Characterization of Chemical Composition in PM2.5 in Beijing before, during, and after a Large-Scale International Event

Abstract

To commemorate the 70th anniversary of the victory of the Chinese people's Anti-Japanese War and the World AntiFascist War, an international parade was held in Beijing in September 2015. In order to ensure satisfactory air quality during this event, a phased emission control measures were taken in Beijing and its surrounding provinces. The 24-h PM 2.5 samples were collected in Beijing from August 1 to September 15, 2015 covering the period before, during and after this large-scale event. The observed PM 2.5 data, meteorological data, emission reduction measures, and air mass trajectory simulation results were systematically analyzed to understand the pollution characteristics and chemical compositions of PM 2.5 in Beijing. The results indicated that PM 2.5 concentration during the two emission control phases was reduced by 61.7% comparing to the non-control period, but the regional transport of pollutants and meteorological conditions had a more prominent impact on PM 2.5 than emission reduction during phase 2. The secondary water-soluble ions including SO 4 2-, NO 3 -, and NH 4 + were found as the main ions present in PM 2.5 . During the entire emission control period, organic carbon (OC) and elemental carbon (EC) mass concentrations were decreased by 53.1% and 57.9%. A PM 2.5 mass balance was analyzed, and it was found that the organic matter accounted for 29.3, 37.6 and 28.5% of the PM 2.5 mass before, during and after the emission control, while the contribution of mobile sources to PM 2.5 was relatively outstanding after a series of emission control measures.

Significant Climate Impact of Highly Hygroscopic Atmospheric Aerosols in Delhi, India

“…This is consistent with a recent long‐term observational study in Delhi (Sharma et al, ), which reported an annual averaged F OM in PM 2.5 is in a range of 15%–20% during 2012–2016 (mass of organic matter is usually calculated as 1.4 times of organic carbon). However, the F OM in Beijing is usually in a range of 20%–40% (Hu et al, ; Huang et al, ; Tao et al, ; Yang et al, ), where more than half of the organic matter originates from secondary organic aerosol (SOA; Hu et al, ; Huang et al, ; Jimenez et al, ). Stronger solar radiation in Delhi may increase photochemical reactions and oxidation of volatile organic compounds, therefore, may enhance SOA formation (Guo et al, ; Hu et al, ; McFiggans et al, ; Zhang, Wang, et al, ; Zhu et al, ).…”

Comparison of PM2.5 Chemical Compositions during Haze and Non-haze Days in a Heavy Industrial City in North China

“…The sample was added to 10 mL of deionized water and sonicated for 20 minutes, centrifuged for 5 minutes, and then filtered through a microporous membrane (pore size = 0.45 µm; diameter = 25 mm). The concentrations of six anions (F -, Cl -, NO 2 -, NO 3 -, C 2 O 4 2and SO 4 2-) and five cations (Na + , NH 4 + , K + , Mg 2+ and Ca 2+ ) were analyzed by ion chromatography (Dionex ICS-1100; Thermo Fisher Scientific, USA) (Wang et al, 2005;Yang et al, 2017).…”

Lidar vertical observation network and data assimilation reveal key processes driving the 3-D dynamic evolution of PM<sub>2.5</sub> concentrations over the North China Plain

“…Joint observations and analyses have been widely performed in an effort to reveal the heavy aerosol pollution (HAP) in the NCP region (Li et al, 2016;Zhang et al, 2018). The key processes of a HAP event, from aerosol pollution development to dissipation, usually include an early phase (EP), a transport phase (TP), an accumulation phase (AP), and a re- moval phase (RP) (Yuan et al, 2019;Zhong et al, 2017), classifications that are based on the increase and decrease of PM 2.5 mass concentration in Beijing (BJ) caused by changes in meteorological conditions. Here, the curves in Fig.…”