Surface Area Concentration Research Articles

RETRACTED: Health risks and respiratory intake of submicron particles in the working environment: A case study

Background: Powder-coating processes have been extensively used in various industries. The submicron particles generated during the powder-coating process in the workplace have complex compositions and can cause serious diseases. The purpose of this study was to better understand the health risks and respiratory intake of submicron particles during the powder coating process.Methods: The concentrations of and variations in submicron particles were measured using real-time instruments. The health risks of submicron particles were analyzed using the Stoffenmanager Nano model. A new computational fluid dynamics model was used to assess the respiratory intake of ultrafine particles (UFPs), which was indicated by the deposited dosage of UFPs in the olfactory area, nasal cavity, and lungs. The deposited doses of UFPs were used to calculate the average daily doses (ADDs) of workers, according to the method described by the Environmental Protection Agency.Results: The number concentration (NC), mass concentration, surface area concentration, personal NC, and lung-deposited surface area concentration of submicron particles were >105 pt/cm3, 0.2–0.4 mg/m3, 600–1,200 μm2/cm3, 0.7–1.4 pt/cm3, and 100–700 μm2/cm3, respectively. The size distribution showed that the submicron particles mainly gathered between 30 and 200 nm. The health risk of submicron particles was high. Upon respiratory intake, most UFPs (111.5 mg) were inhaled into the lungs, a few UFPs (0.272 mg) were trapped in the nasal cavity, and a small minority of UFPs (0.292 mg) were deposited in the olfactory area. The ADD of male workers with 10 years of exposure in the olfactory area, nasal cavity, and lung were 1.192 × 10–3 mg/kg·d−1, 1.11 × 10–3 mg/kg·d−1, and 0.455 mg/kg·d−1, respectively.Conclusion: Owing to the high concentrations of submicron particles, the workers involved in the powder-coating process are at a high health risk. Moreover, the respiratory intake of UFPs by workers is high, which is suggested by the highly deposited dosage of UFPs in the lungs and the corresponding high ADD in workers. Control measures, including engineering control, management control, and personal protective equipment, must be improved for the protection of workers.

Sol-gel-based porous Ti-doped tungsten oxide films for high-performance dual-band electrochromic smart windows

Dual-band electrochromic smart windows (DESWs) with independent control of the transmittance of near-infrared and visible light show great potential in the application of smart and energy-saving buildings. The current strategy for building DESWs is to screen materials for composite or prepare plasmonic nanocrystal films. These rigorous preparation processes seriously limit the further development of DESWs. Herein, we report a facile and effective sol–gel strategy using a foaming agent to achieve porous Ti-doped tungsten oxide film for the high performance of DESWs. The introduction of foaming agent polyvinylpyrrolidone during the film preparation can increase the specific surface area and free carrier concentration of the films and enhance their independent regulation ability of near-infrared electrochromism. As a result, the optimal film shows excellent dual-band electrochromic properties, including high optical modulation (84.9% at 633 nm and 90.3% at 1200 nm), high coloration efficiency (114.9 cm2 C-1 at 633 nm and 420.3 cm2 C-1 at 1200 nm), quick switching time, excellent bistability, and good cycle stability (the transmittance modulation losses at 633 and 1200 nm were 11% and 3.5% respectively after 1000 cycles). A demonstrated DESW fabricated by the sol–gel film showed effective management of heat and light of sunlight. This study represents a significant advance in the preparation of dual-band electrochromic films, which will shed new light on advancing electrochromic technology for future energy-saving smart buildings.

Exposure characteristics and risk assessment of air particles in a Chinese hotel kitchen.

