cr and Mg than Buenos Aires (SBBA), but similar concentrations of Mn and Ni. The use of bark for biomonitoring metals allowed us to detect concentration differences related to the urban fabric and the different kinds of vehicles and their fuels. In the cities, the differences in metal concentrations detected in bark were more striking between the sectors than between centers, despite CBA being much larger than CMVD in population, extension and vehicular traffic.

Differential Individual Particle Analysis (DIPA): applications in particulate matter characterization

Operator-controlled and computer-controlled scanning electron microscopy (CCSEM) are used extensively to characterize particulate matter in environmental media. Analysis in a scanning electron microscope (SEM) coupled with chemical extraction is a potentially powerful tool that is capable of determining how various sample components are associated at the individual particle level. This involves initial characterization in a SEM, after which the material is exposed to a liquid or gas phase reaction for a specified time, and once exposure is concluded, the particles are reanalyzed in the SEM. This particle analysis by difference, or differential individual particle analysis (DIPA), possesses considerable potential for describing the behavior of environmental particles under changing chemical conditions. Here we describe DIPA applications with illustrative examples drawn from the analysis of particulate matter modified by reactions in a fluid environment. In situ DIPA permits the same particles to be analyzed in the SEM before and after modification. Repeated exposure to the same, or different modifying conditions, provides information on the time dependence of specific reactions. Significant numbers of particles can be analyzed using CCSEM, and the same particles can be analyzed after the reaction by accurate sample relocation in the SEM. Ex situ DIPA, which involves a bulk sample modification, uses CCSEM to characterize significant numbers of particles pre- and postreaction. The CCSEM approach is extremely efficient; recent developments in silicon drift detectors have increased the speed of characteristic X-rays detection, and very large numbers of particles can be analyzed in a short period of time.

Is there a future for sequential chemical extraction?

Since their introduction in the late 1970s, sequential extraction procedures have experienced a rapid increase in use. They are now applied for a large number of potentially toxic elements in a wide range of sample types. This review uses evidence from the literature to consider the usefulness and limitations of sequential extraction and thereby to assess its future role in environmental chemical analysis. It is not the intention to provide a comprehensive survey of all applications of sequential extractions or to consider the merits and disadvantages of individual schemes. These aspects have been covered adequately in other, recent reviews. This review focuses in particular on various key issues surrounding sequential extractions such as nomenclature, methodologies, presentation of data and interpretation of data, and discusses typical applications from the recent literature for which sequential extraction can provide useful and meaningful information. Also covered are emerging developments such as accelerated procedures using ultrasound- or microwave energy-assisted extractions, dynamic extractions, the use of chemometrics, the combination of sequential extraction with isotope analysis, and the extension of the approach to non-traditional analytes such as arsenic, mercury, selenium and radionuclides.

Characterization and source apportionment of particulate matter < or = 2.5 micrometer in Sumatra, Indonesia, during a recent peat fire episode

An intensive field study was conducted in Sumatra, Indonesia, during a peat fire episode to investigate the physical and chemical characteristics of particulate emissions in peat smoke and to provide necessary data for source-receptor analyses. Ambient air sampling was carried out at three different sites located at varying distances from the peatfires to determine changes in mass and number concentrations of PM2.5 and its chemical composition (carbonaceous and nitrogenous materials, polycyclic aromatic hydrocarbons, water-soluble inorganic and organic ions, and total and water-soluble metals). The three sites represent a rural site directly affected by the local peat combustion, a semirural site, and an urban site situated downwind of the peat fires. The mass concentration of PM2.5 and the number concentration of airborne particles were as high as 1600 microg/m3 and 1.7 x 10(5) cm(-3), respectively, in the vicinity of peat fires. The major components of PM2.5 in peat smoke haze were carbonaceous particles, particularly organic carbon, NO3-, and SO4(2-), while the less abundant constituents included ions such as NH4+, NO2-, Na+, K+, organic acids, and metals such as Al, Fe, and Ti. Source apportionment by chemical mass balance receptor modeling indicates that peat smoke can travel long distances and significantly affect the air quality at locations downwind.