Zang-Ho Shon

Characteristics of Asian dust transport based on synoptic meteorological analysis over Korea.

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 (∼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 (∼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.

Identification of control parameters for the sulfur gas storability with bag sampling methods

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.

A modeling study of halogen chemistry's role in marine boundary layer ozone

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.

A Review of Atmospheric Mercury in the Polar Environment

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, Finland (1.26 ng m−3). A comparison of temporal patterns between different studies also indicates that rather dynamic variations occur due to the effects of certain phenomenon, known as atmospheric mercury depletion events (AMDE). During such depletion events, the GEM concentrations frequently dropped below 1.0 ng m−3, while the RGM and Hg(p) exhibited oposing trends. The distribution of GEM in polar environments is, however, fairly comparable in spatial scale, while those of RGM and Hg(p) vary fairly dynamically in such respects. Evidence suggests that the distribution of Hg species at each measurement site in the polar environments is affected more effectively by site-specific meteorological conditions.

The effect of man made source processes on the behavior of total gaseous mercury in air: A comparison between four urban monitoring sites in Seoul Korea

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.

Nationwide shift in CO concentration levels in urban areas of Korea after 2000

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.

Analysis of Chemical and Meteorological Effects on the Concentration Difference of Photochemical Air Pollutants between Coastal and Inland Regions in Busan

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.

Long-term monitoring of airborne nickel (Ni) pollution in association with some potential source processes in the urban environment

The environmental behavior and pollution status of nickel (Ni) were investigated in seven major cities in Korea over a 13-year time span (1998-2010). The mean concentrations of Ni measured during the whole study period fell within the range of 3.71 (Gwangju: GJ) to 12.6ngm(-3) (Incheon: IC). Although Ni values showed a good comparability in a relatively large spatial scale, its values in most cities (6 out of 7) were subject to moderate reductions over the study period. To assess the effect of major sources on the long-term distribution of Ni, the relationship between their concentrations and the potent source processes like non-road transportation sources (e.g., ship and aircraft emissions) were examined from some cities with port and airport facilities. The potential impact of long-range transport of Asian dust particles in controlling Ni levels was also evaluated. The overall results suggest that the Ni levels were subject to gradual reductions over the study period irrespective of changes in such localized non-road source activities. The pollution of Ni at all the study sites was maintained well below the international threshold (Directive 2004/107/EC) value of 20ngm(-3).

Demonstration of long-term increases in tropospheric O3 levels: Causes and potential impacts

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<0.01). Changes in O3 levels are closely associated with both environmental (e.g., NOx (NO+NO2), SO2, CO, and total suspended particles (TSPs) (p<0.01), temperature, and sunshine hours) and common anthropogenic variables (e.g., population density and number of vehicles). Evidence collected in this study suggests that the atmospheric conditions in most major cities of Korea should be volatile organic compounds (VOCs) sensitive or NOx saturated with respect to O3 formation. As such, establishment of a proper management strategy seems a sensible approach to control tropospheric ozone concentrations in densely populated cities.

Emissions of Air Pollutants and Greenhouse Gases from Aircraft Activities at the Gimhae International Airport

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.