An Integrated Magnetic Approach to Assess Spatiotemporal Airborne Pollution Impacts Related to Different Stages in the Steel Production Process

Abstract:

Particulate matter (PM) emitted in the steel production and cement industry, as well as in the transport and energy production sector, possesses enhanced magnetic properties which enable to delineate the impact of airborne pollution once the particles have deposited onto the Earth’s surface. Topsoil magnetic susceptibility, for instance, has been shown a suitable parameter for airborne pollution monitoring in areas with homogeneous soil type and land use. However, when study areas comprise multiple types of land use, the distribution of magnetic particles down the soil profile can vary strongly and impede reliable investigation of pollution impacts. Here, we demonstrate how an adaptive approach involving depth-integrated magnetic susceptibility records can mediate adverse effects of varied land use on topsoil magnetic records for pollution studies (Declercq et al., 2020). Furthermore, in tandem with other receptors of magnetic PM (strawberry and grass leaves, plastic coated cardboards (PCCs) and wiped anthropogenic surfaces), long-term variations captured in soil magnetic records were compared to short-term pollution impacts. Although this approach enables to reliably discriminate spatiotemporal variations in airborne pollution impacts, a straightforward means to relate environmental magnetic signatures more directly to specific emission outputs, and pollutant sources – facilitating the development of control measure strategies – remains lacking. To this end, we characterised the physicochemical properties of PM generated by the largest emitter of magnetic PM in our study area, a steel mill. Particular PM loads involved in different steps of the steel production process (crude iron ore, sinter plant, blast furnace and steel mill), as well as ambient PM collected on PCCs nearby the factory, were magnetically, morphologically and chemically characterized and mutually compared. Source-specific fingerprints facilitated the interpretation of magnetic pollution impacts and revealed how emissions from the blast furnace and steel mill strongly affected the observed magnetic signatures in the environment. We show how the presented magnetic approach supports spatial investigation of source-specific airborne pollution impacts, both on the short and long term.