scholarly journals Relative humidity-dependent viscosity of secondary organic material from toluene photo-oxidation and possible implications for organic particulate matter over megacities

2016 ◽  
Author(s):  
M. Song ◽  
P. F. Liu ◽  
S. J. Hanna ◽  
R. A. Zaveri ◽  
K. Potter ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Relative Humidity ◽  
Diffusion Coefficients ◽  
Organic Material ◽  
Organic Molecules ◽  
Mixing Times ◽  
Organic Particulate Matter ◽  
Photo Oxidation ◽  
Diffusion Rates ◽  
And Diffusion

Abstract. To improve predictions of air quality, visibility, and climate change, knowledge of the viscosities and diffusion rates within organic particulate matter consisting of secondary organic material (SOM) is required.Most qualitative and quantitative measurements of viscosity and diffusion rates within organic particulate matter have focused on SOM particles generated from biogenic VOCs such as α-pinene and isoprene. In this study, we quantify the relative humidity (RH)-dependent viscosities at 295 ± 1 K of SOM produced by photo-oxidation of toluene, an anthropogenic VOC. The viscosities of toluene-derived SOM were 2 × 10−1 to ∼6 × 106 Pa·s from 30 to 90 % RH, and greater than ~2 × 108 Pa·s (similar to or greater than the viscosity of tar pitch) for RH ≤ 17 %. These viscosities correspond to Stokes-Einstein-equivalent diffusion coefficients for large organic molecules of ~2 × 10−15 cm2·s−1 for 30 % RH, and lower than ~3 × 10−17 cm2·s−1 for RH ≤ 17 %. Based on these estimated diffusion coefficients, the mixing time of large organic molecules within 200 nm toluene-derived SOM particles is 0.1–5 hr for 30 % RH, and higher than ~100 hr for RH ≤ 17 %. These results were used, as a first-order approximation, to estimate if organic particulate matter will be in well-mixed over the world's top 15 most populous megacities. If the organic particulate matter in the megacities is similar to the toluene-derived SOM in this study, in Kolkata, Istanbul, Dhaka, Tokyo, Shanghai, and Mumbai, mixing times in organic particulate matter during extended periods of the year will be very short, and well-mixed particles can be assumed. On the other hand, the mixing times of large organic molecules in organic particulate matter in Delhi, Beijing, Mexico City, Cairo, and Karachi may be long and the particles may not be well-mixed in the afternoon (3:00–5:00 local time) during certain times of the year.

scholarly journals Relative humidity-dependent viscosity of secondary organic material from toluene photo-oxidation and possible implications for organic particulate matter over megacities

2016 ◽  
Vol 16 (14) ◽  
pp. 8817-8830 ◽  
Author(s):  
Mijung Song ◽  
Pengfei F. Liu ◽  
Sarah J. Hanna ◽  
Rahul A. Zaveri ◽  
Katie Potter ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Relative Humidity ◽  
Diffusion Coefficients ◽  
Organic Material ◽  
Organic Molecules ◽  
Mixing Times ◽  
Organic Particulate Matter ◽  
Photo Oxidation ◽  
Diffusion Rates ◽  
And Diffusion

Abstract. To improve predictions of air quality, visibility, and climate change, knowledge of the viscosities and diffusion rates within organic particulate matter consisting of secondary organic material (SOM) is required. Most qualitative and quantitative measurements of viscosity and diffusion rates within organic particulate matter have focused on SOM particles generated from biogenic volatile organic compounds (VOCs) such as α-pinene and isoprene. In this study, we quantify the relative humidity (RH)-dependent viscosities at 295 ± 1 K of SOM produced by photo-oxidation of toluene, an anthropogenic VOC. The viscosities of toluene-derived SOM were 2  ×  10−1 to  ∼  6  ×  106 Pa s from 30 to 90 % RH, and greater than  ∼  2  ×  108 Pa s (similar to or greater than the viscosity of tar pitch) for RH  ≤  17 %. These viscosities correspond to Stokes–Einstein-equivalent diffusion coefficients for large organic molecules of  ∼  2  ×  10−15 cm2 s−1 for 30 % RH, and lower than  ∼  3  ×  10−17 cm2 s−1 for RH  ≤  17 %. Based on these estimated diffusion coefficients, the mixing time of large organic molecules within 200 nm toluene-derived SOM particles is 0.1–5 h for 30 % RH, and higher than  ∼  100 h for RH  ≤  17 %. As a starting point for understanding the mixing times of large organic molecules in organic particulate matter over cities, we applied the mixing times determined for toluene-derived SOM particles to the world's top 15 most populous megacities. If the organic particulate matter in these megacities is similar to the toluene-derived SOM in this study, in Istanbul, Tokyo, Shanghai, and São Paulo, mixing times in organic particulate matter during certain periods of the year may be very short, and the particles may be well-mixed. On the other hand, the mixing times of large organic molecules in organic particulate matter in Beijing, Mexico City, Cairo, and Karachi may be long and the particles may not be well-mixed in the afternoon (15:00–17:00 LT) during certain times of the year.

