title: Light absorption enhancement of black carbon from urban haze in Northern China winter.
abstract: Atmospheric black carbon (BC) is an important pollutant for both air quality and Earth's energy balance. Estimates of BC climate forcing remain highly uncertain, e.g., due to the mixing with non-absorbing components. Non-absorbing aerosols create a coating on BC and may thereby act as a lens which may enhance the light absorption. However, this absorption enhancement is poorly constrained. To this end a two-step solvent dissolution protocol was employed to remove both organic and inorganic coatings, and then investigate their effects on BC light absorption. Samples were collected at a severely polluted urban area, Jinan, in the North China Plain (NCP) during February 2014. The BC mass absorption cross-section (MAC) was measured for the aerosol samples before and after the solvent-decoating treatment, and the enhancement of MAC (EMAC) from the coating effect was defined as the ratio. A distinct diurnal pattern for the enhancement was observed, with EMAC1.3 ± 0.3 (1 S.D.) in the morning, increasing to 2.2 ± 1.0 in the afternoon, after that dropping to 1.5 ± 0.8 in the evening-night. The BC absorption enhancement primarily was associated with urban-scale photochemical production of nitrate and sulfate aerosols. In addition to that, regional-scale haze plume with increasing sulfate levels strengthened the absorption enhancement. These observations offer direct evidence for an increased absorption enhancement of BC due to severe air pollution in China.
authors.affiliation: Environmental Research Institute, Shandong University, Jinan 250100, China; Collaborative Innovation Center of Climate Change, Jiangsu Province, China. Electronic address: bingchen@sdu.edu.cn.
authors.forename: Bing
authors.initials: B
authors.lastname: Chen
authors.affiliation: Environmental Research Institute, Shandong University, Jinan 250100, China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Bai
authors.affiliation: Environmental Research Institute, Shandong University, Jinan 250100, China.
authors.forename: Xinjuan
authors.initials: X
authors.lastname: Cui
authors.affiliation: Environmental Research Institute, Shandong University, Jinan 250100, China. Electronic address: jmchen@sdu.edu.cn.
authors.forename: Jianmin
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Environmental Science and Analytical Chemistry (ACES) and the Bolin Centre for Climate Research, Stockholm University, SE-10691 Stockholm, Sweden.
authors.forename: August
authors.initials: A
authors.lastname: Andersson
authors.affiliation: Department of Environmental Science and Analytical Chemistry (ACES) and the Bolin Centre for Climate Research, Stockholm University, SE-10691 Stockholm, Sweden.
authors.forename: Örjan
authors.initials: Ö
authors.lastname: Gustafsson
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000393:Air Pollutants / Q000032:analysis / Q000737:chemistry*; D000397:Air Pollution / Q000032:analysis / Q000706:statistics & numerical data; D002244:Carbon / Q000032:analysis; D002681:China; D002980:Climate; D004784:Environmental Monitoring; D009566:Nitrates; D012621:Seasons; D053260:Soot / Q000032:analysis / Q000737:chemistry*; D013431:Sulfates; D013472:Sunlight
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D009566:Nitrates; D053260:Soot; D013431:Sulfates; D002244:Carbon
keywords: Aerosol mixing states; Black carbon; Lens effect; Radiative absorption; Urban air pollution