Hygroscopicity of Organic Compounds as a Function of Their Physicochemical Properties

The present study elucidates on PM2.5 (particle aerodynamic diameter ≤ 2.5 μm) bound trace metals characterization from on-road light-duty vehicles during on-road operation and their health risk assessment for adults and children. The vehicles assessed in present work included 4-wheelers passenger cars with a different age group of Bharat Stage (BS) II, III, and IV and different fuel type [diesel, gasoline and compressed natural gas (CNG)]. To understand the particle losses, particle formation, and homogenous mixing, firstly, a new portable dilution system (PDS) was designed for diluting the exhaust with adequate aerosol formation and growth, and evaluated beforehand under controlled condition in laboratory for diesel vehicles over a wide range of dilution ratio (30:1, 60:1, and 90:1). For on-road experiments, a PDS, a heated duct, a gas analyzer, an exhaust velocity probe, a temperature, and relative humidity probe were mounted on Aerosol Emissions Measurement System (AEMS) and it was towed behind the vehicle. Total 46 experiments were performed on a mixed traffic route in Delhi city, and PM2.5 mass was collected on Teflon and quartz filter using multi-stream PM2.5 sampler. Total 17 trace metals (Al, Ag, As, Ba, Co, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, Sr, Ti, V, and Zn) were characterized on Teflon filters using Induced Coupled Plasma-Mass Spectrometry (ICP-MS). Out of these metals, the non-carcinogenic and carcinogenic risks for adults and children were calculated for 5 metals namely Cr, Mn, Ni, Zn, and Pb. Trace metals concentration was highest in exhaust emitted from 4W-diesel followed by 4W-gasoline, 3W-CNG, and 2W-gasoline. Trace metals such as Cr, Mn, Ni, Zn, and Pb were present in high amount (25.2 ± 8.6 μg m−3). The carcinogenic risk from Cr was considerably higher than tolerable risk (10−4), while the risk from other metals such as Ni, As, Cd, and Pb was within the range of safe (10−6) and tolerable (10−4) level. Overall, the human health risks associated with the exposure to PM2.5 emitted from gasoline and CNG vehicles were higher than that from diesel vehicle. This estimated risk in this work can help in refining the burden of disease and crafting policy to help reduce the exposures. This study is limited only for PM2.5 bound trace metals and associated health risk from on-road vehicle emissions. However, poly-aromatic hydrocarbons (PAHs), perfluorinated compounds (PFCs), and semi-volatile compounds in vehicular exhaust can also impose a severe risk to human health which needs to be assessed to evaluate combined risk.

Measurements of the molecular composition of organic aerosol (OA) constituents improve our understanding of sources, formation processes, and physicochemical properties of OA. One instrument providing such data at a time resolution of minutes to hours is the Chemical Ionization time-of-flight Mass Spectrometer with Filter Inlet for Gases and AEROsols (FIGAERO-CIMS). The technique collects particles on a filter, which are subsequently desorbed, and the evaporated molecules are ionized and analyzed in the mass spectrometer. However, long-term measurements using this technique and/or field deployments at several sites simultaneously, require substantial human and financial resources. The analysis of filter samples collected outside the instrument (offline) may provide a more cost-efficient alternative and makes this technology available for the large number of particle filter samples collected routinely at many different sites globally. Filter-based offline use of the FIGAERO-CIMS limits this method albeit to particle-phase analyses, likely at reduced time resolution compared to online deployments. Here we present the application and assessment of offline FIGAERO-CIMS, using Teflon and Quartz fiber filter samples that were collected in autumn 2018 in urban Beijing. We demonstrate the feasibility of the offline application with “sandwich” sample preparation for the identified over 900 organic compounds with (1) high signal-to-noise ratios, (2) high repeatability, and (3) linear signal response to the filter loadings. Comparable overall signals were observed between the Quartz fiber and Teflon filters for 12-h and 24-h samples, but with larger signals for semi-volatile compounds for the Quartz fiber filters, likely due to adsorption artifacts. We also compare desorption profile (thermogram) shapes for the two filter materials. Thermograms are used to derive volatility qualitatively based on the desorption temperature at which the maximum signal intensity of a compound is observed (Tmax). While we find that Tmax can be determined with high repeatability for one filter type, we observe considerable differences in Tmax between the Quartz and Teflon filters, warranting further investigation into the thermal desorption characteristics of different filter types. Overall, this study provides a basis for expanding OA molecular characterization by FIGAERO-CIMS to situations where and when deployment of the instrument itself is not possible.

