Regional classification of high PM10 concentrations in the Seoul metropolitan and Chungcheongnam-do areas, Republic of Korea.

Since the Seoul metropolitan area is a highly developed megacity, many people are often exposed to high concentrations of particulate matter (PM), with mean aerodynamic diameters equal to or less than 10 µm (PM10), in cold seasons. PM10 concentrations can be influenced by a combination of various factors, including meteorological conditions, anthropogenic emissions, atmospheric chemical reactions, transboundary transport, and geographic characteristics. However, the establishment of an efficient air quality management plan remains challenging due to the limited understanding of the regional PM concentration characteristics. Here, the Seoul metropolitan (Seoul, Gyeonggi-do, and Incheon) and Chungcheongnam-do (Chungcheongnam-do, Daejeon, and Sejong) areas were regionally classified to identify the spatiotemporal air quality in areas where megacities and emission sources are mixed. The four representative regions were determined using the K-means clustering method based on the temporal variations in the observed PM10 concentrations. The first cluster consisted of small cities in the southern and eastern parts of Gyeonggi-do and Chungcheongnam-do, respectively, while the second cluster consisted of Incheon, West Gyeonggi-do, and Seoul. In addition, the third and fourth clusters included West Chungcheongnam-do and East Gyeonggi-do, which are adjacent to the Yellow Sea and downstream area of the westerly wind, respectively. The characteristics of each cluster during the high PM10 concentration events are explainable by wind patterns and the local air pollutant emissions, including nitrogen oxides and sulfur oxides. The obtained regional classification was different from the provincial-level administrative division of South Korea. Therefore, the present study is expected to be a scientific basis for overcoming the limitations of air quality management in administrative districts.

Significant light absorption of brown carbon during the 2020 California wildfires.

In this study, the contribution of brown carbon (BrC) to the absorption aerosol optical depth (AAOD) during the August to October 2020 California wildfires in Fresno, Monterey, and the University of California Santa Barbara (UCSB) was investigated using Aerosol Robotic Network (AERONET) column measurements with Moderate Resolution Imaging Spectroradiometer (MODIS) fire pixel counts. There was an approximate three to five times increase in AAOD and fine-mode aerosols during intensive wildfires in August-October 2020 compared to the wildfires in the previous 18 years (2002-2019). Substantial daily variation in the contribution of BrC to AAOD was correlated with the fire pixel counts (correlation coefficients of 0.63, 0.40, and 0.57 at Fresno, Monterey, and UCSB, respectively). This variation was influenced by regional topography, atmospheric conditions, and distance from the fire. Between August and October 2020, the average contribution of BrC to AAOD at 440 nm due to wildfires was 35.3 ± 5.6, 35.1 ± 6.8, and 40.6 ± 9.5% at Fresno, Monterey, and UCSB, respectively. This was approximately twice as high as for those sites without a direct wildfire influence. The BrC contribution with direct wildfire influence over the period of January-December 2020 at Fresno, Monterey, and UCSB (32.8 ± 7.5, 31.6 ± 7.9, and 40.0 ± 3.5%, respectively) and from 2002 to 2019 (30.7 ± 8.3, 28.5 ± 4.8, and 35.7 ± 14.6%, respectively) was approximately 20% greater than other BrC sources including vehicles, fossil fuel combustion, and residential heating.

Light-absorption enhancement of black carbon in the Asian outflow inferred from airborne SP2 and in-situ measurements during KORUS-AQ.

We investigated the changes in the size distribution, coating thickness, and mass absorption cross-section (MAC) of black carbon (BC) with aging and estimated the light absorption enhancement (Eabs) in the Asian outflow from airborne in-situ measurements during 2016 KORUS-AQ campaign. The BC number concentration decreased, but mass mean diameter increased with increasing altitude in the West Coast (WC) and Seoul Metropolitan Area (SMA), reflecting the contrast between freshly emitted BC-containing particles at the surface and more aged aerosol associated with aggregation during vertical mixing and transport. Contradistinctively, BC number and mass size distributions were relatively invariant with altitude over the Yellow Sea (YS) because sufficiently aged BC from eastern China were horizontally transported to all altitudes over the YS, and there are no significant sources at the surface. The averaged inferred MAC of refractory BC in three regions reflecting differences in their size distributions increased to 9.8 ± 1.0 m2 g-1 (YS), 9.3 ± 0.9 m2 g-1 (WC), and 8.2 ± 0.9 m2 g-1 (SMA) as BC coating thickness increased from 20 nm to 120 nm. The absorption coefficient of BC calculated from the coating thickness and MAC were highly correlated with the filter-based absorption measurements with the slope of 1.16 and R2 of 0.96 at 550 nm, revealing that the thickly coated BC had a large MAC and absorption coefficient. The Eabs due to the inferred coatings was estimated as 1.0-1.6, which was about 30% lower than those from climate models and laboratory experiments, suggesting that the increase in the BC absorption by the coatings in the Asian outflow is not as large as calculated in the previous studies. Organics contributed to the largest Eabs accounting for 69% (YS), 61% (WC), and 64% (SMA). This implies that organics are largely responsible for the lensing effect of BC rather than sulfates in the Asian outflow.

