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Characteristics of Organic Carbon and Elemental Carbon in Atmospheric Aerosols in the Urban Area in Beibei, a Suburb of Chongqing

Category: Aerosol and Atmospheric Chemistry

Article In Press
DOI: 10.4209/aaqr.2017.11.0450
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Xiaole Peng1, Qingju Hao1, Tianxue Wen2, Dongsheng Ji2, Zirui Liu2, Yuesi Wang2, Xinhua He1, Xiaoxi Li1, Changsheng Jiang 1

  • 1 Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, Chongqing 400715, China
  • 2 State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China

Highlights

SOC concentration was estimated by the method of OC/EC ratio.
OC showed a “bi-modal” size distribution, while EC showed a “Uni-modal”. Relationships among meteorological factors and OC or EC are reported.
Concentration of OC and EC are mainly concentrated in the fine particle.
Beibei aerosol pollution mainly came from vehicle exhaust and biomass combustion.


Abstract

To investigate the pollutive characteristics of atmospheric carbonaceous aerosols in Beibei District, a suburb of Chongqing Municipal City, graded aerosol samples were continuously collected by cascade impactors over one year, from March 2014 to February 2015. Carbonaceous aerosols, including organic carbon (OC) and elemental carbon (EC), were detected by a DRI 2001A carbon analyzer. The results showed that the average annual concentrations of OC and EC in the PM2.1 were 16.3 ± 7.6 and 1.8 ± 0.7 µg m–3, and in the PM9.0 were 25.0 ± 9.6 and 3.2 ± 1.2 µg m–3, respectively. On the one hand, a more seasonal distribution of OC concentrations appeared in the PM2.1 (winter > spring > summer > autumn) than in the PM9.0 (winter ≈ spring ≈ summer > autumn); furthermore, whereas the OC significantly positively correlated with wind speed for both the PM2.1 (P < 0.05) and the PM9.0 (P < 0.01), it was negatively correlated with relative humidity (P < 0.05) for the latter. On the other hand, both the PM2.1 and the PM9.0 exhibited a more seasonal distribution of EC concentrations (winter > spring > summer > autumn), and the EC in the PM2.1 significantly negatively correlated with temperature (P < 0.05). Additionally, both the OC and the EC were concentrated mainly in the fine particles (< 2.10 µm), and the size distributions of the OC in all four seasons displayed a bi-modal pattern that peaked in the size ranges of 0.43–0.65 µm (for fine particles) and 4.7–5.8 µm (for coarse particles), whereas the EC displayed a uni-modal pattern that peaked in the size range of 4.7–5.8 µm (for coarse particles). Furthermore, the correlations between the OC and the EC were analyzed, and the SOC (secondary organic carbon) in the PM2.1 was estimated using the primary OC/EC ratio. It was found that the OC highly significantly correlated with the EC (P < 0.01), with the average annual concentration of the SOC being 6.3 ± 5.9 µg m–3, which accounted for 33.5 ± 22.6% of the OC. Analyzing the sources of the pollutive atmospheric aerosol in Beibei further demonstrated that it mainly originated in biomass burning, gasoline-vehicle exhaust, and coal combustion.

Keywords

Organic carbon Elemental carbon Size distribution Seasonal patterns Atmospheric aerosol


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