Characteristics of chemical composition and role of meteorological factors during heavy aerosol pollution episodes in northern Beijing area in autumn and winter of 2015

Abstract

Heavy aerosol pollution episodes (HPEs) usually start from late autumn and become more serious in winter in Beijing and its vicinity (BIV). In this study, we examine the reasons for the formation and change of HPEs in the areas of northern BIV. The size-resolved chemical components of PM 1 and meteorological conditions were investigated during HPEs in autumn and winter of 2015. Stable regional atmosphere and higher atmospheric condensation processes associated with southerly and lower speed wind led to the formation of HPEs. After the start of these HPEs, the concentration of fine particles increased more than twice in several hours. ~80% of the 'explosive' growth in PM mass can be considered as a positive feedback of meteorological factors that come from even more stable atmosphere and larger condensation rate of water vapour, which was derived from the interaction between formed aerosol pollution and the meteorological factors within boundary layer. Nitrate was the largest fraction of PM 1 in autumn, and the most significantly increased component during HPEs relative to clean period during both of autumn and winter. The proportion of organic aerosol (OA) was similar to that of nitrate in autumn, but its rise in HPE was much smaller, mainly because of the high concentration of OA existed during clean periods. Compared with the largest increase of nitrate, the similar uplift was found for ammonium production, showing that a large amount of ammonium was mainly formed by the combination of NO − 3 in HPEs, rather than SO 2− 4. In addition to the lower southerly wind carrying pollutants from southern part of BIV, westerly wind from central Inner Mongolia and north Shanxi can also bring air pollutants originating from coal combustion, contributing to the heavy pollution in the northern BIV area in winter, and resulting in higher sulphate, nitrate and OA masses.

The interdecadal worsening of weather conditions affecting aerosol pollution in the Beijing area in relation to climate warming

“…The joint effect of inversion suppression and surface cooling results in appreciable near-ground moisture accumulation, which further accelerates heterogeneous and liquid-phase reactions and enhances aerosol hy- groscopic growth to increase PM 2.5 mass concentration. The noted positive meteorological feedback dominates PM 2.5 explosive growth (Zhong et al, 2017(Zhong et al, , 2018Zhang et al, 2017).…”

“…Particularly, in the last 8 years between 2010 and 2017, the mean of PLAM increased more than the growth rate of the mean of each of the previous 10 years, which exhibited more noticeable unfavorable weather conditions. When the PM 2.5 mass pollution accu-mulated to a certain extent, it caused the further deterioration of weather conditions, which has been found in almost all HPEs in the Beijing area since 2013 (Zhong et al, 2017(Zhong et al, , 2018Zhang et al, 2017). Therefore, we hypothesized that the substantial rise in mean PLAM between 2010 and 2017 should have benefited from the further worsening of meteorological conditions caused by higher PM 2.5 mass concentra-tions that reached a certain extent.…”

“…(2) for the PLAM Zhang et al, 2009). This index has been employed to evaluate the contribution of meteorological factors to changes in atmospheric composition and optical properties over Beijing during the 2008 Olympic Games, identify the contribution of specific meteorological factors to a 10-day haze-fog event in 2013 , estimate the relative contribution of meteorological factors to changes in aerosol mass concentrations and chemical compositions in different regions of China during winter from 2006 to 2013 and distinguish the feedback effect of meteorological conditions on the explosive increase in PM 2.5 mass concentration during accumulation stages in the Beijing area (Zhong et al, 2017;Zhang et al, 2017).…”

Using a coupled LES-aerosol radiation model to investigate urban haze: Sensitivity to aerosol loading and meteorological conditions

“…conditions such as temperature inversions, increased humidity and decreased wind speed (Dou et al, 2015;Zhang et al, , 2017Wang et al, 2019;Zhong et al, 2019b).…”

Reply to RC1

“…2for the PLAM (Wang et al, 2012(Wang et al, , 2013Zhang et al, 2009). This index has been employed to evaluate the contribution of meteorological factors to changes in atmospheric composition and optical properties over Beijing during the 2008 Olympic Games, identify the contribution of specific meteorological factors to a 10-day haze-fog event in 2013 (Zhang et al, 2013), estimate the relative contribution of meteorological factors to changes in aerosol mass concentrations and chemical compositions in different regions of China during winter from 2006 to 2013 and distinguish the feedback effect of meteorological conditions on the explosive increase in PM 2.5 mass concentration during accumulation stages in the Beijing area (Zhong et al, 2017;Zhang et al, 2017).…”