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The impact of land cover change in the intertidal zone (8.2% of the total surface area) on meteorology was evaluated using the Weather Research and Forecasting (WRF) model during summer (19 - 21 August 2016) and winter (9 - 11 February 2016). The heat flux change in the intertidal zone due to the tidal effects was greater in summer than in winter. During high tide in summer, the heat flux increased before sunrise and after sunset and decreased after sunrise and before sunset. During low tide, the overall heat flux decreased. In winter, a notable feature was the positive sensible heat flux before sunrise and after sunset during high tide due to a high sea surface temperature. The horizontal and vertical impacts of the tidal phenomena on the coastal meteorology were more pronounced during high tide than during low tide. The temperature decreased in inland areas and intertidal zone in summer afternoons, and increased at sea in winter mornings. The water vapor mixing ratio during the summer period increased in inland from the coastline. The wind speed during high tide at sea increased overall in summer and winter due to the decreased roughness length. During the summer period, the westerly wind speed significantly increased in the lower atmosphere (within 0.4 km) over coastal areas, and the easterly wind speed increased at the heights (approximately 1 km) of the return current of the sea breeze. These horizontal and vertical variations in sea breeze circulation induced horizontal meteorological differences in the Seoul metropolitan areas (approximately 30 km away from the coastline) and vertical differences within the planetary boundary layer (approximately 1.5 km altitude).

Measurements for size-resolved chemical composition were made at the Anmyeon Island station on the western coast of the Republic of Korea between May 28 and June 20, 2016. This study determined the main chemical compositions of size-resolved particulate matter (i.e., organic carbon, elemental carbon, water-soluble organic carbon, water-soluble ions, and benzene carboxylic acids) from a total of eight chemically size-resolved sets using micro-orifice uniform deposit impactors. The sum of the species presents a prominent accumulation mode peak at a diameter of 0.56 μm without the coarse mode peak. In the accumulation mode, SO42− (49.3%) was the dominant particle component in the size range of 0.1–1.8 μm. Organic carbon and elemental carbon accounted for 13.5% and 0.4%, respectively. Benzene carboxylic acids indicate the accumulation mode peak at the diameter of 0.56 μm. The size-resolved equivalent ion concentration ratios between all measured cations and anions and the ion neutralization model, which uses four major ions, were compared. As a result, the concentration of Na+ is of importance in the accumulation mode for the equivalent ion concentration.

This study evaluated the impact of the largest point source of particulate matter ≤2.5 μm (PM2.5) in South Korea (the coal-fired power plant) on the air quality in the southeastern region based on the transient reduction (30% less than the previous month) in coal consumption by the power plant. The impacts of the power plant during the period of coal consumption reduction were assessed based on an in-depth analysis of the forward air mass trajectory, such as the effects of meteorological parameter changes (temperature and relative humidity) on aerosol chemistry and long-range transport, and changes in anthropogenic emissions from May through June 2017. The study determined that the emission reduction from the coal-fired power plant resulted in a significant decrease in the local and regional concentrations of PM2.5, as well as the major inorganic components. The effects of the coal-fired power plant on the air quality downwind were different between local and regional areas, with a higher impact in the regional area due to the significant secondary aerosol formation. Keywords: Power plant, PM2.5, SO2, NOX, Inorganic ions, Air mass trajectory

In this study, the long-term trend in atmospheric carbon monoxide (CO) concentration was analyzed using the CO levels measured (intermittently) at an air quality monitoring (AQM) station in Seoul, Korea, between the years 1987 and 2013. Temporal trends in CO were analyzed on an annual and seasonal basis in reference to other important air pollutants such as methane (CH4), particulate matter (PM10), sulfur dioxide (SO2), nitrogen monoxide (NO), nitrogen dioxide (NO2), mercury (Hg), and ozone (O3). The annual mean of CO for the entire period was 0.93 ± 0.22 ppm. CO levels were reduced by 83% from 3.25 ± 0.78 ppm (1987) to 0.51 ± 0.31 ppm (2013). Its relative reduction was compared over three periods chosen arbitrarily as period 1 (fast reduction, 1987–1988), period 2 (intermediate reduction, 1999–2000), and period 3 (slow reduction, 2004–2013). The concentrations of CO were strongly correlated with others (e.g., SO2, NO, NO2, O3, and Hg), suggesting the effects of similar source processes (e.g., fuel combustion). The reduction in its level was marginally consistent with the decreasing trend in the total CO column concentration in Seoul by the Measurements of Pollution in the Troposphere (MOPITT) satellite between 2000 and 2013, indicating decreasing anthropogenic CO emissions (despite increasing anthropogenic CO2 emissions). The rapid relative reduction of CO in period 1 and the subsequent slower but moderate reduction thereafter appear to reflect the effects of both enforcement of administrative regulations and advances in emissions control technologies.

The contributions of various PM2.5 emission sources to ambient PM2.5 levels during 2013 in the main hub port city (Busan, South Korea) of East Asia was quantified using several receptor modeling techniques. Three receptor models of principal component analysis/absolute principal component score (PCA/APCS), positive matrix factorization (PMF), and chemical mass balance (CMB) were used to apportion the source of PM2.5 obtained from the target city. The results of the receptor models indicated that the secondary formation of PM2.5 was the dominant (45–60%) contributor to PM2.5 levels in the port city of Busan. The PMF and PCA/APCS suggested that ship emission was a non-negligible contributor of PM2.5 (up to about 10%) in the study area, whereas it was a negligible contributor based on CMB. The magnitude of source contribution estimates to PM2.5 levels differed significantly among these three models due to their limitations (e.g., PM2.5 emission source profiles and restrictions of the models). Potential source contribution function and concentration-weighted trajectory analyses indicated that long-range transport from sources in the eastern China and Yellow Sea contributed significantly to the level of PM2.5 in Busan.

