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The impact of a considerable increase in traffic volume on the emission and concentrations of air pollutants was investigated at three beaches (Haeundae (HB), Gwanganri (GB), and Songjeong (SB)) in Busan during beach opening period (BOP) in 2011. During the BOP, passenger car was the major vehicle type, followed by taxi, and van. CO was the major contributor of total air pollutant emissions followed by NOx, VOC, and PM 10 . For the temporal variation of the emission of air pollutants during the BOP, it was generally the highest in the afternoon followed by the evening and morning, except for SB. For the spatial variation of their emission, it was the highest at GB followed by SB and HB. The emissions of air pollutants during the BOP were generally higher than those during the Non-BOP, except for HB. In contrast, the significant impact of the traffic volume increase on the concentrations of air pollutants at monitoring sites near the three beaches during the BOP were not found compared to the Non-BOP due to the significant distances between monitoring sites of air pollutants and monitoring sites of traffic volume at the beaches.

Emissions of air pollutants and greenhouse gases (GHGs) by aircraft at the Gimhae International Airport (GIA) were investigated using the Emissions and Dispersion Modeling System (EDMS) version 5.1.3. The number of Landing and Take-Off (LTO) at the GIA for aircraft B737 was dominant, accounting for more than 60% of the total LTOs. For air pollutant emissions, CO was the most dominant pollutant by aircraft, followed by , VOCs, , etc. The emissions of CO, , and VOCs in 2009 (and 2010) at the GIA were 974 (968), 447 (433), 118 (122) ton/yr, respectively. The emissions of GHGs such as , , and in 2009 (and 2010) were 110,795 (111,114), -0.157 (-0.151), and 1,989 (1,998) ton/yr, respectively. The negative number in emission represents the consumption of atmospheric in the engine. In addition, the emissions of most air pollutants (except for ) and GHGs were estimated to be high in Taxi-Out and Climb-Out modes.

The quantitative composition of total suspended particulates (TSP) in the atmosphere is identified to consist mainly of ions, organic carbon (OC), element carbon (EC), and metals. In terms of environmental analysis, the rest of the TSP composition may be defined as unknown fraction () which is yet difficult to analyze both quantitatively and qualitatively. In this study, the major components of TSP were measured at an urban residential area (Gang Seo) in Seoul, Korea from February to December 2009. These TSP data were analyzed in various respects to explain the relationship between known and unknown constituents. During this study period, TSP was comprised mainly of unknown compounds (48.6%) followed by ions, OC, EC, and metals. The results of this study indicate that the distribution of exhibits a strong similarity with , as they both increase with increasing TSP levels. However, if the concentrations of and are normalized against TSP, they exhibit a strong inverse correlation with each other due probably to larges differences in solubility. To establish a better strategy for air quality control in urban atmosphere, more efforts are needed to characterize unidentified proportion of particulate matters.

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).

In this study, a series of experiments were carried out to measure temporal stability of reduced sulfur compounds (RSCs) in Tedlar bag samples as a function of elapsed storage time. To this end, temporal variability of 4 RSC standard gases (, , DMS, DMDS) was measured up to 29 days. For the purpose of comparison, RSC samples were stored in both individual and mixed state. In the case of mixed standard, samples were also examined to allow comparison between light and dark condition. Then results of data were the most stable with the least change in its concentrations through the end of exps (29 days). When compared with previous studies, the extent of stability appeared to be influenced by the initial concentration levels of samples. When the patterns were compared between individual and mixture samples, differences were not significant in the case of and DMS. The effects of light conditions on temporal stability were seen to be fairly sensitive on most RSC other than . The results of our study confirm that the stability of RSC storage is affected by their involvement in photochemical reactions.

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.

