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Optical properties of secondary organic aerosols generated by photooxidation of aromatic hydrocarbons.

Li K, Wang W, Ge M, Li J, Wang D - Sci Rep (2014)

Bottom Line: The retrieved RIs at 532 nm for the SOAs range from 1.38-1.59, depending on several factors, such as different precursors and NOx levels.The RIs of the SOAs are altered differently as the NOx concentration increases as follows: the RIs of the SOAs derived from benzene and toluene increase, whereas those of the SOAs derived from ethylbenzene and m-xylene decrease.Finally, by comparing the experimental data with the model values, we demonstrate that the models likely overestimate the RI values of the SOA particles to a certain extent, which in turn overestimates the global direct radiative forcing of the organic particles.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.

ABSTRACT
The refractive index (RI) is the fundamental characteristic that affects the optical properties of aerosols, which could be some of the most important factors influencing direct radiative forcing. The secondary organic aerosols (SOAs) generated by the photooxidation of benzene, toluene, ethylbenzene and m-xylene (BTEX) under low-NOx and high-NOx conditions are explored in this study. The particles generated in our experiments are considered to be spherical, based on atomic force microscopy (AFM) images, and nonabsorbent at a wavelength of 532 nm, as determined by ultraviolet-visible light (UV-Vis) spectroscopy. The retrieved RIs at 532 nm for the SOAs range from 1.38-1.59, depending on several factors, such as different precursors and NOx levels. The RIs of the SOAs are altered differently as the NOx concentration increases as follows: the RIs of the SOAs derived from benzene and toluene increase, whereas those of the SOAs derived from ethylbenzene and m-xylene decrease. Finally, by comparing the experimental data with the model values, we demonstrate that the models likely overestimate the RI values of the SOA particles to a certain extent, which in turn overestimates the global direct radiative forcing of the organic particles.

No MeSH data available.


Related in: MedlinePlus

Dependence of the RI values on the surface mean diameter of the ethylbenzene SOA generated in the L3–L6 experiments.The solid data points represent the L3–L5 experiments with different concentrations of hydrogen peroxide, whereas the green (solid and open) data points represent the L5 and L6 experiments with different hydrocarbon concentrations.
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f5: Dependence of the RI values on the surface mean diameter of the ethylbenzene SOA generated in the L3–L6 experiments.The solid data points represent the L3–L5 experiments with different concentrations of hydrogen peroxide, whereas the green (solid and open) data points represent the L5 and L6 experiments with different hydrocarbon concentrations.

Mentions: The dependence of the RI value on the initial HC and oxidiser concentrations under the low-NOx condition was also investigated. As shown in Fig. 5, the RI values decrease as the particles grow for the ethylbenzene SOA. The solid points represent the L3–L5 experiments with different concentrations of hydrogen peroxide, whereas the green (solid and open) points represent the L5 and L6 experiments with different hydrocarbon concentrations. Clearly, the oxidiser concentration does not influence the RI value under the same diameter but influences the final size mode; the hydrocarbon concentration slightly influences the RI value with a negative correlation. Generally, the different initial concentrations exert only a slight influence on the RIs.


Optical properties of secondary organic aerosols generated by photooxidation of aromatic hydrocarbons.

Li K, Wang W, Ge M, Li J, Wang D - Sci Rep (2014)

Dependence of the RI values on the surface mean diameter of the ethylbenzene SOA generated in the L3–L6 experiments.The solid data points represent the L3–L5 experiments with different concentrations of hydrogen peroxide, whereas the green (solid and open) data points represent the L5 and L6 experiments with different hydrocarbon concentrations.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4017213&req=5

f5: Dependence of the RI values on the surface mean diameter of the ethylbenzene SOA generated in the L3–L6 experiments.The solid data points represent the L3–L5 experiments with different concentrations of hydrogen peroxide, whereas the green (solid and open) data points represent the L5 and L6 experiments with different hydrocarbon concentrations.
Mentions: The dependence of the RI value on the initial HC and oxidiser concentrations under the low-NOx condition was also investigated. As shown in Fig. 5, the RI values decrease as the particles grow for the ethylbenzene SOA. The solid points represent the L3–L5 experiments with different concentrations of hydrogen peroxide, whereas the green (solid and open) points represent the L5 and L6 experiments with different hydrocarbon concentrations. Clearly, the oxidiser concentration does not influence the RI value under the same diameter but influences the final size mode; the hydrocarbon concentration slightly influences the RI value with a negative correlation. Generally, the different initial concentrations exert only a slight influence on the RIs.

Bottom Line: The retrieved RIs at 532 nm for the SOAs range from 1.38-1.59, depending on several factors, such as different precursors and NOx levels.The RIs of the SOAs are altered differently as the NOx concentration increases as follows: the RIs of the SOAs derived from benzene and toluene increase, whereas those of the SOAs derived from ethylbenzene and m-xylene decrease.Finally, by comparing the experimental data with the model values, we demonstrate that the models likely overestimate the RI values of the SOA particles to a certain extent, which in turn overestimates the global direct radiative forcing of the organic particles.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.

ABSTRACT
The refractive index (RI) is the fundamental characteristic that affects the optical properties of aerosols, which could be some of the most important factors influencing direct radiative forcing. The secondary organic aerosols (SOAs) generated by the photooxidation of benzene, toluene, ethylbenzene and m-xylene (BTEX) under low-NOx and high-NOx conditions are explored in this study. The particles generated in our experiments are considered to be spherical, based on atomic force microscopy (AFM) images, and nonabsorbent at a wavelength of 532 nm, as determined by ultraviolet-visible light (UV-Vis) spectroscopy. The retrieved RIs at 532 nm for the SOAs range from 1.38-1.59, depending on several factors, such as different precursors and NOx levels. The RIs of the SOAs are altered differently as the NOx concentration increases as follows: the RIs of the SOAs derived from benzene and toluene increase, whereas those of the SOAs derived from ethylbenzene and m-xylene decrease. Finally, by comparing the experimental data with the model values, we demonstrate that the models likely overestimate the RI values of the SOA particles to a certain extent, which in turn overestimates the global direct radiative forcing of the organic particles.

No MeSH data available.


Related in: MedlinePlus