Respiratory and lung irritants can be a by-product of the surgical pyrolysis of human tissues. Seven prostate tissues were collected during the transurethral resection of a prostate (TURP). Tissue samples, pyrolyzed in a pyrolysis sampling system, were collected and analyzed for the characterization of aerosols in the surgical smoke. In the pyrolyzed particulate matter (PM) from the TURP, Cholestra-3,5-diene was identified as the most dominant component along with 9-methylanthracene, hentriacontane, and dotriacontane based on the mass fragment structure determined using gas chromatography-mass spectrometry (GC-MS). As a molecular marker, Cholesta-3,5-diene can be associated with a cytotoxic in primary human oral keratinocytes (HOK). In this research, the presence of Cholestra-3,5-diene is reported for the first time as a by-product of surgical pyrolysis.

In this study, the air pollutants emitted from aircraft within the boundary layer (BL) were investigated for their impacts on the ozone (O3) concentration at and around three international airports (Incheon, RKSI; Gimpo, RKSS; and Jeju, RKPC) using the WRF-CMAQ modeling system during the summer of 2010. The analysis was performed using two sets of simulation scenarios: (1) with (i.e., TOTAL case) and (2) without aircraft emissions (i.e., BASE case). The model study suggested that aircraft emissions within the BL over the three airports can have a significant impact on the O3 (and NOx) concentrations in the source regions (the airports) and their surrounding/downwind areas. A significant negative impact of aircraft emissions on the O3 concentrations in the late afternoon (19:00 LST) was predicted near the three airports with their largest impact of −20 ppb near the RKSI at 19:00 LST. This was attributed mainly to the high NOx conditions in the VOC-limited areas and possibly in part to the rapid titration of O3 by NO around these airports. The rate of photochemical O3 destruction due to the aircraft emissions near the three airports was the most dominant contributor to the O3 levels compared to the other physical processes.

Emissions of ozone precursors (NO x and VOCs) and photochemical ozone creation potentials (POCPs) of VOC emission sources were investigated in the largest port city (i.e., Busan), Korea during the year 2011. This analysis was performed using the Clean Air Policy Support System (CAPSS) national emission inventory provided by the National Institute of Environmental Research (NIER), Korea. For NO x , the emissions from off-road mobile sources in Busan were the most dominant (e.g., 31,202 ton yr -1 ), accounting for about 60% of the total NOx emissions. The emission from shipping of off-road mobile sources (e.g., 24,922 ton yr -1 ) was a major contributor to their total emissions, amounting to 47% of the total NO x emissions due to the port-related activities in Busan. For VOCs, the emission source category of solvent usage was predominant (e.g., 36,062 ton yr -1 ), accounting for approximately 82% of the total VOC emissions. Out of solvent usages, the emission from painting was the most dominant (22,733 ton yr -1 ), comprising 52% of the total emissions from solvent usages. The most dominant VOC species emitted from their sources in Busan was toluene, followed by xylene, butane, ethylbenzene, n-butanol, isopropyl alcohol, and propane. The major emission sources of toluene and xylene were found to be painting of coil coating and ship building, respectively. The value of POCP for the offroad mobile source (61) was the highest in ten major activity sectors of VOC emissions. Since the POCP value of ship transport of off-road mobile source (72) was also high enough to affect ozone concentration, the ship emission can play a significant role in ozone production of the port city like Busan.

PM2.5 emissions from open biomass burning (BB) in Northeast Asia (NEA: China, Mongolia, Korea, and Japan) during 2000–2013 were estimated using satellite-derived data (GFASv1.0 and GFED3). The annual mean BB PM2.5 emission in NEA during the study period was 660 Gg yr−1, in which considerable inter-annual variability was observed. In general, PM2.5 emissions in NEA were the highest in spring (Mar.–May), likely due to the burning of crop residues and forest fire. The contribution of PM2.5 from open BB in Northeast Asia was less than 10% of the anthropogenic PM2.5 emission, except in Mongolia, wherein BB emission was the predominant source of PM2.5. Although the emissions calculated by GFASv1.0 were significantly higher than GFED3 by a factor of 2.66 (Mongolia) to 10.9 (South Korea) due to difficulty in small fire detection by GFED3, they generally showed consistent temporal variation on average. In general, statistically significant long-term trends of open BB PM2.5 emissions were not observed in NEA, except in South Korea.

The emissions of ozone precursors, NOx and VOCs from a biogenic source and port-related sources (ship, shipping container truck, and cargo handling equipment) were estimated in Busan during 2013. Total biogenic isoprene emission in Busan during 2013 was estimated to be 4,434 ton yr -1 with the highest emission (e.g., 28 ton day -1 ) in summer using a BEIS method. Seasonal ozone production rates by isoprene ranged from 0.15 (winter) to 2.08 (summer) ppb hr -1 , contributing the predominant portion to ambient ozone levels. Total emissions of NOx and VOCs from ship traversing Busan ports were estimated to be 29,537 and 814 ton yr -1 , respectively, showing the significant contribution to total NOx emission in Busan. The emissions of ozone precursors were significantly different depending on ship tonnage and port location. Compared to the ship emission, the emissions of NOx and VOCs from the shipping container trucks in Busan were insignificant (2.9% for NOx and 3.9% for VOCs). Total NOx and VOCs emissions from the cargo handling equipment were estimated to be 1,440 and 133 ton yr -1 , respectively with the predominance of yard tractors.

