Characteristics of carbon species and its spatio-temporal trends in ambient fine particles (PM2.5) measured in Seoul, Korea

Abstract

Background

The carbonaceous aerosols are major contributors to ambient fine particles (PM2.5) and play a significant role in climate change. Carbon species are substantially linked to increases in respiratory and cardiovascular diseases. Despite various studies, most of the atmospheric monitoring in Asia started in the late 2000s and the obtained data lacked long-term analysis. Futhermore, high-resolution time-scale research is required for more detailed analysis. For a deeper understanding of aerosols, this study is focused on the changes in carbon species in the air of Seoul by year to hour unit.

Methods

Carbonaceous species in the PM2.5 sampled at Bulgwang and Yeongeon were analyzed. Both sites are located in commercial and residential areas in Seoul, Korea. In addition to 24-hour integrated filter sampling at both sites, realtime online measurements were conducted at Bulgwang. A long term investigation of the Yeongeon data (2003～2015) and 1-year intercomparison study with Bulgwang data were done. The concentrations of PM2.5, organic carbon (OC), elemental carbon (EC) and water soluble organic carbon (WSOC) in atmosphere were measured. Also, primary organic carbon (POC) and secondary organic carbon (SOC) were estimated using EC tracer model applied with Deming regression method. For analysis of long-range transported carbon aerosols, PSCF (back trajectory analysis) was used, which can track the potential source of air pollution.

Results

The data collected at two sites were highly correlated. Overall, slight decline of concentrations on yearly basis were observed in PM2.5 and carbonaceous species, OC, EC, SOC, and POC. Among the carbonaceous constituents of PM2.5, OC covered the largest portion, POC was the second and EC, SOC concentrations were similar to each other on both sites. From hourly analysis, temporal characteristics of SOC and POC show good agreement with those of OC and EC respectively. Apparent increase of SOC and high correlation of EC with rush hour in winter were observed. Unlike the general tendency, SOC showed the highest value in winter in both sites. In the analysis of PM2.5, OC, and EC, the increase in the concentration of commuting time and the increase in concentration due to the atmospheric mixing and decline at night were observed. Especially, the ratio of POC was high and EC was associated with commuting time. The concentration patterns of weekday and weekend were similar but the concentration level of weekday was higher than of weekend. According to the PSCF results, the carbonaceous aerosol of Seoul are mainly influenced by the air parcel of the east coast of China and Japan in summer, while the air parcel from the continent including Gobi desert, Mongolia and Hebei province of China are presented to affect in autumn and winter.

Conclusions

It is thought that the local sources of carbon species and long-range transported sources are important contributors to PM2.5 and carbon species concentration in the air of Seoul. In order to reduce the PM2.5 concentration, the separated control strategy for local-originated aerosol and long-range transported is suggested. For valuable steps to improve the air quality, it is requested that the cooperation of neighboring countries should be induced and precise emission patterns should be investigated as well.