Particle-phase Concentrations Research Articles

Widespread occurrence of pesticides in low-income housing

BackgroundLow socioeconomic status (SES) residents living in social housing, which is subsidized by government or government-funded agencies, may have higher exposures to pesticides used in indoor residences since pesticides are applied due to structural deficiencies, poor maintenance, etc.ObjectiveTo estimate exposure of residents in low-SES social housing built in the 1970s to legacy and current-use pesticides and to investigate factors related to exposures.MethodsTwenty-eight particle-phase pesticides were measured in the indoor air of 46 units in seven low-income social housing, multi-unit residential buildings (MURBs) in Toronto, Canada using portable air cleaners deployed for 1 week in 2017. Pesticides analyzed were legacy and current use in the classes: organochlorines, organophosphates, pyrethroids, and strobilurins.ResultsAt least one pesticide was detected in 89% of the units with detection frequencies (DF) for individual pesticides of up to 50%, including legacy organochlorines and current-use pesticides. Current-use pyrethroids had the highest DF and concentrations, with the highest particle-phase concentration for pyrethrin I at 32,000 pg/m3. Heptachlor, restricted for use in Canada in 1985, had the highest estimated maximum total air (particle plus gas phase) concentration of 443,000 pg/m3. Heptachlor, lindane, endosulfan I, chlorothalonil, allethrin, and permethrin (except in one study) had higher concentrations than those measured in low-income residences reported elsewhere. In addition to the intentional use of pesticides to control pests and their use in building materials and paints, tobacco smoking was significantly correlated with the concentrations of five pesticides used on tobacco crops. The distribution of pesticides with high DF in individual buildings suggested that pest eradication programs by the building management and/or pesticide use by residents were the major sources of measured pesticides.ImpactLow-income social housing fills a much-needed demand, but the residences are prone to pest infestation and hence pesticide use. We found exposure to at least 1 of 28 particle-phase pesticides in 89% of all 46 units tested, with the highest DF and concentrations for current-use pyrethroids and long-banned organochlorines (e.g., DDT, heptachlor) due to very high persistence indoors. Also measured were several pesticides not registered for use indoors, e.g., strobilurins used to treat building materials and pesticides used on tobacco crops. These results, which are the first Canadian data for most pesticides indoors, show widespread exposure to numerous pesticides.

Urban air PCDD/Fs: Atmospheric concentrations, temporal changes, gas/particle partitioning, possible sources and cancer risks

Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) are pollutants of concern due to their toxic effects. No active sampling study on PCDD/Fs has been conducted in Bursa. This study aimed to fill this gap by measuring PCDD/F levels in the region. Accordingly, the samples were collected from an urban area in Bursa, covering four seasons between June 2022 and April 2023. The total (gas+particulate) ambient air concentrations were between 312.23 and 829.80 fg/m3 (mean: 555.05 ± 173.62 fg/m3). In terms of toxic equivalents (TEQ), the average concentration was 43.29 ± 9.18 fg WHOTEQ/m3. Based on the concentration values obtained, cancer and non-carcinogenic risk values of PCDD/Fs were calculated for three different age groups. The results indicated negligible health risks for all age groups. In addition, a seasonal assessment was also made and it was observed that PCDD/F concentration values varied with the ambient air temperatures. In general, higher values were measured in colder months compared to warmer months. This was probably due to the additional sources and adverse meteorological conditions. Moreover, the gas/particle partitioning of PCDD/Fs was investigated in detail. The average gas and particulate phase concentrations for PCDD/Fs were 101.81 ± 20.77 and 453.24 ± 172.50, respectively. It was found that an equilibrium state was not reached in the gas/particle partitioning. Two different gas/particle partition models based on adsorption and absorption mechanisms were compared, and the absorption model gave more consistent predictions. The Principal Component Analysis (PCA) was employed to identify the possible PCDD/F sources. The results indicated that the region was influenced by vehicle emissions, residential heating, organized industrial zones and metal recycling facilities. In addition, 72-hour backward air mass trajectory analyses were performed to understand the long-range transported air masses. However, it was found that the transported air masses did not significantly affect the concentration values measured in the sampling site.