In this study, the pollution status of particulate matter (PM) in ambient air was investigated based on the concentration data of three important PM fractions (PM2.5, PM10, and TSP) measured from a central area in Seoul, Korea during the period from 2004 to 2013. The mean concentrations of each fraction measured for the entire study period were found to be 26.6 ± 2.59, 54.0 ± 15.0, and 75.3 ± 16.6 μg m−3, respectively. The seasonal mean of PM2.5 varied in the range of 22.9 ± 7.10 (fall) to 30.2 ± 7.58 μg m−3 (winter). In contrast, PM10 and TSP showed a summer minimum (40.1 ± 12.6 and 55.6 ± 17.8 μg m−3, respectively) and a spring maximum (67.1 ± 16.7 and 93.7 ± 21.1 μg m−3, respectively). The contribution of regional or long-range transport to the observed PM levels in the study area, if estimated by comparison to the data of the regional background area, was found to explain up to 72% of its input. The long-term trend of PM indicated a gradual decreasing pattern over a 10 year period, although that of PM2.5 was rather complicated to interpret in the recent years. The overall results of our study nonetheless confirm the potent role of legislation efforts put consistently to improve the air quality through the years.

Concentrations of ozone were continuously measured at four urban monitoring sites (Gu Ro (G); No Won (N); Song Pa (S); and Yong San (Y)) in Seoul, Korea from 2009 to 2011. The annual mean concentrations of ozone (in ppb) at these sites were found on the order of N (21.8 ± 19.3) > S (21.4 ± 20.14) > G (20.9 ± 18.0) > Y (18.8 ± 17.4). During peak hours (12–6 pm), the ozone concentrations were significantly higher (75, 69, 67, and 64% at site S, Y, N, and G, respectively) than overall 24 hour mean values. Seasonal variations of ozone have quite similar patterns at every site with systematic increases during spring (March–May) and summer (June–August) with the summer daytime mean (12–6 pm) values of 40.7 (site Y)–49.3 ppb (site S). The concentrations of ozone exhibited strong inverse correlations with other criteria pollutants (e.g., oxides of nitrogen and carbon monoxide), while a significant positive correlation was observed with some meteorological parameters (e.g., ultraviolet ray and solar radiation). Evidence collected in this study confirm that the spatio-temporal distribution of ozone in the study areas should be affected by the anthropogenic sources (e.g., vehicles, residential, and industrial sources) in concert with such well-known variables as the NO x –VOC chemistry and a number of natural parameters (e.g., wind speed, geographic position, and solar radiation).

A detailed description of an interactive relationship is made between water-soluble ionic components in PM 2.5 and their precursor gases using the hourly resolution data measured at an urban monitoring site in Seoul during the year of 2010. Their diurnal variability was found to be correlated with their precursor gases (HNO 3 and NH 3 ). In the case of NO 3 − and NH 4 + , a close similarity was seen in their diurnal trends, especially during spring. There were no noticeable differences in the formation pathway of NO 3 − , SO 4 2− , and NH 4 + aerosols between day and night. For NO 3 − formation, heterogeneous hydrolysis of N 2 O 5 might play a significant role in the nighttime enhancement of the oxidation rate. In addition, the concentrations of major anions (e.g. NO 3 − , SO 4 2− , and Cl − ) exhibited highly diverse seasonal patterns with their maximum values occurring in spring, summer, and winter, respectively. The overall results of this study suggest that the formation pathway of NO 3 − and SO 4 2− aerosols should be regulated by a competing relationship between the NH 3 -lean (spring and winter) and NH 3 -rich conditions (summer and fall).

The impact of pollutant emissions by the significant amount of road traffic around beaches on the ozone (O 3 ) concentrations in the surrounding regions were evaluated using a numerical modeling approach during 6 days (29 July through 3 August) of the beach opening period (BOP) in 2010. On-road mobile emissions at several roads close to beaches in Busan, Korea during the study period were estimated from the emission factors, vehicle kilometers traveled, and deterioration factors. The emission data was then applied to the 3-D chemical transport model. A process analysis (PA) was also used to assess the contributions of the individual physical and chemical processes to the production or loss of O 3 in the study area. The model study suggested the possibility that road traffic emissions near the beach area can have a significant impact on the O 3 concentrations in the source regions as well as their surrounding/downwind regions. The maximum negative impact of mobile emissions on the O 3 concentrations was predicted near the beach areas: by −9 ppb during the day due to both the high NO x emissions with the high NO x /VOC ratio and meteorological conditions and −9 ppb at night due to the fast titration of O 3 by NO. The PA showed that the contribution of chemical process to the decrease in O 3 concentrations (up to −5.5 ppb h −1 ) due to mobile emissions near the beach areas was the most dominant compared to the other physical processes.

