Development of Time-Resolved Description of Aerosol Properties at the Particle Scale During an Episode of Industrial Pollution Plume

摘要

Single-particle analysis of short-term aerosol samplings can provide unique information on the rapid evolution of size distribution and chemical composition of industrial aerosols. In this work, the potential of scanning electron microscopy equipped with energy-dispersive X-ray spectrometry (SEM-EDX) for the time-resolved description of physicochemical properties of individual aerosol particles is investigated. Two sampling campaigns were carried out at a densely populated and industrialised coastal site. The first sampling campaign corresponded to low and stable atmospheric particle loads. Low temporal variations in PM_(10) and PM_(2.5) mass concentrations during the preceding hours and during samplings were observed. In these conditions suitable to evaluate the accuracy of our sampling and analytical methodologies, very low temporal variation of physicochemical characteristics of atmospheric particles were observed, as expected. During the second sampling campaign, the ability of automated SEM-EDX to describe short temporal variation in PM_(10) and PM_(2.5) chemical composition was demonstrated. We report the tracking of a steelworks emission plume transported over an urban area by means of short-term aerosol samplings and explore how this transient industrial emission contributed to ambient particulates. Steelworks are important point-source emitters of metallic pollutants such as iron, manganese, and zinc species. Detailed assessment of the microphysical and chemical properties of aerosols collected in the vicinity of steelworks enables to precisely describe how industrial aerosols affect the composition of urban particulate matter. The studied pollution event caused dramatic changes in the composition of urban aerosols by an input of fine metallic particles containing Fe, Mn or Zn oxides and mixed particles (Mn-Fe, Zn-Mn, Zn-Fe oxides). Metal-rich particles were often found internally mixed with marine and/or continental compounds, demonstrating how industrial aerosols efficiently coagulate with particles from other sources, thereby acting as carriers of heavy metals.