scholarly journals Viscosities, diffusion coefficients, and mixing times of intrinsic fluorescent organic molecules in brown limonene secondary organic aerosol and tests of the Stokes–Einstein equation

2019 ◽  
Vol 19 (3) ◽  
pp. 1491-1503 ◽  
Author(s):  
Dagny A. Ullmann ◽  
Mallory L. Hinks ◽  
Adrian M. Maclean ◽  
Christopher L. Butenhoff ◽  
James W. Grayson ◽  
...  
Keyword(s):  
Einstein Equation ◽  
Diffusion Coefficients ◽  
Organic Molecules ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
High Mass ◽  
Einstein Relation ◽  
Mixing Times ◽  
Diffusion Rates ◽  
And Diffusion

Abstract. 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 7.1×10-13 cm2 s−1 and the mixing times of intrinsic fluorescent organic molecules within 200 nm brown LSOA particles increases from 0.002 to 14 s. These results suggest that the mixing times of large organics in the brown LSOA studied here are short (<1 h) 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 (∼1000 µg m−3), biogenic SOA particles found in the atmosphere with mass loadings ≤10 µg m−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 104 Pa s. These results have important implications for predicting diffusion and mixing within SOA particles in the atmosphere.

scholarly journals Viscosities, diffusion coefficients, and mixing times of intrinsic fluorescent organic molecules in brown limonene secondary organic aerosol and tests of the Stokes-Einstein equation

2018 ◽  
Author(s):  
Dagny A. Ullmann ◽  
Mallory L. Hinks ◽  
Adrian Maclean ◽  
Christopher Butenhoff ◽  
James Grayson ◽  
...  
Keyword(s):  
Diffusion Coefficients ◽  
Organic Molecules ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Mixing Times ◽  
Average Diffusion Coefficient ◽  
Average Diffusion ◽  
Rectangular Area ◽  
Diffusion Rates ◽  
And Diffusion

Abstract. Viscosities and diffusion rates of organics within secondary organic aerosol (SOA) remain uncertain. Using the bead-mobility technique, we measured the 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 cm2 s-1 to 7.1∙10-13 cm2 s-1 and the mixing times of intrinsic fluorescent organic molecules within 200 nm brown LSOA particles increases from 0.002 s to 14 s. These results suggest that the mixing times of large organics in the brown LSOA studied here are short (

scholarly journals Relative humidity-dependent viscosities of isoprene-derived secondary organic material and atmospheric implications for isoprene-dominant forests

2015 ◽  
Vol 15 (9) ◽  
pp. 5145-5159 ◽  
Author(s):  
M. Song ◽  
P. F. Liu ◽  
S. J. Hanna ◽  
Y. J. Li ◽  
S. T. Martin ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Diffusion Coefficients ◽  
Organic Material ◽  
Amazon Basin ◽  
Organic Molecules ◽  
Mixing Time ◽  
Einstein Relation ◽  
Chemical Compositions ◽  
Short Time

