Search

In this study, chemical characteristics of PM2.5 collected between October 1 and November 4, 2019 at Chungcheong region air quality research center in Seosan, were studied to understand reasons leading to PM2.5 increases. 24-hr integrated PM2.5 samples were analysed for organic and elemental carbon (OC and EC), water-soluble OC (WSOC), and eight water-soluble inorganic ions. Over the study period, increase in PM2.5 concentration was attributed to enhancement of organic mass (OM=1.8×OC) and NO₃- concentrations. Relationships of OC and WSOC with EC, K+, Cl-, and secondary NO₃- showed good-to-strong correlations, suggesting primary emissions (e.g., traffic and biomass burning sources) and secondary organic aerosol (OA) formation contributed to WSOC and OC concentrations. Moreover, high WSOC/OC (mean: 0.54) and OC/EC (mean: 9.0) ratios support the existence of various OA sources at the site. Four PM2.5 pollution episodes (October, 10 (event I), 17 (event II), 20~22 (event III), and November 02 (event IV)), which exceeded 24-hr PM2.5 Korean standard of 35 μg/m³, occurred and were related to concentration increases in OM and secondary ionic species. Based on synoptic weather patterns, PM2.5 forecast results, and air mass transport pathways, it was concluded that events I, II, and IV were significantly influenced by locally produced pollutions, while event III was impacted by both long-range transport of air pollutants and local emissions, with the highest concentration of SO₄2- (7.3 μg/m³). Among the four events, highest OM and NO₃- concentrations were found in the events IV and III, respectively. Results from this study suggest that strategies to reduce nitrogen oxides and organic aerosols in the study region are formulated to control PM2.5 levels.

This study investigates the existence of light-absorbing organic aerosols in ship emissions measured at a seashore site. In-situ measurements of aerosol light absorption at a port of Gangneung located on the East Sea on the Korean Peninsula were made using a multi-wavelength aethalometer for approximately 10 days. Moreover, 7- to 24-hr integrated filter-based measurements were performed to analyze the concentration of water-soluble organic carbon (WSOC). During the study period, short-term excursions of black carbon (BC) concentrations at 880 nm (BC880) and aerosol light absorption coefficients at 370 nm (babs,370) occurred repeatedly, as did absorption Angstrom exponent (AAE) values at 370–520 nm (AAE370-520). The babs,370 values during the excursions were 4.8 times higher than the background absorption levels. The AAE370-520 values were close to 1.0 at the onset of the excursion; however, they increased to 1.9–2.3 during the excursion. Furthermore, the contribution of brown carbon (BrC) light absorption at 370 nm (BrC babs,370) to the total light absorption ranged from 2.5–11.0% at the onset of the excursion to 45.2–59.8% during the excursion. The WSOC showed good-to-strong correlation with the babs,370, babs,880, and BrC babs,370, with R2 of 0.63–0.77. This suggests that primary combustion sources contributed to the aerosol light absorption. Enhanced BC880, babs,370, AAE370-520, and contribution of BrC absorption at the seashore site without traffic and industrial sources could be attributed to the light-absorbing organic aerosols in ship emissions. It was observed that absorption by BrC in ship engine exhaust can be as important as BC absorption in shorter visible wavelengths.

This study investigates the absorption characteristics of brown carbon (BrC) obtained from water and methanol extracts of fine particulate matter measured at an urban site in Gwangju, Korea during the KOREA U.S. – Air Quality campaign (May 2–June 11, 2016). The measurement period was classified into two intervals: biomass burning (BB) and non-BB periods. During the non-BB period, water-soluble organic carbon (WSOC) and humic-like substances (HULIS) primarily resulted from secondary organic aerosol (SOA) formation and primary vehicle emissions. Water-soluble organic aerosols during the BB period, meanwhile, were closely related to SOA formation and regionally transported BB emissions. The light absorption coefficient measured at 365 nm (babs,365) by methanol extracts was 2.6 and 6.1 times higher than the coefficients from the water and HULIS extracts, respectively, indicating the importance of BrC absorption by water-insoluble organic carbon. This was demonstrated by a good correlation between the water-insoluble BrC absorption and the elemental carbon concentration. A comparison of babs,365 between the methanol- and water-extracted BrC indicated that water-insoluble BrC accounted for approximately 61% (33–86%) of the total BrC absorption. The contributions of SOA, primary BB emissions, and traffic emissions to the water extract babs,365 were estimated using a stepwise multiple linear regression (MLR) analysis and found to be 1.17 ± 0.55, 0.65 ± 0.62, and 0.25 ± 0.09 Mm− 1, respectively, accounting for 59.6, 26.1, and 14.3% of the absorption coefficient by the water-soluble BrC. Further, it was determined that the contribution of the BB emissions to the water-soluble BrC absorption was approximately two times higher in the BB period than in the non-BB period. The average absorption Angstrӧm exponent was 4.8 ± 0.3, 5.3 ± 0.7, and 6.8 ± 0.8 for the methanol, water, and HULIS extracts, respectively. The average mass absorption efficiency (MAE365) of methanol extracted BrC was 1.3 ± 0.4 m2/g·C. Water- and HULIS-extracted BrC had a MAE365 of 1.0 ± 0.3 and 0.8 ± 0.3 m2/g·C, respectively. These results suggest that methanol-extracted BrC could provide a better estimation of BrC absorption compared to WSOC and HULIS.