Long-term monitoring of ammonia concentration and other trace gases was made at hourly intervals along with meteorological parameters in Seoul, Korea for a one-year period (1 September 2010–23 August 2011). The mean ammonia concentrations measured at two sites (Gwang-Jin (GJ) and Gang-Seo (GS) districts) were 10.9 ± 4.25 and 12.3 ± 4.23 ppb, respectively. A comparison of the seasonal data shows its relative dominance at both GJ and GS sites during the warm period (summer and spring) over the cool period (winter and fall). Likewise, over the diurnal scale, relative dominance during daytime was also apparent (p

The emissions of greenhouse gases (GHGs) and air pollutants from aircraft in the boundary layer at four major international airports in Korea over a two-year period (2009–2010) were estimated using the Emissions and Dispersion Modeling System (EDMS) (i.e. activity-based (Landing/Take-Off (LTO) cycle) methodology). Both domestic and international LTOs and ground support equipment at the airports were considered. The average annual emissions of GHGs (CO 2 , N 2 O, CH 4 and H 2 O) at all four airports during the study period were 1.11 × 10 3 , 1.76 × 10 −2 , −1.85 × 10 −3 and 3.84 × 10 8 kt yr −1 , respectively. The emissions of air pollutants (NO x , CO, VOCs and particulate matter) were 5.20, 4.12, 7.46 × 10 −1 and 3.37 × 10 −2 kt yr −1 , respectively. The negative CH 4 emission indicates the consumption of atmospheric CH 4 in the engine. The monthly and daily emissions of GHGs and air pollutants showed no significant variations at all airports examined. The emissions of GHGs and air pollutants for each aircraft operational mode differed considerably, with the largest emission observed in taxi-out mode.

In this study, fine-particle (PM2.5) ionic composition in the city of Seoul was investigated using short-term measurement data (1 h interval) collected during the year 2010. The partitioning of semi-volatile inorganic species and phase state of aerosols were studied using ISORROPIA II thermodynamic equilibrium model. The analysis of ionic composition identified the relative dominance of NO 3 − , SO 4 2 − , and NH 4 + in the fine particles. The presence of strong correlation between these components indicates similarity of their formation pathways. Seasonal patterns of these ionic components and their gas-phase precursors were somewhat different from each other. The observed SO 4 2 − / SO 2 mass ratio indicated a significant role of the gas-phase oxidation of SO2 (to H2SO4) in the SO 4 2 − formation. Moreover, both SO42− and NO3− were almost completely neutralized by NH4+ to form (NH4)2SO4 and NH4NO3. The formation of NO3− aerosol would be ammonia-sensitive (i.e., deficit ammonia), as evidenced by smaller total ammonia concentration than the sum of total sulfate and nitrate concentrations. The uptake of SO2 on dust particles during Asian dust event is also likely to exert controls on SO42− concentrations.

The environmental behavior of particle-bound secondary organic carbon (SOC) was investigated with respect to its fractionation at four urban sites in Seoul, a megacity in Korea from Feb to Dec 2009. Empirical estimates of SOC formation were comparatively evaluated using the multiple linear regression and constrained mass balance (i.e., CO and EC tracers) methods. The SOC fraction estimates were significantly different depending on the applied methods. The multiple linear regression method used for the estimation of SOC fraction was more reliable than the constrained mass balance approach due to the limited number of available daily PM measurement during each season. Seasonal and spatial patterns in the SOC fractions were examined at the four urban sites. Seasonally averaged SOC fractions ranged from 15 to 65% of the total organic carbon concentration. According to this study, the SOC fractions were significantly high in the spring and summer relative to other seasons.

The ionic composition of PM2.5 samples was investigated by their datasets of cationic (Na?, NH₄?, K?, Mg 2+ , and Ca 2+ ) and anionic components (Cl?, NO₃?, and SO₄ 2- ) along with relevant environmental parameters collected from an urban monitoring site in Korea at hourly intervals in 2010. The mean (and SD) annual concentration of PM 2.5 was computed as 25.3 ㎍ m -3 with the wintertime maximum. In addition, sum concentrations (neq m -3 ) of five cationic species (291) were slightly lower than 3 anionic species (308). Most cations exhibited the highest seasonal values in spring, while anions showed more diversified seasonal patterns. According to PCA, five major source categories were apparent with the relative dominance of secondary inorganic aerosols (SIA). The results of our study suggest consistently that the distribution of ionic constituents in an urban area is affected by the combined effects of both natural and anthropogenic processes.

The photochemical characteristics of ozone (O3) and its main precursors (e.g. NOx and VOCs) were investigated in relation to the photochemical O3 budget and O3eNOxeVOC sensitivity, based on a modeling approach using data sets observed during intensive field campaigns conducted under various environmental conditions (i.e. urban (Seoul), rural (Yang Pyeong), landfill (Dae Gu), coastal (Gwang Yang), and remote sites (Jeju Island). The production of O3 under most environmental conditions (especially, spring season at the urban site) was found to be more strongly sensitive to VOCs than NOx .A t the landfill site and during summer at the rural and coastal sites, the production of O3 was partially sensitive to NOx. On the other hand, despite the remote air on Jeju Island, the production of O3 was mainly VOC-sensitive (high NOx levels), but in part NOx-sensitive (low NOx levels), due to the transport processes from different environmental regions (e.g. heavily and less polluted locations).

