AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Optical Absorption Properties of Brown Carbon Aerosols in the Pearl River Delta Region of China
JUN ZHENG, Zhujie Li, Yan Ma, Haobo Tan, Nanjing University of Information Science & Technology
Abstract Number: 325 Working Group: Carbonaceous Aerosol
Abstract We have conducted a set of comprehensive measurements of aerosol compositions and optical properties at a suburban station in Guangzhou, a megacity in the Pearl-River-Delta region of China. Brown carbon (BrC) source origins and radiative forcing effects were investigated. The particle absorption Ångström exponent (AAE) was deduced and utilized to differentiate light absorption by BrC from that by black carbon (BC). The results showed that the average absorption contributions of BrC were 34.1±8.0% at 370 nm, 23.7±7.3% at 470 nm, 16.0±6.7% at 520 nm, 13.0±5.4% at 590 nm and 8.7±4.3% at 660 nm. A sensitivity analysis of the evaluation of the absorption Ångström exponent of BC (AAEBC) was conducted based on the Mie theory calculation assuming that the BC-containing aerosol was mixed with the core-shell and external-mixing configurations. We found that variations in the imaginary refractive index (RI) of the BC core can significantly affect the estimation of AAEBC. However, AAEBC was relatively less sensitive to the real RI of the BC core and was least sensitive to the real RI of the non-light-absorbing shell. BrC absorption was closely related to aerosol potassium content, which was most likely associated with straw burning in the region. Diurnal variation in BrC absorption revealed that primary organic aerosols had a larger BrC absorption capacity than SOA. Radiative transfer simulations showed that BrC absorption may cause 2.3±1.8 W m−2 radiative forcing at the top of the atmosphere and contribute to 15.8±4.4% of the aerosol warming effect. BrC radiative forcing efficiency in the studied area with reference to certain aerosol SSA and BrC absorption contributions at various wavelengths were systematically evaluated. Evidently, the BrC radiative forcing efficiency was higher at shorter wavelengths.