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DOI	10.5194/acp-19-1491-2019
	Viscosities; diffusion coefficients; and mixing times of intrinsic fluorescent organic molecules in brown limonene secondary organic aerosol and tests of the Stokes-Einstein equation
	Ullmann D.A.; Hinks M.L.; MacLean A.M.; Butenhoff C.L.; Grayson J.W.; Barsanti K.; Jimenez J.L.; Nizkorodov S.A.; Kamal S.; Bertram A.K.
发表日期	2019
ISSN	16807316
起始页码	1491
结束页码	1503
卷号	19 期号:3
英文摘要	Viscosities and diffusion rates of organics within secondary organic aerosol (SOA) remain uncertain. Using the bead-mobility technique, we measured viscosities as a function of water activity (aw) of SOA generated by the ozonolysis of limonene followed by browning by exposure to NH3 (referred to as brown limonene SOA or brown LSOA). These measurements together with viscosity measurements reported in the literature show that the viscosity of brown LSOA increases by 3-5 orders of magnitude as the aw decreases from 0.9 to approximately 0.05. In addition, we measured diffusion coefficients of intrinsic fluorescent organic molecules within brown LSOA matrices using rectangular area fluorescence recovery after photobleaching. Based on the diffusion measurements, as the aw decreases from 0.9 to 0.33, the average diffusion coefficient of the intrinsic fluorescent organic molecules decreases from 5.5×10-9 to 7.1×10-13cm2s-1 and the mixing times of intrinsic fluorescent organic molecules within 200nm brown LSOA particles increases from 0.002 to 14s. These results suggest that the mixing times of large organics in the brown LSOA studied here are short (<1h) for aw and temperatures often found in the planetary boundary layer (PBL). Since the diffusion coefficients and mixing times reported here correspond to SOA generated using a high mass loading (∼1000μgm-3), biogenic SOA particles found in the atmosphere with mass loadings ≤ 10μgm-3 are likely to have higher viscosities and longer mixing times (possibly 3 orders of magnitude longer). These new measurements of viscosity and diffusion were used to test the accuracy of the Stokes-Einstein relation for predicting diffusion rates of organics within brown LSOA matrices. The results show that the Stokes-Einstein equation gives accurate predictions of diffusion coefficients of large organics within brown LSOA matrices when the viscosity of the matrix is as high as 102 to 104Pas. These results have important implications for predicting diffusion and mixing within SOA particles in the atmosphere. © Author(s) 2019.
语种	英语
scopus关键词	aerosol; boundary layer; diffusion; equation; mixing; viscosity
来源期刊	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/144672
作者单位	Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada; Department of Chemistry, University of California, Irvine, CA 92697, United States; Department of Physics, Portland State University, Portland, OR, United States; Cooperative Institute for Research in the Environmental Sciences, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, United States; Department of Chemical and Environmental Engineering, Center for Environmental Research and Technology, University of California, Riverside, CA V6T 1Z1, United States
推荐引用方式 GB/T 7714	Ullmann D.A.,Hinks M.L.,MacLean A.M.,et al. Viscosities; diffusion coefficients; and mixing times of intrinsic fluorescent organic molecules in brown limonene secondary organic aerosol and tests of the Stokes-Einstein equation[J],2019,19(3).
APA	Ullmann D.A..,Hinks M.L..,MacLean A.M..,Butenhoff C.L..,Grayson J.W..,...&Bertram A.K..(2019).Viscosities; diffusion coefficients; and mixing times of intrinsic fluorescent organic molecules in brown limonene secondary organic aerosol and tests of the Stokes-Einstein equation.Atmospheric Chemistry and Physics,19(3).
MLA	Ullmann D.A.,et al."Viscosities; diffusion coefficients; and mixing times of intrinsic fluorescent organic molecules in brown limonene secondary organic aerosol and tests of the Stokes-Einstein equation".Atmospheric Chemistry and Physics 19.3(2019).