Thermal dynamics assessment for multi-phase flow analysis with motile cilia and electric double layer effects: Application of Levenberg–Marquardt backpropagation NNs

Ciliary movement holds substantial importance in the realm of biomedical research. Disorders arising from impaired ciliary motion, such as primary ciliary dyskinesia and specific respiratory ailments, underscore the critical need to investigate both the normal functioning and dysfunction of cilia. Such research is fundamental to the development of effective treatments and therapies. This work explores the application of Levenberg–Marquardt backpropagation neural networks (LMBP-NNs) for simulating the flow of a non-Newtonian Jeffery fluid in peristaltic motion. Inspired by synchronous ciliary movement, microfluidic systems mimicking cilia functionality have been developed. These artificial cilia can generate controlled fluid flow patterns, enabling various applications such as drug delivery, mixing, and particle sorting in lab-on-a-chip devices. The present study focuses on measuring thermal and mass transfer in beating cilia during multiphase peristaltic pumping of Jeffery fluid in two- and three-dimensional channels using transverse magnetohydrodynamics in a porous medium. The governing equations for the non-Newtonian Jeffery fluid in both the fluid and dusty phases are formulated, and exact solutions are calculated for fluid phase velocity, particulate phase velocity, temperature, concentration, and pressure gradient. The physical behavior is investigated by graphing dimensionless parameters for velocity, temperature, and concentration profiles in both solid and liquid phases. The trapping phenomena is depicted by showing streamlines of various dimensionless characteristics such as porosity velocity and volume percentage. The LMBP-NNs approach is then used to train, test, and verify the neural network models using the reference datasets. The accuracy of the LMBP-NN is assessed using statistical data such as mean square error, curve fitting graphs, regression plots, and error histograms. The study also investigates flow model limits for momentum, temperature, and concentration profiles using visual representations. This study illustrates the computational capability of LMBP-NNs in modeling the peristaltic flow of Jeffery fluid and gives useful insights into fluid flow behavior in microfluidic devices containing artificial cilia. The findings help to better understand and optimize these systems for a variety of fluid manipulation and transportation applications.

Gas–particle partitioning of semivolatile organic compounds when wildfire smoke comes to town

Abstract. Wildfires have become an increasingly important source of organic gases and particulate matter in the western USA. A large fraction of organic particulate matter emitted in wildfires is semivolatile, and the oxidation of organic gases in smoke can form lower-volatility products that then condense on smoke particulates. In this research, we measured the gas- and particle-phase concentrations of semivolatile organic compounds (SVOCs) during the 2017 northern California wildfires in a downwind urban area, using semivolatile thermal desorption aerosol gas chromatography (SV-TAG), and measured SVOCs in a rural site affected by biomass burning using cTAG (comprehensive thermal desorption aerosol gas chromatography mass spectrometry) in Idaho in 2018. Commonly used biomass burning markers such as levoglucosan, mannosan, and nitrocatechols were found to stay predominantly in the particle phase, even when the ambient organic aerosol (OA) was relatively low. The phase partitioning of SVOCs is observed to be dependent on their saturation vapor pressure, while the equilibrium absorption model underpredicts the particle-phase fraction of most of the compounds measured. Wildfire organic aerosol enhanced the condensation of polar compounds into the particle phase but not some nonpolar compounds, such as polycyclic aromatic hydrocarbons.

Measurement of thermal radiative and mass transfer of peristaltic pumping of electrically-conducting bio-bi-phase flow due to metachronal wave: Eukaryotic cells in biological applications

Cilia motion are commonly located in mammalian cells of living organisms which is continually grow and feature conspicuously. The ciliary apparatus is associated to cell cycle movement and proliferation, and cilia show a dynamic part in human and animal growth and in everyday life. The measurement of a solo cilium is one to tenth micrometres and width is less than 1 μm. A large number of varieties is originated such as inner ear, kidney, oviduct, eye, testes, olfactory epithelium and respiratory tract. Protozoa, algae, and several small invertebrates are examples of creatures that frequently exhibit metachronal waves in their cilia and flagella. These waves generate an overall propulsive force that enables the movement of these organisms in fluid settings. Cilia or flagella can provide fluid flow that drives the creature ahead or allows it to move particles or other materials around it by producing a travelling wave motion. Motivation of these applications, Present study is measurement of thermal and mass transfer in beating cilia of multiphase peristaltic pumping of non-Newtonian Ree-Eyring fluid in two- and three-dimensional channel using transvers magnetohydrodynamics in porous medium. Two systems of the governing equations both phases dusty and fluid phase are formulated for the non-Newtonian Ree-Eyring fluid. Calculated exact solutions for fluid phase velocity, particulate phase velocity, temperature, concentration and pressure gradient respectively. Also, physical behaviour is discussed by plotting the graph of different dimensionless parameters on both phases solid-liquid on velocity, thermal and concentration. Trapping phenomenon is visualized by plotting the stream lines of different dimensionless parameters on velocity of Ree-Eyring fluid and magnetic field.

