Impact of terephthalic acid emissions from intensive nocturnal biomass incineration on oxidative potential in Seoul, South Korea.

This study investigated the impact of large-scale incineration facilities on PM2.5 levels in Seoul during winter. Due to the challenge of obtaining accurate combustion data from external sources, heat supply records were used as a proxy for combustion activity. To assess health risks, dithiothreitol-oxidative potential (DTT-OP) was analyzed to identify potential hazards to human health. By comparing DTT-OP with PM2.5 sources related to combustion, the study aimed to understand the impact of local pollution sources on human health in Seoul. The diurnal analysis showed that oxidative potential (0.19 µM/m3) and the biomass burning factor (5.53 µg/m3) peaked between 4:00 and 8:00 AM, with lower levels observed from 12:00 to 20:00. A significant correlation was found between combustion sources and oxidative potential, with a high correlation coefficient (r2 = 0.92). The presence of terephthalic acid (TPA) in the Cellulose combustion source profile, which is produced by the pyrolysis of plastics like polyester fiber and polyethylene terephthalate (PET), further supported the link to emissions from incineration facilities. These findings suggest that the biomass burning source is strongly correlated with DTT-OP, indicating a significant association with health risks among various local sources of PM2.5 in Seoul.

Effects of long-range transport on carboxylic acids, chlorinated VOCs, and oxidative potential in air pollution events.

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-, SO42-, NH4+, and di-carboxylic acids. Back trajectory analysis showed that the airflows originated from China and passed through the west coast of Korea to the Korean Peninsula. In the PMF results using PM2.5 and VOCs, long-range transport factors were identified in both analyses, and the high correlation observed between these factors confirms that they were transported from abroad. The dithiothreitol oxidation potential normalized to quinine showed the highest oxidation potential during the same period as the long-range transport factors increased. In conclusion, PM2.5 from external sources significantly contribute to elevated levels of dithiothreitol assay-oxidative potential (DTT-OP) in Korea. The toxic concentration, expressed as the mean ± standard deviation, was determined to be 0.29 ± 0.05 µM/m³, peaking at 0.39 µM/m³. This level is 1.8 times higher than that observed outside the event period. A notable increase in secondary pollutants was observed during these periods. These pollutants are known to enhance oxidative potential, thereby potentially impacting human health.

Insights into national distribution of NH3 concentrations in Republic of Korea: findings from passive sampler observations and implications for sources and management.

Gas-phase NH3 is one of the significant contributors to secondary aerosol formation in the atmosphere, and it is a crucial consideration in any strategy aiming to reduce PM2.5 emissions. This study aimed to investigate the spatial distributions of NH3 in verity source areas in Republic of Korea using passive samplers. NH3 concentrations were observed at 45 locations over a period of approximately 35 weeks, from June 2022 to February 2023. As a result, NH3 concentration was found to be more affected by local sources rather than long-distance influx from outside. The average concentration of NH3 observed in 7 source areas excluding the background area was all less than 20.91 ppb, except for livestock sources. These results suggest that atmospheric NH3 concentrations are significantly influenced from livestock sources. In addition, in major cities, the need for NH3 management was confirmed to be more focused on emissions from automobiles and industrial complexes than emissions from livestock and farmland. Moreover, even for the same source, NH3 concentrations varied depending on the type of livestock species, breeding methods and scale, products produced, crops cultivated, and vehicle traffic volume. These findings indicate the importance of considering factors such as breeding methods and manure treatment practices in emission factors, and it is expected that the results can be used as basic data for NH3 emission estimation and management.

Effects of combustion condition and biomass type on the light absorption of fine organic aerosols from fresh biomass burning emissions over Korea.

In this study, the light absorption properties of fine organic aerosols from the burning emissions of four biomass materials were examined using UV-spectrophotometry and Aethalometer-measurements, respectively. For wood chips and palm trees, the burning experiments were carried out with different combustion temperatures (200, 250, and 300 οC) in an adjustable, electrically heated combustor. The light absorptions of water and methanol extracts of aerosols, and smoke particles showed strong spectral dependence on the burning emissions of all biomass materials. However, the burning aerosols of wood chips showed stronger absorption than those of the other biomass burning (BB) emissions. For the burning aerosols of wood chips and palm trees, organic carbon/elemental carbon (OC/EC) decreased as the combustion temperature increased from 200 to 300 °C. Absorption Ångström exponent (AAE) values tended to decrease when combustion temperature increased for smoke aerosols and methanol extracts in smoke samples. The mass absorption efficiency at 365 nm (MAE365, m2 g-1∙C-1) of water- and methanol-extractable OC fractions was highest in wood chip burning smoke samples. MAE365 values of methanol extracts for rice straw, pine needles, wood chips, and palm trees burning emission samples were 1.35, 0.92, 2.36-3.37, and 0.86-1.42, respectively. For wood chip and palm tree burning emissions, AAE320-430nm values of methanol extracts were strongly correlated with OC/EC (i.e., combustion temperature) with slopes of 0.11 (p < 0.001) and 0.02 (p < 0.001), and R2 values of 0.87 and 0.74, respectively. Moreover, a linear regression between MAE365 of methanol extractable OC and OC/EC showed slopes of -0.05 (p < 0.001) and -0.004 (p < 0.001) and R2 of 0.72 and 0.74, respectively. The results of this study clearly demonstrate that burning condition and biomass type influence the light absorption properties of organic aerosols from BB emissions.

Influence of haze pollution on water-soluble chemical species in PM2.5 and size-resolved particles at an urban site during fall.

