Effect of ambient humidity on the light absorption amplification of black carbon in Beijing during January 2013. (January 2016)

• Record Type: Journal Article
• Authors: Wu, Yunfei; Zhang, Renjian; Tian, Ping; Tao, Jun; Hsu, S.-C.; Yan, Peng; Wang, Qiyuan; Cao, Junji; Zhang, Xiaoling; Xia, Xiangao
• Is Part Of: Atmospheric environment. Volume 124:Part B(2016)
• Page Start: 217
• Page End: 223
• Publication Date: 2016-01
• Subjects: Haze -- Black carbon -- Light absorption -- Ambient humidity; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2015.04.041
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Black carbon (BC) and its mixing state were measured with a ground-based single particle soot photometer in urban Beijing during the extremely polluted winter of 2013. Up to 70 ± 14% of the BC-containing particles were thickly-coated during periods of haze, compared to 37 ± 9% on non-hazy days. The thickly-coated number fraction (NFBC-thick ) increased with increasing BC, reaching a plateau at ∼80–90% when BC concentrations were ≥15 μg m −3 and visibility was ≤2 km. Regional inflows brought more aged, highly thickly-coated BC to Beijing during haze. The absorption coefficient showed a distinct linear correlation with BC concentration; the mass absorption efficiency (MAE) of BC was acquired, with an overall mean of 4.2 ± 0.01 m 2 g −1 at 870 nm. The MAE of BC amplified with increasing ambient relative humidity. This was largely explained by the increase in NFBC-thick, which was likely due to the enhanced production of secondary aerosol under humid conditions. Highlights: BC concentrations and mixing states were investigated using an SP2 in urban Beijing. BC fraction in PM2.5 decreased during haze though its concentrations increased. The number fraction of thickly-coated BC increased significantly during haze periods. The light absorption of BC was amplified in response to the increasing ambient RH.