Hang Thi Nguyen

The influence of long-range transport on atmospheric mercury on Jeju Island, Korea.

The concentrations of total gaseous mercury (TGM) and relevant environmental parameters were measured at a remote area on Jeju Island, Korea from May 2006 to May 2007. The hourly mean concentration of Hg for the entire study period was 3.85+/-1.68ng m(-3) (range of 0.10-17.9: n=7450). The temporal patterns of Hg at the island site were characterized by the relative dominance in spring/fall over summer/winter and in daytime over nighttime. The possible impact of Asian dust (AD) on Hg distribution was examined by assessing its relationship with PM(10) data. Because of a strong inverse log-log correlation between Hg and PM(10) levels (above 200microg m(-3)), a direct relationship between the two parameters is difficult to account for. However, the analysis of air mass movement patterns confirmed that the Hg levels on Jeju Island were affected most by the combined effects of major source processes in the surrounding areas: industrial and AD (China), industrial (Korea), and volcanic activity (Japan).

Volatile organic compounds at an urban monitoring station in Korea

Measurements of 56 volatile organic compounds (VOC) were undertaken at a monitoring site in Seoul, Korea in 2004. The VOC pollution at the site was evaluated for both functional groups and individual compounds. The highest concentrations for the functional groups were recorded by aromatic (AR: 430ppbC) followed by paraffin (PR), olefin (OF), and alkyne (AK). The mean concentrations of individual VOCs ranged from 0.05ppb (1-hexene) to 39.8ppb (toluene). For the VOC groups, there were peak concentrations during winter (AK and OF) and summer (AR). Although most aromatic VOCs generally peaked during summer, this was not true for benzene (e.g., winter peak). The distribution of VOCs at the study site was characterized by significantly enhanced concentrations of toluene and aromatic VOCs from local industrial and mobile sources. Despite excursions that were occasionally observed from aromatic groups or benzene, strong correlations occurred frequently between different groups and between individual components. The overall results of this study suggest that anthropogenic emissions have contributed greatly to increases in VOC pollution at the study site.

A dramatic shift in CO and CH4 levels at urban locations in Korea after the implementation of the Natural Gas Vehicle Supply (NGVS) program

Concentrations of carbon monoxide (CO) and methane (CH(4)) in air were measured at both urban roadside (U-RS) and urban background (U-BG) stations in Seoul, Korea over an 11 yr period (1996-2006). The overall mean values of CO were 1.16+/-0.63 (U-RS) and 1.08+/-0.77 ppm (U-BG), while those of CH(4) were 2.24+/-0.42 (U-RS) and 2.06+/-0.31 ppm (U-BG). The diurnal patterns of CO tended to peak near rush hour, while those of CH(4) showed increases at night. An examination of the seasonal data showed that the CO values were consistently higher during winter, while CH(4) values were highly variable across seasons with relatively large spatial variations. Because of the noticeable change in air quality parameters after the year 2000, the mean data for both compounds were examined between 1996-2000 (period I) and 2001-2006 (period II). The analysis of long-term trends revealed that the concentrations of both compounds decreased very rapidly during period I, while changes were not significant during period II. The results of this comparative study confirm that both urban locations have experienced dramatic changes in the major pollutant levels, particularly in CO after the implementation of the Natural Gas Vehicle Supply (NGVS) program.

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.

