Meehye Lee

Hydrogen peroxide and organic hydroperoxide in the troposphere: a review

The current knowledge of gas-phase hydrogen peroxide and organic hydroperoxide in the troposphere is reviewed: chemistry, properties, measurement methodology and tropospheric distribution.

Synopsis, transport, and physical characteristics of Asian dust in Korea

Historical records in association with Asian dust events were retrieved from ancient Korean literature, which in conjunction with modern observations, indicate that dust events have occurred most frequently in the springtime during the last two centuries. Recent observations through surface network exhibit that Asian dust took place more often in the western part of the Korean peninsula over the last 20 years. In this study, two dust cases, April 1998 and January 1999, were selected to examine detailed conditions most favorable for dust generation, emission, and transport to Korea and to investigate the effect of dust particles on physical and optical properties of aerosols collected in Seoul. Dust transported to the Korean peninsula is closely linked to dust storms generated in upstream regions of the Yellow River or Manzurian plain, which are known as main source regions. Judged from synoptic conditions for both spring and winter dust events, meteorological settings favorable for dust emission are high surface winds and baroclinic instability at 1.5 km level. A strong wind belt, formed at a 5 km level, expedites dust transport, and this is typically much faster in winter. It was confirmed from a backward trajectory analysis that the air carrying mineral dust particles originated from deserts in central Asia and in 1 day passed through the Korean peninsula during wintertime. The effect of mineral dust on aerosol particles is well depicted in the size-separated number concentrations of aerosols observed in Seoul. In both cases, concentrations of coarse particles larger than 0.82 μm were distinctly enhanced while those of fine particle smaller than 0.5 μm were reduced. The measurements of optical depth also indicate that the atmosphere is more turbid with larger particles during dust events.

Chemical composition and source signature of spring aerosol in Seoul, Korea

The measurement of atmospheric aerosol was made in Seoul during the spring of 1998. The objective of this study was to investigate the chemical characteristics of atmospheric aerosol with an emphasis on the effect of Asian dust. Total suspended particles (TSP) and particles smaller than 10 mm (PM10) were collected during March-

Organic and inorganic compositions of marine aerosols from East Asia: Seasonal variations of water-soluble dicarboxylic acids, major ions, total carbon and nitrogen, and stable C and N isotopic composition

Atmospheric particles were collected for 1 year (2001–2002) at a site Gosan on Jeju Island, South Korea. The samples were analyzed for water-soluble dicarboxylic acids and related compounds using a capillary GC and GC/MS. Total carbon and nitrogen contents, as well as their stable isotopic ratios, were also determined using elemental analyzer (EA) and EA/IR/MS, respectively. Elemental and isotopic analyses were also performed after the HC1 fume treatment of aerosol samples. The results demonstrate that calcium carbonate of dust origin was not a significant component, except for a few dust event samples. Carbonates most likely reacted with acidic species (such as H2SO4, HNO3 and organic acids) in the atmosphere during a long-range transport, and did not contribute to the total aerosol carbon, except for few strong dust episodes that occurred in spring. This study also demonstrates that nitrate and ammonium largely contribute to aerosol nitrogen, and organic nitrogen is a minor component in the Asian aerosols. Acidic aerosols enriched with sulfate likely adsorb NH3 gas that is emitted from soils in Asia whereas mineral dust particles containing carbonate may adsorb HNO3 and volatile organic acids. Homologous series of dicarboxylic acids (C2–C12) including unsaturated structures as well as ketocarboxylic acids (C2–C9) were detected in the aerosol samples with oxalic (C2) acid being the most abundant species followed by malonic (C3) or succinic (C4) acids. Total concentrations of diacids (130–2070 ng m-3) are one or two orders of magnitude greater than those reported for remote marine aerosols in the North Pacific, but are equivalent to those reported for urban aerosols. Very high concentrations of dusts (up to 880 μg m-3) and water- soluble dicarboxylic acids were often observed in early spring. However, their correlation (r = 0.27) is not strong throughout the campaign. Although both mineral dusts and diacids are derived from the Asian continent, they originate from different sources and source regions. Diacids are probably emitted from urban sources in East Asia and produced by secondary photochemical oxidation of their precursors, whereas dusts are derived from the arid interior regions. This study provides evidence for photochemical production of water-soluble organic acids in East Asia and the western North Pacific rim.

