Professor James Jay Schauer

Large amounts of the submicron carbon black are emitted in urban areas. Here, we developed a quantitative method using dual-wavelength ultraviolet–visible spectroscopy and Raman spectroscopy (respectively) for carbon black with amorphous structures and with ordering in a graphene sheet. Further, the dithiothreitol (DTT) assay and the ascorbic acid (AA) assay, were used to assess the oxidative potential (OP) of water extracts of leaf samples. Humic acids were adopted as a reference for the OP comparisons with carbon black in both assays. Using dual-wavelength ultraviolet–visible spectroscopy to determine carbon black with amorphous structures, our results achieved coefficients of determination greater than 0.99 in the linear range between 0.5 and 200 μg mL−1. Determination of carbon black with ordering in a graphene sheet using dual-wavelength Raman spectroscopy showed a linear in the range from …

Recently, biomass has been regarded as a promising option for solid energy in China, which is promoted in the residential sector and firing power plants. We collected 200 PM2.5 samples (particulate matter with a aerodynamic diameter smaller than 2.5 μm) at multi-sites across Beijing from three individual sampling cases from 2015 to 2017. The levels of OC, OC fractions, EC, EC fractions, as well as K+ were measured. Then, we adopted the Positive Matrix Factorization 5.0 to apportion the sources of carbonaceous aerosols. The source apportionment results were compared with the estimates of source contribution using the bottom-up technical method with the latest emission inventories after the Action Plan was put into effect in 2013. Our results demonstrate that high pollution of carbonaceous aerosols originated from wood smoking based on the receptor modeling and bottom-up technical method in Beijing from …

In the context of air quality research, the collection and analysis of fine particulate matter (PM2.5, with a diameter less than 2.5 μm) and volatile organic compound (VOCs) play a pivotal role in understanding and addressing environmental issues across the Korean Peninsula. PM2.5 and VOCs were collected over 4-hr intervals from October 17 to November 26, 2021 during the 2021 Satellite Integrated Joint Monitoring of Air Quality campaign at Olympic Park in the Republic of Korea to understand the factors controlling air quality over the Seoul Metropolitan Area. Source apportionment was performed using the positive matrix factorization (PMF) model incorporating PM2.5 and VOCs. The factor identified by chlorinated VOCs as a major component was presumed to be due to transboundary influx and was referred to as the long-range transport factor. The long-range transport factor of PM2.5 was composed of NO3 …

HighlightsLevels of total and extractable Pt in size-fractionated atmospheric aerosols from urban & rural regions of Europe determined.Order-of-magnitude differences in air concentrations of total Pt were observed between urban sites; from 2.4 to 45.6 pg/m 3.Consistent and low levels of total Pt were measured at rural background sites (0.9–4.9 pg/m 3, mean= 2.7 pg/m 3).For the TSP (sum of size-fractions), the extractable fraction of Pt ranged from 6.1 to 21.1%, trending with the solvent pH.

Even though methane concentrations have contributed an estimated 23% of climate forcing, part of the recent increases in the global methane background concentrations remain unexplained. Satellite remote sensing has been used extensively to constrain emission inventories, for example with the TROPOspheric Monitoring Instrument which has been measuring methane since November 2017. We have identified enhancements of methane over 61 urban areas around the world and estimate their emissions using a two-dimensional Gaussian model. We show that methane emissions from urban areas may be underestimated by a factor of 3–4 in the Emissions Database for Global Atmospheric Research (EDGAR) greenhouse gas emission inventory. Scaling our results to the 385 urban areas with more than 2 million inhabitants suggests that they could account for up to 22% of global methane emissions. The …

Regional air pollution is rising in Northeast Asia due to increasing energy consumption resulting from a growing population and intensifying industrialization. This study analyzes the sources of air pollution using fine particulate matter (PM2.5) sampling from the atmosphere over Korea and China. We then use this analysis to further investigate the relationship between organic compounds (source tracers) and the oxidative potential of PM2.5. The PM2.5 concentration during winter measured at a measurement stations in Korea showed no significant variation year-to-year. The PM2.5 concentrations measured during winter at a site near Beijing, China were 62.45 μg/m3 in 2018 and 33.07 μg/m3 in 2020. The sources, as determined from PMF, were analyzed at a site in Korea, the sources as secondary nitrate (34.10 %), secondary sulfate (20.20 %), coal combustion (4.01 %), vehicle emission (8.55 %), cooking and …

Computational chemistry calculations are broadly useful for guiding the atom-scale design of hard–soft material interfaces including how molecular interactions of single-component liquid crystals (LCs) at inorganic surfaces lead to preferred orientations of the LC far from the surface. The majority of LCs, however, are not single-component phases but comprise of mixtures, such as a mixture of mesogens, added to provide additional functions such as responsiveness to the presence of targeted organic compounds (for chemical sensing). In such LC mixtures, little is understood about the near-surface composition and organization of molecules and how that organization propagates into the far-field LC orientation. Here, we address this broad question by using a multiscale computational approach that combines density functional theory (DFT)-based calculations and classical molecular dynamics (MD) simulations to …

The Beijing “Coal to Electricity” program provides a unique opportunity to explore air quality impacts by replacing residential coal burning with electrical appliances. In this study, the atmospheric ROS (Gas-phase ROS and Particle-phase ROS, abbreviated to G-ROS and P-ROS) were measured by an online instrument in parallel with concurrent PM2.5 sample collections analyzed for chemical composition and cellular ROS in a baseline year (Coal Use Year-CUY) and the first year following implementation of the “Coal to Electricity” program (Coal Ban Year-CBY). The results showed PM2.5 concentrations had no significant difference between the two sampling periods, but the activities of G-ROS, P-ROS, and cellular ROS in CBY were 8.72 nmol H2O2/m3, 9.82 nmol H2O2/m3, and 2045.75 µg UD /mg PM higher than in CUY.Six sources were identified by factor-analysis from the chemical components of PM2.5 …