Carbonaceous Aerosol Measurements at Coastal, Urban, and Inland Sites in Central Taiwan

Abstract

The concentrations of elemental carbon (EC) and organic carbon (OC) of particulate matter (PM)_2.5 were investigated at coastal, urban, and inland sites in central Taiwan during October 1999 and March 2000, and the carbon contents were analyzed using a total organic carbon analyzer (TOC). The results showed that the average EC concentrations at the various sites were from 2.7–4.4 μ g/m³, while the mean OC concentrations were from 6.9–12.3 μ g/m³. Both higher EC and OC levels were found in inland areas. Good correlations of OC and EC were found in coastal and urban areas, indicating that OC was mainly from the primary combustion emissions, whereas OC was weakly correlated with EC at the inland sites, suggesting that the contributions of OC were unrelated combustion sources (i.e., secondary organic carbon). The optimal Deming regression was used to estimate the ratio of OC/EC, leading to calculate the amount of secondary organic aerosols in this study. On average, secondary organic carbon constituted 13%–48% of the total organic carbon for PM_2.5 with high levels observed in inland areas. Moreover, higher secondary OC concentration was observed at low wind speed, high relative humidity and high oxidants sum (O₃ + NO₂) levels atmosphere.

Keywords:

• organic carbon
• elemental carbon
• secondary organic carbon
• optimal Deming regression
• OC/EC

Acknowledgement

The authors would like to thank the Environmental Protection Administration and the National Science Council of the Republic of China for financially supporting this research under Contract Nos. EPA-89-FA11-0-231 and NSC-89-EPA-Z-005-003.

Notes

¹Carbon is the summation of elemental carbon and organic carbon particulates.

² Cao et al. (2004).

³Molnár et al. (1999).

⁴ Park et al. (2001).

⁵ Liu et al. (2005).

⁶ Andréa et al. (2001).

⁷ Tanner et al. (2004).

⁸ Lin and Tai (2001).

⁹This study.

¹This study.

² Cao et al. (2004).

³ Na et al. (2004).

⁴ Russell and Allen (2004).

⁵ Lin and Tai (2001).