Abstract. Oxidation of isoprene is an important source of secondary organic material (SOM) in atmospheric particles, especially in areas such as the Amazon Basin. Information on the viscosities, diffusion rates, and mixing times within isoprene-derived SOM is needed for accurate predictions of air quality, visibility, and climate. Currently, however, this information is not available. Using a bead-mobility technique and a poke-flow technique combined with fluid simulations, the relative humidity (RH)-dependent viscosities of SOM produced from isoprene photo-oxidation were quantified for 20–60 μm particles at 295 ± 1 K. From 84.5 to 0% RH, the viscosities for isoprene-derived SOM varied from ~ 2 × 10−1 to ~ 3 × 105 Pa s, implying that isoprene-derived SOM ranges from a liquid to a semisolid over this RH range. These viscosities correspond to diffusion coefficients of ~ 2 × 10−8 to ~ 2 × 10−14 cm2 s−1 for large organic molecules that follow the Stokes–Einstein relation. Based on the diffusion coefficients, the mixing time of large organic molecules within 200 nm isoprene-derived SOM particles ranges from approximately 0.1 h to less than 1 s. To illustrate the atmospheric implications of this study's results, the Amazon Basin is used as a case study for an isoprene-dominant forest. Considering the RH and temperature range observed in the Amazon Basin and with some assumptions about the dominant chemical compositions of SOM particles in the region, it is likely that SOM particles in this area are liquid and reach equilibrium with large gas-phase organic molecules on short time scales, less than or equal to approximately 0.1 h.

scholarly journals Relative humidity-dependent viscosities of isoprene-derived secondary organic material and atmospheric implications for isoprene-dominant forests

2015 ◽  
Vol 15 (1) ◽  
pp. 1131-1169 ◽  
Author(s):  
M. Song ◽  
P. F. Liu ◽  
S. J. Hanna ◽  
S. T. Martin ◽  
A. K. Bertram
Keyword(s):  
Relative Humidity ◽  
Diffusion Coefficients ◽  
Organic Material ◽  
Amazon Basin ◽  
Organic Molecules ◽  
Mixing Time ◽  
Einstein Relation ◽  
Chemical Compositions ◽  
Short Time

Abstract. Oxidation of isoprene is an important source of secondary organic material (SOM) in atmospheric particles, especially in areas such as the Amazon Basin. Information on the viscosities, diffusion rates, and mixing times within isoprene-derived SOM is needed for accurate predictions of air quality, visibility, and climate. Currently, however, this information is not available. Using a bead-mobility technique and a poke-flow technique combined with fluid simulations, the relative humidity (RH)-dependent viscosities of SOM produced from isoprene photo-oxidation were quantified for 20–60 μm particles at 295 ± 1 K. From 84.5 to 0% RH, the viscosities for isoprene-derived SOM varied from ~2 × 10−1 to ~3 × 105 Pa s, implying that isoprene-derived SOM ranges from a liquid to a semisolid over this RH range. These viscosities correspond to diffusion coefficients of ~2 × 10−8 to ~2 × 10−14 cm2 s−1 for large organic molecules that follow the Stokes–Einstein relation. Based on the diffusion coefficients, the mixing time of large organic molecules within 200 nm isoprene-derived SOM particles ranges from approximately 0.1 h to less than 1 s. To illustrate the atmospheric implications of this study's results, the Amazon Basin is used as a case study for an isoprene-dominant forest. Considering the RH range observed and with some assumptions about the dominant chemical compositions of SOM particles in the Amazon Basin, it is likely that SOM particles in this region are liquid and reach equilibrium with large gas-phase organic molecules on short time scales, less than or equal to approximately 0.1 h.

scholarly journals Quantifying the Role of the Relative Humidity-Dependent Physical State of Organic Particulate Matter in the Uptake of Semivolatile Organic Molecules

2019 ◽  
Vol 53 (22) ◽  
pp. 13209-13218
Author(s):  
Yuemei Han ◽  
Zhaoheng Gong ◽  
Jianhuai Ye ◽  
Pengfei Liu ◽  
Karena A. McKinney ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Relative Humidity ◽  
Physical State ◽  
Organic Molecules ◽  
Organic Particulate Matter

scholarly journals Deliquescence, efflorescence, and phase miscibility of mixed particles of ammonium sulfate and isoprene-derived secondary organic material

