Temporal variations of black carbon during haze and non-haze days in Beijing

Abstract

Black carbon (BC) aerosol has been identified as one of key factors responsible for air quality in Beijing. BC emissions abatement could help slow regional climate change while providing benefits for public health. In order to quantify its variations and contribution to air pollution, we systematically studied real-time measurements of equivalent black carbon (eBC) in PM2.5 aerosols at an urban site in Beijing from 2010 to 2014. Equivalent black carbon (eBC) is used instead of black carbon (BC) for data derived from Aethalometer-31 measurement. Equivalent BC concentrations showed significant temporal variations with seasonal mean concentration varying between 2.13 and 5.97 μg m−3. The highest concentrations of eBC were found during autumn and winter, and the lowest concentrations occurred in spring. We assessed the temporal variations of eBC concentration during haze days versus non-haze days and found significantly lower eBC fractions in PM2.5 on haze days compared to those on non-haze days. Finally, we observed a clear inverse relationship between eBC and wind speed. Our results show that wind disperses PM2.5 more efficiently than eBC; so, secondary aerosols are not formed to the same degree as primary aerosols over the same transport distance during windy conditions.

Intra-regional transport of black carbon between the south edge of North China Plain and Central China during winter haze episodes

“…The average values of eBC increased by 163%, 139%, 96.2%, 51.8% and 26.4% at SX, XY, LH, HA and WH, respectively from clean to pollution. The enhancement of eBC along with the deterioration of air quality was also reported elsewhere (Wang et al, 2014a;Liu et al, 2016Liu et al, , 2018b. At LH and HA, the enhancement eBC level from clean to pollution period was due to both the elevated BC emissions from biomass burning (BCbb) and fossil fuel combustion (BCff) ( Fig.…”

The impact of aerosols on photolysis frequencies and ozone production in Beijing during the 4-year period 2012–2015

“…The absorption and scattering coefficients were measured with an aethalometer (AE-31, Magee) and a Single Wavelength Integrating Nephelometer (Aurora-1000), respectively, with a time resolution of 1 min. As aerosol particles were dried by decreasing relative humidity (RH) to < 40 % when SSA was measured, we used the measured hygroscopic factor (Liu et al, 2009) and measured RH to correct the SSA. The 5 min averages of AOD, SSA, and photolysis frequencies were analysed in this study.…”

“…However, due to the absence of more SSA data of the period 2012-2015, we cannot give more sufficient evidence for the dependence of SSA on AOD. From another perspective, owing to the biomass burning and soot emission generated from heating, the fine-mode heavily absorbing aerosol percentage is higher in winter than in summer (Zheng et al, 2017;Liu et al, 2016;Zhang et al, 2013), and thus aerosols in winter have a stronger ability to reduce the photolysis frequencies. Table S1 in the Supplement indicates that SSA in summer is significantly higher than in winter.…”

Numerical simulations of the effects of regional topography on haze pollution in Beijing

“…Given the rapid urbanization and industrial development over the past several decades, Beijing and its adjacent areas are becoming more and more important in China and for the global economy. However, the rapid economic growth and urbanization have increased the level of air pollution in recent decades 1–8 . Beijing and eastern China have suffered from severe haze or smog days frequently in recent years.…”