Long-term trend in emission ratio of NO2 to NOx was analyzed in relation to traffic activities using ambient monitoring data (such as NO, NO2, NOx, and O3) collected from 7 urban roadside (U-RS) and 7 urban background (U-BG) locations in Seoul, Korea over a 14-year period (1996–2009). In general, the temporal trend of NO2 concentrations is less distinctive than that of NOx, whether being downward or upward. However, if their differences are checked statistically, only a few cases were significant. The mean emission ratio of NO2 to NOx values varied slightly across the 7 U-RS sites during the study period, ranging from 0.11 to 0.19. In general, there was no significant annual trend in the relative fraction of NO2 in NOx emission (f(NO2)) at U-RS, with an exceptional downward trend at one site (slope of −0.008 y−1). On the other hand, diurnal variations of f(NO2) were likely affected by driving conditions and fuel type of vehicles. The overall results of this study suggest that NOx emission control strategies such as diesel particulate filter (DPF) or diesel oxidation catalyst (DOC) should have direct influences on f(NO2) values at U-RS sites.

In an effort to assess long-term variations of urban air quality over a broad spatial scale, the concentrations of PM10 (particulate matters with aerodynamic size below 10 μm) measured from a total of 16 urban roadside (U-RS) stations in Korea over a decadal period (1998 and 2008) were analyzed in a number of respects. As a major criterion for evaluation, these PM data were examined with respect to landmarking active clean-up activities (e.g., Natural Gas Vehicle Supply (NGVS) program enforced since 2000 and upgrading of fuel quality since 2004) and emission control retrofits since 2003 throughout major urban areas in Korea. The mean concentrations of PM10 from all 16 U-RS stations varied from 51.3 ± 10.3 (before 2000) to 70.3 ± 19.4 μg m−3 (after 2001). The results derived from 4 regional background stations were also analyzed as a reference to the urban data sets. The analysis of our PM data between before and after such clean-up activity for air quality indicates the existence of highly diversified temporal patterns. The measured PM values from only a few U-RS stations exhibited statistically significant declining trends over a decadal period. It is thus concluded that the effect of clean-up activity like NGVS and emission control retrofits, although claimed to make zero-emissions of fine particles, did not result in an overall reduction in PM10 levels.

To establish a proper regulation strategy on the emissions of major halocarbons including chlorofluorocarbons (CFCs), carbon tetrachloride (CCl4), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), it is essential to assess their environmental behavior in relation to social and technological changes for their control. The production and release of CFCs and CCl4 increased rapidly to peak between the 1970s and 1980s and then decreased dramatically from the end of the 1980s in good accordance with the phase out schedules set by the Montreal Protocol. Both HCFCs (e.g., HCFC-124, HCFC-141b, and HCFC-142b) and HFCs (e.g., HFC-134a) have been introduced as CFCs alternatives between the late 1980s and early 1990s. However, these alternatives have already been or will be scheduled to be phased out because of their involvement in ozone destruction and global warming. In light of all the complexities associated with the global chemistry of CFCs and their alternatives, this paper provides an overview of their production and emission trends, their relationship with the ozone depletion phenomenon, the chemistry regulating their removal processes, and their distribution patterns with diverse temporal and spatial scales.

An oil spill on the west coast of the Republic of Korea was investigated with regard to its impact on ozone (O 3 ) concentration levels in the surrounding regions. The accident occurred on December 7, 2007 with the total estimate of 12,500 tons of Iranian Heavy plus Kuwait Export crude oils. The evaporation rates of the volatile hydrocarbon fractions in these crude oils were estimated based on the molar fractions of crude oils and their mass transfer coefficients. Their emission rates parameterized with several key environmental parameters (e.g., wind speed, seawater temperature, and salinity) along with oil type information were then applied in the 3-D chemical transport model. Photochemical production of O 3 in winter just after the accident was relatively insignificant due to very low photochemical activity. For the case/sensitivity study, the photochemical production of O 3 simulated under the hot summer weather conditions was predicted to be significant at the same magnitude of the oil spill. This study confirms that an oil spill, if occurring around coastal regions, can alter O 3 levels to a large extent depending on the meteorological conditions.

Long-term trend in nitrogen dioxide (NO 2 ) levels was analyzed from 16 urban roadside (U-RS) locations in 7 major cities along with 5 reference background areas in Korea over an 11-year period (1998–2008). These NO 2 data were examined after being grouped into periods I (1998–2000) and II (2001–2008) in light of the major emission control strategy such as the natural gas vehicle supply (NGVS) program initiated since June 2000. There were contrasting signals between Seoul (capital) and others. Although the long-term trends were dominantly toward decline from most stations (5 out of 7) in Seoul, an increasing trend was dominant in other cities (7 out of 9 stations). A line of evidence collected in this study indicated that NO 2 levels and the emission ratio of NO 2 to NO x (f(NO 2 )) in U-RS sites have gradually decreased over the years due to the combined effects of various control efforts (e.g., the implementation of NGVS and the use of low emission diesel engines).

Concentrations of carbon monoxide (CO) in air were analyzed from seven urban roadside (U-RS) stations in Seoul, Korea over an 11-year period (1998-2008). As noticeable changes in CO levels coincided with the Natural Gas Vehicle Supply (NGVS) program in the year 2000, its concentration data were examined between 1998-2000 (period Ⅰ) and 2001-2008 (period Ⅱ). The mean values of CO from all 7 stations for the whole study period were recorded as 1.19±0.22 ppm with large drops in its mean from 1.83±0.43 ppm in period I to 0.94±0.21 ppm in period Ⅱ. As such, CO levels between the two periods undertook the mean reduction rate of 46.9±16.2% (range of 18.3 to 59.9%). According to the analysis of longterm trends of CO, its concentrations in the U-RS stations decreased very rapidly with the annual mean reduction rate of 9.5% yr?¹. A line of evidence collected in this study suggests that the implementation of the NGVS program has been quite effective to induce the alterations in CO levels in all urban roadside locations throughout the city of Seoul.

