TY - JOUR
T1 - Optical properties and molecular compositions of water-soluble and water-insoluble brown carbon (BrC) aerosols in northwest China
AU - Li, Jianjun
AU - Zhang, Qi
AU - Wang, Gehui
AU - Li, Jin
AU - Wu, Can
AU - Liu, Lang
AU - Wang, Jiayuan
AU - Jiang, Wenqing
AU - Li, Lijuan
AU - Fai Ho, Kin
AU - Cao, Junji
N1 - Publisher Copyright:
© 2020 Copernicus GmbH. All rights reserved.
PY - 2020/4/27
Y1 - 2020/4/27
N2 - Brown carbon (BrC) contributes significantly to aerosol light absorption and thus can affect the Earth's radiation balance and atmospheric photochemical processes. In this study, we examined the light absorption properties and molecular compositions of water-soluble (WS-BrC) and water-insoluble (WI-BrC) BrC in PM2:5 collected from a rural site in the Guanzhong Basin - a highly polluted region in northwest China. Both WS-BrC and WI-BrC showed elevated light absorption coefficients (Abs) in winter (4-7 times those in summer) mainly attributed to enhanced emissions from residential biomass burning (BB) for heating of homes. While the average mass absorption coefficients (MACs) at 365 nm (MAC365) of WS-BrC were similar between daytime and nighttime in summer (0:99-0:17 and 1:01-0:18m2 g-1, respectively), the average MAC365 of WI-BrC was more than a factor of 2 higher during daytime (2:45-1:14m2 g-1) than at night (1:18-0:36m2 g-1). This difference was partly attributed to enhanced photochemical formation of WI-BrC species, such as oxygenated polycyclic aromatic hydrocarbons (OPAHs). In contrast, the MACs of WS-BrC and WIBrC were generally similar in winter and both showed few diel differences. The Abs of wintertime WS-BrC correlated strongly with relative humidity, sulfate and NO2, suggesting that aqueous-phase reaction is an important pathway for secondary BrC formation during the winter season in northwest China. Nitrophenols on average contributed 2:44-1:78% of the Abs of WS-BrC in winter but only 0:12-0:03% in summer due to faster photodegradation reactions. WS-BrC and WI-BrC were estimated to account for 0:83-0:23% and 0:53-0:33 %, respectively, of the total down-welling solar radiation in the ultraviolet (UV) range in summer, and 1:67-0:72% and 2:07-1:24 %, respectively, in winter. The total absorption by BrC in the UV region was about 55 %- 79% relative to the elemental carbon (EC) absorption.
AB - Brown carbon (BrC) contributes significantly to aerosol light absorption and thus can affect the Earth's radiation balance and atmospheric photochemical processes. In this study, we examined the light absorption properties and molecular compositions of water-soluble (WS-BrC) and water-insoluble (WI-BrC) BrC in PM2:5 collected from a rural site in the Guanzhong Basin - a highly polluted region in northwest China. Both WS-BrC and WI-BrC showed elevated light absorption coefficients (Abs) in winter (4-7 times those in summer) mainly attributed to enhanced emissions from residential biomass burning (BB) for heating of homes. While the average mass absorption coefficients (MACs) at 365 nm (MAC365) of WS-BrC were similar between daytime and nighttime in summer (0:99-0:17 and 1:01-0:18m2 g-1, respectively), the average MAC365 of WI-BrC was more than a factor of 2 higher during daytime (2:45-1:14m2 g-1) than at night (1:18-0:36m2 g-1). This difference was partly attributed to enhanced photochemical formation of WI-BrC species, such as oxygenated polycyclic aromatic hydrocarbons (OPAHs). In contrast, the MACs of WS-BrC and WIBrC were generally similar in winter and both showed few diel differences. The Abs of wintertime WS-BrC correlated strongly with relative humidity, sulfate and NO2, suggesting that aqueous-phase reaction is an important pathway for secondary BrC formation during the winter season in northwest China. Nitrophenols on average contributed 2:44-1:78% of the Abs of WS-BrC in winter but only 0:12-0:03% in summer due to faster photodegradation reactions. WS-BrC and WI-BrC were estimated to account for 0:83-0:23% and 0:53-0:33 %, respectively, of the total down-welling solar radiation in the ultraviolet (UV) range in summer, and 1:67-0:72% and 2:07-1:24 %, respectively, in winter. The total absorption by BrC in the UV region was about 55 %- 79% relative to the elemental carbon (EC) absorption.
UR - https://www.scopus.com/pages/publications/85084176257
U2 - 10.5194/acp-20-4889-2020
DO - 10.5194/acp-20-4889-2020
M3 - 文章
AN - SCOPUS:85084176257
SN - 1680-7316
VL - 20
SP - 4889
EP - 4904
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
IS - 8
ER -