Characteristics of iron-containing magnetic particles in household dust from an urban area: A case study in the megacity of Shanghai

In order to characterize the magnetic properties and trace sources of household dust particles, magnetic measurements, geochemical and SEM/TEM analyses were performed on vacuum dust from 40 homes in Shanghai, China. Iron-containing magnetic particles (IMPs) in the household dust were dominated by magnetite, while maghemite, hematite and metallic iron were also present. The IMPs were mainly composed of coarse-grained particles (e.g., >0.1 µm). Ultrafine superparamagnetic (SP) grains (<30 nm) increased proportionately with the abundance of the total IMPs. Household dust had more and coarser IMPs than background soil, but less and finer IMPs than street dust and industrial emissions (coal combustion and metallurgy). Metallic Fe and spherical IMPs, originating from brake wear abrasion and coal combustion, respectively, have been observed using the SEM/TEM. Contents of magnetic particles were positively correlated to Mo, Ni and Sb, while HIRM was associated with As, Mo, Pb and Sb. The multiple lines of evidence including magnetic measurements, geochemical and SEM/TEM analyses suggested that industrial and traffic emissions and street dust were dominant contributors to the IMPs. Such an approach can help to establish more precisely the sources of household dust particles and could be applied to other indoor contexts and further urban environments.