10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Sources and Physicochemical Characteristics of Black Carbon Aerosol in the Southeastern Tibetan Plateau: Internal Mixing Enhances Light Absorption
QIYUAN WANG, Junji Cao, Yongming Han, Institute of Earth Environment, Chinese Academy of Sciences
Abstract Number: 450 Working Group: Carbonaceous Aerosol
Abstract Black carbon (BC) aerosol over the Tibetan Plateau (TP) has important effects on regional climate and hydrological processes. An intensive measurement campaign was conducted at Lulang (~3300 m above sea level), southeastern TP, from September to October 2015 to investigate the sources and physicochemical characteristics of refractory BC (rBC) aerosol. The grand average rBC mass concentration was 0.31 ± 0.55 µg m-3, which is higher than most BC results for the TP. A clear diurnal cycle in rBC showed high values in the morning and low values in the afternoon. A bivariate polar plot showed that rBC loadings were affected by wind speed and direction, which was used to infer the dominant transport directions. The estimated net surface transport intensity for rBC was +0.05 ± 0.29 µg s-1 m-2, indicating that stronger transport from outside the TP compared with the interior of the TP. Cluster analysis and a concentration-weighted trajectory model indicated that emissions from north India had important contribution to the high rBC, but the effects of internal TP sources cannot be overlooked. The average mass median diameter (MMD) of rBC was 160 ± 23 nm, with smaller size on rainy days (145 nm) compared with non-rainy days (164 nm). The average number fraction of thickly-coated rBC (FrBC) was 39 ± 8%. The FrBC increased with the enhanced O3 mixing ratio from 10:00–14:00 local time, indicating that the photochemical oxidation played an important role in forming rBC coatings. The average rBC absorption enhancement (Eabs) was estimated to be 1.8, suggesting that light absorption by coated rBC particles was greater than that for the uncoated ones. The Eabs was strongly positively correlated with the FrBC, indicating an amplification of light absorption for internally-mixed rBC. When rBC core 170 nm. Our study provides insight into the sources and evolution of rBC aerosol on the TP. It is useful for further modelling studies improving precise of evaluating the radiative forcing of carbonaceous aerosols in this area.