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This study investigated the potential of fine nitrate (NO3− in PM2.5) formation in Seoul Metropolitan Area (SMA) by nighttime dinitrogen pentoxide (N2O5) heterogeneous chemistry during March 16–18, 2016, relatively dry and stagnant early spring days, by intervening N2O5 uptake coefficients (reactive uptake probability, γN2O5) in modeling with WRF-CMAQ. Simulations of a base case and two sensitivity tests with default (Davis et al., 2008), zero and decupled (tenfold) γN2O5 showed that impacts of γN2O5 on NO3− and PM2.5 are sensitive to relative humidity (RH) and sulfate-nitrate-ammonium (SNA) conditions. The base case simulation generally underestimated NO3− and PM2.5 levels in comparison to observations. Even with decupled γN2O5, modeled NO3− and PM2.5 concentrations showed relatively small increases under conditions that RH is relatively low in the range of 20 to 40% and SNA levels are severely underestimated (e.g., lower by one third) in the base case simulation. Comparisons of NO3− and PM2.5 concentrations in SMA between simulations with differently specified γN2O5 indicated that N2O5 heterogeneous chemistry has potential to (1) form additional nitric acid (HNO3), (2) further react with ammonia (NH3) emitted from various sources including agricultural sources outside of SMA urban-core areas, and (3) contribute to NO3− and PM2.5 formation in SMA. Additional modeling and observational studies on heterogeneous N2O5 chemistry are needed to improve our understanding of NO3− and PM2.5 formation and better forecast PM2.5 pollution levels over SMA or other urban areas with abundant nitrogen oxides emissions and ammonia emissions such as agricultural emissions from surrounding areas.

Ozone concentrations in East Asia were simulated using the Community Multi-scale Air Quality (CMAQ) model, and its source contributions were estimated by multiple source–receptor modeling techniques. To study relationships between ozone concentrations and precursor emission sources, three approaches were applied to four months (January, April, July, and October 2009) to represent seasonal characteristics and compare results, with a particular focus on South Korea. Brute force (BF) is a traditional sensitivity analysis method used to estimate model output response to an input change. The high-order decoupled direct method (HDDM), a computational method, is an efficient and accurate alternative to the BF method for sensitivity. The Ozone and Particulate Precursor Tagging Methodology (OPTM) provides contribution information quantified by tracking emissions from selected sources throughout the simulation period. The approaches generally show that most of the receptor regions were substantially influenced by emissions from central China, which is the largest anthropogenic emissions source region in East Asia. Local emissions were still major contributors, especially South Korea and Japan during July 2009. On the other hand, a case study of maximum 8-h ozone concentrations derived from CMAQ–OPTM on April 9 in South Korea shows that the NOx and VOCs emissions from China contributed approximately 82% and 91%, respectively, to maximum 8-h ozone in Region 4 (South Korea) without boundary inflow, which indicates that Chinese emissions are the dominant contributor in this episode. A comparison study of the three approaches shows that HDDM tends to estimate biogenic source contributions lower than that from OPTM in China but similar to OPTM in South Korea and Japan. When comparing the BF method and HDDM, the sensitivity results show a reasonably good agreement during a given period. The location- and time-dependent maximum 8-h ozone isopleths over South Korea as a receptor region created by HDDM suggest that most ozone was being transported from central China, whereas almost no ozone was formed locally during April 2009, and local conditions were heavily VOC limited. On the other hand, local emissions were the dominant contributor during July 2009, and every source region showed a NOx-limited regime, which indicates that ozone concentrations in South Korea strongly depend on NOx emissions during this month.

In this study, we analyzed the chemical composition of fine particulate matter 2.5 μm or less (PM) collected at Incheon, the coastal area in Seoul, Korea every third day from June 2009 to May 2010. Based on the analyzed chemical species in the PM samples, the sources of PM were identified using a positive matrix factorization (PMF). Nine sources of PM were determined from PMF analysis. The major sources of PM were secondary nitrate (25.4%), secondary sulfate (19.0%), motor vehicle 1 (14.8%) with a lesser contribution from industry (8.5%), motor vehicle 2 (8.2%), biomass burning (6.1%), soil (6.1%), combustion and copper production emissions (6.1%), and sea salt (5.9%). From a paired t-test, it was found that yellow sand samples were characterized as having higher contribution from soil sources (p

The objectives of this research were to investigate the accumulation and distribution of Cd and Pb in plant parts and to evaluate the potential problem caused by heavy metals when biofuel is produced by plant seeds cultivated from Cd and Pb contaminated soil. Based on the germination test results, sunflowers were selected as the target plant because of their high germination rate and IC50 compared to other plants. The trends of accumulated amounts and concentrations of Cd and Pb in sunflowers were not identical. The accumulation of Cd in the plant parts was in the order of: seeds > stem > leaves > petals > roots, with the accumulation of Pb: stem > roots > leaves > petals > seeds. Pb did not accumulate in the seeds. Our findings show that there should not be any significant problem producing biofuel from sunflower seeds cultivated in Pb contaminated soil.