Emission of air pollutants such as nitrogen oxides (NO x ), hydrocarbons (HC), SO 2 , and particulate matter (PM) and CO 2 from ship during 2009 in Busan port was estimated based on activity-based method. The significant fraction (> 50%) of ship emission resulted from container and general cargo ships. Emission at port operation mode was the most dominant compared to at sea and maneuvering modes. Emission at North port was the largest source of air pollutants among ports. The magnitudes of air pollutants NO x , SO 2 , HC, CO 2, and PM in Busan port were 8.7 × 10 3 , 8.23 × 10 3 , 0.35 × 10 3 , 4.86×10 6 , and 0.67 × 10 3 ton/yr, respectively. The ratio of NO x to VOC is about 25. Our ship emission estimate is 2 times higher than that in CAPSS emission inventory. Key Words :NO x , Vessel category, Engine power, Actual speed, Emission factor 1) 1. 서 론 세계화의 가속화로 늘어가는 인적, 물적 교통량은 선박의 물동량을 증가 시키고 이로 인한 선박의 엔진배출로부터 발생하는 대기오염은 심각한 수준으로 인식되고 있다. 선박배출은 특히 선박 입 ․ 출항이 빈번한 주요 무역항 인접지역의 대기질(NO

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.

Photochemical characteristics of ozone () and its precursors such as budget and -VOC sensitivity were analyzed in different physico-chemical properties of air masses around the Mexico City Metropolitan Area (MCMA) using aircraft observations during March 2006. The physico-chemical properties of air masses were categorized into 5 groups: boundary layer (BL), biomass burning (BB), free tropospheric continent (FTCO) and marine (FTMA), and Tula industrial complex (TIC). Results from the budget analysis indicated that production for BL, FTCO, and FTMA (for BB and TIC) was mainly controlled by a photochemical production pathway, a reaction of NO with (with ), while the main pathway of photochemical destruction for BL, FTCO, and FTMA (for BB and TIC) was a reaction of with (of with (D)). In addition, most of air mass categories (especially FTCO) were estimated to be -sensitive for production with lower , higher ratios of the other indicator species (e.g., ), , etc.), and the lower removal rate of radicals (0.5) by the reaction of OH with than those of the VOC-sensitive condition.

We examined high ozone episodes observed during the intensive measurement periods (11 May~21 June and 30 July~11 August 2009) in the Gulf of Gwangyang. During that period, there were a few events (or days) in which 1 hr averaged ozone concentrations were greater than 100 ppbv. The analysis of ozone budget and photochemical characteristics related to the ozone production was carried out using a photochemical box model. Ozone sensitivity to and VOCs was also examined in the study area during the measurement period. Diurnal variation of ozone during the episodes was similar to that of odd hydrogen radicals (, and ), suggesting significant correlation with photochemical production of ozone during the episodes. In general, ozone concentration in the study area during the measurement period was sensitive to VOCs, whereas ozone was sensitive to under certain conditions. Ozone sensitivity assessment using a radical budget analysis and /VOCs-control strategy was consistent with that using indicator species ( ratio).

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.

In this study, the environmental behavior of malodor pollutants (MPs: , , DMS, and DMDS) was investigated around areas influenced by strong anthropogenic processes based on observations and modeling study (a CALPUFF dispersion model). The MP emission concentrations were measured from 8 industrial source regions (tire plants (S1-S3), waste water disposal plant (S4), and oil refinery (S5) in an urban center area and paper mill/incineration plant (S6) and livestock feedlots (S7-S8) in Ungsang area) in Yangsan city during a fall period in 2008 (21 October 2008). Overall, the most MPs emitted from the urban center area were found to affect the malodor pollution in their downwind areas during early morning (06:00 LST) and nighttime (18:00 and 21:00 LST), compared with those in the Ungsang area. For malodor intensity, the most MPs in the urban center area (especially S1 and S2) were found to be a significant contributor, whereas and in the Ungsnag area (especially S6) were the dominant contributor. The model study showed agreement in the spatial distributions of simulated MPs with those of the observations. The largest impact of MPs in the urban center area on the malodor pollution in its residential areas occurred at S1, S2, and S3 sites during nighttime, while that of MPs in the Ungsang area occurred at S6 and S8 sites. This may be caused mainly by the high MP emissions and in part by wind conditions (prevailing northeasterly winds with low wind speeds of 2-3 m/s).