Molecular Understanding of the Enhancement in Organic Aerosol Mass at High Relative Humidity.

The mechanistic pathway by which high relative humidity (RH) affects gas-particle partitioning remains poorly understood, although many studies report increased secondary organic aerosol (SOA) yields at high RH. Here, we use real-time, molecular measurements of both the gas and particle phase to provide a mechanistic understanding of the effect of RH on the partitioning of biogenic oxidized organic molecules (from α-pinene and isoprene) at low temperatures (243 and 263 K) at the CLOUD chamber at CERN. We observe increases in SOA mass of 45 and 85% with increasing RH from 10-20 to 60-80% at 243 and 263 K, respectively, and attribute it to the increased partitioning of semi-volatile compounds. At 263 K, we measure an increase of a factor 2-4 in the concentration of C10H16O2-3, while the particle-phase concentrations of low-volatility species, such as C10H16O6-8, remain almost constant. This results in a substantial shift in the chemical composition and volatility distribution toward less oxygenated and more volatile species at higher RH (e.g., at 263 K, O/C ratio = 0.55 and 0.40, at RH = 10 and 80%, respectively). By modeling particle growth using an aerosol growth model, which accounts for kinetic limitations, we can explain the enhancement in the semi-volatile fraction through the complementary effect of decreased compound activity and increased bulk-phase diffusivity. Our results highlight the importance of particle water content as a diluting agent and a plasticizer for organic aerosol growth.

Nucleation of jet engine oil vapours is a large source of aviation-related ultrafine particles

Large airports are a major source of ultrafine particles, which spread across densely populated residential areas, affecting air quality and human health. Jet engine lubrication oils are detectable in aviation-related ultrafine particles, however, their role in particle formation and growth remains unclear. Here we show the volatility and new-particle-formation ability of a common synthetic jet oil, and the quantified oil fraction in ambient ultrafine particles downwind of Frankfurt International Airport, Germany. We find that the oil mass fraction is largest in the smallest particles (10-18 nm) with 21% on average. Combining ambient particle-phase concentration and volatility of the jet oil compounds, we determine a lower-limit saturation ratio larger than 1 × 105 for ultra-low volatility organic compounds. This indicates that the oil is an efficient nucleation agent. Our results demonstrate that jet oil nucleation is an important mechanism that can explain the abundant observations of high number concentrations of non-refractory ultrafine particles near airports.

Assessment of factors affecting the diurnal variations of atmospheric PAHs based on a numerical simulation

Atmospheric polycyclic aromatic hydrocarbons (PAHs) are a type of organic pollutants that seriously endanger human health. Obtaining the diurnal variations of PAHs and clarifying their impact mechanisms are significant for the government to formulate targeted prevention and control measures. However, the influencing factors that dominate the diurnal variations of common PAHs are currently unclear. In order to solve this problem, 16 PAHs selected by the United States Environmental Protection Agency (EPA) as priority-controlled pollutants were simulated with high resolution. The simulation results were validated based on diurnal observations in the vertical direction. Although the model underestimated the particle-phase concentrations of most components, it captured their diurnal variations fairly well. In addition, we assessed the factors affecting the diurnal variations of PAHs with sensitivity tests, including chemical reactions and atmospheric diffusion. The results showed that the transforming ratios of PAHs by oxidants were higher during the day than that at night due to the dominant reactions with OH radical. Atmospheric dispersion affected the vertical distribution of PAHs, which resulted in higher day/night ratios at high altitudes than near the ground. We also compared the strength of atmospheric diffusion and chemical reaction on the diurnal trends of PAHs. Near the ground, atmospheric diffusion was the most dominant factor in determining their diurnal trends. At high altitudes, their diurnal trends were determined by a combination of atmospheric diffusion and chemical reactions. These findings can provide a comprehensive understanding of the diurnal variations of common PAHs, which are informative for the prevention and control of PAHs pollution.