The influence of ship emissions on ozone (O 3 ) concentrations in a coastal area (CA) including Busan port, Korea was examined based on a numerical modeling approach during a high O 3 episode. The analysis was performed by two sets of simulation scenarios: (1) with ship emissions (e.g., TOTAL case) and (2) without ship emissions (e.g., BASE case). A process analysis (PA) (the integrated processes rate (IPR) and integrated reaction rate (IRR) analyses) was used to evaluate the relative contributions of individual physical and chemical processes in O 3 production in and around the CA (e.g., sites of Dong Sam (DS) and Dae Yeon (DY)). The model study suggested the possibility that pollutant gases emitted from the ships traversing Busan port can exert a direct impact on the O 3 concentration levels in the CA. Largest impacts of ship emissions on the O 3 concentrations were predicted at the coast (up to 15 ppb) and at inland locations (about 5 ppb) due to both the photochemical production of pollutant gases emitted from the ships and meteorological conditions. From the PA, the photochemical production of O 3 (P(O 3 )) due to ship emissions in the CA was found to increase by a mean of 1.5 ppb h −1 (especially by ≥10 ppb h −1 at the DS site) during the day.

The photochemical oxidation and dispersion of reduced sulfur compounds (RSCs: H2S, CH3SH, DMS, CS2, and DMDS) emitted from anthropogenic (A) and natural (N) sources were evaluated based on a numerical modeling approach. The anthropogenic emission concentrations of RSCs were measured from several sampling sites at the Donghae landfill (D-LF) (i.e., source type A) in South Korea during a series of field campaigns (May through December 2004). The emissions of natural RSCs in a coastal study area near the D-LF (i.e., source type N) were estimated from sea surface DMS concentrations and transfer velocity during the same study period. These emission data were then used as input to the CALPUFF dispersion model, revised with 34 chemical reactions for RSCs. A significant fraction of sulfur dioxide (SO2) was produced photochemically during the summer (about 34% of total SO2 concentrations) followed by fall (21%), spring (15%), and winter (5%). Photochemical production of SO2 was dominated by H2S (about 55% of total contributions) and DMS (24%). The largest impact of RSCs from source type A on SO2 concentrations occurred around the D-LF during summer. The total SO2 concentrations produced from source type N around the D-LF during the summer (a mean SO2 concentration of 7.4 ppbv) were significantly higher than those (≤0.3 ppbv) during the other seasons. This may be because of the high RSC and SO2 emissions and their photochemistry along with the wind convergence.

Synoptic-scale meteorological features controlling the trans-Pacific transport (TPT) of Asian dust (AD) and its temporal and spatial distributions were examined in the regions between East Asia and North America, especially over the North Pacific Ocean during a dust episode in April 2001. These analyses were performed based on the meteorological maps, aerosol index (AI), aerosol optical depth (AOD), PM10 measurements, and model studies (e.g., dust concentrations, geopotential heights, horizontal winds, and potential temperature). The dominant meteorological conditions affecting the TPT of AD (TPTAD) were found to be associated with the two synoptic features: (1) behavior of the strong westerlies along the trough path connected to surface cyclones in high latitudes and (2) the acceleration of westerlies merged with the airflows traveled along the conveyor belt (CB) zone over the North Pacific Ocean. The merged strong westerlies that developed from the CB (a strong wind velocity ( ⩾ 25 m s - 1 ) and the strong gradient of potential temperature ( ∼ 15 K )) played a significant role in the TPTAD. The TPTAD simulation showed agreement in the patterns and the concentration levels of modeled dust with those of the observations. Further evidences for the TPTAD were AI of ∼ 2 , AOD range of ⩽ 0.7 , and an increase of PM10 concentrations (e.g., exceeding 80 μ g m - 3 ) in most of the counties of California during the dusty days.

In this study, the environmental behavior of reduced sulfur compounds (RSCs: H2S, DMS, CS2, DMDS, and CH3SH) was investigated in an area influenced by strong anthropogenic processes based on a numerical modeling approach. The RSC emission concentrations were measured from multiple locations around the Ban-Wall industrial complex (BWIC) in the city of An San (AS), Korea, during a series of field campaigns held between August 2004 and September 2005. These emissions were then used as input for a CALPUFF dispersion model with the 34 dominant chemical reactions for RSCs. The impact of RSC emission on SO2 concentrations was assessed further in the study areas. The model study indicated the possibility that RSCs emitted in and around the BWIC can exert a direct impact on the ambient SO2 concentration levels in its surrounding areas with the most prominent effect observed during summer. Our prediction indicated that a significant fraction of SO2 was produced photochemically in and around the BWIC during the summer (about 30% of total SO2 concentrations) and fall events (∼20%). These photochemical productions of SO2 were mainly ascribable to H2S (∼60% of total contributions) and DMDS (∼25%) out of all five target RSCs. Meteorological contribution (dispersion) to SO2 concentration level was also highest during summer.

