Evolution of the Complex Refractive Index of Secondary Organic Aerosols during Atmospheric Aging

Quanfu He; Nir Bluvshtein; Lior Segev; Daphne Meidan; J. Michel Flores; Steven S. Brown; William Brune; Yinon Rudich

doi:10.1021/acs.est.7b05742

Evolution of the Complex Refractive Index of Secondary Organic Aerosols during Atmospheric Aging

Quanfu He, Nir Bluvshtein, Lior Segev, Daphne Meidan, J. Michel Flores, Steven S. Brown, William Brune, Yinon Rudich^*

^*Corresponding author for this work

Department of Earth and Planetary Sciences

Research output: Contribution to journal › Article › peer-review

43 Citations (Scopus)

Abstract

The wavelength-dependence of the complex refractive indices (RI) in the visible spectral range of secondary organic aerosols (SOA) are rarely studied, and the evolution of the RI with atmospheric aging is largely unknown. In this study, we applied a novel white light-broadband cavity enhanced spectroscopy to measure the changes in the RI (400-650 nm) of β-pinene and p-xylene SOA produced and aged in an oxidation flow reactor, simulating daytime aging under NO_x-free conditions. It was found that these SOA are not absorbing in the visible range, and that the real part of the RI, n, shows a slight spectral dependence in the visible range. With increased OH exposure, n first increased and then decreased, possibly due to an increase in aerosol density and chemical mean polarizability for SOA produced at low OH exposures, and a decrease in chemical mean polarizability for SOA produced at high OH exposures, respectively. A simple radiative forcing calculation suggests that atmospheric aging can introduce more than 40% uncertainty due to the changes in the RI for aged SOA.

Original language	English
Pages (from-to)	3456-3465
Number of pages	10
Journal	Environmental Science and Technology
Volume	52
Issue number	6
DOIs	https://doi.org/10.1021/acs.est.7b05742
Publication status	Published - 20 Mar 2018

All Science Journal Classification (ASJC) codes

General Chemistry
Environmental Chemistry

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10.1021/acs.est.7b05742

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title = "Evolution of the Complex Refractive Index of Secondary Organic Aerosols during Atmospheric Aging",

abstract = "The wavelength-dependence of the complex refractive indices (RI) in the visible spectral range of secondary organic aerosols (SOA) are rarely studied, and the evolution of the RI with atmospheric aging is largely unknown. In this study, we applied a novel white light-broadband cavity enhanced spectroscopy to measure the changes in the RI (400-650 nm) of β-pinene and p-xylene SOA produced and aged in an oxidation flow reactor, simulating daytime aging under NOx-free conditions. It was found that these SOA are not absorbing in the visible range, and that the real part of the RI, n, shows a slight spectral dependence in the visible range. With increased OH exposure, n first increased and then decreased, possibly due to an increase in aerosol density and chemical mean polarizability for SOA produced at low OH exposures, and a decrease in chemical mean polarizability for SOA produced at high OH exposures, respectively. A simple radiative forcing calculation suggests that atmospheric aging can introduce more than 40% uncertainty due to the changes in the RI for aged SOA.",

author = "Quanfu He and Nir Bluvshtein and Lior Segev and Daphne Meidan and Flores, {J. Michel} and Brown, {Steven S.} and William Brune and Yinon Rudich",

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doi = "10.1021/acs.est.7b05742",

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AU - He, Quanfu

AU - Bluvshtein, Nir

AU - Segev, Lior

AU - Meidan, Daphne

AU - Flores, J. Michel

AU - Brown, Steven S.

AU - Brune, William

AU - Rudich, Yinon

PY - 2018/3/20

Y1 - 2018/3/20

N2 - The wavelength-dependence of the complex refractive indices (RI) in the visible spectral range of secondary organic aerosols (SOA) are rarely studied, and the evolution of the RI with atmospheric aging is largely unknown. In this study, we applied a novel white light-broadband cavity enhanced spectroscopy to measure the changes in the RI (400-650 nm) of β-pinene and p-xylene SOA produced and aged in an oxidation flow reactor, simulating daytime aging under NOx-free conditions. It was found that these SOA are not absorbing in the visible range, and that the real part of the RI, n, shows a slight spectral dependence in the visible range. With increased OH exposure, n first increased and then decreased, possibly due to an increase in aerosol density and chemical mean polarizability for SOA produced at low OH exposures, and a decrease in chemical mean polarizability for SOA produced at high OH exposures, respectively. A simple radiative forcing calculation suggests that atmospheric aging can introduce more than 40% uncertainty due to the changes in the RI for aged SOA.

AB - The wavelength-dependence of the complex refractive indices (RI) in the visible spectral range of secondary organic aerosols (SOA) are rarely studied, and the evolution of the RI with atmospheric aging is largely unknown. In this study, we applied a novel white light-broadband cavity enhanced spectroscopy to measure the changes in the RI (400-650 nm) of β-pinene and p-xylene SOA produced and aged in an oxidation flow reactor, simulating daytime aging under NOx-free conditions. It was found that these SOA are not absorbing in the visible range, and that the real part of the RI, n, shows a slight spectral dependence in the visible range. With increased OH exposure, n first increased and then decreased, possibly due to an increase in aerosol density and chemical mean polarizability for SOA produced at low OH exposures, and a decrease in chemical mean polarizability for SOA produced at high OH exposures, respectively. A simple radiative forcing calculation suggests that atmospheric aging can introduce more than 40% uncertainty due to the changes in the RI for aged SOA.

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U2 - 10.1021/acs.est.7b05742

DO - 10.1021/acs.est.7b05742

M3 - Article

SN - 0013-936X

VL - 52

SP - 3456

EP - 3465

JO - Environmental Science and Technology

JF - Environmental Science and Technology

IS - 6

ER -

Evolution of the Complex Refractive Index of Secondary Organic Aerosols during Atmospheric Aging

Abstract

All Science Journal Classification (ASJC) codes

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