This paper is an overview of Hg measurements made in the Arctic and Antarctic regions, with an emphasis on the evaluation of the methodological approaches employed in both sampling and analysis between different Hg species as well as the fundamental aspects of their behavior. There have been numerous efforts to measure the concentrations of different Hg species, including gaseous elemental mercury (GEM), reactive gaseous mercury (RGM), and particulate mercury (Hg(p)) in polar environments. The mean concentration value for GEM, if evaluated on the basis of numerous studies conducted previously, was moderately higher in the Arctic region (1.56 ng m−3) than the Antarctic counterpart with the limited data sets (1.08 ng m−3). The mean GEM concentration in the Arctic environment varied moderately between different locations so that the highest mean values occurred in sub-Arctic locations with a complicated climatology (e.g., Kuujjuarapik, Quebec: 1.80 ng m−3), while the lowest one was recorded in Pallas, Finlan...

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.

The chemical and meteorological effects on the concentration variations of air pollutants ( and its precursors) were evaluated based on ground observation data in coastal and inland regions, Busan during springs and summers of 2005-2006. For the purpose of this study, study areas were classified into 5 categories: coastal area (CA), industrial area (IA), downtown area (DA), residential area (RA), and suburban area (SA). Two sites of Dongsam (DS) and Yeonsan (YS) were selected for the comparison purpose between the coastal and inland regions. concentrations in CA and SA were observed to be highest during spring (e.g., 40 ppb), whereas those in DA and RA were relatively low during summer (e.g., ppb). It was found that concentrations in IA were not significantly high although high VOCs (especially toluene of about 40 ppb) and ( 35 ppb) were observed. On the other hand, the concentration levels of and at the DS site were significantly higher than those at the YS site, but was slightly lower than that at the YS site. This might be caused by the photochemical activity and meteorological conditions (e.g., sea-land breeze and atmospheric stagnance). When maximum (an index of photochemical activity) exceeds 100 ppb, the contribution of secondary to total observed concentrations was estimated up to 32% and 17% at the DS and YS sites, respectively. In addition, the diurnal variations of at the DS site were similar to those of regardless of season, which suggests that they are mostly secondary produced from photochemical reactions.

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 environmental behavior of major aromatic VOC (including benzene, toluene, ethylbenzene and xylene, commonly called BTEX) in the ambient air was investigated from a mid-size municipal landfill site located in Dae Gu city, Korea in the winter of 2004. A series of field campaigns were conducted in the course of the study to cover eight different locations within and near this landfill site along with a number of VOC vent systems. The mean concentrations of different VOC species in ambient air fell in a comparable range of at or above a few ppb (e.g., the most abundant toluene approximately 10 ppb). An inspection of the VOC data sets at the studied LF sites also indicated that they are quite analogous to those typically found in other urban areas in terms of their absolute magnitude and relative pattern (e.g., the general dominance of toluene over the other species). In light of the fact that there is active ventilation of landfill gas (LFG: e.g., with their LFG concentrations above a few to a few tens of ppm) in the study area with no other distinct source processes, it can be concluded that the effects of the landfill processes may be as important as other point sources in maintaining VOC concentration levels in certain urban areas.

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.