The hazards of kitchen particles have attracted social attention, but their distribution characteristics and risk assessment are rarely reported. To explore the temporal and spatial distribution characteristics of kitchen particles, analyze the variations in characteristics of number concentration (NC), mass concentration (MC), surface area concentration (SAC), and particle size distribution, provide reference indexes for evaluating worker exposure, evaluate the risk of kitchen particles, as well as suggest improvements and control measures. Different cooking posts in a Chinese hotel kitchen were selected to monitor exposure to particles, explore the temporal and spatial distribution characteristics of NC, MC, and SAC of particles in the cooking post, analyze changes in the particle size, compare the individual exposure of particles between the cooking and steaming posts, and analyze the correlation between NC, MC, and SAC. Risk assessment of kitchen ultrafine particles was performed using a Nanotool. The sizes and fluctuation ranges of NC10 - 500nm at cooking posts during lunch preparation and at peak periods were significantly higher than those at the end of the lunch period. The mean values of MC10 - 500nm during the lunch preparation peak and ending periods were 0.149, 0.229, and 0.151 mg m-3, respectively. The mean values of SAC10 - 500nm were 225, 961, and 466 μm2·cm-3, respectively. The mode diameter of exposed particles at the cooking post [(34.98 ± 2.33) nm] was higher than that at the steaming post [(30.11 ± 2.17) nm] (P < 0.01). The correlation between SAC10 - 500nm and NC10 - 500nm (r = 0.703) was the strongest. Nanotool gave a hazard rating ratio, exposure rating ratio, and risk ratio of 0.75. The sizes of the NC, MC, and SAC of the particles at the cooking post were related to the kitchen operations. Since kitchen particles are of high exposure and risk levels, protective measures should be formulated and implemented to deal with them safely.

Belt-like In2O3 based sensor for methane detection: Influence of morphological, surface defects and textural behavior

Herein, gas sensors based on mesoporous belt-like In2O3 products derived from a single-step electrospinning method were produced, and the influence of the annealing temperature on their sensing performance was evaluated. A detailed comparison of the morphology, surface defects and textural behavior of the belt-like In2O3 products was carried out to understand the observed gas sensing trends. The In2O3 sensor produced at an annealing temperature of 550 ℃ displayed improved sensing capabilities with a response of 1.1 to 90 ppm of methane at a lower operating temperature of 100 ℃. The response and recovery times of this sensor were only 36 and 44 s, respectively, and it displayed good stability and selectivity as well as a lower detection limit of 0.18 ppm. Experimental characterization revealed that this enhanced sensing behavior originate from the mesoporous nature of belt-like In2O3 products composed of small-sized particles which offered a large number of active sites for methane gas molecules as a result of the high surface area and high concentration of oxygen vacancies, which enabled greater channels for methane gas adsorption and desorption capacity.

High time-resolution measurements of ultrafine and fine woodsmoke aerosol number and surface area concentrations in biomass burning kitchens: A case study in Western Kenya.

Indoor air pollution associated with biomass combustion for cooking remains a significant environmental health challenge in rural regions of sub-Saharan Africa; however, routine monitoring of woodsmoke aerosol concentrations continues to remain sparse. There is a paucity of field data on concentrations of combustion-generated ultrafine particles, which efficiently deposit in the human respiratory system, in such environments. Field measurements of ultrafine and fine woodsmoke aerosol (diameter range: 10-2500 nm) with field-portable diffusion chargers were conducted across nine wood-burning kitchens in Nandi County, Kenya. High time-resolution measurements (1Hz) revealed that indoor particle number (PN) and particle surface area (PSA) concentrations of ultrafine and fine woodsmoke aerosol are strongly temporally variant, reach exceedingly high levels (PN > 106 /cm3 ; PSA > 104 μm2 /cm3 ) that are seldom observed in non-biomass burning environments, are influenced by kitchen architectural features, and are moderately to poorly correlated with carbon monoxide concentrations. In five kitchens, PN concentrations remained above 105 /cm3 for more than half of the day due to frequent cooking episodes. Indoor/outdoor ratios of PN and PSA concentrations were greater than 10 in most kitchens and exceeded 100 in several kitchens. Notably, the use of metal chimneys significantly reduced indoor PN and PSA concentrations.