In this study, the fundamental aspects governing the environmental behavior of nitrogen oxides were explored from two air quality-monitoring stations (AQM) in Seoul, Korea, over an 11-year period (1996–2006). The two stations were selected to represent an urban roadside (U-RS) and urban background station (U-BG). The mean concentration levels of NO x at the U-RS area exhibited a gradual decrease through years (from ∼290 ppb (1996) to 100 ppb (2003)), while those measured at the U-BG site maintained fairly stable values (∼70 ppb) throughout the years. The mean concentration levels of NO and NO 2 at the U-BG site were almost the same (∼35 ppb), while the U-RS site showed that the mean value of NO (∼127 ppb) is significantly higher than that of NO 2 (∼60 ppb). The observation of larger differences in NO level between the two sites reflects the direct impact of vehicular emissions at the U-RS site. Both correlation and factor analyses were conducted between the hourly data sets of NO x species ( N =∼90,000) and relevant environmental variables for both the sites. The results of both tests confirm the prominent role of vehicular activities in determining the level of nitrogen oxides at urban roadside environments, although such effects appear to be rather intricate at U-BG. Our comparative analysis of NO x data sets collected over varying temporal scales indicate that their distributions in the urban environment can be distinguished more clearly in spatial factors (i.e., between urban background and urban roadside) than other criteria.

In this study, long-term monitoring of gaseous elemental mercury (Hg(0), GEM) was carried out at an urban site in Seoul, Korea from September 1997 to January 2005. There was no discernible long-term trend to predict the future direction of Hg(0) concentration shift across a 9-year study period. In contrast, seasonal trend analysis indicated that maximum Hg(0) concentrations occurred in the winter, while the minimum occurred in the fall. In addition, Hg(0) concentrations varied diurnally with the nighttime dominance, especially in the winter. It was suggested that the distribution of Hg(0) was controlled mainly by anthropogenic sources and in part by interplay of photochemical oxidation (through OH and O 3 ), meteorological conditions (e.g., precipitation), and dry deposition during the study period. The contribution of the O 3 -dependent photochemical oxidation leading to Hg(0) loss was significantly larger than its OH counterpart. The photochemical lifetime of Hg(0), when induced based on the oxidation by O 3 and OH, was estimated to vary from 1.1 to 2.4 years.

In this study, the distribution characteristics of reduced sulfur compounds (RSCs) in ambient air were investigated in two coastal landfill (LF) facilities and their surrounding areas. The photochemical conversion of RSCs to sulfur dioxide (SO2) was also evaluated using a photochemical box model (PCBM). Measurements of RSCs were carried out from both in and around areas of two coastal LFs in Gunsan (G) and Donghae (D) city, Korea during several field campaigns (May through December 2004). The dominant RSCs at the Gunsan landfill (G-LF) were found to be DMS and H2S, whereas those at the Donghae landfill (D-LF) were H2S and DMDS. The concentrations of DMS at these study sites were likely to be affected not only by LF processes but also by an oceanic source, while such a pattern was more prominent at the D-LF. The chemical species of RSCs that can exert significant influences on the photochemical production of SO2 in the LF environment were identified to be H2S, DMS, or DMDS.

The effect of large-scale firework events on urban background trace metal concentrations was investigated using 24 hr data collected over 3 days at three sites in Busan Metropolitan City, Republic of Korea, during the falls (Oct.) of 2011–2013. The firework events increased local background concentrations of trace metals as follows: K (1.72 times), Sr (2.64 times), As (2.86 times), Pb (2.91 times), and Al (5.44 times). The levels of some metals did not always drop to background level one day after the firework event. The contribution of fireworks to trace metal concentration levels (and emissions) for 2011 event was negligible compared to 2012 and 2013 events due to different meteorological conditions (precipitation). In addition, the impact of firework events on the ambient concentration levels of trace metals was likely to be different depending on their chemical speciation. The impact of firework events in Busan on urban air quality (trace metal) was less intense compared to other similar festivals worldwide. The largest emission of trace metals and elements from firework burning was represented by K (128–164 kg), followed by Pb, Cd, Cu, Mg, Ba, As, Al, Ga, Co, and Na.

This study examines the distribution characteristics of reduced sulfur compounds (RSCs such as DMS, CS2 ,H 2S, DMDS, and CH3SH) and their photochemical reactions in landfill air. The photochemical conversions of RSCs to a further oxidized form, SO2 were evaluated in the landfill site using a photochemical box model. Measurements of RSCs were carried out from landfill areas in Daegu, Korea, during a wintertime period (e.g., 13–16 Jan 2004). This study indicated that H2S was the most dominant RSC in the landfill, with the concentrations of 4.275.8 ppbv. The chemical species of RSCs, which may exert influences on the SO2 production depending on sampling conditions, were found to include DMS, DMDS, and H2S. In general, the RSC contribution to the observed SO2 levels was insignificant in the sampling sites investigated. Overall, the extent of the RSC oxidation to the observed SO2 varied dramatically during the sampling period. The photochemical conversion of the RSCs in the landfill environment can account for about 15% of the observed SO2, on average. There was a strong correlation between DMS and SO2 concentration levels during the study period. r 2005 Elsevier Ltd. All rights reserved.

