Aerosol Composition Change due to Dust Storm: Measurements between 1992 and 1999 at Gosan,Korea

Aerosol composition change between dust storm and non duststorm periods is studied using the TSP (Total SuspendedParticulate) data measured at Gosan, Korea between 1992 and1999. The concentrations of elements measured between 1993and 1996 and those of ions between 1992 and 1999 duringdust storms are compared with those during non-dust stormperiods in spring (March, April, and May). Among theanalyzed ions, the concentrations of crustal species(potassium, calcium, magnesium, and chloride) andanthropogenic species (nitrate and non-sea salt (nss)-sulfate) increased when dust storm occurs while those ofammonium and sodium did not increase. Among the analyzedelements, the concentrations of crustal species (Fe, Al,Ca, Ti, and Zn) increased when dust storm occurs whilethose of anthropogenic species (Mn, V, Ni, Cu, Cd, and Cr)did not increase. The only anthropogenic element of whichconcentration increased during dust storm periods was Pb.It was found that the concentrations of nitrate and nss-sulfatewere highest during spring. Also, the ratio of theyearly average concentrations of nitrate to nss-sulfateincreases, probably due to the emission trend change innortheast Asia, especially, in China.     

Mercury leaching characteristics of waste treatment residues generated from various sources in Korea

In this study, mercury (Hg) leaching characteristics of the waste treatment residues (fly ash, bottom ash, sludge, and phosphor powder) generated from various sources (municipal, industrial, medical waste incinerators, sewage sludge incinerator, oil refinery, coal-fired power plant, steel manufacturing plant, fluorescent lamp recycler, and cement kiln) in Korea were investigated. First, both Hg content analysis and toxicity characteristic leaching procedure (TCLP) testing was conducted for 31 collected residue samples. The Hg content analysis showed that fly ash from waste incinerators contained more Hg than the other residue samples. However, the TCLP values of fly ash samples with similar Hg content varied widely based on the residue type. Fly ash samples with low and high Hg leaching ratios (R_L) were further analyzed to identify the major factors that influence the Hg leaching potential. Buffering capacity of the low-R_L fly ash was higher than that of the high-R_L fly ash. The Hg speciation results suggest that the low-R_L fly ashes consisted primarily of low-solubility Hg compounds (Hg₂Cl₂, Hg⁰ or HgS), whereas the high-R_L fly ashes contain more than 20% high-solubility Hg compounds (HgCl₂ or HgSO₄).     

The estimation of N2O emissions from municipal solid waste incineration facilities: The Korea case

The greenhouse gases (GHGs) generated in municipal solid waste (MSW) incineration are carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). In South Korea case, the total of GHGs from the waste incineration facilities has been increasing at an annual rate 10%. In these view, waste incineration facilities should consider to reduce GHG emissions.This study is designed to estimate the N₂O emission factors from MSW incineration plants, and calculate the N₂O emissions based on these factors. The three MSW incinerators examined in this study were either stoker or both stoker and rotary kiln facilities. The N₂O concentrations from the MSW incinerators were measured using gas chromatography-electron capture detection (GC-ECD) equipment.The average of the N₂O emission factors for the M01 plant, M02 plant, and M03 plant are 71, 75, and 153 g-N₂O/ton-waste, respectively. These results showed a significant difference from the default values of the intergovernmental panel on climate change (IPCC), while approaching those values derived in Japan and Germany. Furthermore, comparing the results of this study to the Korea Energy Economics Institute (KEEI) (2007) data on waste incineration, N₂O emissions from MSW incineration comprised 19% of the total N₂O emissions.     

The behaviors of H2, CH4, C2H4 and C3H6 from the decomposition of polypropylene by NiO/Si–Al catalyst

The purpose of this study was to investigate the possibility of light gases produced from polypropylene, specifically hydrogen. In particular, we examined the effect of operating conditions on gaseous product and compositions in the catalytic cracking of polypropylene. We also characterized the gaseous product generated from polypropylene cracking. The feedstock (2.0 g) mixed with NiO/SiO₂–Al₂O₃ (Si–Al) was used, under non-isothermal conditions at low temperature range between 380 and 500 °C. Argon gas was used to carry the pyrolyzed gas, and the gas collected in a tedlar bag was analyzed for its behavior. We observed the behavior of major gases (H₂, CH₄, C₂H₄ and C₃H₆, etc.) according to reaction time and temperature. Finally, the effect of reaction conditions on evolved gases from catalytic cracking of polypropylene was analyzed.     