Characteristics of aerosol size distribution and liquid water content under ambient RH conditions in Beijing

The variation of ambient relative humidity (RH) affects the water uptake of aerosols in the atmosphere, thereby altering the aerosol size distribution and mass concentration. In this study, aerosol size distributions under both dry and ambient RH conditions are measured using an active RH-controlled dry-ambient aerosol size spectrometer (DAASS) at an urban site in Beijing during the springtime of 2021, and the aerosol liquid water content (ALWC) is derived accordingly. During the measurement period, a sharp increase of the ALWC was commonly observed when ambient RHs reached above 50%, demonstrating a potential phase change of the aerosol which further increases the rate of water uptake. Considerably high ALWC events were observed during the nighttime, with further elevated ambient RH above 60%. The liquid water accounts for up to 42.5% of the total aerosol volume, corresponding to a maximum ALWC of 8.79 μg m−3. The evolution of geometric mean diameter of accumulation mode particles agrees well with the enhancement of the ALWC (R2 of 0.73), revealing a significant growth of accumulation mode particles resulting from water uptake. Besides, by investigating the RH-dependent ambient aerosol surface area concentration, it is found that the aerosol surface area concentration can be underestimated by ∼20% under dry conditions when the ambient RH elevates to above 70%.

A bio-inspired, plant-derived admixture for metakaolin blended cement mortars

Partially replacing ordinary Portland cement (OPC) with metakaolin (MK) can refine the pore structure, improve mechanical properties, and enhance the durability of concretes. However, MK tends to agglomerate due to its high surface area and high concentration of hydroxyl groups. To overcome this problem, this study exploits a plant-derived polyphenol, tannic acid (TA), as an eco-friendly admixture to disperse MK. Due to its similar chemical functional groups as the adhesive protein in the mussel byssus, TA can adhere to various surfaces like the mussel’s adhesive protein. An experimental program was carried out to characterize the TA treated MK and investigate the effects of the proposed method on the properties of the cement paste and mortar. After mixing with the MK, TA can be adsorbed on the surface of MK particles, achieving deflocculation and dispersion of mineral grains by electrostatic repulsion forces and steric effect, significantly improving the workability of the mortar. Pore structure analysis suggests that TA dispersion densifies the hydration products, as revealed by the much-reduced gel and interhydrate pores. The nanoindentation results indicated that all low-density calcium hydrate silicate (CSH) was converted to high density by the TA dispersion, leading to a drastic improvement in the compressive strength of the produced mortars. As a result, the 28 days compressive strength of cement mortar prepared with TA dispersed MK was enhanced by up to 97 % compared with the one prepared without MK substitution, which exhibits great potential in reducing the carbon footprint of cement-based construction materials.

Particle surface area, ultrafine particle number concentration, and cardiovascular hospitalizations

Background and aim: While the human health impacts of larger particulate matter, such as PM10 and PM2.5, have been studied extensively, research regarding ultrafine particles (UFPs or PM0.1) and particle surface area is lacking. This case-crossover study assessed the associations between exposure to particle surface area concentration (PSC) and UFP particle number concentration (UFPnc) and hospital admissions for cardiovascular diseases (CVDs) in New York State (NYS), 2013-2018. Methods: We used a time-stratified case-crossover design to compare the PSC and UFPnc levels between hospitalization days and control days (similar days without admissions) for each CVD case. We utilized NYS hospital discharge data to identify all CVD cases who resided in NYS. We used UFP simulation data from GEOS-Chem, a state-of-the-art chemical transport model, to define PSC and UFPnc. Using a multi-pollutant model and conditional logistic regression, we assessed CVD risk per inter-quartile change of PSC and UFPnc after controlling for meteorological factors, co-pollutants, and time-varying variables. Results: Our results indicate an immediate and robust positive association between PSC and overall CVDs (lag0– lag0-1: 1.0%) and a delayed, lasting effect between UFPnc and CVDs (lag0-3–lag0-6: 0.4%). Exposure to larger PSC was associated with immediate increases in stroke, hypertension, and ischemic heart diseases (0.7%, 0.8%, 0.8%, respectively). The adverse effects of PSC on CVDs were highest among youngest children (0-4 years old), in fall and winter, and during cold temperature days (2.0%, 1.4%, 1.3%, 1.5%, respectively) compared to those on other days. Conclusion: We found an immediate, positive effect of PSC on overall CVDs and a delayed, lasting impact of UFPnc. PSC was a more sensitive indicator than UFPnc. The PSC-related effects were higher among certain CVD subtypes, in the youngest children, in certain seasons, and during cold days. Keywords: ultrafine particles, particle surface area, air pollutants, cardiovascular admission, vulnerability, seasonality