Gas-Particle Uptake and Hygroscopic Growth by Organosulfate Particles

Organosulfate compounds make up a substantial fraction of the particle mass concentration in some regions of the Earth’s atmosphere, and organosulfate particles can have sufficiently high viscosity to limit rates of gas-particle interactions. Viscosity varies with relative humidity (RH). Herein, organosulfate particles were exposed to the gas-phase products of α-pinene photooxidation. The gas-particle partitioning of these species was studied from 15 to 70% RH and <1 to 16 ppb NO at 299 K. The uptake of the α-pinene oxidation products increased with the increase in RH, and higher gas-phase NO concentrations resulted in increased particle-phase concentrations of nitrogen compounds. Particle hygroscopicity was examined by optical microscopy. Hygroscopic growth at elevated RH was sufficient to explain the RH-dependent uptake measurements, and kinetic limitations tied to particle viscosity were not observed. The lack of kinetic limitations combined with the Stokes–Einstein equation implied a viscosity much less than 1 × 106 Pa s. This value is consistent with estimated viscosities based on literature parameterizations for water mass fractions in the particles of at least 0.05 at 15% RH. Overall, these results suggest that organosulfate hygroscopicity plays a key role in their viscosity and hence in regulating gas-particle partitioning, thereby simplifying the treatment of atmospheric chemistry and transport of pollutants in models of the Earth’s atmosphere. The role of organosulfates is expected to take on increasing importance for projected future emission trends.

Predicting spatio-temporal distribution of indoor multi-phase phthalates under the influence of particulate matter

Due to the complexity of phthalates spatial and temporal distribution in indoor environment, mechanistic that govern indoor phthalates concentrations and fates need to be explored. A dynamic partition model of phthalates considering the dynamic behavior and segmented emission of size-resolved particulate matter is developed to investigate the distribution of phthalates in the gas phase, airborne particles, and settled dust and on the fixed surface. The impacts of outdoor and indoor particle source on the multi-phase concentrations of phthalates are analyzed. Outdoor haze can suddenly increase indoor particle concentration and particle-phase concentration of Di-2-ethylhexyl phthalate (DEHP). However, the haze decreases gas-phase and dust-phase concentration of DEHP. The particle emission rate Sp for cooking affects the maximum concentration of indoor particle, while cooking frequency has no effect on it. When cooking frequency increases, gas-phase concentration and particle-phase peak concentration of DEHP decreases significantly, which means the particulate matter may be a good carrier for DEHP removal. Increasing emission rate Sp of particles can significantly reduce the minimum gas-phase concentration of DEHP, nevertheless it can increase particle-phase maximum concentration of DEHP. Overall, the proposed model considering interactions of particle and phthalate can improve further understanding of phthalates’ fate and transport in residential environment, which is beneficial to the implementation of control strategy.

The dynamic partitioning of airborne phthalates in indoor environment: effects of ventilation

Low energy consumption buildings with strong air tightness such as passive buildings are the development trend in the world. However, ventilation directly affects the emission and dynamic transport of indoor phthalates. A transient partition model considering the dynamic behavior of size-resolved particle was utilized to investigate the influence of ventilation on the airborne Di-2-ethylhexyl phthalate (DEHP). The air exchange rate (a) was set to 0.15 h-1, 0.3 h-1, 0.6 h-1, 2h-1 for the different conditions. The predicted gas-phase concentration of DEHP in the initial 70 days is unaffected for different a and constant hms, whereas it raises until the a increases to 2 h-1. The equilibrium gas-phase concentration decreases from 0.257 to 0.203 μg/m3. Meanwhile, the higher a also reduced the particle-phase concentration of DEHP. Furthermore, the changes of airborne DEHP were analyzed by considering the impact of a on hms caused by ventilation. The results indicates that more ventilation leads to higher gas-phase concentration for the whole stage. The gas-phase concentration at equilibrium increases from 0.237 to 0.440 μg/m3. The total airborne (gas-phase + particle-phase) concentration decreases with the higher ventitation rate, which indicates that the ventitation has a positive effect on indoor airborne DEHP.