We examined the characteristics, sources, and distribution of PM 2.5 and carbonaceous species in particulate samples collected from June 2009 to May 2010 in Incheon, Korea. The average PM 2.5 concentration (41.9 ± 9.0 μg m −3 ) exceeded the annual level set by the United States' National Ambient Air Quality Standards (15 μg m −3 ). The major fraction of PM 2.5 consisted of ionic species (accounting for 38.9 ± 8.8%), such as NO 3 − , SO 4 2− , and NH 4 + , as well as organic carbon (OC) (accounting for 18.9 ± 5.1%). We also analyzed the seasonal variation in PM 2.5 and secondary aerosols such as NO 3 − and SO 4 2− in PM 2.5 . While SO 4 2− concentrations were higher in spring and summer, the concentration of PM 2.5 and NO 3 − were the highest in winter. SO 4 2− concentrations were higher during the spring and summer, but PM 2.5 and NO 3 − were highest during the winter. As an important aerosol indicator, water-soluble organic carbon (WSOC) (mean 4.7 ± 0.8 μg m −3 , 58.9 ± 10.7% of total OC) showed a strong relationship with NO 3 − , SO 4 2− , and SOC ( R 2 = 0.56, 0.67, and 0.65, respectively), which was indicative of favorable conditions for SOC formation during the sampling period. Among the individual organic aerosols measured, n-alkanes, n-alkanoic acids, levoglucosan, and phthalates were major components, whereas PAHs (polycyclic aromatic hydrocarbons), oxy-PAHs, hopanes, and cholestanes were minor components. The concentration of organic compounds during smoggy periods was higher than during non-event periods. The n-alkane and n-alkanoic acid species during the smoggy periods were 10–14 times higher than during the normal period. Using principal component analysis coupled with multiple linear regression analysis, we identified the primary sources of PM 2.5 to be motor vehicle/sea salt, secondary organic aerosols, combustion, biogenic/meat cooking, and soil sources.

This study aims to identify the characteristics of soil in Mongolia, one of the major Asian dust sources that influence the Korean Peninsula. Soil particle size was analyzed and the result shows that sand (57.5~97.3%) was identified prominently in most regions, followed by silt (2.5~34.7%) and clay (0.0~7.8%). Soil pH of the covered regions were in the range 7.1~10.1, either weak alkaline or strong alkaline. Analysis of ion species in the soil samples exhibited that (), (), and () were detected more in the soil than other species such as (), (), (), (), and (). As for heavy metal content in the soil, concentrations of soil-borne metals including Fe, Al, Ca, Mg, and K tended to be high, while metals that come from manmade sources Pb, Cd, Cr, V, and Ni were remarkably low. The concentration of organic carbon (OC) was relatively high at , while elemental carbon (EC), directly released in the process of fossil fuel combustion, was not detected at all or found in very small amounts. The result indicates that pollution from manmade sources scarcely occurred. The analysis results from this study may contribute to improving modeling accuracy by providing input data for Asian dust prediction models, and be used as base data for determining the process of physiochemical transformation of Asian dust during long-range transport.

This study was carried out to identify possible sources and to estimate their contribution to total suspended particle (TSP) organic aerosol (OA) contents. A total of 120 TSP and PM2.5 samples were collected simultaneously every third day over a one-year period in urban area of Incheon, Korea. High concentration in particulate matters (PM) and its components (NO3−, water soluble organic compounds (WSOCs), and n-alkanoic acids) were observed during the winter season. Among the organics, n-alkanes, n-alkanoic acids, levoglucosan, and phthalates were major components. Positive matrix factorization (PMF) analysis identified seven sources of organic aerosols including combustion 1 (low molecular weight (LMW)-polycyclic aromatic hydrocarbons (PAHs)), combustion 2 (high molecular weight (HMW)-PAHs), biomass burning, vegetative detritus (n-alkane), secondary organic aerosol 1 (SOA1), secondary organic aerosol 2 (SOA2), and motor vehicles. Vegetative detritus increased during the summer season through an increase in biogenic/photochemical activity, while most of the organic sources were prominent in the winter season due to the increases in air pollutant emissions and atmospheric stability. The correlation factors were high among the main components of the organic carbon (OC) in the TSP and PM2.5. The results showed that TSP OAs had very similar characteristics to the PM2.5 OAs. SOA, combustion (PAHs), and motor vehicle were found to be important sources of carbonaceous PM in this region. Our results imply that molecular markers (MMs)-PMF model can provide useful information on the source and characteristics of PM.

In response to increasing trends in sulfur deposition in Northeast Asia, three countries in the region (China, Japan, and Korea) agreed to devise abatement strategies. The concepts of critical loads and source-receptor (S-R) relationships provide guidance for formulating such strategies. Based on the Long-range Transboundary Air Pollutants in Northeast Asia (LTP) project, this study analyzes sulfur deposition data in order to optimize acidic loads over the three countries. The three groups involved in this study carried out a full year (2002) of sulfur deposition modeling over the geographic region spanning the three countries, using three air quality models: MM5-CMAQ, MM5-RAQM, and RAMS-CADM, employed by Chinese, Japanese, and Korean modeling groups, respectively. Each model employed its own meteorological numerical model and model parameters. Only the emission rates for SO(2) and NO(x) obtained from the LTP project were the common parameter used in the three models. Three models revealed some bias from dry to wet deposition, particularly the latter because of the bias in annual precipitation. This finding points to the need for further sensitivity tests of the wet removal rates in association with underlying cloud-precipitation physics and parameterizations. Despite this bias, the annual total (dry plus wet) sulfur deposition predicted by the models were surprisingly very similar. The ensemble average annual total deposition was 7,203.6 ± 370 kt S with a minimal mean fractional error (MFE) of 8.95 ± 5.24 % and a pattern correlation (PC) of 0.89-0.93 between the models. This exercise revealed that despite rather poor error scores in comparison with observations, these consistent total deposition values across the three models, based on LTP group's input data assumptions, suggest a plausible S-R relationship that can be applied to the next task of designing cost-effective emission abatement strategies.