Ozone depletion in the Arctic and Antarctic stratosphere induced by wildfire smoke

Abstract. A record-breaking stratospheric ozone loss was observed over the Arctic and Antarctica in 2020. Strong ozone depletion occurred over Antarctica in 2021 as well. The ozone holes developed in smoke-polluted air. In this article, the impact of Siberian and Australian wildfire smoke (dominated by organic aerosol) on the extraordinarily strong ozone reduction is discussed. The study is based on aerosol lidar observations in the North Pole region (October 2019–May 2020) and over Punta Arenas in southern Chile at 53.2∘ S (January 2020–November 2021) as well as on respective NDACC (Network for the Detection of Atmospheric Composition Change) ozone profile observations in the Arctic (Ny-Ålesund) and Antarctica (Neumayer and South Pole stations) in 2020 and 2021. We present a conceptual approach on how the smoke may have influenced the formation of polar stratospheric clouds (PSCs), which are of key importance in the ozone-depleting processes. The main results are as follows: (a) the direct impact of wildfire smoke below the PSC height range (at 10–12 km) on ozone reduction seems to be similar to well-known volcanic sulfate aerosol effects. At heights of 10–12 km, smoke particle surface area (SA) concentrations of 5–7 µm2 cm−3 (Antarctica, spring 2021) and 6–10 µm2 cm−3 (Arctic, spring 2020) were correlated with an ozone reduction in terms of ozone partial pressure of 0.4–1.2 mPa (about 30 % further ozone reduction over Antarctica) and of 2–3.5 mPa (Arctic, 20 %–30 % reduction with respect to the long-term springtime mean). (b) Within the PSC height range, we found indications that smoke was able to slightly increase the PSC particle number and surface area concentration. In particular, a smoke-related additional ozone loss of 1–2 mPa (10 %–20 % contribution to the total ozone loss over Antarctica) was observed in the 14–23 km PSC height range in September–October 2020 and 2021. Smoke particle number concentrations ranged from 10 to 100 cm−3 and were about a factor of 10 (in 2020) and 5 (in 2021) above the stratospheric aerosol background level. Satellite observations indicated an additional mean column ozone loss (deviation from the long-term mean) of 26–30 Dobson units (9 %–10 %, September 2020, 2021) and 52–57 Dobson units (17 %–20 %, October 2020, 2021) in the smoke-polluted latitudinal Antarctic belt from 70–80∘ S.

Observation Analyses of Aerosol Size Distribution Properties from February to March, 2019 in Tianjin Urban Area

