Unraveling the role of silicon in atmospheric aerosol secondary formation: a new conservative tracer for aerosol chemistry

Abstract

Abstract. Aerosol particles are ubiquitous in the atmosphere and affect the quality of human life through their climatic and health effects. The formation and growth of aerosol particles involve extremely complex reactions and processes. Due to limited research tools, the sources and chemistry of aerosols are still not fully understood, and until now have normally been investigated by using chemical species of secondary aerosols (e.g., NH4+, NO3-, SO42-, SOC) as tracers. Here we investigated the role of silicon (Si), an ubiquitous but relatively inert element, during the secondary aerosol formation process. We analyzed the correlation of Si in airborne fine particles (PM2.5) collected in Beijing – a typical pollution region – with the secondary chemical species and secondary particle precursors (e.g., SO2 and NOx). The total mass of Si in PM2.5 was found to be uncorrelated with the secondary aerosol formation process, which suggested that Si is a new conservative tracer for the amount of primary materials in PM2.5 and can be used to estimate the relative amount of secondary and primary compounds in PM2.5. This finding enables the accurate estimation of secondary aerosol contribution to PM2.5 by using Si as a single tracer rather than the commonly used multiple chemical tracers. In addition, we show that the correlation analysis of secondary aerosols with the Si isotopic composition of PM2.5 can further reveal the sources of the precursors of secondary aerosols. Therefore, Si may provide a new tool for aerosol chemistry studies.

Elucidation of the Critical Role of Core Materials in PM2.5-Induced Cytotoxicity by Interrogating Silica- and Carbon-Based Model PM2.5 Particle Libraries

“…After their emission into the environment, in particular, the atmosphere, carbon-or silica-based particulate matter first meet and interact with various airborne pollutants to suffer complex transformation to form the secondary aerosol particles. 37 The initial physicochemical properties of the carbon and silica cores are among the most important factors that determine the particle−pollutant interactions but have long been ignored. In the present study, carbon-and silicabased model PM 2.5 particles were synthesized and applied to explore how the core materials of carbon and silica affected the loadings of various pollutants.…”

ToF‐SIMS analysis of chemical composition of atmospheric aerosols in Beijing

“…The data points from April 6 were quite different from others, resulting from the combination of a high level of O 3 and the small number of residual pollutants in the air, which are caused by seasonal characteristics and fossil fuel combustion in motor vehicles, respectively, considering sampling time and position. Compared with Table , Si + and SiH + appeared in Table , which may correspond to substances in soil, cement, or lime . Beijing has frequent sandstorms in spring, during which the sand and dust from the north contribute greatly to the PM 2.5 in the spring in Beijing.…”

“…41,42 Even though the concentrations of SO 2 and NO 2 on that day are relatively low, they could still make a great contribution to particulate mat- Table 4, which may correspond to substances in soil, cement, or lime. 23,25,44 Beijing has frequent sandstorms in spring, during which the sand and dust from the north contribute greatly to the PM 2.5 in the spring in Beijing. The dust can stay in the near-surface atmosphere for a long time so the silicon can be found even in the good air quality days in spring.…”

Two-Dimensional Silicon Fingerprints Reveal Dramatic Variations in the Sources of Particulate Matter in Beijing during 2013–2017

“…In our previous studies, we have shown that different primary sources of PM 2.5 (e.g., coal burning, industrial emission, dusts, and vehicle emission) have distinguishable Si isotopic fingerprints, thus enabling the direct tracing of primary sources of PM 2.5 by the Si isotopic composition . Furthermore, as a relatively inert element, Si content in PM 2.5 is predominantly emitted from primary sources and the total mass of Si in PM 2.5 is unlikely to be affected by the secondary aerosol formation process . Thus, the secondary aerosol formation can cause a dilution of the Si abundance in PM 2.5 .…”

“…Thus, the secondary aerosol formation can cause a dilution of the Si abundance in PM 2.5 . On the basis of such an Si-dilution effect, it is possible to rapidly estimate the contribution of secondary aerosols to PM 2.5 . These studies have revealed the great potentials of Si as a new tracer for PM 2.5 .…”