Gas–particle partitioning of polyol tracers at a suburban site in Nanjing, east China: increased partitioning to the particle phase

Abstract. Gas–particle partitioning of water-soluble organic compounds plays a significant role in influencing the formation, transport, and lifetime of organic aerosols in the atmosphere, but is poorly characterized. In this work, gas- and particle-phase concentrations of isoprene oxidation products (C5-alkene triols and 2-methylterols), levoglucosan, and sugar polyols were measured simultaneously at a suburban site of the western Yangtze River Delta in east China. All target polyols were primarily distributed into the particle phase (85.9 %–99.8 %). Given the uncertainties in measurements and vapor pressure predictions, a dependence of particle-phase fractions on vapor pressures cannot be determined. To explore the impact of aerosol liquid water on gas–particle partitioning of polyol tracers, three partitioning schemes (Cases 1–3) were proposed based on equilibriums of gas vs. organic and aqueous phases in aerosols. If particulate organic matter (OM) is presumed as the only absorbing phase (Case 1), the measurement-based absorptive partitioning coefficients (Kp,OMm) of isoprene oxidation products and levoglucosan were more than 10 times greater than predicted values (Kp,OMt). The agreement between Kp,OMm and Kp,OMt was substantially improved when solubility in a separate aqueous phase was included, whenever water-soluble and water-insoluble OM partitioned into separate (Case 2) or single (Case 3) liquid phases, suggesting that the partitioning of polyol tracers into the aqueous phase in aerosols should not be ignored. The measurement-based effective Henry's law coefficients (KH,em) of polyol tracers were orders of magnitude higher than their predicted values in pure water (KH,wt). Due to the moderate correlations between log⁡(KH,em/KH,wt) and molality of sulfate ions, the gap between KH,em and KH,wt of polyol tracers could not be fully parameterized by the equation defining “salting-in” effects and might be ascribed to mechanisms of reactive uptake, aqueous phase reaction, “like-dissolves-like” principle, etc. These study results also partly reveal the discrepancy between observation and modeling of organic aerosols.

Carbonaceous aerosol composition in air masses influenced by large-scale biomass burning: a case study in northwestern Vietnam

Abstract. We investigated concentrations of organic carbon (OC), elemental carbon (EC), and a wide range of particle-bound organic compounds in daily sampled PM2.5 at the remote Pha Din (PDI) – Global Atmosphere Watch (GAW) monitoring station in northwestern Vietnam during an intense 3-week sampling campaign from 23 March to 12 April 2015. The site is known to receive trans-regional air masses during large-scale biomass burning (BB) episodes. BB is a globally widespread phenomenon and BB emission characterization is of high scientific and societal relevance. Emissions composition is influenced by multiple factors (e.g., fuel and thereby vegetation type, fuel moisture, fire temperature, available oxygen). Due to regional variations in these parameters, studies in different world regions are needed. OC composition provides valuable information regarding the health- and climate-relevant properties of PM2.5. Yet, OC composition studies from PDI are missing in the scientific literature to date. Therefore, we quantified 51 organic compounds simultaneously by in situ derivatization thermal desorption gas chromatography and time-of-flight mass spectrometry (IDTD-GC-TOFMS). Anhydrosugars, methoxyphenols, n-alkanes, fatty acids, polycyclic aromatic hydrocarbons, oxygenated polycyclic aromatic hydrocarbons, nitrophenols, and OC were used in a hierarchical cluster analysis highlighting distinctive patterns for periods under low, medium, and high BB influence. The highest particle phase concentration of the typical primary organic aerosol (POA) and possible secondary organic aerosol (SOA) constituents, especially nitrophenols, were found on 5 and 6 April. We linked the trace gas mixing ratios of methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), and ozone (O3) to the statistical classification of BB events based on OA composition and found increased CO and O3 levels during medium and high BB influence. Likewise, a backward trajectory analysis indicates different source regions for the identified periods based on the OA clusters, with cleaner air masses arriving from the northeast, i.e., mainland China and the Yellow Sea. The more polluted periods are characterized by trajectories from the southwest, with more continental recirculation of the medium cluster and more westerly advection for the high cluster. These findings highlight that BB activities in northern Southeast Asia significantly enhance the regional organic aerosol loading and also affect the carbonaceous PM2.5 constituents and the trace gases in northwestern Vietnam. The presented analysis adds valuable data on the carbonaceous and chemical composition of PM2.5, in particular of OC, in a region of scarce data availability, and thus offers a reference dataset from Southeast Asian large-scale BB for future studies. Such a reference dataset may be useful for the evaluation of atmospheric transport simulation models, or for comparison with other world regions and BB types, such as Australian bush fires, African savannah fires, or tropical peatland fires.