The aerosol size distribution is an important physical parameter reflecting the source, formation process, and pollution characteristics of aerosol particles. In order to study the properties of aerosol number concentration and size distributions in the Tianjin urban area,the aerosol number concentration and size distributions ranging from 10-600 nm were detected using a scanning mobility particle sizer (SMPS) during February and March, 2019. The results showed that in the Tianjin urban area, the aerosol number concentration,surface area concentration. and volume concentration in the size range of 10-600 nm were 22188.22 cm-3, 1581.08 μm2·cm-3, and 70.76 μm3·cm-3,respectively, in late winter and early spring. The aerosol number concentration,surface area concentration, and volume concentration spectrum were all unimodally distributed,and the peak value sizes were 109.40, 269.00, and 429.40 nm. The number concentrations of the nucleation mode (10-20 nm),Aitken mode (20-100 nm), and accumulation mode (100-600 nm) aerosols accounted for 1.40%, 52.44%, and 46.16% of the total number concentration. The diurnal variation in aerosol number concentration showed three peaks (06:00-08:00, 12:00-14:00, and 18:00-20:00) on work days and two peaks (07:00-08:00 and 19:00-21:00) on weekends. The peaks appeared 1-2 hours later on weekends,and the increment of aerosol number concentration was attributed to vehicle exhaust emissions. Meteorological factors had a significant influence on the aerosol size distribution in Tianjin; aerosol number concentration values were high in east and southwest wind. On non-precipitation days,the aerosol number size distribution moved to larger size ranges with the increment of relative humidity (RH); as the RH increased from <20% to 50%-60%,the size peak increased from 50 nm to 131 nm. The precipitation removed 100-200 nm aerosol particles discernibly,which resulted in the size peak decreasing to 98 nm.

Doped biochar from an invasive plant “Eichhornia crassipes” for the oxygen reduction reaction

N-doped carbon derived from Eichhornia crassipes biomass is appealing since it transforms a weed into a sustainable resource for Fuel Cell applications. Activated carbons were prepared using KOH at 700 °C with N2; before being doped with hydrazine. As a result of the activation process, the samples EC-SAP (not doped) and EC-SAPD got a surface area (SBET) of 1577 and 1222 m2 g−1, respectively. Besides, both samples showed the carbonaceous D and G bands indicative. The presence of carbon in EC-SAP and 3.56% of N in EC-SAPD was corroborated by elemental analysis CHNS. The testing system for the Oxygen Reduction Reaction activity consisted of a three-electrode cell with 0.5 M KOH. The EC-SAPD sample showed promising performance for ORR with a high cathodic reaction potential of 0.82 V and a transfer of 3.6 electrons. Its surface area and nitrogen concentration improve its performance compared to EC-SAP.

Particle surface area, ultrafine particle number concentration, and cardiovascular hospitalizations

While the health impacts of larger particulate matter, such as PM10 and PM2.5, have been studied extensively, research regarding ultrafine particles (UFPs or PM0.1) and particle surface area concentration (PSC) is lacking. This case-crossover study assessed the associations between exposure to PSC and UFP number concentration (UFPnc) and hospital admissions for cardiovascular diseases (CVDs) in New York State (NYS), 2013–2018. We used a time-stratified case-crossover design to compare the PSC and UFPnc levels between hospitalization days and control days (similar days without admissions) for each CVD case. We utilized NYS hospital discharge data to identify all CVD cases who resided in NYS. UFP simulation data from GEOS-Chem-APM, a state-of-the-art chemical transport model, was used to define PSC and UFPnc. Using a multi-pollutant model and conditional logistic regression, we assessed excess risk (ER)% per inter-quartile change of PSC and UFPnc after controlling for meteorological factors, co-pollutants, and time-varying variables. We found immediate and lasting associations between PSC and overall CVDs (lag0–lag0-6: ERs% (95% CI%) ranges: 0.4 (0.1,0.7) - 0.9 (0.7–1.2), and delayed and prolonged ERs%: 0.1–0.3 (95% CIs: 0.1–0.5) between UFPnc and CVDs (lag0-3–lag0-6). Exposure to larger PSC was associated with immediate ER increases in stroke, hypertension, and ischemic heart diseases (1.1%, 0.7%, 0.8%, respectively, all p < 0.05). The adverse effects of PSC on CVDs were highest among children (5–17 years old), in the fall and winter, and during cold temperatures. In conclusion, we found an immediate, lasting effects of PSC on overall CVDs and a delayed, prolonged impact of UFPnc. PSC was a more sensitive indicator than UFPnc. The PSC effects were higher among certain CVD subtypes, in children, in certain seasons, and during cold days. Further studies are needed to validate our findings and evaluate the long-term effects.