The surfaces of secondary organic aerosol particles are notoriously difficult to access experimentally, even though they are the key location where exchange between the aerosol particle phase and its gas phase occurs. Here, we overcome this difficulty by applying standard and sub- 1 cm(-1) resolution vibrational sum frequency generation (SFG) spectroscopy to detect C-H oscillators at the surfaces of secondary organic material (SOM) prepared from the ozonolysis of α-pinene at Harvard University and at the University of California, Irvine, that were subsequently collected on Teflon filters as well as CaF2 windows using electrostatic deposition. We find both samples yield comparable SFG spectra featuring an intense peak at 2940 cm(-1) that are independent of spectral resolution and location or method of preparation. We hypothesize that the SFG spectra are due to surface-active C-H oscillators associated with the four-membered ring motif of α-pinene, which produces an unresolvable spectral continuum of approximately 50 cm(-1) width reminiscent of the similar, albeit much broader, O-H stretching continuum observed in the SFG spectra of aqueous surfaces. Upon subjecting the SOM samples to cycles in relative humidity (RH) between <2% RH and ∼95% RH, we observe reversible changes in the SFG signal intensity across the entire spectral range surveyed for a polarization combination probing components of the vibrational transition dipole moments that are oriented parallel to the plane of incidence, but no signal intensity changes for any other polarization combination investigated. These results support the notion that the C-H oscillators at the surfaces of α-pinene-derived SOM deposited on CaF2 windows shift back and forth between two different molecular orientation distributions as the RH is lowered (more ordered) or raised (less ordered). The findings thus point toward the presence of a reversible surface switch for hindering (more ordered, <2%RH) and promoting (less ordered, ∼95%RH) exchange between the aerosol particle phase and its gas phase.

Abstract. The formation of sulfate and secondary organic aerosol mass in the aqueous phase (aqSOA) of cloud and fog droplets can significantly contribute to ambient aerosol mass. While tracer compounds give evidence that aqueous-phase processing occurred, they do not reveal the extent to which particle properties have been modified in terms of mass, chemical composition, hygroscopicity, and oxidation state. We analyze data from several field experiments and model studies for six air mass types (urban, biogenic, marine, wild fire biomass burning, agricultural biomass burning, and background air) using aerosol size and composition measurements for particles 13–850 nm in diameter. We focus on the trends of changes in mass, hygroscopicity parameter κ, and oxygen-to-carbon (O ∕ C) ratio due to chemical cloud processing. We find that the modification of these parameters upon cloud processing is most evident in urban, marine, and biogenic air masses, i.e., air masses that are more polluted than very clean air (background air) but cleaner than heavily polluted plumes as encountered during biomass burning. Based on these trends, we suggest that the mass ratio (Rtot) of the potential aerosol sulfate and aqSOA mass to the initial aerosol mass can be used to predict whether chemical cloud processing will be detectable. Scenarios in which this ratio exceeds Rtot∼0.5 are the most likely ones in which clouds can significantly change aerosol parameters. It should be noted that the absolute value of Rtot depends on the considered size range of particles. Rtot is dominated by the addition of sulfate (Rsulf) in all scenarios due to the more efficient conversion of SO2 to sulfate compared to aqSOA formation from organic gases. As the formation processes of aqSOA are still poorly understood, the estimate of RaqSOA is likely associated with large uncertainties. Comparison to Rtot values as calculated for ambient data at different locations validates the applicability of the concept to predict a chemical cloud-processing signature in selected air masses.

