Chemical composition of aerosol particles and light extinction apportionment before and during the heating season in Beijing, China

Abstract

Despite extensive efforts into characterization of the sources and formation mechanisms of severe haze pollution in the megacity of Beijing, the response of aerosol composition and optical properties to coal combustion emissions in the heating season remain poorly understood. Here we conducted a 3 month real‐time measurement of submicron aerosol (PM1) composition by an Aerosol Chemical Speciation Monitor and particle light extinction by a Cavity Attenuated Phase Shift extinction monitor in Beijing, China, from 1 October to 31 December 2012. The average (±σ) PM1 concentration was 82.4 (±73.1) µg/m3 during the heating period (HP, 15 November to 31 December), which was nearly 50% higher than that before HP (1 October to 14 November). While nitrate and secondary organic aerosol (SOA) showed relatively small changes, organics, sulfate, and chloride were observed to have significant increases during HP, indicating the dominant impacts of coal combustion sources on these three species. The relative humidity‐dependent composition further illustrated an important role of aqueous‐phase processing for the sulfate enhancement during HP. We also observed great increases of hydrocarbon‐like OA (HOA) and coal combustion OA (CCOA) during HP, which was attributed to higher emissions at lower temperatures and coal combustion emissions, respectively. The relationship between light extinction and chemical composition was investigated using a multiple linear regression model. Our results showed that the largest contributors to particle extinction were ammonium nitrate (32%) and ammonium sulfate (28%) before and during HP, respectively. In addition, the contributions of SOA and primary OA to particle light extinction were quantified. The results showed that the OA extinction was mainly caused by SOA before HP and by SOA and CCOA during HP, yet with small contributions from HOA and cooking aerosol for the entire study period. Our results elucidate substantial changes of aerosol composition, formation mechanisms, and optical properties due to coal combustion emissions and meteorological changes in the heating season.

Rapid formation and evolution of an extreme haze episode in Northern China during winter 2015

“…S6c). This is similar to the composition reported in Wang et al 29 who showed that coal combustion emissions had a dominant impact on these species. In fact, the difference in OA composition was dominated by CCOA, accounting for 45% and 53% during D3 and D4, respectively (Fig.…”

Source apportionment of organic aerosol from two-year highly time-resolved measurements by an aerosol chemical speciation monitor in Beijing, China

“…The meteorological parameters, temperature (T) and relative humidity (RH) at ground site, and wind direction (WD) and wind speed (WS) at 240 m were obtained from the measurements on the Beijing 325 m meteorological tower. More detailed descriptions of the sampling site, the operations of the ACSM, and the collocated 5 measurements are given elsewhere Ge et al, 2013;Wang et al, 2015).…”

Vertical Characterization of Aerosol Particle Composition in Beijing, China: Insights From 3‐Month Measurements With Two Aerosol Mass Spectrometers

“…A recent study showed the comparable contributions between SOA and SIA in severe haze pollution in China, highlighting the importance of SOA in haze formation (Huang et al, 2014). However, previous studies also found that POA was more important than SOA in heating season due to enhanced coal combustion emissions Wang et al, 2015). However, most of these measurements were conducted at ground sites, which are subject to the influences of local source emissions.…”