2012 ◽  
Vol 12 (4) ◽  
pp. 9903-9943 ◽  
Author(s):  
M. L. Smith ◽  
A. K. Bertram ◽  
S. T. Martin
Keyword(s):  
Liquid Phase ◽  
Relative Humidity ◽  
Ammonium Sulfate ◽  
Organic Material ◽  
Important Variable ◽  
Oxidation Products ◽  
Liquid Separation ◽  
Inorganic Particles ◽  
Photo Oxidation ◽  
Hygroscopic Properties

Abstract. The hygroscopic phase transitions of ammonium sulfate mixed with isoprene-derived secondary organic material were investigated in aerosol experiments. The organic material was produced by isoprene photo-oxidation at 40% relative humidity. The low volatility fraction of the photo-oxidation products condensed onto ammonium sulfate particles. The particle-phase organic material had oxygen-to-carbon ratios of 0.67 to 0.74 for mass concentrations of 20 to 30 μg m−3. The deliquescence, efflorescence, and phase miscibility of the mixed particles were investigated using a dual arm tandem differential mobility analyzer. The isoprene photo-oxidation products induced deviations in behavior relative to pure ammonium sulfate. Compared to an efflorescence relative humidity (ERH) of 30 to 35% for pure ammonium sulfate, efflorescence was eliminated for mixed aqueous particles having organic volume fractions ε of approximately 0.6 and greater. Compared to a deliquescence relative humidity (DRH) of 80% for pure ammonium sulfate, the DRH steadily decreased for increasing ε, approaching a DRH of 40% for ε of 0.9. Parameterizations of the DRH(ε) and ERH(ε) curves were as follows: DRH(ε)= Σ i ci,d xi valid for 0 ≤ ε ≤ 0.86 and ERH(ε)= Σ i ci,e xi valid for 0 ≤ ε ≤ 0.55 for the coefficients c0,d= 80.67, c0,e = 28.35, c1,d= −11.45, c1,e = −13.66, c2,d = 0, c2,e = 0, c3,d = 57.99, c3,e = −83.80, c4,d = −106.80, and c4,d = 0. The molecular description that is thermodynamically implied by these strongly sloped DRH(ε) and ERH(ε) curves is that the organic isoprene photo-oxidation products, the inorganic ammonium sulfate, and water form a miscible liquid phase even at low relative humidity. This phase miscibility is in contrast to the liquid-liquid separation that occurs for some other types of secondary organic material. These differences in liquid-liquid separation are consistent with a prediction recently presented in the literature that the bifurcation between liquid-liquid phase separation versus mixing depends on the oxygen-to-carbon ratio of the organic material. The conclusions are that the influence of secondary organic material on the hygroscopic properties of ammonium sulfate varies with organic composition and that the degree of oxygenation of the organic material, which is a measurable characteristic of complex organic materials, is an important variable influencing the hygroscopic properties of mixed organic-inorganic particles.

scholarly journals Tensile Behavior and Diffusion of Moisture through Flax Fibers by Desorption Method

2019 ◽  
Vol 11 (13) ◽  
pp. 3558 ◽  
Author(s):  
Swarda S. Radkar ◽  
Ali Amiri ◽  
Chad A. Ulven
Keyword(s):  
Diffusion Coefficients ◽  
Natural Fibers ◽  
Woven Fabrics ◽  
Tensile Behavior ◽  
Flax Fiber ◽  
Additional Absorption ◽  
Flax Fibers ◽  
Diffusion Rates ◽  
Desorption Method ◽  
And Diffusion

There has been a substantial increase in the usage of natural fibers and biodegradable polymers in composite materials due to the recent focus on sustainability of materials. Flax fibers have exhibited higher mechanical properties compared to most other natural fibers available. However, one of the major challenges faced in the use of flax fiber is its hydrophilicity. In this study, the tensile behavior of flax fiber tows removed from commercially available woven fabrics were investigated at different moisture levels. The breaking tenacity of fiber tows was shown to increase with an increase in moisture content of up to 25%. After this point, additional absorption of moisture resulted in a decrease of fiber tenacity. In addition, the diffusion process through flax fiber mat with different areal densities was investigated and the diffusion coefficients were determined using the desorption curves. Diffusion rates were not found to significantly change with varying areal densities of 200 to 400 gsm, but were significantly different when exposed to temperatures of 55 °C versus 80 °C.

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