AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Black Carbon in Beijing: Mixing State, Sources and Optical Properties
JING CAI, Mei Zheng, Jiandong Wang, Yanjun Zhang, Shuxiao Wang, Peking University
Abstract Number: 315 Working Group: Aerosol Chemistry
Abstract Sources and mixing state have significant influence on the properties of black carbon (BC) such as mass absorption cross-section (MAC), lifetime and health effects. Single particle aerosol mass spectrometry (SPAMS) can provide information of chemical species that BC is mixed with for particles in the size range of 200-2000 nm. With SPAMS, mixing state and sources of BC-containing particles can be obtained in high-time resolution. During March 9 - 31, 2015, online water-soluble ions, organic matter and BC concentration of fine particles in Beijing were obtained by Gas Aerosol Collector (GAC), Aerosol Chemical Speciation Monitor (ACSM) and OCEC analyzer, respectively. Optical properties of BC were obtained by aethalometer and Photoacoustic Extinctiometer (PAX). The count and spectra of particles by SPAMS were calibrated with scanning mobility particle sizer (SMPS) and aerosol particle sizer (APS), GAC, ACSM and OCEC analyzer.
In this study, the sources and mixing state of BC particles were analyzed by quantitative SPAMS data. It is found that most BC particles of 200-2000 nm in Beijing during the campaign were internally mixed with secondary species such as sulfate and nitrate. The ratio of externally/internally mixed BC particles was higher in early March and aged BC particles were more likely to be internally mixed with sulfate. When externally/internally mixed ratio of BC particles was low in late March, these aged BC particles were more internally mixed with nitrate. It is likely due to different BC sources and aging process, which will affect the optical properties of BC. A quantitative single particle diversity model developed recently is also used to quantify mixing state of BC-containing particles and the extent of aging. The relationship of MAC, sources and mixing state of BC will be discussed in detail in the presentation.