Enhancements of hydroperoxides and formaldehyde in biomass burning impacted air and their effect on atmospheric oxidant cycles

Hydrogen peroxide, organic hydroperoxide species, and formaldehyde were measured in the troposphere over the South Atlantic, Brazil, and southern Africa during the NASA Global Tropospheric Experiment (GTE) Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE-A) experiment, an investigation into the cause of an observed seasonal ozone maximum in this region. H2O2 and CH2O concentrations were extremely high, up to 14 and 5 ppbv, respectively, and are the result of direct production in fire plumes as well as secondary photochemical production in the atmosphere. Enhanced hydroperoxide and formaldehyde concentrations have a significant effect in both odd-hydrogen and odd-oxygen cycles in the troposphere. The odd-hydrogen radical production from hydroperoxide and formaldehyde photolysis exceeded that from ozone photolysis at high altitudes. At low altitudes where air was impacted by biomass burning the contribution of these species to odd-hydrogen radical production was comparable to that of O(1D). The fraction of radical production due to H2O2 and CH2O photolysis linearly increased with their concentrations. Odd-hydrogen radical production from hydroperoxides is ∼30% of the total. These species also react with OH and cycle odd-hydrogen from OH to HO2 and CH3O2 radicals. In and near biomass burning plumes, more hydroperoxide and formaldehyde reacted with OH than was photolyzed, and HO2 radical production from H2O2 and CH2O oxidation was also important. Hydroperoxide and formaldehyde from fires together with nitric oxide initiate odd-oxygen production and contribute to new O3 formation. The greatest destruction of odd-oxygen in continental outflows leads to additional photochemical enhancement of the hydroperoxide. Therefore enhanced hydroperoxide and formaldehyde from biomass burning increases the oxidizing capacity of the atmosphere near fires and their high concentrations downwind reflect the stimulated chemistry.

Method for the Collection and HPLC Analysis of Hydrogen Peroxide and Cl and C2 Hydroperoxides in the Atmosphere

Abstract An HPLC (high-performance liquid chromatography) method was developed to quantify hydrogen peroxide, methyl hydroperoxide. Hydroxymethyl hydroperoxide, ethyl hydroperoxide, and peroxyaectic acid in the atmosphere. Gas-phase hydroperoxides are collected in aqueous solution using a continuous-flow glass scrubbing coil and then analyzed by an HPLC postcolumn derivatization system. The detection system is based on fluorescence, produced by the product of the reaction of hydroperoxides with peroxidase and p-hydroxyphenylacetic acid. Reproducibilities are better than 3% for all hydroperoxides in aqueous concentrations of 1 × 10−7–6 × 10−7 M. Detection limits in aqueous concentration are 1.2 × 10−9 M for hydrogen peroxide, 1.5 × 10−9 M for hydroxymethyl hydroperoxide, 2.9 × 10−9 M for methyl hydroperoxide, 16 × 10−9 M for peroxyaectic acid, and 19 × 10−9 M for ethyl hydroperoxide. Corresponding gas-phase detection limits are 5 PPtv for hydrogen peroxide, 7 pptv for hydroxymethyl hydroperoxide, 13 pptv f...

Characteristic behavior of peroxyacetyl nitrate (PAN) in Seoul megacity, Korea

We measured the concentrations of peroxyacetyl nitrate (PAN) and other photochemically reactive species, including O3, NO2, and non-methane hydrocarbons (NMHCs), in the Seoul Metropolitan area (SMA) during May through June in 2004 and 2005. PAN was determined using a fast chromatograph with luminol-based chemiluminescence detection. Mixing ratios of PAN ranged from below the detection limit (0.1ppbv) to 10.4ppbv with an average of 0.8ppbv. O3 concentrations ranged from 0 to 141ppbv. The average PAN/O3 ratio of 0.07 was higher than that observed in cities of Europe and North America (0.02) where control strategies have been enforced to reduce hydrocarbon emissions through extensively reformulated gasoline programs. Strong positive correlations between daily PAN and O3 maxima during the day demonstrate that similar photochemical factors controlled the production of these two chemicals. However, relationships between PAN and its precursors, NO2 and NMHCs, suggest that PAN production was more sensitive to NO2 than NMHCs levels whereas O3 production was limited by the overall availability of NMHCs. It is likely that the compositions of NMHCs in SMA were favorable for PAN production because of the low fractions of oxygenated compounds in automobile fuels. PAN maxima were observed around noon, which was 2-3h earlier than the much broader O3 maxima that occurred in the midafternoon. After reaching the maximum, PAN concentrations rapidly dropped within a few hours, which could be largely due to thermal destruction and to limited production under the typically low NO2 levels that occurred in the early afternoon. The heterogeneous destruction of particulate matter could be an additional sink for PAN in SMA.