The atmospheric concentrations of several reduced sulfur compounds (RSCs) including H(2)S, CH(3)SH, DMS, CS(2), and DMDS were measured concurrently from a series of field campaigns covering multiple locations in the surroundings of a large industrial region (August 2004 to September 2005). These field studies have been designed and undertaken to inspect the concentrations of RSCs in ambient air. The RSC concentrations were found to occur in a highly variable range. H(2)S (1.06 +/- 2.07 ppb) was found to be the most abundant RSC followed by CS(2) (0.84 +/- 0.54 ppb), DMDS (0.36 +/- 1.21 ppb), DMS (0.24 +/- 0.83 ppb), and CH(3)SH (0.11 +/- 0.23 ppb). The RSC levels measured at the study area were comparable to those observed previously from other polluted environmental settings. When these RSC data were examined further in terms of spatial (industrial vs. non-industrial sites) and seasonal (summer vs. winter seasons) grouping schemes, differences in their concentration levels were statistically insignificant in most cases. In contrast, there were fairly strong variations in temporal patterns over a diurnal cycle. If these RSC concentration data were converted to diagnose the malodor strengths, their effects were in most cases insignificant with minor contribution towards odor nuisances.

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.

The environmental behavior of gaseous elemental mercury (Hg) in the ambient air was investigated from the center of a municipal landfill site (area ∼0.6 km2) located in Dae Gu, Korea in the winter of 2004. In order to provide insight on the Hg exchange processes in strong source areas, we continuously analyzed Hg concentration gradients developed across two heights between 1 m and 5 m over soil surfaces at hourly intervals. The results displayed Hg concentrations in the lower and upper levels in the range of 1.46–13.1 ng m−3 (3.33 ± 1.29 ng m−3: N = 139) and 1.20–13.7 ng m−3 (3.27 ± 1.23 ng m−3: N = 139), respectively. The results of our analysis, when divided separately into emission and dry deposition, showed that emission of Hg was fairly dominant in frequency (up to 58%) over dry deposition. By multiplying our Hg gradient data with the K-values predicted indirectly from the results of previous studies, the emission and deposition fluxes of Hg were estimated as 39.0 ± 43.3 ng m−2 h−1 (N = 80) and −60.0 ± 80.2 ng m−2 h−1 (N = 59), respectively. Although the magnitudes of exchange were moderately lower than previously investigated anthropogenic sources, the overall results of this study suggest that an active landfill site can act as an important source of Hg in an urban environment along with other man-made activities.

In order to investigate the regional background concentration levels of mercury (Hg), measurements were routinely recorded on An-Myun Island off the coast of Korea (December 2004 to April 2006). The mean concentration of Hg computed from the entire measurement period was 4.61 ± 2.21 ng m−3 with a range of 0.10–25.4 ng m−3 (N = 10,485). Using these data, we inspected various aspects of Hg behavior from the relatively remote island of An-Myun in Korea. Inspection of the seasonal patterns of Hg indicated that its concentration levels generally peaked in spring, while reached a minimum in summer. The summertime deficiency of Hg along with the lack of diurnal variation suggests that the environmental behavior of Hg at the study site was strongly suppressed by heavy precipitation during specific period. The diurnal variations of Hg, typically characterized by a relative daytime dominance, are distinguishable between seasons so that such patterns disappear during the summer. The results of our analysis, when inspected in terms of long-range transport of airborne pollutants, imply that Hg concentration levels can be affected intensively by trans-boundary input processes over certain period of time. Its springtime dominance hence suggests the combined effects of various local source processes and the meteorological conditions favorable for the massive air mass transport phenomenon (such as Asian Dust storms) during that time period.

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 oxidation of reduced sulfur compounds (RSCs) in urban ambient air. The photochemical conversions of RSC (such as DMS, CS2 ,H 2S, DMDS, and CH3SH) to a further oxidized form (e.g., SO2, MSA, and H2SO4) were assessed using a photochemical box model. For our model simulation of RSC oxidation, measurements were taken at an urban monitoring station in Seoul, Korea (37.6� N, 127� E) during three separate time periods (e.g., Sept. 17–18, Oct. 23, and Oct. 27–28, 2003). The results indicate that DMS and H2S were the dominant RSCs with concentrations of 370 ± 140 and 110 ± 60 pptv, respectively. The photochemical conversion of DMDS to SO2 was found to occur more efficiently than other RSCs. The overall results of our study suggest that photochemical conversion of RSCs accounted for less than 15% of the observed SO2 during the measurement period. The SO2 production from DMS oxidation (mainly by the reaction with OH) was found to be affected primarily by the abstraction channel due to high NOx levels during the experimental conditions. � 2005 Elsevier Ltd. All rights reserved.

