New health index derived from oxidative potential and cell toxicity of fine particulate matter to assess its potential health effect.

Toxicological data and exposure levels of fine particulate matters (PM2.5) are necessary to better understand their health effects. Simultaneous measurements of PM2.5 oxidative potential (OP) and cell toxicity in urban areas (Beijing, China and Gwangju, Korea) reveal their dependence on chemical composition. Notably, acids (Polar), benzocarboxylic acids, and Pb were the chemical components that affected both OP and cell toxicity. OP varied more significantly among different locations and seasons (winter and summer) than cell toxicity. Using the measured OP, cell toxicity, and PM2.5 concentration, a health index was developed to better assess the potential health effects of PM2.5. The health index was related to the sources of PM2.5 derived from the measured chemical components. The contributions of secondary organic aerosols and dust to the proposed health index were more significant than their contributions to PM2.5 mass. The developed regression equation was used to predict the health effect of PM2.5 without further toxicity measurements. This new index could be a valuable health metric that provides information beyond just the PM2.5 concentration level.

Key results from the salt lake regional smoke, ozone, and aerosol study (SAMOZA).

The Northern Wasatch Front area is one of ~ 50 metropolitan regions in the U.S. that do not meet the 2015 O3 standard. To better understand the causes of high O3 days in this region we conducted the Salt Lake regional Smoke, Ozone and Aerosol Study (SAMOZA) in the summer of 2022. The primary goals of SAMOZA were: Measure a suite of VOCs, by Proton Transfer Reaction Mass Spectrometry (PTR-MS) and the 2,4-dinitrophenylhydrazine (DNPH) cartridge method.Evaluate whether the standard UV O3 measurements made in SLC show a positive bias during smoke events, as has been suggested in some recent studies.Use the observations to conduct photochemical modeling and statistical/machine learning analyses to understand photochemistry on both smoke-influenced and non-smoke days.Implications: The Northern Wasatch Front area is one of ~50 metropolitan regions in the U.S. that do not meet the 2015 O3 standard. To better understand the causes of high O3 days in this region we conducted the Salt Lake regional Smoke, Ozone and Aerosol Study (SAMOZA) in the summer of 2022. A number of policy relevant findings are identified in the manuscript including role of smoke and NOx vs VOC sensitivity.

We found no significant difference in the O₃ measurements using a "scrubber-less" UV instrument compared to the standard O₃ measurements at PM_2.5 concentrations up to 60 µg m⁻³.On days with smoke, we found that PM_2.5, CO, O₃ and nearly all VOCs were significantly enhanced. On average, NO_x was also enhanced on days with smoke, but this was complicated by day of week effects.Photochemical modeling of O₃ production rates at the Utah Tech Center demonstrates a strong sensitivity to VOC concentrations and less sensitivity to NOx. For non-smoke days, achieving the current O₃ standard would require regional reductions in VOCs of ~40% or reductions in NO_x ~ 60%.The photochemical modeling shows that formaldehyde and other OVOCs, along with alkenes, were the most important O₃ precursors.Generalized Additive Modeling (GAM) gave similar MDA8 O₃ enhancements on smoky days as the photochemical modeling. Analysis of the GAM results show that 23% of the smoke days have GAM residuals that exceed the U.S. EPA's criteria for inclusion as exceptional event documentation.

Impact of wildfire smoke on ozone concentrations using a Generalized Additive model in Salt Lake City, Utah, USA, 2006-2022.