In this study, PM2.5 samples collected between October 29 and December 23, 2018 at a roadway site in Gwangju, Korea, were comprehensively characterized by chemical, optical, and spectroscopic methods. Aerosol light absorption was observed with a time resolution of 1 min using a dual-spot aethalometer. An Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy analysis was also applied to characterize organic and inorganic components in the PM2.5 samples. Three PM2.5 pollution episodes which exceeded the 24-hr Korean PM2.5 standard (35 μg/m3) were classified; Episode I was associated with local air stagnation and long-range transportation of aerosol particles from northeast China and upwind regions; Episode II was affected by Asian dust (AD) particles and local pollution under low relative humidity (RH) conditions; and Episode III was strongly associated with accumulation of local pollution due to very high RH and low wind speed, along with regional transport of aerosol particles from eastern China. The contribution of organic aerosols to PM2.5 was higher during episodes I and II than during episode III, while the contribution of NO3− particles was greater during episode III, possibly due to very high RH and low wind speed conditions. Unexpectedly, SO42− was not an important component of PM2.5 during the three episodes. The light absorption coefficient (bBrC,370) of brown carbon (BrC) at 370 nm was estimated to range from 9 Mm−1 during episode II to 14 Mm−1 during episode III, but the contribution of bBrC,370 to total aerosol absorption was the lowest during episode III. Multiple linear regression analysis indicated that the contributions of the traffic emissions, biomass burning (BB) emissions, and secondary formation processes to bBrC,370 absorption were, on average, 37, 39, and 14% of the total estimated bBrC,370, respectively, suggesting that primary traffic emissions are an important contributor to BrC absorption at the roadway site. ATR-FTIR analysis showed that aliphatic carbon group (C–H), carbonyl group (C O), ammonium, sulfate, and nitrate were identified in all filter samples collected during the three pollution episodes; the corresponding bands had the highest intensities in the filter sample from episode III. However, the presence of mineral dusts related to hydroxyl group (-OH), gypsum, Al–Al–OH group, CO32−, and SO32− were clearly detected at the absorbance bands at 3400–3700 and 650–900 cm−1 in the AD sample only (episode II). Furthermore, the absorbance bands observed at 2910 and 2850 cm−1 during the pollution episodes were assigned to methylene groups (–CH2–), which are associated with BB emissions, and the intensities of those bands during pollution episodes were consistent with the concentrations of BB indicators (e.g., levoglucosan and K+). These FTIR method can provide valuable chemical insights into the nature of the organic and inorganic components present in ambient aerosol particles during different pollution episodes.

It is crucial to investigate the chemical species that cause increases in PM2.5 concentration and to quantitatively estimate source contributions to PM2.5 in urban environments in order to establish strategies to control anthropogenic air pollution. In this study, measurements of 24-hr integrated PM2.5 were performed for 1 year at an urban site in Gwangju, Korea. The collected samples were analyzed for organic and elemental carbon (OC and EC), water-soluble OC (WSOC), eight ionic species, and elemental species, which were used to estimate source contribution of PM2.5 using a positive matrix factorization (PMF) model. The dominant species that contributed to PM2.5 during the study period was organic matter (OM), which accounted for 24% of PM2.5. The major chemical species resulting in PM2.5 pollution episodes (>24-hr Korean PM2.5 standard of 35 μg/m3) depended on the season. For example, PM2.5 increases in winter were strongly associated with increases in secondary nitrate and OM concentrations, while rapid increases in secondary sulfate concentration brought on summertime PM2.5 increases. A total of eight sources of PM2.5 were identified using PMF analysis: secondary nitrate (26%), secondary sulfate (23%), traffic emissions (14%), metallurgical and smelting processes (11%), brake and tire wearing processes (9%), biomass burning emission (8%), crustal source (7%), and industrial sources (1%). The brake and tire wearing processes were a non-negligible contributor to total PM2.5 at the study site, accounting for 7% of PM2.5 in summer and 18% in fall. Metallurgical and smelting processes, which are highly enriched in elements such as Pb, Cu, As, Se, and Zn, were also found to be an important source of PM2.5 at the study site, contributing 7% of PM2.5 in summer and 14% in fall. Moreover, the total contribution of mobile-related emissions, such as vehicles and brake and tire wearing processes, to PM2.5 ranged from 15.2% in summer to 40.0% in winter with an average of 23%. Overall, the results of this study suggest that control of mobile-related sources is crucial to reducing the high PM2.5 levels in the Gwangju metropolitan area.

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 5.2 μm during the non-haze and haze periods. However, during the non-haze period they exhibited dominant size distributions at the condensation mode peaking at 0.32 μm, while on October 21 when the heaviest haze event occurred, they had predominant droplet mode size distributions peaking at 1.00 μm. Moreover, strong correlations of WSOC and HULIS with SO42 −, oxalate, and K+ at particle sizes of

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 Angstrom 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

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.

To investigate the influence of haze on the chemical composition and formation processes of ambient aerosol particles, PM

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.