Polycyclic Aromatic Hydrocarbon Concentration Levels on the Korean Peninsula between 2006 and 2008

Concentrations of seven polycyclic aromatic hydrocarbon (PAH) compounds — benzo(a)anthracene (BaA), chrysene (CHRY), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), dibenz(a,h)anthracene (DahA), indeno(1,2,3-cd)pyrene (I123P), and benzo(a)pyrene (BaP) — in air were measured as the sum of gas and particle fractions at 32 monitoring stations dispersed across Korea during a 2-year period (February 2006 to January 2008). The data sets were collected at intervals of 1 day (24 h) per month from each monitoring station. According to our analysis, the spatial distribution of PAH is distinguished by manmade activities between different land use types. Evaluation of total PAH (T-PAH) concentration levels, which were derived by summing up all individual compounds, revealed that the T-PAH value varied on the order of commercial (4.85 ± 4.40 ng m-3) rural (4.42 ± 2.73 ng m-3), industrial (4.27 ± 1.79 ng m-3), greenland (3.09 ± 3.86 ng m-3), and background (2.60 ± 2.54 ng m-3) areas. The PAH values, when compared across seasons, tend to peak consistently during the winter (or spring) due to the active consumption of fossil fuels. The overall results of this study confirm that the pollution status of PAH compounds are clearly discernible not only between areas with different levels of anthropogenic activities, but also between periods with changes in environmental conditions.

Mercury in air in an area impacted by strong industrial activities

The concentrations of total gaseous mercury (TGM) and its relevant environmental parameters were measured at a highly industrialized area in the Ban Wall industrial complex (BWIC) in An San city, Korea from March to May 2005. The mean concentrations of Hg measured during the entire study period were computed to be 6.32+/-8.56 ng m(-3) (range of 2.32-181 ng m(-3); N=1,160). Due to the effects of strong man-made activities, the significantly high Hg concentration levels (e.g., at or above 10 ng m(-3)) comprised about 7.5% of all data with the mean of 21.8+/-26.3 ng m(-3) (N=87). By separating the data into daytime and nighttime periods, the Hg values exhibited a notable daytime enhancement possibly due to strong man-made activities during working hours. The results of the correlation analysis indicated the possible relationship between the Hg concentration and the temperature as well as several pollutant species (e.g., NO(2) and NO(x)). Evaluation of the Hg data in relation with the air mass transport pattern confirms that the Hg concentration levels in this industrial area are affected most eminently by local, rather than distant, pollution sources.

Concentrations of TSP-bound metals in four urban residential locations in Seoul, Korea.

Concentrations of 17 trace metals bound in total suspended particulate (TSP) were measured at four urban residential locations (Jong Ro [JR], Gwang Jin [GJ], Gang Seo [GS], and Yang Jae [YJ]) in Seoul, Korea from February to July 2009. The maximum concentrations of metals were recorded by Fe in the range of 2599 (JR) to 2914 ng m-3 (GJ), while the least values were observed from Ag or Co with a few ng m-3. The relative ordering of the mean concentration (ng m-3) at these sites is generally found on the order of Fe > Zn > Ba > Mn > Pb > Cu > B > Cr > Ni > Sr >V > As > Li > Cd > Mo > Co > Ag or with a few exceptions (e.g., a reversal between Ba and Mn or between Ni and Sr). Calculation of the enrichment factor suggests the significant role of man-made processes on such metals as Cd, Zn, and Pb. Inspection of the temporal patterns indicates the peak occurrence of most metals during the spring season due in part to the Asian Dust (AD) event. However, according to the factor analysis, sources of these metals were dominated by both resuspended soil/road dust and the combustion of fossil fuels. The overall results of our study suggest that the interaction between the environmental conditions and roadside traffic activities are paramount in explaining the metal pollution in these urban residential areas.

Mercury in Air

In this work, an overview on all major aspects of mercury (Hg) in the atmosphere is presented to cover emission sources, chemical properties, sink processes (dry plus wet deposition), and transportation of Hg. The concentration levels of atmospheric Hg are compared geographically between different studies. The observed concentration levels of Hg in a given location can reflect the combined effects of the interplay between emission source properties and the efficiency of removal processes. Owing to the improvements in the emission control techniques, the large reduction in Hg concentration levels is observed consistently in many advanced countries, while it is not the case for developing countries. An evaluation of the Hg exposure levels also indicated that its impacts on human health are to be distinguished by various factors controlling its environmental behavior.