We investigated the impact of wildfires on maximum daily 8-hr average ozone concentrations (MDA8 O3) at four sites in Salt Lake City (SLC), Utah for May to September for 2006-2022. Smoke days, which were identified by a combination of overhead satellite smoke detection and surface PM2.5 data and accounted for approximately 9% of the total number of days, exhibited O3 levels 6.8 to 8.9 ppb higher than no-smoke days and were predominantly characterized by high daily maximum temperatures and low relative humidity. A Generalized Additive Model (GAM) was developed to quantify the impact of wildfire contributions to O3. The GAM, which provides smooth functions that make the interpretation of relationships more intuitive, employed 17 predictors and demonstrated reliable performance in various evaluation metrics. The mean of the residuals for all sites was approximately zero for the training and cross-validation data and 5.1 ppb for smoke days. We developed three approaches to estimate the contribution of smoke to O3 from the model residuals. These generate a minimum and maximum contribution for each smoke day. The average of the minimum and maximum wildfire contributions to O3 for the SLC sites was 5.1 and 8.5 ppb, respectively. Between 2006 and 2022, an increasing trend in the wildfire contributions to O3 was observed in SLC. Moreover, trends of the fourth-highest MDA8 O3 before and after removing the wildfire contributions to O3 at the SLC Hawthorne site in 2006-2022 were quite different. Whereas the unadjusted data do not meet the current O3 standard, after removing the contributions from wildfires the SLC region is close to achieving levels that are consistent with meeting the O3 standard. We also found that the wildfire contribution during smoke days was particularly high under conditions of high temperature, high PM2.5 concentration, and low cloud fraction.Implications: In this study, we quantified the impact of wildfires on maximum daily 8-hr average ozone concentrations (MDA8 O3) in Salt Lake City, Utah, using a Generalized Additive Model (GAM). The GAM results demonstrate the importance of wildfires as contributors to O3 air pollution. Our results suggest that states could use the GAM approach to assist in quantifying the wildfire contribution to MDA8 O3 under the U.S. EPA exceptional events rule. These findings also highlight the need for strategies to manage wildfires and their subsequent impacts on air quality in an era of climate warming.

Morphological and chemical classification of fine particles over the Yellow Sea during spring, 2015-2018.

Airborne fine particles can affect climate change and human health; moreover, they can be transported over significant distances. However, studies on characteristics of individual particles and their morphology, elemental composition, aging processes, and spatial distribution after long-range transport over the Yellow Sea are limited. Therefore, in this study, we conducted shipborne measurements of fine particulate matter of less than 2.5 µm in diameter (PM2.5) over the Yellow Sea and classified the individual particles into seven types based on their morphology and composition. Overall, the percentage of organic-rich particles was the highest, followed by that of sea spray, sulfur-rich, dust, metals, fly ash, soot, and other particles. Near Shandong, China, the percentage of fly ash and sulfur-rich particles increased, while an increased percentage of only sulfur-rich particles was observed near the Korean Peninsula. In the open sea, the PM2.5 concentrations were the lowest, and sea spray particles predominated. During the cruises, three types (Types 1, 2, and 3) of events with substantially increased PM2.5 concentrations occurred, each with different dominant particles. Type 1 events frequently featured air masses from northern China and Mongolia with high wind speeds and increased dust particles. Type 2 events involved air masses from China with high wind speeds; fly ash, soot, organic-rich particles, and the sulfate percentage in PM2.5 increased. Type 3 events displayed stagnant conditions and local transport (from Korea); soot, dust particles, and the secondary sulfate and nitrate percentages in PM2.5 increased. Thus, different types of transport affected concentrations and dominant types of fine particles over the Yellow Sea during spring.

Potential sources, scavenging processes, and source regions of mercury in the wet deposition of South Korea.

In this study, the potential sources, scavenging processes, and emission regions for Hg in wet deposition were investigated in rural (Jeju), suburban (Gwangju), and urban sites (Incheon and Seoul) of South Korea. The annual volume-weighted mean concentrations of Hg in wet deposition were four to five times higher in Incheon (16.6 ng L-1) and Seoul (22.5 ng L-1) than in Jeju (4.0 ng L-1) and Gwangju (4.1 ng L-1). The variations in the Hg concentrations in wet deposition of Jeju and Gwangju were related to Cl-, Na+, Mg2+, and K+ originating from marine and crustal sources, and those in Incheon and Seoul were related to SO42-, NO3-, and NH4+ emitted from anthropogenic sources. The below-cloud scavenging was considered a major inclusion process of Hg in Jeju and Gwangju, while the within-cloud scavenging was suggested in Incheon and Seoul, based on the results of correlation analysis with Hg and major ions in wet deposition, and meteorological data. The cluster analysis of backward trajectories demonstrated that the Hg concentration in wet deposition was highest in the cluster transported from Hebei and Shandong of China in Gwangju, but in Seoul, the Hg concentrations of each cluster were comparable. This suggests that regional transport is the major source of Hg in the wet deposition of Gwangju while local transport provides substantial amount of Hg in the wet deposition of Seoul. This was further supported by the results of concentration-weighted trajectories: the most probable source region was east China for Gwangju, and the mid-west of South Korea and east China for Seoul. It is noted that the peak methylmercury concentrations were found every spring with simultaneous increases in atmospheric Al, Ca, Mg, and Fe concentrations, indicating a concurrence with Asian dust. The formation process of methylmercury in Asian dust should be confirmed in future studies.