We have explored the direct and indirect radiative effects on climate of organic particles likely to have been present on early Earth by measuring their hygroscopicity and cloud nucleating ability. The early Earth analog aerosol particles were generated via ultraviolet photolysis of an early Earth analog gas mixture, which was designed to mimic possible atmospheric conditions before the rise of oxygen. An analog aerosol for the present-day atmosphere of Saturn's moon Titan was tested for comparison. We exposed the early Earth aerosol to a range of relative humidities (RHs). Water uptake onto the aerosol was observed to occur over the entire RH range tested (RH=80-87%). To translate our measurements of hygroscopicity over a specific range of RHs into their water uptake ability at any RH < 100% and into their ability to act as cloud condensation nuclei (CCN) at RH > 100%, we relied on the hygroscopicity parameter κ, developed by Petters and Kreidenweis. We retrieved κ=0.22 ±0.12 for the early Earth aerosol, which indicates that the humidified aerosol (RH < 100 %) could have contributed to a larger antigreenhouse effect on the early Earth atmosphere than previously modeled with dry aerosol. Such effects would have been of significance in regions where the humidity was larger than 50%, because such high humidities are needed for significant amounts of water to be on the aerosol. Additionally, Earth organic aerosol particles could have activated into CCN at reasonable-and even low-water-vapor supersaturations (RH > 100%). In regions where the haze was dominant, it is expected that low particle concentrations, once activated into cloud droplets, would have created short-lived, optically thin clouds. Such clouds, if predominant on early Earth, would have had a lower albedo than clouds today, thereby warming the planet relative to current-day clouds.

Airborne mineral dust particles, next to sea salt, are the most abundant aerosol type by mass globally (Andreae, 1995). Not only these particles affect the Earth&amp;#8217;s radiation budget, but they also modify cloud properties by serving as cloud condensation nuclei (CCN), or ice nuclei. The composition of mineral dust aerosol (i.e. pure or processed) or its origin, however, may have a different effect on cloud formation processes, and cloud characteristics, influencing not only aerosol-cloud interactions, but also global climate (Karydis et al. 2011).In this study, we investigate whether there are any differences in the particle hygroscopicity parameter &amp;#954; in mineral dust-dominated air masses. We use in situ measurements of CCN number concentration (at water vapor supersaturation (SS) up to 0.14 %), number size distributions (0.005-50 &amp;#956;m in diameter), and particle chemical composition made on board of DLR Falcon research aircraft during the ERC-funded A-LIFE project in the Eastern Mediterranean in April 2017.The classification of mineral dust-dominated air masses is based on aerosol chemical composition data from the scanning electron microscope coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), with the particle projected area (circle equivalent diameter) between 0.2 and 3 &amp;#956;m. We examine the CCN properties of mineral dust-dominated air masses (i.e. pure and polluted dust aerosol), and in particular, show that the hygroscopicity parameter &amp;#954; for SS of 0.1% varies between 0.01 and 0.2, and the corresponding particle activation diameters are found to be between 0.17 and 0.5 &amp;#956;m. The analysis supports our hypothesis that the hygroscopicity parameter &amp;#954; increases with increasing pollution. We show the composition resolved &amp;#954; and CCN concentration, as well as the particle volatility measurements, and compare these observations with other parameters measured during A-LIFE, as well as with results from the SALTRACE field campaign. Further, we identify the sources of mineral dust-dominated air masses using the Lagrangian transport and dispersion model FLEXPART.

Hydrogen-Bonding-Induced H-Aggregation of Charge-Transfer Complexes for Ultra-Efficient Second Near-Infrared Region Photothermal Conversion

&amp;#160; &amp;#160; Secondary organic aerosols (SOAs) account for a large fraction of atmospheric aerosol mass and play significant roles in visibility impairment by scattering solar radiation. However, comprehensive evaluations of SOA scattering abilities under ambient relative humidity (RH) conditions on the basis of field measurements are still lacking due to the difficulty of simultaneously direct quantifications of SOA scattering efficiency in dry state and SOA water uptake abilities. In this study, field measurements of aerosol chemical and physical properties were conducted in winter in Guangzhou using a humidified nephelometer system and aerosol chemical speciation monitor. A modified multilinear regression model was proposed to retrieve dry-state mass scattering efficiencies (MSE, defined as scattering coefficient per unit aerosol mass) of aerosol components. The more oxidized oxygenated organic aerosol (MOOA) with O/C ratio of 1.17 was identified as the most efficient light scattering aerosol component. On average, 34% mass contribution of MOOA to total submicron organic aerosol mass contributed 51% of dry-state organic aerosol scattering. The overall organic aerosol hygroscopicity parameter &amp;#954;OA was quantified directly through hygroscopicity closure, and hygroscopicity parameters of SOA components were further retrieved using multilinear regression model by assuming hydrophobic properties of primary organic aerosols. The highest water uptake ability of MOOA among organic aerosol factors was revealed with &amp;#954;MOOA reaching 0.23, thus further enhancing the fractional contribution of MOOA in ambient organic aerosol scattering. In particular, the scattering abilities of MOOA was found to be even higher than those of ammonium nitrate under RH of

