Seoyeong Choe

The identification and characterization of air pollutants in metropolitan environments are of paramount global concern due to their significant implications for air quality and public health. This study investigates the chemical composition of fine particulate matter (PM_2.5) at two strategically selected urban sites in Seoul, South Korea, during 2020: Gwanghwamun Plaza, representing a high-density central location, and Bokjeong Station, situated in the metropolitan periphery. A key aspect of this research is the detection of terephthalic acid (TPA)—a distinct marker of polyethylene terephthalate (PET) combustion—using high-resolution liquid chromatography–time-of-flight tandem mass spectrometry (LC-ToF-MS/MS). Results from the simultaneous measurement campaign demonstrate that nighttime conditions strongly influence PM_2.5 at both sites, with increases observed not only in absolute concentrations (levoglucosan, TPA, As, CO, and NH₃) but also in OC-normalized ratios (levoglucosan/OC and TPA/OC). The consistent nighttime enhancement of these ratios suggests that the observed increases cannot be explained solely by reduced planetary boundary layer height but instead indicate relatively stronger emission contributions. These increases are likely influenced by waste incineration activities, wherein PET-based plastics and wood materials are combusted. Furthermore, assessment of the dithiothreitol assay-derived oxidative potential (DTT-OP) underscores the heightened oxidative stress associated with these emissions, posing substantial health risks.

This study explores the efficiency and applicability of a HONO collection system that incorporates an ultrasonic nozzle and spray chamber for the measurement of ambient air. The system demonstrates (1) a remarkable efficiency of 97.7% across two serial stages, (2) lower detection limits of 0.15 ppbv for HONO, and (3) an absence of interference from NO₂ or OH radicals. Practical ambient monitoring with the HONO collection system revealed typical diurnal variations in HONO, O₃, and HNO₃ concentrations, aligning with photolysis dynamics. Notably, HONO concentrations peaked at 0.37 ppb during nighttime and decreased to 0.27 ppb by midday. O₃ demonstrated an inverse relationship with HONO, especially during ozone depletion phases, with r² values of 0.94, 0.81, and 0.52 across various intervals. The HONO/NO_x ratio during periods of enhanced HONO suggested the presence of additional formation mechanisms beyond heterogeneous NO_x reactions. Moreover, ozone levels often fell below 20 ppb, indicating a consistent inverse correlation with HONO, thereby reaffirming further mechanisms of HONO formation beyond heterogeneous NO_x reactions. The real-time atmospheric chemical reactions involving HONO, monitored concurrently with O₃ and NO_x, were effectively validated by the HONO collection system employed in this investigation.

This study explores the efficiency and applicability of a HONO collection system that incorporates an ultrasonic nozzle and spray chamber for the measurement of ambient air. The system demonstrates (1) a remarkable efficiency of 97.7% across two serial stages, (2) lower detection limits of 0.1 ppbv for HONO, and (3) absence of interference from NO2 or OH radicals. Practical ambient monitoring with the HONO collection system revealed typical diurnal variations in HONO, O3, and HNO3 concentrations, aligning with photolysis dynamics. Notably, HONO concentrations peaked at 0.37 ppb during nighttime and decreased to 0.27 ppb by midday. O3 demonstrated an inverse relationship with HONO, especially during ozone depletion phases, with r2 values of 0.94, 0.81, and 0.52 across various intervals. The HONO/NOx ratio during periods of enhanced HONO suggested the presence of additional formation mechanisms beyond heterogeneous NOx reactions. Moreover, ozone levels often fell below 20 ppb, indicating a consistent inverse correlation with HONO, thereby confirming periods and highlighting further mechanisms of HONO formation beyond heterogeneous NOx reactions. The real-time atmospheric chemical reactions involving HONO, monitored concurrently with O3 and NOx, were effectively validated by the HONO collection system employed in this investigation.

This study investigated the aerosol particle properties and light absorption properties of brown carbon (BrC) by utilizing a seven-wavelength aethalometer, and analyzed NH₄⁺, NO₃⁻, SO₄²⁻, K⁺, K, organic carbon, elemental carbon, levoglucosan, and mannosan in PM_2.5. The research was conducted in a rural area of Jeonnam, South Korea, during the winter season. In addition, the dithiothreitol assay-oxidative potential normalized to 9,10-phenanthrenequinone (QDTT-OP) was investigated throughout the study period. The absorption coefficient was found to be 2.6 to 5.6 times higher at 370 nm compared to 880 nm, suggesting the presence of light-absorbing substances in addition to black carbon (BC) particles. The estimated absorption coefficient of BrC₃₇₀ was 29.9% of the total light absorption coefficient at 370 nm. Furthermore, BrC₃₇₀ exhibited a strong affinity with levoglucosan while showing a weak correlation with K⁺, confirming the suitability of levoglucosan as a tracer for biomass burning. The QDTT-OP was 5.3 nM m⁻³, and highly correlated with the carbonaceous components levoglucosan and mannosan, suggesting a relatively high contribution of biomass combustion emissions to oxidative potential. Further research should be conducted to assess the health risks associated with future PM_2.5 exposure related to biomass burning in the atmosphere.

This study aimed to identify the characteristics of atmospheric pollutants emitted by agricultural activities and to evaluate factors that may cause harm to human health. For the research, atmospheric pollutants were measured over the course of a year in representative rice farming and field crop farming areas in South Korea. The results confirmed that the characteristics of atmospheric pollutants in agricultural areas are influenced by the nature of agricultural activities. Specifically, when comparing rice paddies and field crop areas, during summer, the correlation between oxidative potential and levoglucosan—a marker for biomass burning—weakens due to less burning activity in the rice-growing season, leading to lower oxidative potential despite different PM_2.5 across areas. The study also finds that methyl sulfonic acid, indicating marine influence, plays a big role in keeping oxidative potential low in summer. This suggests that the main causes of PM_2.5-related health risks in the area are from biomass burning and external sources, with burning being a significant factor in increasing oxidative potential. Based on these results, it is hoped that measures can be taken in the future to reduce atmospheric pollutants in agricultural areas.

In this study, the impact of long-range transport, one of the factors contributing to the presence of PM_2.5, was examined, and an analysis of marker compounds associated with its long-range transport was conducted. Aerosol optical depth, wind field, CO/CO₂ back-trajectory analysis, and satellite observation results were performed to determine PM_2.5, volatile organic compound (VOC), CO, CO₂, SO₂, O₃, NO, NO₂, and NH₃ levels at an orchard located in Jeollabuk-do, Republic of Korea. The characteristic of long-range transport at the observation area was evaluated during the research period. The concentrations for long-range transport based on concentration changes in gaseous materials and composition changes in PM_2.5 were analyzed. A back-trajectory analysis for the ratio of CO to CO₂ with satellite observation results was used to identify long-range transport. Furthermore, the proportionality between the ratio of 1,2-dichloroethane to naphthalene in VOCs and the quantity of precursor compounds linked to long-range transport were observed.