Particle bound phthalate acid esters (PAEs) and total estimated ambient air PAEs concentrations study at a mixed (commercial, urban, and traffic) site in central Taiwan

Since there have not been any atmospheric phthalate acid ester (PAE) concentration-related studies in central Taiwan during the past few years, our first atmospheric PAE study was focused on the measurement of ambient air particle-bound PAE concentrations in central Taiwan (Fang et al., 2019). However, atmospheric PAEs in the gas phase have not yet been detected. Therefore, this study was aimed toward estimating atmospheric PAE concentrations in the gas phase from known PAE concentrations in the particle-phase. Then, the total PAE concentration in the atmosphere (estimated gas-phase concentrations and measured particle-phase concentrations) could be obtained. In this study, atmospheric PAE concentrations in the gas phase are estimated from known PAE concentrations in the particle phase, and ambient air total PAE (gas phase + particle-phase) concentrations at a mixed sampling site are estimated. Mean gas-phase and particle-phase PAE concentrations are estimated and calculated as percentages of the total estimated PAE concentrations at a mixed sampling site. The particle-bound PAE concentrations were measured using a PS-1 sampler from July to December of 2018; they were also analyzed using pyrolysis-gas chromatography/mass spectrometry. The solvent extraction method was used to determine the concentrations of the PAE species. In this study, total ambient air PAE concentrations using the known PAE concentrations in the particle phase were successfully estimated. The results indicated that the average measured P-DBP, P-DEHP, and P-DnOP concentrations were 33.94, 109.70, and 12.88 ng/m3, respectively. In addition, the average estimated gas-phase DBP, DEHP, and DnOP concentrations were 776.43, 26.11, and 2.95 ng/m3, respectively. Therefore, the average total estimated concentrations for total estimated DBP, DEHP, and DnOP concentrations were found to be 810.37, 135.81, and 15.83 ng/m3, respectively, at a mixed sampling site from July to December of 2018. In addition, the DEHP concentration was the highest when measured in the particle phase, and the DBP concentration was the highest when estimated in the gas phase; the average DEHP and DBP concentrations were highest in the autumn. DnOP had the lowest measured and estimated concentrations in the gas phase in all seasons. DnOP also had the lowest average concentration in the summer. Finally, the average particulate PAE species (DBP, DEHP, and DnOP) concentrations were highest in Taichung, Taiwan (mixed site) in the period from 2000 to 2018.

Characterization of 56 airborne persistent organic pollutants (POPs) in gas-phase and particle-phase

A systematic investigation was conducted on 56 persistent organic pollutants (POPs) in the atmosphere at seven functional regions of Jinan, China. The POPs included 16 polycyclic aromatic hydrocarbons (PAHs), 6 phthalic acid esters (PAEs), 17 polychlorinated biphenyls (PCBs), and 17 organochlorine pesticides (OCPs). The concentrations in gas-phase and particle-phase were monitored and analyzed to assess the contamination status and to identify the pollution sources according to the mass ratios between POP congeners and the distribution among the sampling regions and periods. The results show that the pollution level at a recreational area was lower than that in other regions of the city and it was higher in winter than in summer for all the 7 sampling sites. Sixteen polycyclic aromatic hydrocarbons (PAHs) were evenly distributed between gas-phase and particle-phase. The total concentration of phthalic acid esters (∑PAEs) in particle-phase was 96.4% larger than that in gas-phase, which was possibly derived from artificial plastics. PCB-126 was one of the major pollutants of the 17 polychlorinated biphenyls (PCBs) in the atmosphere. High-Cl PCBs favored adhering to airborne particles, while low-Cl PCBs tended to stay in gas-phase. The total concentration of 17 organochlorine pesticides (∑OCPs) in gas-phase accounted for 68.0%, while methoxychlor, dieldrin, and endrin aldehyde preferred to particle-phase. Additionally, the preliminary investigation suggests that local pollution sources contributed to most PAHs in urban sites, while the sources could be complex for the suburban area and adjacent towns in winter. Residues of some OCPs could also come from long-distance transportation.