Evaluation of the physicochemical and textural properties of pomelo fruit following storage. Abstract - Introduction. Because of the long transportation times and storage durations that are often experienced, it is important to understand how pomelo properties change over time; that will be indicative of how long samples can be stored before they drop below acceptable quality limits. As no information is available regarding storage of pomelo fruit in the literature, the goal of our work was to study the change in pomelo physicochemical and textural properties following storage over a period of approximately 4 months. Materials and methods. The changes in physical, chemical and textural properties of commercial pomelo fruit were extensively evaluated over the course of a 4-month storage period. The correlation among physical, color, chemical and textural properties were also assessed. Results. Color properties (L*, a*, b*) changed significantly with storage; however, they did not change much during the initial 45 days of storage. The change in soluble solids content (SSC), acidity (A) and the ((SSC) / (A)) ratio suggested that pomelo fruit should not be stored for more than 75 days. Crucially, our study demonstrates that the a* parameter (greenness, R = -0.556) cor- relates best with the chemical property the ((SSC) / (A)) ratio, which is a recognized measurement of the consumer acceptability of citrus fruit. This means that measuring a* is a non-destructive way of monitoring the taste characteristics of pomelos in storage. This property also correlated well with the average firmness of the fruit and with the flesh texture. Conclusion. This fundamental informa- tion on the pomelo fruit could prove useful in the physical handling and processing of the fruit by breeders and postharvest technologists as well as distributors, market agents, importers and exporters. Thailand / Citrus grandis / fruits / pomelos / storage / physicochemical properties / texture / rheological properties

Two-stage chemical fractionation method for the analysis of elements and non-volatile inorganic ions in PM10 samples: Application to ambient samples collected in Rome (Italy)

L–Arabinose-based coordination polymers were synthesized by the oxidation of L–arabinose using warm HNO3 to form arabinaric acid and allowing the resulting arabinaric acid to react with the different metal ions such as zinc(II), lead(II), copper(II), iron(III), and chromium(III). Only zinc(II) and lead(II) ions produced crystalline coordination polymers suitable for analysis while copper(II) produced a gummy solid. Preliminary characterization of the coordination polymers was based on their solubility, melting points, UV–Visible spectra, and infrared spectra. The coordination polymers were insoluble in common organic solvents and in acidic aqueous solutions but soluble in moderately basic aqueous solutions (pH 12). The zinc(II) and lead(II) coordination polymers have melting points above 300°C while the copper(II) polymer melts from 218–225°C. UV–Visible spectra showed that these polymers have maximum absorption in the ultraviolet region. Zinc(II), lead(II), and copper(II) arabinarate coordination polymers had maximum absorbance at λmax = 217 nm, λmax = 240 nm, and λmax = 220 nm, respectively. The infrared spectra of the coordination polymers indicated the association of the arabinarate ligand with the metal ions. Introduction and incorporation of molecular species such as azobenzene and molecular iodine to the coordination polymers were also investigated. Infrared spectra obtained from the azobenzene inclusion experiments showed additional infrared absorption bands below 1000 cm –1 implying absorption of azobenzene within the polymers. Iodometric titrations also confirmed the inclusion of iodine in the coordination polymers. The potential of the coordination polymers to incorporate lead(II) ions in aqueous solutions was also investigated using column elution of different sample concentrations of lead(II). Atomic Absorption Spectrometric analysis illustrated significant lead reduction of up to 80.70 ppm of lead(II) on the eluted samples. Introduction Rapid industrialization in the modern world today causes severe pollution in the environment. This may be due to toxic, inorganic, or non-biodegradable materials released to the environment as waste products during industrial processes. Heavy metals, like lead, are among the most harmful of the environmental elemental pollutants. Lead contamination from excessive exposure has been found to cause several health hazards and long term detrimental effects. Prominent conventional processes for the removal of lead from aqueous mixtures, such as sludge separation, chemical precipitation, and electrochemical treatments are relatively expensive and can cause secondary pollutants (Manahan, 1993 as cited in Acabal et al., 2000). Due to the problems of pollution, “green” industrial productions of compounds and their derivatives based on renewable starting materials and biodegradable products are developed (Kiely, 2001). Carbohydrates are biodegradable, widely available, and generally economical. Hence, their study for chemical and industrial applications would be very sensible. Because of their ease in functionalization forming sugar derivatives, they could serve as valuable building blocks for potentially useful polymers (Abrahams et al., 2003). Heavy metal sequestering properties of certain types of these polymers provide an alternative and potentially economical treatment process for heavy metal removal and recovery.

