title: Markedly enhanced absorption and direct radiative forcing of black carbon under polluted urban environments.
abstract: Black carbon (BC) exerts profound impacts on air quality and climate because of its high absorption cross-section over a broad range of electromagnetic spectra, but the current results on absorption enhancement of BC particles during atmospheric aging remain conflicting. Here, we quantified the aging and variation in the optical properties of BC particles under ambient conditions in Beijing, China, and Houston, United States, using a novel environmental chamber approach. BC aging exhibits two distinct stages, i.e., initial transformation from a fractal to spherical morphology with little absorption variation and subsequent growth of fully compact particles with a large absorption enhancement. The timescales to achieve complete morphology modification and an absorption amplification factor of 2.4 for BC particles are estimated to be 2.3 h and 4.6 h, respectively, in Beijing, compared with 9 h and 18 h, respectively, in Houston. Our findings indicate that BC under polluted urban environments could play an essential role in pollution development and contribute importantly to large positive radiative forcing. The variation in direct radiative forcing is dependent on the rate and timescale of BC aging, with a clear distinction between urban cities in developed and developing countries, i.e., a higher climatic impact in more polluted environments. We suggest that mediation in BC emissions achieves a cobenefit in simultaneously controlling air pollution and protecting climate, especially for developing countries.
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China;
authors.forename: Jianfei
authors.initials: J
authors.lastname: Peng
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China; renyi-zhang@tamu.edu minhu@pku.edu.cn mjmolina@ucsd.edu.
authors.forename: Min
authors.initials: M
authors.lastname: Hu
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China; Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843;
authors.forename: Song
authors.initials: S
authors.lastname: Guo
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China;
authors.forename: Zhuofei
authors.initials: Z
authors.lastname: Du
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China;
authors.forename: Jing
authors.initials: J
authors.lastname: Zheng
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China;
authors.forename: Dongjie
authors.initials: D
authors.lastname: Shang
authors.affiliation: Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843;
authors.forename: Misti
authors.initials: M
authors.lastname: Levy Zamora
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China;
authors.forename: Limin
authors.initials: L
authors.lastname: Zeng
authors.affiliation: Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843;
authors.forename: Min
authors.initials: M
authors.lastname: Shao
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China;
authors.forename: Yu-Sheng
authors.initials: YS
authors.lastname: Wu
authors.affiliation: Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843;
authors.forename: Jun
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125;
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843;
authors.forename: Crystal R
authors.initials: CR
authors.lastname: Glen
authors.affiliation: Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843;
authors.forename: Donald R
authors.initials: DR
authors.lastname: Collins
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093 renyi-zhang@tamu.edu minhu@pku.edu.cn mjmolina@ucsd.edu.
authors.forename: Mario J
authors.initials: MJ
authors.lastname: Molina
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China; Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843; renyi-zhang@tamu.edu minhu@pku.edu.cn mjmolina@ucsd.edu.
authors.forename: Renyi
authors.initials: R
authors.lastname: Zhang
mesh_terms: D000327:Adsorption; D000393:Air Pollutants / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D002681:China; D008956:Models, Chemical; D013781:Texas; D014506:Urban Renewal
chemical_list: D000393:Air Pollutants; D002244:Carbon
keywords: absorption; air quality; black carbon; climate; radiative forcing