Classification of synoptic patterns and their correlation with dust events over East Asia were performed by means of cluster analysis. The average linkage and K-means clustering techniques were used to identify two major weather types during Asian dust events (ADEs; total 26 ADEs with 47 dusty days) of six spring seasons from 1996 to 2001. The first weather type mainly influenced neighboring Asian countries and frequently occurred with ADEs (approximately 23% of ADE cases). It mostly occurred under a surface high (low)-pressure system over the west (east) of the Korean peninsula coupled with an upper-level trough and cutoff low passage over the center of the Korean peninsula. It showed strong advection in the middle/ upper troposphere with both a high aerosol index and enhanced coarse particulate matter (PM) loading over Korea. In contrast, the second weather type was mostly associated with long distance or continental-scale transport and occurred less frequently with ADEs (approximately 15%). It appeared with an upper-level trough and a cutoff low vertically connected with a surface low system that was formed by a strong cyclonic vortex over the north of the Korean peninsula. There were weak advection, low aerosol index, and low coarse PM concentration over the Korean peninsula during the second weather type. In addition, it was found to be mostly associated with the trans-Pacific transport of Asian dust to the western coast of North America.

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.

In this study, we examined the influence of the long-range transport of dust particles and air pollutants on the photochemistry of OH and NO3 on Jeju Island, Korea (33.17 degrees N, 126.10 degrees E) during the Asian-dust-storm (ADS) period of April 2001. Three ADS events were observed during the periods of April 10-12, 13-14, and 25-26. Average concentration levels of daytime OH and nighttime NO3 on Jeju Island during the ADS period were estimated to be about 1x10(6) and 2x10(8) moleculescm(-3) ( approximately 9 pptv), respectively. OH levels during the ADS period were lower than those during the non-Asian-dust-storm (NADS) period by a factor of 1.5. This was likely to result from higher CO levels and the significant loading of dust particles, reducing the photolysis frequencies of ozone. Decreases in NO3 levels during the ADS period was likely to be determined mainly by the enhancement of the N2O5 heterogeneous reaction on dust aerosol surfaces. Averaged over 24 h, the reaction between HO2 and NO was the most important source of OH during the study period, followed by ozone photolysis, which contributed more than 95% of the total source. The reactions with CO, NO2, and non-methane hydrocarbons (NMHCs) during the study period were major sinks for OH. The reaction of N2O5 on aerosol surfaces was a more important sink for nighttime NO3 during the ADS due to the significant loading of dust particles. The reaction of NO3 with NMHCs and the gas-phase reaction of N2O5 with water vapor were both significant loss mechanisms during the study period, especially during the NADS. However, dry deposition of these oxidized nitrogen species and a heterogeneous reaction of NO3 were of no importance.

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.

Ion exchange performance to remove nitrate in surface and underground water was studied experimentally in batch and continuous operation systems under various conditions. Data were collected by using commercially available strong-base anion-exchange resins of C1 and OH types. Equilibrium curves, obtained through the batch system and plotted as the concentration ratio versus run time, were used to evaluate the effects of temperature, resin type, and initial feed concentration on the equilibrium characteristics of nitrate. The selectivity coefficients of the resins were correlated as a function of temperature by using the Kraus-Raridon equation. Breakthrough curves, obtained through the continuous column system and plotted as the ratio of effluent to influent concentration versus solution volume passed through the experimental column, gave detailed results about the effects of the system parameters, such as temperature, resin type, feed concentration, volumetric flow rate, column diameter and height on the performance of the anion exchange to remove nitrate. The results of this study could be scaled up and used as a design tool for a water-purification system of real ground water and surface water treatment processes.