This study used fine and coarse PM concentrator technology in a Mobile Particle Concentrator Platform (MPCP) designed and built to allow the collection of large amounts of ambient PM, enabling time-resolved speciation analysis, which would not be feasible using conventional methods. One hour of sampling yielded sufficient sample loading for trace elemental analysis using X-Ray Fluorescence (XRF). In addition, we developed a novel Road Dust Aerosolizer (RDA) sampler in order to collect PM2.5 and PM10 surface road dust in situ. This sampler aerosolizes dust from the road surface, simulating ambient road dust resuspension, resulting in measured PM composition and size more appropriately (and less labor-intensive) than those obtained from studies using bulk road dust sieved and re-suspended in the laboratory. Overall, our modified fine and coarse particle concentrators yielded good reproducibility between co-located samples and sufficient loading for trace elemental analysis. For particle mass concentration, we observed a relative error of 3% and 4% among pairs of filters for fine and coarse concentrators, respectively; confirming that the mass collected on an unweighted quartz filter in parallel with a Teflon filter will have the same PM mass as the weighed Teflon filter. For samples with elements that are well above the LOD, relative uncertainty values were between 5% and 10% for the fine and 3% and 10% for the coarse. Our results show that the RDA system has an excellent precision for mass and elements as well. The relative error for mass is 7% for PM10 and 3% for PM2.5 within pairs and ranged from 2 to10% for elements. In conclusion, we developed a method for collecting PM10 and PM2.5 near-road air and surface road dust for short durations, which allows investigation of the composition of direct (airborne) and indirect (re-suspended road dust) non-tailpipe vehicular emissions. Implications: The methods we developed in this study allow the collection of one-hour PM10-2.5 and PM2.5–0.2 samples from near-road ambient air at several distances from the same roadway in 1 day, and collection of road dust directly from the road surface, with sufficient loading for trace elemental analysis. This will allow investigation of the composition of direct (airborne) and indirect (re-suspended road dust) vehicular emissions.

