Pollution characteristics of organic and elemental carbon in PM2.5 in Xiamen city, China

Abstract

<p>Xiamen, located on the southeastern coastal line of China, is undergoing rapid urbanization and industrialization, so its air quality has a trend of degradation. However, studies on level, temporal and spatial changes of fine particles (PM_2.5) and their carbonaceous fractions are scarce. In this article, abundance, sources, seasonal and spatial variations, distribution of organic carbon (OC) and elemental carbon (EC) in PM_2.5, were studied at suburban, urban and industrial sites in Xiamen during four season-representative months in 2009&ndash;2010. PM_2.5 samples were collected with middle volume sampler and were analyzed for OC and EC with thermal optical transmittance (TOT) method. Results showed that the annual average PM_2.5 concentrations were 63.88&ndash;74.80 &mu;g/m³ at three sites. While OC and EC concentrations were in the range of 15.81&ndash;19.73 &mu;g/m³ and 2.74&ndash;3.49 &mu;g/m³, respectively, and clearly presented the summer minima and winter maxima in this study. The carbonaceous aerosol accounted for 42.8%&ndash;47.3% of the mass of PM_2.5. The annual average of secondary organic carbon (SOC) concentrations in Xiamen were 9.23&ndash;11.36 &mu;g/m³, accounting for approximately 56% of OC. Strong correlations between OC and EC was found in spring (<em>R</em>² = 0.50) and autumn (<em>R</em>² = 0.73), suggesting that there were similar emission and transport processes for carbonaceous aerosols in these two seasons, while weak correlations were found in summer (<em>R</em>² = 0.33) and winter (<em>R</em>² = 0.41). The OC/EC ratios in PM_2.5 varied from 2.1 to 8.7 with an annual average of 5.7, indicating that vehicle exhaust, coal smoke and biomass burning were main source apportionments of carbonaceous fractions in Xiamen.</p><!-- articleText --