Physicochemical characterisation of atmospheric particles in the vicinity of iron and steel industries in Australia

Atmospheric particulate matter is one of the major air pollutants which is complex in behavior, heterogeneous in mixture, variety in size, unknown in dose-response and mounted to the priority in air quality research. Emission of particles to the atmosphere from iron and steel processing industries is an increasing concern due to deleterious effects on process efficiency, human health, and environment. The negative impacts of atmospheric particles on human health and environment are dependent on their physical (particle size, morphology) and chemical properties (concentration, chemistry and speciation of metals and other elements of concern). The comprehensive understanding of the characteristics of these air particles is essential to ensure the healthier air quality, safe human health and environment. This PhD study provides a detailed physicochemical assessment of atmospheric particles collected in the vicinity of three iron and steelmaking plants and to indicate the importance of trace metal content and their distribution, bonding structure, mineral content and speciation of the particles, in addition to the assessment of the particle size and concentrations. In this study, atmospheric sampling sites were selected downstream of three iron and steel processing operations in Australia and one background site in an urban area with little industrial activity. An eight staged Micro Orifice Uniform Deposit Impactor (MOUDI) sampler with Teflon substrate was deployed to the study areas to collect the air particles. The collected particles were analysed using a series of non-destructive cutting-edge analytical techniques such as Proton Induced X-Ray emission (PIXE) for elemental content and distribution, Fourier Transform Infra-Red (FTIR) for bonding structure, X-Ray Diffraction (XRD) for mineral content, Scanning Electron Microscopy (SEM) for surface morphology, and synchrotron-based X-Ray Emission near Edge Structure (XANES) for speciation of air particles. This study revealed significantly higher metal concentrations in the atmospheric particles collected in the industrial sites, comparing to the background urban site, demonstrating local influence of the industrial activities to the air quality. The PM₂.₅ fractions in the PM₁₀ particles at all sampling sites are found ranged from 35 to 62% indicating fine particles made a significant contribution to this size fraction at these sampling sites. Similarly, PM₁ to the total PM₁₀ at all sites varied from 20 to 46% and contributed significantly to the PM₁₀ mass loading. When compared to the background sampling site, all detected metals in the particles collected near the iron and steelmaking operations had 3.4 to 14 times higher concentrations of PM₁₀, PM₂.₅ and PM₁. The modality types of the particles were found variable between the mass and elements, and among elements in the urban and industrial areas indicating the elemental modal distribution are as important as particle mass for particle pollution modelling. Iron (Fe) was found to be the dominant metal in the particles collected in vicinity of the iron and steel processing industries contributing up to 12% of the total particle mass loading. The industrial Fe fraction in the submicron and ultrafine size particles was estimated at up to 95% which may be released from high temperature industrial activities with the iron and steelmaking industries being one of the major contributors. The iron in the particles collected near the steelmaking site equipped with electric arc furnace indicated dominant Fe(III) oxide iron phases in all particle size fractions. The atmospheric particles collected near the integrated iron and steelmaking facilities operated by the blast furnace route, had similar iron phase speciation with presence of both Fe(II) and Fe(III) iron phases in the coarse and fine particle size ranges, while for the ultrafine size range of particles, Fe(III) was the dominant form of iron. This study suggests that the metal composition of size resolved air particles varies significantly between sites and the associated metal exposure value is considerably higher in the vicinity of iron and steel processing industries than in the urban area for the same particle concentration level. Hence, these industrial elemental loadings can highly influence the atmospheric pollution at local urban and regional levels and are required to consider in the atmospheric particles monitoring, modelling, risk assessment, and PM standards settings.