Application of laser-induced breakdown spectroscopy for detection of elements in flowback water samples from shale gas wells.

Laser-induced breakdown spectroscopy (LIBS) was applied to rapidly detect elements in flowback water samples from shale gas wells in Oklahoma. Two types of LIBS systems (aerosolization and collection on a substrate) were used. The LIBS with an aerosolization system provided rapid determination of elements in flowback water, but moisture present in the chamber and variation in the water droplet size could make quantification difficult. In the substrate collection system, a comparison among substrate types showed that a hydrophilic cellulose filter gave the most homogeneous sample distribution after drying and provided the best performance. The elements in flowback water samples were also determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES). ICP-OES data showed spatial variations for the elements among the different wells. Among the elements, K showed the highest variation (relative standard ${\rm deviation} = {62.8}\% $deviation=62.8%) and Mg the lowest (relative standard ${\rm deviation} = {39.1}\% $deviation=39.1%). Good correlations (${ r} = {0.98 - 0.99}$r=0.98-0.99) were observed between Ca, K, Mg, and Na LIBS peak areas determined using the cellulose filter and their mass concentrations (ppm) measured by ICP-OES for aqueous solutions. The limits of detection for Ca, K, Mg, and Na by LIBS were 122 ppm, 68 ppm, 36 ppm, and 142 ppm, respectively. Both the LIBS and ICP-OES data showed that element concentrations in the flowback water samples were in the order of Na, Ca, Mg, and K from highest to lowest. Our data suggest that the LIBS technique could rapidly detect elements in flowback water samples on site. However, accurate quantification of elements present in low concentrations in water samples is limited.

Application of laser-induced breakdown spectroscopy for real-time detection of contamination particles during the manufacturing process.

A stand-off laser-induced breakdown spectroscopy (LIBS) system was developed to determine the elemental composition of contamination particles during semiconductor manufacturing. It successfully detected laboratory-generated monodisperse (size=200 nm and 300 nm) CaCl2 particles and internally mixed particles of CaCl2, MgCl2, NaCl, and KCl. Temperature and pressure effects on the LIBS emission signals were investigated. The peak area and signal-to-noise ratio of the emission lines increased with the temperature (25°C-250°C). Stronger emission lines were observed at higher pressure. Although temperature and pressure affect the LIBS signals, the developed stand-off LIBS could be employed for real-time detection of the elemental composition of contamination particles.

3D strain measurement in electronic devices using through-focal annular dark-field imaging.

Spherical aberration correction in high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) allows us to form an electron probe with reduced depth of field. Using through-focal HAADF imaging, we experimentally demonstrated 3D strain measurement in a strained-channel transistor. The strain field distribution in the channel region was obtained by scanning an electron beam over a plan-view specimen. Furthermore, the decrease in the strain fields toward the silicon substrate was revealed at different focal planes with a 5-nm focal step. These results demonstrate that it is possible to reconstruct the 3D strain field in electronic devices.

A study on the characteristics of excellent lecturers in medical school.

PURPOSE: This study analyzed the characteristics of excellent lecturers, as perceived by medical students, and identified the teaching competency that lecturers should possess to enhance the quality of medical education in medical school. METHODS: To examine the characteristics of excellent lecturers and teaching competency, we administered open-ended questionnaires to a sample of 128 Year 2 medical students in May 2011. RESULTS: The students placed high value on the ability to organize and summarize the lecture as the most significant competence of lecturers, due to the massive amounts of information that is disseminated in medical college. Further, they chose lecturers who communicated to students actively and used real clinical cases properly with regard to how medical knowledge applied. They also considered generating an interest in learning by linking knowledge and its application as an important priority of excellent lecturers. CONCLUSION: We conclude that there are differences in the characteristics and competencies of excellent lecturers, as perceived by medical students and others. To increase the quality of teaching, it might be necessary to offer the opportunity to observe excellent lecturers, develop faculty development programs, and create educational culture.