Monitoring of ambient particles and heavy metals in a residential area of Seoul, Korea

In this study, ambient TSP, PM10, and PM2.5 in a residential area located in the northern part of Seoul were monitored every other month for 1 year from April 2005 to February 2006. The monthly average levels of TSP, PM10, and PM2.5 had ranges of 71∼158, 40∼106, and 28∼43 μg/m³, respectively. TSP and PM10 showed highest concentration in April; this seems to be due to Asian dust from China and/or Mongolia. However, the fine particle of PM2.5 showed a relatively constant level during the monitoring period. Heavy metals in PM 10 and PM2.5, such as Cr, As, Cd, Mn, Zn and Pb, were also analysed during the same period. The monthly average concentrations of heavy metal in PM2.5 were Cr:1.9∼22.7 ng/m³; As:0.9∼2.5 ng/m³; Cd: 0.6∼7 ng/m³; Mn:6.1∼22.6 ng/m³; Zn: 38.9∼204.8 ng/m³, and Pb: 21.6∼201.1 ng/m³. For the health risk assessment of heavy metals in ambient particles, excess cancer risks were calculated using IRIS unit risk. As a result, the excess cancer risks of chromium, cadmium, and arsenic were shown to be more than one per million based on the annual concentration of heavy metals, and chromium showed the highest excess cancer risk in ambient particles in Seoul.     

Characterization of metal aerosols in PM10 from urban, industrial, and Asian Dust sources

Metallic elements (As, Be, Ca, Cd, Co, Cr, Fe, K, Mn, Ni, Pb, Sb, Se, and Zn) in PM10 aerosols were determined at urban and industrial sites, which are affected by traffic and residential sources, metallurgical activity, and petrochemical and steel works. The effect of the long-range transported Asian Dust on the metal content of aerosols was also examined. At the urban sampling site, concentrations of As, Cd, Pb, Se, and Zn were assigned to road traffic and combustion sources, Ca and Fe to soil dust sources from long-range transported Asian Dusts, and Cr and Ni to metallurgical sources transported from the nearby industrial complex, based on Principal Component Analysis (PCA). Enhanced Cr and Ni concentrations at the metallurgical industrial site suggest that local emissions from metal-assembly facilities and manufacture of alloys contributed to elevated levels of those metals. We also observed that petrochemical activities contributed to increased levels of Sb and Zn. When Asian Dust events occurred, Ca, Fe, K, and Zn concentrations dramatically increased compared to values without the Asian Dust. Two different types of Asian Dust events were observed. For the Asian Dust event 1 (4/1/2007), the Fe and K concentrations were much higher by a factor of 2–3 than those for the Asian Dust event 2 (3/2/2008), while As, Mn, and Zn concentrations were significantly higher on the Asian Dust event 2. Backward trajectory analysis showed that for the Asian Dust event 2, the air mass had passed over the heavily industrialized zones in China during long-range transport to the current sampling site, suggesting that the As, Mn, and Zn may have originated from industrial sources.     

Background monitoring and long-range transport of atmospheric CFC-11 and CFC-12 at Kosan, Korea

The background concentrations of atmospheric CFC-11 and CFC-12were monitored to assess their impact on stratospheric ozone depletion and global warming from September 1995 to March 1999 at Kosan, Korea, located at eastern margin of the Asian Continent. The concentrations of atmospheric CFC-11 at Kosan have decreased slightly, at a rate of –2.5 pptv yr^-1, over the period in response to the Montreal Protocol. The CFC-12 mixing ratio at Kosan continues to increase in the atmosphere at a rate of 5.7 pptv yr^-1 despite international regulations, because of its extreme atmosphere persistence. Recent trends ofthese two chlorofluorocarbons at Kosan, Korea were concordant with those of the northern hemispheric background monitored unitat Mauna Loa, Hawaii. The maximum seasonal mean mixing ratios of CFC-11 and CFC-12 at Kosan, Korea, were 270±4 pptv inthe spring and 538±9 pptv in the winter, and the corresponding seasonal minima were 267±7 and 529±12 pptv. This occurred in the summer and was due to southeasterlywinds from the northwestern Pacific Ocean. By performing a three-day isentropic backward trajectory analysis, it was shownthat air masses at Kosan, and with the exception of summer, mainly originated from central and northern China. In particular, the mixing ratios of these two contaminant speciesare closely related with their air mass trajectories.     