Fabrication and visible-light photocatalytic activity of Si-α-Fe2O3/In2S3 composites

The synthesis of visible-light-driven photocatalysts with a high activity using simple and efficient techniques remains an existing challenge. The highly active Si-α-Fe2O3 nanosheets were obtained by adding SiO32−. And the Si-α-Fe2O3/In2S3 composites were prepared by hydrothermal method and employed effectively as visible-light-driven photocatalysts for the 4-nitrophenol (4-NP) degradation. Compared with the single component, the Si-α-Fe2O3/In2S3 composites increased the specific surface area and OVs concentration and improved the photocatalytic degradation activity of 4-NP. The combination of OV defects, heterojunction, and photo-Fenton, promoted the separation of photocarriers and the production of oxygen species (•OH, •O2−and h+), which significantly improved the visible-light photocatalytic performance. This work provides a new idea to improve the degradation performance of organic pollutants under visible-light irradiation.

A predictive model to estimate fever after receipt of the second dose of Pfizer-BioNTech coronavirus disease 2019 vaccine: An observational cohort study.

Background and AimsFever after coronavirus disease 2019 (COVID‐19) vaccination is generally a mild and benign event, but can cause excessive anxiety in younger adults. This study aimed to find key factors that include allergic diseases or physique that determine fever after vaccination.MethodsWe conducted an observational cohort study in our hospital to assess post‐COVID‐19 vaccination fever from April to June 2021. A total of 153 medical personnel aged 22–86 years of age were involved in the study to receive two doses, intramuscularly 21 days apart, of the Pfizer‐BioNTech COVID‐19 vaccine (30 μg per dose). Vaccination records were taken more than 72 h after vaccination. Clinical and laboratory variables (age, sex, allergy history, weight, height, serum hemoglobin concentration, and these derivatives) were examined by multivariable logistic regression analysis using the peak axillary temperature in the 4‐day period after the second vaccination as a dependent variable.ResultsNo serious safety problems were detected. The incidence of a postsecond vaccination fever of 37.3°C or above was 29.4%. Logistic regression analysis found age, history of perennial allergic rhinitis, body surface area, body weight, percent overweight, and serum hemoglobin concentration as independent predictors of postvaccination fever. The characteristics of this individual were incorporated into the numerical model of human thermoregulation. The evaluation of this model had a sensitivity of 66.1% and a specificity of 90.7% in the detection of postvaccination fever. The multiple coefficient of determination (R 2) was 0.410.ConclusionThe COVID‐19 vaccine induced higher rates of fever during the 4‐day period after the second vaccination. Younger age, part of the allergy history, small and light body, and concentrated blood were associated with postvaccination fever.

Characterization of in-stack particulate emissions from residential wood hydronic heater appliances under different combustion conditions

ABSTRACT In the current work, we provide measurements of size-resolved particle number concentration (PNC), particle mass concentration (PMC), lung-deposited surface area (LDSA), and black carbon (BC) concentration for three biomass fired hydronic heaters during operation in four different combustion conditions. The appliances include one woodchip-fueled hydronic heater and two outdoor cordwood-fueled hydronic heaters. The operating conditions included startup, low output, high output, and burnout. Measurements were made using a custom dilution sampling system and a suite of commercially available, time-resolved, ambient aerosol measurement instrumentation. The PNC, as measured using an Dekati Electrical Low Pressure Impactor+ (ELPI), had operating condition mean values ranging between 4.1 and 52 million particles per cubic centimeter (#/cm3). The highest reported PNC occurred during the startup condition in all cases. Calculating the particle size distribution measured across each operating phase for the same instrument gave geometric mean diameters (dg ) in the range of 0.080–0.256 µm. The largest dg per appliance was nearly always attributable to the startup condition (for hydronic heater 1, startup dg ranked second). We did not observe the same trends when we transformed the ELPI PNC to PMC and particle surface area concentration estimates across operating conditions, suggesting PNC and dg are highly variable. Furthermore, simultaneous measurements of PNC, PMC, and PSAC using instrumentation with different working principles gave varying results, potentially suggesting that particles of different composition and morphology are produced under different combustion conditions.Implications: In this work we compare the results from testing of 3 biomass fired hydronic heaters including one chip-fired appliance and two cordwood-fired appliances. The emissions from these appliances were made across four operating conditions and using three different non-regulatory emissions metrics. This work: describes the difference between chip and cordwood fired units and the effect of operating condition on emissions across the three emissions metrics.