Boundary layer versus free tropospheric submicron particle formation: A case study from NASA DC-8 observations in the Asian continental outflow during the KORUS-AQ campaign.

In this study, we contrasted major secondary inorganic species and processes responsible for submicron particle formation (SPF) events in the boundary layer (BL) and free troposphere (FT) over the Korean Peninsula during Korea-United States Air Quality (KORUS-AQ) campaign (May-June, 2016) using aircraft observations. The number concentration of ultrafine particles with diameters between 3 nm and 10 nm (NCN3-10) during the entire KORUS-AQ period reached a peak (7,606 ± 12,003 cm -3) at below 1 km altitude, implying that the particle formation around the Korean Peninsula primarily occurred in the daytime BL. During the BL SPF case (7 May, 2016), the SPF over Seoul metropolitan area was more attributable to oxidation of NO2 rather than SO2-to-sulfate conversion. From the analysis of the relationship between nitrogen oxidation ratio (NOR) and temperature or relative humidity (RH), NOR showed a positive correlation only with temperature. This suggests that homogeneous gas-phase reactions of NO2 with OH or O3 contributed to nitrate formation. From the relationship between NCN3-10 (> 10,000 cm-3) and the NOR (or sulfur oxidation ratio) at Olympic Park in Seoul during the entire KORUS-AQ period, it was regarded that the relative importance of nitrogen oxidation was grown as the NCN3-10 increased. During the FT SPF case (31 May, 2016) over the yellow sea, the SO2-to-sulfate conversion seemed to influence SPF highly. The sulfate/CO ratio had a positive correlation with both the temperature and RH, suggesting that aqueous-phase pathways as well as gas-phase reactions might be attributable to sulfate formation in the FT. In particular, FT SPF event on 31 May was possibly caused by the direct transport of SO2 precursors from the continent above the shallow marine boundary layer under favorable conditions for FT SPF events, such as decreased aerosol surface area and increased solar radiation.

Six-Month Lower Limb Aerobic Exercise Improves Physical Function in Young-Old, Old-Old, and Oldest-Old Adults.

The effect of aerobic exercise on physical function and mental health in various adult age groups (young-old, 65-74; old-old, 75-84; oldest-old, ≥ 85 years) is unclear. The aim of this study was to investigate the effects of the Kohzuki Exercise Program (KEP) on physical function and mental health in these age groups. The KEP consisted of 40-min supervised sessions 3 times per week for 6 months as follows: 5 min of warm-up, 30 min of lower limb aerobic exercise, and 5 min of cool-down. A total of 50 participants (22 young-old, 20 old-old, and 8 oldest-old) who participated in the KEP completed at least 88% of the sessions. In statistical analysis, 3 (group: oldest-old, old-old, young-old) × 2 (time: baseline and after 6 months) analyses of variance were used to determine if there were significant main and interaction effects. Significant interactions were probed using the post-hoc paired t test. The Short Physical Performance Battery (SPPB) score showed significant group × time interactions after 6 months (p = 0.031). In the post-hoc test, oldest-old (p < 0.001), old-old (p < 0.001), and young-old (p < 0.01) groups had significantly better physical function after 6 months. However, none of the mental health measures showed group × time interactions at 6-month. Our results suggest that a 6-month KEP led to improved physical function in oldest-old, old-old, and young-old adults. The KEP was effective for oldest-old adults in particular. The KEP exhibits good adherence, making it suitable for a wide age range in society.

Physical Exercise with Multicomponent Cognitive Intervention for Older Adults with Alzheimer's Disease: A 6-Month Randomized Controlled Trial.

AIMS: This study aimed to investigate the effect of 6-month physical exercise with a multicomponent cognitive program (MCP) on the cognitive function of older adults with moderate to severe Alzheimer's disease (AD). METHODS: We included 33 participants with AD in a 6-month randomized controlled trial. The intervention group participated in physical exercise and received a MCP. The control group received only the MCP. Before and after the intervention, cognitive outcomes were assessed using the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-cog), Mini-Mental State Examination, and the Clock Drawing Test. Physical performance was evaluated by exercise time, the number of pedal rotation, total load, grip strength, and the Berg Balance Scale (BBS). RESULTS: In all cognitive measures, there were no significant improvements between the two groups after 6 months in the baseline value-adjusted primary analysis. However, the ADAS-cog score was significantly lower between the two groups in secondary analysis adjusted for baseline value, age, sex, and education years. All physical outcomes were significantly higher in the intervention group except for total load compared with baseline measurements. CONCLUSION: This study indicates that it is possible to improve cognitive function in older adults with moderate to severe AD through 6-month physical exercise with a multicomponent cognitive intervention.