Polycyclic aromatic hydrocarbons in bulk PM2.5 and size-segregated aerosol particle samples measured in an urban environment

To analyze polycyclic aromatic hydrocarbons (PAHs) at an urban site in Seoul, South Korea, 24-hr ambient air PM_2.5 samples were collected during five intensive sampling periods between November 1998 and December 1999. To determine the PAH size distribution, 3-day size-segregated aerosol samples were also collected in December 1999. Concentrations of the 16 PAHs in the PM_2.5 particles ranged from 3.9 to 119.9 ng m⁻³ with a mean of 24.3 ng m⁻³.An exceptionally high concentration of PAHs(∼120 ng m⁻³) observed during a haze event in December 1999 was likely influenced more by diesel vehicle exhaust than by gasoline exhaust, as well as air stagnation, as evidenced by the low carbon monoxide/elemental carbon (CO/EC) ratio of 205 found in this study and results reported by previous studies. The total PAHs associated with the size-segregated particles showed unimodal distributions. Compared to the unimodal size distributions of PAHs with modal peaks at < 0.12 μm measured in highway tunnels in Los Angeles (Venkataraman and Friedlander, 1994), four- to six-ring PAHs in our study had unimodal size distributions, peaking at the larger size range of 0.28–0.53 μm, suggesting the coagulation of freshly emitted ultrafine particles during transport to the sampling site. Further, the fraction of PAHs associated with coarse particles(> 1.8 μm) increased as the molecular weight of the PAHs decreased due to volatilization of fine particles followed by condensation onto coarse particles.     

Study on Size Distribution of Total Aerosol and Water-Soluble Ions During an Asian Dust Storm Event at Jeju Island, Korea

Soil dust particles transported from loess regions of the Asian continent, called Asian dust, highly influences the air quality of north-eastern Asia and the northern Pacific Ocean. In order to investigate the effects of these dust storms on the chemical composition of atmospheric aerosol particles with different size, measurements of size distributions of total aerosol and major ion species were carried out on Jeju Island, Korea during April 2001. Juju Island was chosen for the study because the levels of emissions of anthropogenic air pollutants are very low. A 5-stage cascade impactor was used to sample size-fractionated aerosol particles. Samples were analyzed for major water-soluble ions using Dionex DX-120 ion chromatograph. The average mass concentration of total aerosol was found to be 24.4 and 108.3 microg m(-3) for non-Asian dust and Asian dust periods, respectively. The total aerosol size distribution, measured during the non-Asian dust period, was bimodal, whereas the coarse particles dominated the size distribution of total aerosol during the Asian dust period. It was found that SO4(2-), NH4+ and K+ were mainly distributed in fine particles, while Cl-, NO3-, Na+, Mg2+ and Ca2+ were in coarse particles. Although SO4(2-) was mainly distributed in fine particles, during the Asian dust period, the concentrations in coarse particles were significantly increased. This indicates heterogeneous oxidation of SO2 on wet surfaces of basic soil dust particles. The NH4+ was found to exist as (NH4)2SO4 in fine particles, with a molar ratio of NH4+ to SO4(2-) of 2.37 and 1.52 for non-Asian dust and Asian dust periods, respectively. Taking into account the proximity of the sampling site to the sea, and the observed chloride depletion, coarse mode nitrate, during the non-Asian dust period, is assumed to originate from the reaction of nitric acid with sodium chloride on the surfaces of sea-salt particles although the chloride depletion was not shown to be large enough to prove this assumption. During the Asian dust period, however, chloride depletion was much smaller, indicating coarse nitrate particles were mainly produced by the reaction of nitric acid with surfaces of basic soil particles. Most chloride and sodium components were shown to originate from sea-salt particles. Asian dust aerosols, arriving at Jeju Island, contained considerable amounts of sea-salt particles as they passed over the Yellow Sea. Ca2+ was shown to be the most abundant species in Asian dust particles.