Tracking the occurrence of anthropogenic magnetic particles and potentially toxic elements (PTEs) in house dust using magnetic and geochemical analyses

The influence of anthropogenic outdoor sources on the geochemical composition of house dust material in large cities is poorly understood. In this study, we investigate the magnetic signature and the concentrations of potentially toxic elements (PTEs) in randomly selected house dust samples from the metropolitan area of Athens, the most populated city in Greece. Environmental magnetic measurements, including isothermal remanent magnetization and thermomagnetism, indicated that the main magnetic mineral is coarse-grained low-coercivity magnetite. Detailed microscopic observations of the magnetically extracted material revealed the presence of three different kinds of Fe-rich particles deriving from both combustion-related and non-exhaust vehicular sources: irregularly-shaped grains and spherules of Fe-oxides, and particles consisting of metallic Fe. Further study of the morphology of single anthropogenic magnetic spherules (size > 30 μm) identified the presence of magnetite spherical particles, typically formed by industrial combustion processes. Enrichment factors (EFs) for the PTEs calculated against the Athens urban soil showed that the house dusts were very highly enriched in Cd, Cu, Zn and significantly enriched in Pb (median EF values of 34.1, 26.2, 25.4 and 10.3, respectively). The oral bioaccessibility of PTEs in the house dust, evaluated using a simulated gastric solution (0.4 M glycine), was in the order Pb > Zn > Mn > Cd > Ni > Cu > Cr > Fe. Concentrations of Pb increased with the house age. Principal component and cluster analysis demonstrated the close association of anthropogenic Cu, Pb and Zn with the magnetic susceptibility of the house dusts. We conclude that both traffic-related and industrial sources trigger the occurrence of magnetic Fe/PTEs- rich particles in house dust. These results reinforce the use of environmental magnetism determinations for assessing anthropogenic contamination of PTEs in the indoor environment in large cities.