Australian wildfire smoke in the stratosphere: the decay phase in 2020/2021 and impact on ozone depletion

Abstract. Record-breaking wildfires raged in southeastern Australia in late December 2019 and early January 2020. Rather strong pyrocumulonimbus (pyroCb) convection developed over the fire areas and lofted enormous amounts of biomass burning smoke into the tropopause region and caused the strongest wildfire-related stratospheric aerosol perturbation ever observed around the globe. We discuss the geometrical, optical, and microphysical properties of the stratospheric smoke layers and the decay of this major stratospheric perturbation. A multiwavelength polarization Raman lidar at Punta Arenas (53.2∘ S, 70.9∘ W), southern Chile, and an elastic backscatter Raman lidar at Río Grande (53.8∘ S, 67.7∘ W) in southern Argentina, were operated to monitor the major record-breaking event until the end of 2021. These lidar measurements can be regarded as representative for mid to high latitudes in the Southern Hemisphere. A unique dynamical feature, an anticyclonic, smoke-filled vortex with 1000 km horizontal width and 5 km vertical extent, which ascended by about 500 m d−1, was observed over the full last week of January 2020. The key results of the long-term study are as follows. The smoke layers extended, on average, from 9 to 24 km in height. The smoke partly ascended to more than 30 km height as a result of self-lofting processes. Clear signs of a smoke impact on the record-breaking ozone hole over Antarctica in September–November 2020 were found. A slow decay of the stratospheric perturbation detected by means of the 532 nm aerosol optical thickness (AOT) yielded an e-folding decay time of 19–20 months. The maximum smoke AOT was around 1.0 over Punta Arenas in January 2020 and thus 2 to 3 orders of magnitude above the stratospheric aerosol background of 0.005. After 2 months with strongly varying smoke conditions, the 532 nm AOT decreased to 0.03-0.06 from March–December 2020 and to 0.015–0.03 throughout 2021. The particle extinction coefficients at 532 nm were in the range of 10–75 Mm−1 in January 2020 and, later on, mostly between 1 and 5 Mm−1. Combined lidar–photometer retrievals revealed typical smoke extinction-to-backscatter ratios of 69 ± 19 sr (at 355 nm), 91 ± 17 sr (at 532 nm), and 120 ± 22 sr (at 1064 nm). An ozone reduction of 20 %–25 % in the 15–22 km height range was observed over Antarctica and New Zealand ozonesonde stations in the smoke-polluted air, with particle surface area concentrations of 1–5 µm2 cm−3.

Anti-sulfur selective catalytic reduction of NOx on Sb-doped OMS-2

Sb doped cryptomelane-type manganese oxides (Sb-OMS-2) with Sb/Mn molar ratios of 0–0.4 were synthesized and investigated for low-temperature selective catalytic reduction of NO by CO (CO-SCR). The resulting catalyst was characterized by X-ray diffractometer (XRD), specific surface area analyzer (BET), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). As a result, the doping of Sb increased the specific surface area and oxygen vacancy concentration of the catalyst. At the same time, most Sb entered the lattice of MnO6 to form Sb–O bonds, and a small number of Sb ions replaced K+ in the tunnel. Sb and Mn synergistically catalyzed the reduction of NO. Compared with undoped OMS-2, the NO conversion rate of Sb0.2-OMS-2 increased from 60% at 150 ℃ to 83%, and from 80% at 300 ℃ to 95%. In the presence of SO2, the NO conversion rate of Sb0.2-OMS-2 at 300 ℃ was 88%, while that of OMS-2 was only 60%.