To investigate the influence of haze on the chemical composition and formation processes of ambient aerosol particles, PM2.5 and size-segregated aerosol particles were collected daily during fall at an urban site of Gwangju, Korea. During the study period, the total concentration of secondary ionic species (SIS) contributed an average of 43.9% to the PM2.5, whereas the contribution of SIS to the PM2.5 during the haze period was 62.3%. The NO3- and SO42- concentrations in PM2.5 during the haze period were highly elevated, being 13.4 and 5.0 times higher than those during non-haze period, respectively. The PM, NO3-, SO42-, oxalate, water-soluble organic carbon (WSOC), and humic-like substances (HULIS) had tri-modal size distributions peaks at 0.32, 1.0, and 5.2µm during the non-haze and haze periods. However, during the non-haze period they exhibited dominant size distributions at the condensation mode peaking at 0.32µm, while on October 21 when the heaviest haze event occurred, they had predominant droplet mode size distributions peaking at 1.00µm. Moreover, strong correlations of WSOC and HULIS with SO42-, oxalate, and K+ at particle sizes of <1.8µm indicate that secondary processes and emissions from biomass burning could be responsible for WSOC and HULIS formations. It was found that the factors affecting haze formation could be the local stable synoptic conditions, including the weak surface winds and high surface pressures, the long-range transportation of haze from eastern China and upwind regions of the Korean peninsula, as well as the locally emitted and produced aerosol particles.

Source contributions and potential source regions of size-resolved water-soluble organic carbon measured at an urban site over one year.

In this study, 24 h size-segregated particulate matter (PM) samples were collected between September 2012 and August 2013 at an urban site in Korea to investigate seasonal mass size distributions of PM and its water-soluble components as well as to infer the possible sources of size-resolved water-soluble organic carbon (WSOC) using a positive matrix factorization (PMF) model. The potential source contribution function (PSCF) was also computed to identify the possible source regions of size-resolved WSOC. The seasonal average contribution of water-soluble organic matter to PM1.8 was in the range from 12.7 to 19.7%, but higher (21.0%) and lower contributions (8.9%) were observed during a severe haze event and an Asian dust event, respectively. The seasonal mass size distribution of WSOC had a dominant droplet mode peaking at 0.55 µm and a minor coarse mode peaking at 3.1 µm. The droplet mode WSOC was found to strongly correlate with oxalate, SO42-, NO3-, and K+, suggesting that in-cloud processes and biomass burning emissions are important sources of droplet mode WSOC. This finding was verified by the results obtained using PMF models. Secondary organic aerosols (oxalate + SO42- + NO3-) and biomass burning were the most important contributors (70.3%) to condensation mode WSOC. In the droplet mode, in-cloud processes and secondary NO3- (+biomass burning) were important sources of WSOC, contributing on average 46.4 and 25.9% to the WSOC, respectively. In the coarse mode, soil dust and secondary processes contributed 52.5 and 42.5% to the WSOC, respectively. The PMF analyses and PSCF maps of WSOC, SO42-, and K+ indicate that condensation mode WSOC was mostly influenced by the secondary organic aerosols and biomass burning from both local and long-range transported pollutants, while droplet mode WSOC was primarily the result of atmospheric processing during the long range transport of biogenic and anthropogenic pollutants from the eastern regions of China.

Difference in production routes of water-soluble organic carbon in PM2.5 observed during non-biomass and biomass burning periods in Gwangju, Korea.

4 h integrated PM2.5 samples were collected from an urban site of Gwangju, Korea, for five days and analyzed for organic carbon and elemental carbon (OC and EC), total water-soluble OC (WSOC), hydrophilic and hydrophobic WSOC fractions (WSOCHPI and WSOCHPO), oxalate, and inorganic ionic species (sodium (Na(+)), ammonium (NH4(+)), potassium (K(+)), calcium (Ca(2+)), magnesium (Mg(2+)), chloride (Cl(-)), nitrate (NO3(-)), and sulfate (SO4(2-))) to investigate the possible sources of water-soluble organic aerosols. Two types of sampling periods were classified according to the regression relationship between black carbon (BC) concentrations measured at wavelengths of 370 nm (BC370nm) and 880 nm (BC880nm) using an aethalometer; the first period was traffic emission influence ("non-biomass burning (BB) period") and the second was biomass burning influence ("BB period"). The slope of the regression equation (BC370nm/BC880nm) was 0.95 for the non-BB period and 1.29 for the BB period. However, no noticeable difference in the WSOC/OC ratio, which can be used to infer the extent of secondary organic aerosol (SOA) formation, was found between the non-BB (0.61, range = 0.43-0.75) and BB (0.61, range = 0.52-0.68) periods, due to significant contribution of primary BB emissions to the WSOC. The concentrations of OC, WSOC and K(+), which were used as the BB emission markers, were 15.7 µg C m(-3) (11.5-24.3), 9.4 µg C m(-3) (7.0-12.7), and 1.2 µg m(-3) (0.6-2.7), respectively, during the BB period, and these results were approximately 1.7, 1.7, and 3.9 times higher than those during the non-BB period. During the non-BB period, good correlations among WSOC, SO4(2-) and oxalate, and poor correlations among WSOC, EC, and K(+) suggest that SOA is probably an important source of WSOC (and WSOCHPI) concentration. For the WSOC fractions, better correlations among WSOCHPI, oxalate (R(2) = 0.52), and SO4(2-) (R(2) = 0.57) were found than among WSOCHPO, oxalate (R(2) = 0.23), and SO4(2-) (R(2) = 0.20), suggesting that a significant proportion of the WSOCHPI fraction of OC could be produced through processes (gas-phase and heterogeneous oxidations) such as SOA formation. However, during the BB period, the BB emission source accounted for the high correlations between total WSOC (and WSOC fractions) and other relevant atmospheric parameters (EC, Na(+), Cl(-), K(+), and oxalate), with higher correlations in WSOCHPI than in WSOCHPO. These results suggest a significant contribution of BB emissions to WSOC.