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Simultaneous measurements of gaseous species and fine-mode, particulate inorganic components were performed at the University of Seoul, Seoul in Korea. In the simultaneous measurements, a certain level of nitrous acid (HONO) was observed in the gas-phase, indicating possible heterogeneous HONO production on the surface of the ambient aerosols. On the other hand, high particulate nitrite (NO2−) concentrations of 1.41(±2.26)μg/m3 were also measured, which sometimes reached 18.54μg/m3. In contrast, low HONO-to-NO2 ratios of 0.007(±0.006) were observed in Seoul. This indicates that a significant fraction of HONO is dissolved in atmospheric aerosols. Around the Seoul site, sufficient alkalinity may have been provided to the atmospheric aerosols from the excessive presence of NH3 in the gas-phase. Due to the alkaline particulate conditions (defined in this study as a particle pH >∼3.29), the HONO molecules produced at the surface of the atmospheric aerosols appeared to have been converted into particulate nitrite, thereby preventing their further participation in the atmospheric O3/NOy/HOx photochemical cycles. It was estimated that a minimum average of 65% of HONO was captured by alkaline, anthropogenic, urban particles in the Seoul measurements. [Copyright &y& Elsevier]

In this study, we investigate the physio-chemical and optical properties of Asian spring continental outflow and its relation to synoptic transport patterns. Ground-based highly time-resolved measurements of aerosol chemical and physical properties, and lidar measurements of aerosol vertical distributions at Gosan, Korea during ABC-EAREX2005 have been analyzed. Two selected cases, based on PM10 and PM2.5 mass concentrations, indicate that pollution-dominant airmass preceded by the appearance of a major mineral dust plume with about 12h time-lag. At the ground level, pollution aerosol components (NO3 −, SO4 2−, and NH4 +) showed distinct peaks first and the enhancement of soil components (Ca2+) appeared approximately 12h later. Although lidar measurements reveal that spherical pollution particles were observed near the surface prior to a major plume of non-spherical mineral dust, elevated dust layers were simultaneously observed in the free troposphere overlying the ground-level pollution plume. Chemical transport model simulations of the horizontal distributions of dust and sulfate aerosols illustrate well the pollution plume preceding the dust-laden airmass. Backward trajectory and NCAR/PSU MM5 analysis show that the preceding pollution plume and following dust plume were consecutively transported under fast northwesterly/northerly winds formed between anti-cyclonic and cyclonic flows at the ground level. [Copyright &y& Elsevier]

A formal intercomparison of fine particle elemental (black) carbon is conducted involving three real-time semi-continuous measurement systems. Two-hourly interval time-resolved measurements of organic carbon (OC) and elemental carbon (EC) were performed at the Gosan site, Korea during Atmospheric Brown Clouds–East Asian Regional Experiment 2005 (ABC-EAREX2005) campaign. They were operated by the same semi-continuous field carbon instruments of Sunset Laboratory (thermal optical transmittance) in PM2. 5 particulate. However, their thermal protocols (four and two steps for OC and five and two steps for EC) were different. The co-located 1min black carbon (BC) concentrations were compared by an Aethalometer for an intercomparison study. As a result, the poor R 2 of OC between two different temperature protocols suggested that OC can be significantly more biased by the slight differences of maximum temperature (870 and 840°C) and a number of temperature steps (four steps and two steps) with their hold times. However, EC that is a smaller fraction of total carbon (TC) shows the good agreement between two different protocols, which are under a mixture of 2% O2 and 98% He in six temperature steps and two temperature steps as max as 900 and 880°C with the slope of 1. 05±0. 15 (R 2 of 0. 98). The different slopes between EC and BC, which show the range of 1. 23–1. 61, demonstrate the variability of the attenuation coefficient of the BC particulate. [Copyright &y& Elsevier]