Fluorescence lidar observations of wildfire smoke inside cirrus: a contribution to smoke–cirrus interaction research

Abstract. A remote sensing method, based on fluorescence lidar measurements, that allows us to detect and to quantify the smoke content in the upper troposphere and lower stratosphere (UTLS) is presented. The unique point of this approach is that smoke and cirrus properties are observed in the same air volume simultaneously. In this article, we provide results of fluorescence and multiwavelength Mie–Raman lidar measurements performed at ATOLL (ATmospheric Observation at liLLe) observatory from Laboratoire d'Optique Atmosphérique, University of Lille, during strong smoke episodes in the summer and autumn seasons of 2020. The aerosol fluorescence was induced by 355 nm laser radiation, and the fluorescence backscattering was measured in a single spectral channel, centered at 466 nm and having 44 nm width. To estimate smoke particle properties, such as number, surface area and volume concentration, the conversion factors, which link the fluorescence backscattering and the smoke microphysical properties, are derived from the synergy of multiwavelength Mie–Raman and fluorescence lidar observations. Based on two case studies, we demonstrate that the fluorescence lidar technique provides the possibility to estimate the smoke surface area concentration within freshly formed cirrus layers. This value was used in the smoke ice nucleating particle (INP) parameterization scheme to predict ice crystal number concentrations in cirrus generation cells.

Changes of diesel particle diameter and surface area distributions by non-thermal plasma

A wide literature has demonstrated that internal combustion engines are the main responsible for the emission of fine particles in urban areas. Within this scope, ultrafine particles within diesel exhausted gas have been widely proven to exert a significantly harmful impact on human health and environment. This scenario has led the research community to turn the attention from particle mass to diameter and surface area. In this paper, non-thermal plasma (NTP) technology was applied to a heavy duty diesel engine. Chemical reactions of diesel particles in plasma zone were analyzed. Additionally, variation in diesel particles’ number and surface area distributions, engendered by above reactions, were thoroughly investigated. The results showed that diesel exhausted particles experienced oxidation, aggregation, and crush because of enhanced plasma transports and active species in plasma zone. NTP presents excellent reduction effectiveness of diesel particles covering different sizes. Being more than 50%, the most considerable surface area concentration drop was found in correspondence of 1800 RPM. Differently, the lowest drop of surface area concentration was seen at 1200 RPM. As a result of the NTP actions, surface area concentration distributions were almost the same for diameters being larger than 0.5 μm at different engine modes, except at 900 RPM. This research made a foundation of dropping particle emissions and evaluating the effectiveness of NTP dropping particle harms to human health.

Ultrasound-mediated synthesis of nanoporous fluorite-structured high-entropy oxides toward noble metal stabilization

SummaryHigh-entropy oxides (HEOs) are an emerging class of advanced ceramic materials capable of stabilizing ultrasmall nanoparticle catalysts. However, their fabrication still relies on high-temperature thermal treatment methodologies affording nonporous architectures. Herein, we report a facile synthesis of single-phase, fluorite-structured HEO nanocrystals via an ultrasound-mediated co-precipitation strategy under ambient conditions. Within 15 min of ultrasound exposure, high-quality fluorite-structured HEO (CeHfZrSnErOx) was generated as ultrasmall-sized particles with high surface area and high oxygen vacancy concentration. Taking advantage of these unique structural features, palladium was introduced and stabilized in the form of highly dispersed Pd nanoclusters within the CeHfZrSnErOx architecture. Neither phase segregation of the CeHfZrSnErOx support nor Pd sintering was observed under thermal treatment up to 900°C. The as-afforded Pd/CeHfZrSnErOx catalyst exhibits good catalytic performance toward CO oxidation, outperforming Pd/CeO2 of the same Pd loading, which highlights the inherent advantage of CeHfZrSnErOx as carrier support over traditional oxides.