HISTORICAL RECORDS OF ASIAN DUST EVENTS (HWANGSA) IN KOREA

The observation of dust events in Korea must have been important through its long history because of its geographical and meteorological setting. Descriptions about dust events were well documented in historical archives, such as Samguk sagi (57 BC–AD 938), Goryeo sa (918–1392), Joseon wangjosillok (1392–1853), and Munhuenbigo (~1776). In this study, records of Asian dust events were compiled from the above historical archives, covering the period of the second to the eighteenth century. These historical records were investigated along with the recent data (1915–2005) of dust event days in Seoul, Korea. The first record was made in AD 174 in Silla during the period of the Three Kingdoms. A dust event, now called hwangsa, was commonly written down as Woo-Tou or Tou-Woo standing for “dustfall” in the historical archives. Asian dust events took place most frequently during spring from March to May and there was almost no occurrence in summer. The main seasonal feature of the historical dust events was found ...

Observations of aerosol-bound ionic compositions at Cheju Island, Korea

To investigate the regional cycle of aerosols and their ionic constituents, three field intensive campaigns were conducted during fall and winter of 1997 and spring of 1998. The concentrations of most ionic species were found to decrease significantly across fall, winter, and spring such that the sum for all cation (and anion) species of each season is computed as: 193 > 96 > 73.7 nequiv m(-3) (and 240 > 104 > 51.5 nequiv m(-3)). To examine the fundamental characteristics of aerosol compositions in the study area, we conducted correlation analysis in various manners. The results indicated that the concentrations of major ionic species were strongly affected by some meteorological parameters including wind speed. It was also seen that relative strengths of correlations between important parameters (e.g., between wind speed and most of major inorganic species) maintain close relationships with the factors associated with the air mass origin. In addition, the results of factor analysis indicated the existence of at least three major sources in the study area which include: sea-salt aerosol, secondary aerosol, and organic aerosol component. The springtime occurrence of unexpectedly low concentrations of most ionic constituents is found to sensitively reflect the influence of the inflow of southeasterly winds that prevailed during spring, while it is not common for that season of the year. Because most of those changes are closely tied with the variabilities in the regional circulation patterns for each measurement period, assessment of the ionic composition in concert with the temporal variations of meteorological conditions provided valuable insights into the source signals of different air masses that passed by the study area.

Stable carbon isotopic compositions of low‐molecular‐weight dicarboxylic acids, oxocarboxylic acids, α‐dicarbonyls, and fatty acids: Implications for atmospheric processing of organic aerosols

Stable carbon isotopic compositions (δ13C) were measured for 23 individual organic species including 9 dicarboxylic acids, 7 oxocarboxylic acids, 1 tricarboxylic acid, 2 α-dicarbonyls, and 4 fatty acids in the aerosols from Gosan background site in East Asia. δ13C values of particle phase glyoxal and methylglyoxal are significantly larger than those previously reported for isoprene and other precursors. The values are consistently less negative in oxalic acid (C2, average −14.1‰), glyoxylic acid (−13.8‰), pyruvic acid (−19.4‰), glyoxal (−13.5‰), and methylglyoxal (−18.6‰) compared to other organic species (e.g., palmitic acid, −26.3‰), which can be explained by the kinetic isotope effects during atmospheric oxidation of pre-aged precursors (e.g., isoprene) and the subsequent gas-particle partitioning after the evaporation of clouds or wet aerosols. The δ13C values of C2 is positively correlated with C2 to organic carbon ratio, indicating that photochemical production of C2 is more pronounced than its degradation during long-range atmospheric transport. The isotopic results also suggest that aqueous phase oxidation of glyoxal and methylglyoxal is a major formation process of oxalic acid via the intermediates such as glyoxylic acid and pyruvic acid. This study provides evidence that organic aerosols are intensively photochemically aged in the western North Pacific rim.