Chemical speciation and concentrations of reactive gaseous mercury (RGM) in the urban atmospheric boundary layer (ABL) have been modeled using a photochemical box model. Measurements for gaseous elemental mercury (GEM) and the relevant trace gases were carried out in Seoul (37.6°N, 127°E), Korea, during a one-year period from March 2001 to February 2002. A moderately strong inverse correlation between GEM (Hg(0)) and ozone was observed in the spring. In addition, it was also observed that there were distinct GEM concentration differences between day and night, especially in the winter. Model simulations suggested that the most dominant sink of elemental mercury (Hg(0)) was the reaction with O 3 , which in turn contributed significantly to the formation of mercury oxide (HgO). The dominant RGM species in the urban ABL are likely to be HgO and Hg(HO) 2 . Seasonally averaged concentrations of HgO and Hg(HO) 2 are estimated to range from 0.5×10 4 to 1.1×10 4 and 0.2×10 4 to 3.5×10 4 molecules cm −3 , respectively. According to our model simulations, most RGM species are expected to exhibit relatively enhanced concentrations during the daytime compared to the nighttime.

This study reports the impact of reactive halogen species on diurnal ozone changes in the marine boundary layer (MBL). A photochemical box model has been used to simulate the mixing ratios of ozone, constrained with airborne field observations of Lagrangian flights operated during the ACE 1 campaign, 1995. The model includes bromine, chlorine, and iodine chemistry as well as aqueous-phase chemistry in sea-salt aerosols. Diurnal ozone changes in the MBL depend on photochemical production and loss, entrainment from the buffer layer (BuL), and deposition to the sea surface. Model calculations are compared with ozone observed over the Southern Pacific Ocean near Cape Grim, Tasmania. The model simulates well the observed ozone, reproducing the diurnal cycle in ozone mixing ratios. Based on budget analysis, ozone production in the MBL mainly results from the transport of BuL ozone, while ozone destruction is mainly controlled by a photochemical destruction pathway, a O( 1 D)+HO2 reaction. When the halogen chemistry is included to the model, a slight decrease of ozone mixing ratios and time shifting in a maximum period of time are revealed. The time shifting mainly results from reactive bromine and chlorine species (e.g., Br, BrO, Cl, and ClO), which show peaks after sunrise. On diurnal average, total loss rate by reactive halogen species is 1.2 � 10 � 2 ppbv h � 1 . Model results confirm that the halogen chemistry can significantly affect ozone levels during early morning after sunrise. r 2002 Elsevier Science Ltd. All rights reserved.

The effects of photochemical oxidation of reduced sulfur compounds (RSCs: H2S, CH3SH, DMS, and DMDS) on SO2 production were evaluated at high (HV) and low ventilation (LV) conditions, based on a CALPUFF dispersion model coupled with photo-chemical oxidation mechanisms for four RSCs. The RSC emission concentrations used in the modeling were measured in and around an urban valley during a field campaign held in October 2008. SO2 production with LV (up to 156 ppb at 0900 LST) was found to be significantly higher than that with HV (up to 30 ppb). SO2 produced by photochemical oxidation of RSCs with LV (78% of total SO2 concentrations) was much higher than that with HV (27%), while the predominant RSC species were similar: DMDS (>= 60% of the total contributions) with HV and LV when compared to three other RSCs (< 20%). The difference in SO2 concentration between HV and LV might be caused by the combined effects of photochemical oxidation of RSCs and ventilation condition.

This study estimated greenhouse gas (GHG) and air pollutant emissions from aircraft in the troposphere (aircraft cruise altitudes, 1 - 12 km) over South Korea over a two-year period (2009 - 2010) using an activity-based (Landing and Take-Off (LTO) cycle) methodology. Both domestic and international LTOs covering 4 major airports and 11 smaller airports in South Korea were considered. The annual mean GHG emissions (CO2, N2O, CH4, and H2O) in the troposphere (1 - 12 km) over South Korea during the study period were approximately 3.5 ¡_ 103, 3.4 ¡_ 10-2, -6.6 ¡_ 10-2, and 1.4 ¡_ 103 kiloton (kt) yr-1, respectively. The tropospheric air pollutant emissions (CO, NOx, VOCs, and PM2.5) were approximately 3.0, 20, 1.0, and 0.2 kt yr-1, respectively. The monthly GHG and air pollutant emissions showed no significant variations. The GHG and air pollutant emissions during cruises over the South Korean airspace were significant contributors to (e.g., about 80% for NOx and about 75% for CO2) the total national aviation emissions including the emissions at airports, boundary layer and the free troposphere.

Erratum to ‘‘Monitoring of atmospheric reduced sulphur compounds and their oxidation in two coastal landfill areas’’ [Atmospheric Environment 41 (2007) 974–988] Sang-Keun Song, Zang-Ho Shon , Ki-Hyun Kim, Seong Cheon Kim, Yoo-Keun Kim, Jung-Kwon Kim Department of Atmospheric Sciences, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea Department of Environmental Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714, Republic of Korea Department of Earth & Environmental Sciences, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul, Republic of Korea Department of Environmental Engineering, Kunsan National University, 68 Miryong-dong, Gunsan 573-701, Republic of Korea

In this study, ambient particulate matter pollution was investigated using monthly PM10 concentration data collected from seven major cities in Korea from 1996 to 2010. The highest mean value for the whole study period is seen from the capital city, Seoul (63.2±17.9μg m–3), while the lowest is from Ulsan (46.7±14.8μg m–3). The concentrations of PM10 in all cities exhibited seasonal variations with the peak values occurring consistently in spring (March or April). The PM10 data in each city consistently exhibited strong correlations (p0.05). The analysis of long term trends of PM10 levels indicates a weak but consistent decline in concentrations in most cities with the relative average annual reductions of between 0.4 and 2.8% y–1.