The gas/particle partitioning behavior of phthalate esters in indoor environment: Effects of temperature and humidity

Phthalate esters (PAEs) are ubiquitous and among the most abundant semi-volatile organic compounds (SVOCs) in indoor environments. Due to their low saturated vapor pressure, SVOCs tend to adhere to indoor surfaces and particulate matters, which may result in higher total concentrations than occur in the gas phase alone. Thus, gas/particle partitioning of PAEs plays an important role in their indoor fates and health risks. However, the influence of indoor environmental parameters, including temperature and humidity, on the partitioning of PAEs between air and particles is rarely known. In this study, a novel experimental system was designed to investigate the effects of temperature and humidity on partitioning behavior between gas- and particle-phase PAEs. The chamber experiments were conducted at temperatures of 12.5 °C, 17.5 °C, 24.0 °C, 29.5 °C and 40.0 °C and moisture contents of 3.5 g/kg, 5.0 g/kg, 6.5 g/kg, 8.0 g/kg and 9.5 g/kg dry air. The results showed that higher temperatures led to stronger emission of phthalate esters from the PVC panel, which resulted in higher gas-phase concentrations of phthalate esters and particle-phase concentrations. In addition, temperature has a strong negative effect on the gas/particle partition coefficient (Kp), and an order of magnitude difference in Kp was observed between 12.5 and 40 °C. There are exponential decay laws between Kp and the absolute temperature. However, a smaller effect of humidity than of temperature on Kp was revealed, and no obvious law was found. Moreover, Kp of compounds with larger molecular weights are more obviously influenced by the variations in environmental factors. This study is of positive significance for reducing the health risks of PAEs by guiding the regulation of indoor environmental parameters.

Human uptake of phthalates from indoor home dust in the SELMA study

Background/aim: Phthalates are widely used in consumer products from which they can leach or evaporate, causing every day exposure linked to adverse health effects in humans. However, current knowledge of contributions of different uptake routes to total uptake is incomplete. This study aims to investigate associations between phthalate levels in home indoor dust and biomarkers of phthalate uptake in pregnant women, and model uptake contributions.Methods: Levels of five phthalates in settled bedroom dust from above floor level and corresponding metabolites in urine from 455 Swedish pregnant women were analyzed using GC-MS/MS to estimate uptake from home indoor environment using adapted steady-state models. Gas and airborne particle phase concentrations were extrapolated from dust assuming steady-state partitioning. Three indoor uptake routes were included in estimations: dust ingestion, airborne particle/gas inhalation, and dermal gas contact.Results: Dust levels of di-ethyl phthalate (DEP), di-butyl phthalate (DBP) and butyl-benzyl phthalate (BBzP) significantly (p&lt;0.001) correlates with corresponding urine metabolites (R2=0.23, 0.14 and 0.37 respectively), with no such trend for di-ethyl-hexyl phthalate (DEHP). Indoor exposure at home (13h/day) make a meaningful contribution (%) to total daily uptake of DEP (median 11%) and DBP (median 27%), with dermal gas uptake being dominant. The home indoor contributions to total uptake of less volatile BBzP and DEHP were minor (medians 1-2%), although they dominate uptake from the dust ingestion route. For women with PVC bedroom flooring, the relative contribution of home indoor exposure nearly doubled for uptake of BBzP and DEHP (96% increase each).Conclusion: Our results suggest that home indoor exposure contribute to phthalate uptake in pregnant women, in particular for more volatile compounds. Also, although small compared to total uptake, PVC flooring can increase indoor contribution to uptake of BBzP and DEHP. Our results suggest that reducing indoor exposure will reduce phthalate uptake in pregnant women.

