Abstract

To gain insights into the impacts of emission reduction measures on the characteristics and sources of trace elements during the 2014 Asia-Pacific Economic Cooperation (APEC) summit, PM2.5 samples were simultaneously collected from an urban site and a suburban site in Beijing from September 15th to November 12th, and fifteen metallic elements were analyzed, including five crustal elements (Mg, Al, K, Ca and Fe), nine trace metals (V, Cr, Mn, Co, Cu, Zn, Ag, Cd and Pb) and As. Most of the trace metals (V, Cr, Mn, As, Cd and Pb) decreased more than 40% due to the emission regulations during APEC, while the crustal elements decreased considerably (4–45%). Relative to the daytime, trace metals increased during the nighttime at both sites before the APEC summit, but no significant difference was observed during the APEC summit, suggesting suppressed emissions from anthropogenic activities. Five sources (dust, traffic exhaust, industrial sources, coal and oil combustion and biomass burning) were resolved using positive matrix factorization (PMF), which were collectively decreased by 30.7% at the urban site and 14.4% at the suburban site during the APEC summit. Coal and oil combustion regulations were the most effective for reducing the trace elements concentrations (urban site: 63.1%; suburban site: 52.0%), followed by measures to reduce traffic exhaust (52.8%) at the urban site and measures to reduce biomass burning (37.7%) at the suburban site. Our results signify that future control efforts of metallic elements in megacities like Beijing should prioritize coal and oil combustion, as well as traffic emissions.

Highlights

  • PM2.5, known as atmospheric fine particles, refers to particulate matter with an aerodynamic diameter of less than or equal to 2.5 μm

  • The average PM2.5 mass concentrations before the Asia-Pacific Economic Cooperation (APEC) summit (BAPEC period, from 15 September to 2 November) were 127.6 μg/m3 (JDM) and 87.7 μg/m3 (HR), both of which exceed the second level of the National Ambient Air Quality Standard (75 μg/m3 )

  • If the mass concentration of PM2.5 exceeds 75 for two consecutive days, it is classified as a pollution event in this study

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Summary

Introduction

PM2.5 , known as atmospheric fine particles, refers to particulate matter with an aerodynamic diameter of less than or equal to 2.5 μm. Atmosphere 2019, 10, 105 impact regional atmospheric visibility and environmental climate [1,2,3]. Trace elements are some of the most important components in PM2.5 , as they are non-biodegradable, highly enriched and highly toxic. Besides the effects on human health, trace metals could damage ecological environments through dry and wet deposition to terrestrial and aquatic ecosystems [8] Previous studies have found that Mn, Ni, Cu, Zn, Se and Pb are potentially toxic to the human body, and that As, Cr and Ni are potent carcinogens that can seriously threaten human health [4,5,6,7].

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