The emissions of exhaust gases (NOx , SO2, VOCs, and CO2) and particles (e.g., PM) from ships traversing Busan Port in Korea were estimated over three different years (the years 2006, 2008, and 2009). This analysis was performed according to the ship operational modes ("at sea," "maneuvering," and "in port") and ship types based on an activity-based method. The ship emissions for current (base year 2009) and future scenarios (years 2020 and 2050) were also compared. The annual emissions of SO2, VOCs, PM, and CO2 were highest (9.6 × 10(3), 374, 1.2 × 10(3), and 5.6 × 10(5) ton year(-1), respectively) in 2008. In contrast, the annual NO x emissions were highest (11.7 × 10(3) ton year(-1)) in 2006 due mainly to the high NO x emission factor. The emissions of air pollutants for each ship operational mode differed considerably, with the largest emission observed in "in port" mode. In addition, the largest fraction (approximately 45-67%) of the emissions of all air pollutants during the study period was emitted from container ships. The future ship emissions of most pollutants (except for SO2 and PM) in 2020 and 2050 are estimated to be 1.4-1.8 and 4.7-6.1 times higher than those in 2009 (base year), respectively.

Ground-level ozone (O3) is a well-known atmospheric pollutant with its adverse impacts on the environment and human health. Here, the tropospheric O3 concentrations monitored in seven major cities in Korea at monthly intervals over a 22-year period (1989-2010) are presented, and their long-term variability examined. The analysis of annual mean values of O3 (in nmolmol(-1), or ppb) showed a noticeable increase of 118±69% in all seven cities over the two decades (p

Air samples containing sulfur compounds are often collected and stored in sample bags prior to analysis. The storage stability of six gaseous sulfur compounds (H(2)S, CH(3)SH, DMS, CS(2), DMDS and SO(2)) was compared between two different bag materials (polyvinyl fluoride (PVF) and polyester aluminum (PEA)) at five initial concentrations (1, 10, 100, 1000, and 10,000ppb). The response factors (RF) of these samples were determined after storage periods of 0, 1, and 3 days by gas chromatography-pulsed flame photometric detector (GC-PFPD) combined with an air server (AS)/thermal desorber (TD) system. Although concentration reduction occurred more rapidly from samples of the high concentration standards (1000 and 10,000ppb), such trends were not evident in their low concentration counterparts (1, 10, and 100ppb). As such, temporal changes in RF values and the associated loss rates of most sulfur gases were greatly affected by their initial concentration levels. Moreover, the storability of oxidized sulfur compound (SO(2)) was greatly distinguished from that of reduced sulfur compounds (RSCs), as the former almost disappeared in the PVF bag even after one day. The results of our study confirm that storability of gaseous sulfur species is affected interactively by such variables as initial gas concentration level, bag material type, and oxidation status with the associated reactivity.

Concentrations of total gaseous mercury (TGM) were measured continuously at four urban residential locations (G (Guro-gu); N (Nowon-gu); S (Songpa-gu); and Y (Yongsan-gu)) in Seoul, Korea from 2004 to 2009. The mean concentrations of Hg at these sites were found on the order of N (3.98 ± 1.68 ng m− 3), S (3.87 ± 1.56 ng m− 3), G (3.80 ± 1.60 ng m− 3), and Y (3.36 ± 1.55 ng m− 3). Evidence indicates that the spatial distribution of Hg should be affected by the combined effects of both local anthropogenic (incineration facilities and thermal power plants) and natural (soil) emission sources in association with the meteorological parameters. Inspection of the Hg temporal patterns indicates the co-existence of contrasting seasonal patterns between the central site Y (winter dominance) and all other outbound sites near city borders (summer dominance). The long-term trend of Hg, if examined by combining our previous studies and the present one, shows that Hg levels in this urban area declined gradually across decadal periods despite slight variabilities in spatial scale: (1) above 10 ng m− 3 in the late 1980s, (2) ~ 5 ng m− 3 in the late 1990s, and (3) ~ 3 ng m− 3 toward the late 2000s. The results of the principal component analysis along with observed differences in seasonal patterns (between study sites) suggest that Hg distributions between different urban sites are greatly distinguishable with strong source signatures at each individual site.