Measurement of carcinogenic Cr(VI) in ambient PM is challenging due to potential errors associated with conversion between Cr(VI) (a carcinogen) and Cr(III) (an essential nutrient). Cr(III) conversion is a particular concern due to its >80% atomic abundance in total Cr. U.S. Environmental Protection Agency (EPA) method 6800 that uses water-soluble isotope spikes can be used to correct the interconversion. However, whether the enriched Cr(III) isotope spikes can adequately mimic the Cr(III) species originally in ambient PM is unknown. This study examined the water solubility of Cr(III) in ambient PM and discussed its influence on Cr(VI) measurement. Ambient PM10 samples were collected on Teflon filters at four sites in New Jersey that may have different Cr emission sources. The samples were ultrasonically extracted with 5 mL DI-H2O (pH 5.7) at room temperature for 40 min, and then analyzed by ion chromatography–inductively coupled plasma mass spectrometry (IC-ICPMS). Cr(III) was below detection limit (0.06 ng/m3) for all samples, suggesting water-soluble Cr(III) species, such as CrCl3, Cr(NO3)3, and amorphous Cr(OH)3, in the ambient PM were negligible. Therefore, the enriched 50Cr(III) isotope spike (in the form of Cr(NO3)3) could not mimic the original ambient Cr(III). Only the conversion of 53Cr(VI) (in the form of K2CrO4) was taken into account when correcting the interconversion. We then used NaHCO3-pretreated MCE filters (prespiked with enriched isotope species) to measure Cr(VI) in the ambient PM10. The samples were ultrasonically extracted at 60 C pH 9 solutions for 40 min followed by IC-ICPMS analysis. Due to the correction of Cr(VI) reduction, the Cr(VI) concentrations determined by EPA method 6800, 0.26 ± 0.16 (summer) and 0.16 ± 0.11(winter) ng/m3 (n = 64), were significantly greater than those by the external standard curve, 0.21 ± 0.17 (summer) and 0.10 ± 0.07 (winter) ng/m3 (n = 56) (p < 0.01, Student’s t-test). Our study revealed that appropriate application of EPA method 6800 is important because it only applies to soluble fraction of Cr species in ambient PM.ImplicationsAccurate measurement of carcinogenic Cr(VI) in ambient PM is challenging due to conversion between Cr(VI) (a human carcinogen) and Cr(III) (a human essential nutrient). The conversion of Cr(III) is of particular concern due to its dominant presence in total Cr (>80%). This study examined the water solubility of Cr(III) in ambient PM that was collected at four locations in New Jersey. Then we discussed the influence of Cr(III) solubility on the application of EPA method 6800, which utilizes enriched isotope spikes to correct the interconversion. Our results suggested that appropriate application of EPA method 6800 is important because it only applies to soluble fraction of Cr species.

The effect of fermentation period on the pH, titratable acidity, calcium oxalate, oxalic acid, moisture, ash contents, swelling power, solubility, and color of the taro flours was investigated present research. For this aim, taro corms were cleaned, peeled, washed, sliced into chips. Taro chips were fermented at 0, 24, 48, and 72 hours, drained, dried in a cabinet dryer at 60 °C for 10 h, and ground. Results showed that pH, ash content, solubility, lightness (L *) decreased, and moisture content, titratable acidity dan swelling power increased markedly due to fermentation. Calcium oxalate and oxalic acid of the flours changed 843,83 - 412,07 mg/100 g and 370,52- 949,17 m g / 100 g flour respectively . T he fermentation at 48 h effected a significant reduction in calcium oxalate ( 51,19% ) and oxalic acid contents (64,35 % ). The present study indicated that the taro’s flours oxalate content and physicochemical characteristics properties of the taro flours were significantly affected by the fermentation period.

&amp;lt;p&amp;gt;In this study the OPC-N3 low-cost particle matter counter was used to determine the hygroscopic properties of the aerosol. The work shows the first results of aerosol hygroscopicity conducted in Poland. The study was performed during Spring 2020 (lock-down period) and Winter 2020/2021. The research was conducted in the Geophysics Institute at the University of Warsaw, close to the city center.&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Two OPC-N3 sensors were connected to the outlet from two legs of the Aerosol Conditioning System ACS1000. In one of them, low relative humidity was kept at the level of 20%, and in the other, the relative humidity was changed in the range of 50-90% in cycles.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The calculation of growth factor was done by dividing the PM1 measured from wet pipe by PM1 measured in the dry channel. The hygroscopicity parameter &amp;amp;#954; was calculated from &amp;amp;#954;-K&amp;amp;#246;hler theory, showing a fluctuation of the &amp;amp;#954; parameter which depends on aerosol type.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The variability of &amp;amp;#954; during Spring was ranging from values of 0.075 up to 0.437 (growth factor range 1.294 &amp;amp;#8211; 2.625).&amp;amp;#160; The observed &amp;amp;#954; for Winter oscillates between 0.018 - 0.077 (growth factor range 1.057 &amp;amp;#8211; 1.246). The values of hygroscopicity of aerosol in winter are smaller than the ones corresponding to Spring, in line with respect to previous literature reports.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The study shows possibility to use OPC-N3 for calculation of the hygroscopic properties of the aerosol, however it means that the measurements of PM done by OPC-N3 can be biased by high relative humidity.&amp;lt;/p&amp;gt;