title: Black carbon aerosol characterization in a remote area of Qinghai-Tibetan Plateau, western China.
abstract: The concentrations, size distributions, and mixing states of refractory black carbon (rBC) aerosols were measured with a ground-based Single Particle Soot Photometer (SP2), and aerosol absorption was measured with an Aethalometer at Qinghai Lake (QHL), a rural area in the Northeastern Tibetan Plateau of China in October 2011. The area was not pristine, with an average rBC mass concentration of 0.36 μg STP-m(-3) during the two-week campaign period. The rBC concentration peaked at night and reached the minimal in the afternoon. This diurnal cycle of concentration is negatively correlated with the mixed layer depth and ventilation. When air masses from the west of QHL were sampled in late afternoon to early evening, the average rBC concentration of 0.21 μg STP-m(-3) was observed, representing the rBC level in a larger Tibetan Plateau region because of the highest mixed layer depth. A lognormal primary mode with mass median diameter (MMD) of ~175 nm, and a small secondary lognormal mode with MMD of 470-500 nm of rBC were observed. Relative reduction in the secondary mode during a snow event supports recent work that suggested size dependent removal of rBC by precipitation. About 50% of the observed rBC cores were identified as thickly coated by non-BC material. A comparison of the Aethalometer and SP2 measurements suggests that non-BC species significantly affect the Aethalometer measurements in this region. A scaling factor for the Aethalometer data at a wavelength of 880 nm is therefore calculated based on the measurements, which may be used to correct other Aethalometer datasets collected in this region for a more accurate estimate of the rBC loading. The results present here significantly improve our understanding of the characteristics of rBC aerosol in the less studied Tibetan Plateau region and further highlight the size dependent removal of BC via precipitation.
authors.affiliation: Key Laboratory of Aerosol Science & Technology, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China; Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Qiyuan
authors.initials: Q
authors.lastname: Wang
authors.affiliation: National Oceanic and Atmospheric Administration, Earth System Research Laboratory, NOAA, Boulder, CO, USA; Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Schwarz
authors.affiliation: Key Laboratory of Aerosol Science & Technology, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China; Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an 710049, China. Electronic address: cao@loess.llqg.ac.cn.
authors.forename: Junji
authors.initials: J
authors.lastname: Cao
authors.affiliation: National Oceanic and Atmospheric Administration, Earth System Research Laboratory, NOAA, Boulder, CO, USA.
authors.forename: Rushan
authors.initials: R
authors.lastname: Gao
authors.affiliation: National Oceanic and Atmospheric Administration, Earth System Research Laboratory, NOAA, Boulder, CO, USA; Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA.
authors.forename: D W
authors.initials: DW
authors.lastname: Fahey
authors.affiliation: Key Laboratory of Aerosol Science & Technology, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China.
authors.forename: Tafeng
authors.initials: T
authors.lastname: Hu
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland; Centre for Climate and Air Pollution Studies, Ryan Institute, National University of Ireland Galway, University Road, Galway, Ireland.
authors.forename: R-J
authors.initials: RJ
authors.lastname: Huang
authors.affiliation: Key Laboratory of Aerosol Science & Technology, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China.
authors.forename: Yongming
authors.initials: Y
authors.lastname: Han
authors.affiliation: Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Zhenxing
authors.initials: Z
authors.lastname: Shen
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000393:Air Pollutants / Q000032:analysis*; D002681:China; D004784:Environmental Monitoring; D053260:Soot / Q000032:analysis*
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D053260:Soot
keywords: Mixing state; Refractory black carbon; Size distribution; Tibetan Plateau