Concentrations of carbon monoxide (CO) in urban and rural air were analyzed from 16 urban roadside locations in the 7 major cities along with 5 background areas in Korea during an 11-year period (1998–2008). Because of noticeable changes in CO levels after 2000, temporal evaluation of its roadside data was carried out by grouping them into period I (1998–2000) and II (2001–2008). The mean CO values for all 16 roadside stations between the two study periods I and II were significantly different from each other (1.67 ± 0.31 ppm (I) vs. 0.95 ± 0.17 ppm (II)). This interperiod reduction in CO levels fell, if compared between different stations, in the range of 8.62–59.94% (mean = 39.8 ± 14.7%). The statistical analysis confirms that CO concentrations decreased very rapidly with the annual reduction rate of 0.093 ppm year−1 (9.8% year−1). In contrast, in background areas such distinctions are no longer valid between the two periods. A line of evidence collected in this study thus suggests that the implementation of legal and technical support (e.g., upgrading of fuel quality and the natural gas vehicle supply program) should have been the effective driving forces leading to the gradual reduction in CO levels in roadside locations (10 out of 16 stations) on the peninsula.

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.

In this study, the environmental behavior of malodor pollutants (MPs) [including reduced sulfur compounds (RSCs)] and aromatic volatile organic compounds (AVOCs) were investigated around urban valley areas during several field campaigns (February through December 2006). The MPs measured in the study area include the RSCs (H(2)S, CH(3)SH, DMS, and DMDS), ammonia (NH(3)), and styrene (STY); the AVOCs include benzene (BEN), toluene (TOL), ethylbenzene (EB), m,p-xylene (MPX), and o-xylene (OX). The variation of most MP concentrations (except for DMDS) was found to be larger than that of AVOCs. It was found that STY (2,346 +/- 4,867 ppbv) was the most dominant MP followed by NH(3) (447 +/- 285), CH(3)SH (16 +/- 41), and the others (8). The magnitude of AVOCs was found in the following descending order: TOL (1.4 +/- 2.2 ppbv), EB (1.0 +/- 2.1), MPX (0.9 +/- 2.0), and the others (0.8). The concentration levels of most MPs on industrial (I) and downwind (D) sites were up to an order of magnitude higher than those at non-industrial (N) and upwind (U) sites. For most AVOCs, the former was ~3 times higher than the latter. For malodor intensity in RSCs, CH(3)SH was the dominant contributor. The concentration difference in target compounds between the sites/periods is likely to be caused by the combined effects such as emission sources, geographical features (e.g., semi-closed topography), and meteorological conditions (e.g., wind directions) in and outside the urban valley.

The atmospheric concentrations of dimethylsulfide (DMS) and carbon disulfide (CS 2 ) were measured concurrently with relevant environmental parameters at Gosan, Jeju Island, Korea during 5–26 April 2001. The mean concentrations for these two compounds were 18.7 ± 17.9 and 6.4 ± 9.9 pptv, respectively. Results of our analysis indicated that relative temporal variations between DMS and CS 2 can be best described by dividing the whole data set into three different periods which reflect the variable transport patterns of air masses into the study area. (Periods I, II, and III denote: 5–10, 10–18, and 19–26 April.) The environmental conditions during those three periods varied greatly. The effects of continental and/or oceanic processes were evident for certain periods, yielding diverse relationships between DMS and CS 2 in both absolute and relative terms. Most observed variations were best explained in terms of an interplay between source/sink processes and air mass transport patterns. The sea-to-air flux of DMS, when estimated using our measurement data during this study period, was approximately 4 μmole m −2 d −1 .

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