Occurrence and Gas-Particle Partitioning of Organic UV-Filters in Urban Air.

A retrospective analysis of a comprehensive series of high-volume air samples (n = 70) collected during 2010-2011 in Toronto (Canada) was performed. Seven UV compounds were analyzed by gas chromatography-tandem mass spectrometry (GC-MS/MS) with sum of concentrations (gas + particle phase) ranging from 80 to 2030 pg/m3. Homosalate (HMS) was the most prevalent organic UV-filter in air (47% of the total concentration), followed by 2-ethylhexyl salicylate (EHS, ∼29%), E- and Z-2-ethylhexyl 4-methoxycinnamate (EHMC, ∼17%). Ambient air (gas + particle phase) concentrations of organic UV-filters showed a strong seasonality, with peak levels during the summer. An analysis of Clausius-Clapeyron slopes indicated that much of the ambient burden of organic UV-filters are explained by volatilization from terrestrial and aquatic surfaces and supplemented with human activities and use of lotions and sunscreens, containing organic UV-filters, in addition to its use in plastics, textiles, paints, and pesticides. The results showed that organic UV-filters exist mainly in the gas phase with some exceptions, for instance, octocrylene (OCR), which was associated with both gas and particle phases, and avobenzone (AVB), which was predominantly in the particle phase. Lastly, this study revealed the need for basic physical chemical property data for organic UV-filters, including information on transformation rates and products, for better evaluating their environmental fate and effects.

Tensile strength of granular aggregates: Stress chains across particle phase versus stress concentration by pores.

We use the bond-based peridynamics approach to analyze the strength and fracture of dense granular aggregates with variable amount of a solid binding matrix, distributed according to a simple protocol in the interstitial space between particles. We show the versatility of the peridynamics approach in application to crack propagation and its scaling behavior in a homogeneous medium (in the absence of particles and pores). Then we apply this method to simulate the deformation and failure of aggregates as a function of the amount of the binding matrix under tensile loading. We find that the tensile strength is a strongly nonlinear function of the matrix volume fraction. It first increases slowly and levels off as the gap space in-between touching particles is gradually filled by the binding matrix, up to nearly 90% of the total pore volume, and then a rapid increase occurs to the maximum strength as the remaining interstitial space, composed of isolated pores between four or more particles, is filled. By analyzing the probability density functions of stresses in the particle and matrix phases, we show that the adhesion of the matrix to the particles and the thickening of stress chains (i.e., stresses distributed over larger cross sections) control the strength in the first case whereas the homogenizing effect of the matrix by filling the pores (hence reducing stress concentration) is at the origin of further increase of the strength in the second case. Interestingly, these two mechanisms contribute almost equally to the total strength.

Measurement and Modeling the Phase Partitioning of Organophosphate Esters Using Their Temperature-Dependent Octanol-Air Partition Coefficients and Vapor Pressures.

Atmospheric concentrations of 11 organophosphate esters (OPEs) were measured in an urban area in Izmir, Turkey to explore their phase partitioning. Octanol-air partition coefficients (KOA) and vapor pressures (PL) of the OPEs were also measured as a function of temperature. Average Σ11OPE gas-phase concentrations were 1.77 ± 0.84 and 4.00 ± 1.77 ng/m3, while particle-phase concentrations were 1.95 ± 0.77 and 1.15 ± 0.36 ng/m3 during winter and summer, respectively. TCiPP1 dominated Σ11OPEs, followed by TnBP and TEP. OPE concentrations generally increased and shifted to gas-phase in the summer probably due to higher temperatures that favor partitioning to the gas-phase. Distribution between two phases covered a wide range from being primarily in gas-phase (TEP, TnBP) or particle-phase (EHDPP, TEHP, T2iPPP). Phase partitioning was also examined via four widely used models (KOA, Soot, Steady-State, and pp-LFER). All models underestimated the majority of particle-gas partition coefficients (KP) especially for the compounds having higher volatilities. Estimations based on the recently reported molecular weight of organic matter in urban aerosols (MWOM) and activity coefficients of OPEs in octanol (ξOCT) determined in the present study suggested that the basic assumptions of KOA-based models (i.e., ξOCT/ξOM and MWOCT/MWOM = 1) are not valid.