The absorption enhancement of black carbon (BC) was studied at the Jiangxinzhou site of the Nanjing Bureau of Meteorology (Nanjing, China), using the combination of a thermal denuder (TD) and a three-wavelength, photo acoustic soot spectrometer (PASS-3). With increase TD temperature, the amount of volatile components gradually decreased. While at > 250 °C, most organic substances and inorganic matter, whose contribution to light absorption was approximately 34%—had been volatilized. In the summer of 2014, the average BC absorption enhancement factor (Eabs) was 1.52 ± 0.57, at Jiangxinzhou site, which may have been significantly affected by locally sourced pollutants. Changes in wind direction and air mass source were found to influence the BC Eabs. Concentration of nitrate and BC, mixing ratio of NOx were found to play important roles in BC absorption enhancement, implying the impact from traffic emissions. The photochemical aging (PCA) has not a certain effect on the light absorption of BC. During the period of the strict emission reduction measures, human activity including vehicle emissions and cooking source contributed to enhance BC absorption. Through the analyses and calculations, it was found that the contributions at 405 nm made by BC, coatings and brown carbon, were 62.7%, 32.0% and 5.3%, respectively. Their contribution may be affected by the emission reduction measures. Traffic emissions, with high volatile nitrate and organic matter, may be responsible for absorption enhancement induced by the coatings.
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