Detection of metallic iron in urban dust by magnetic methods and microscopic observations

Beata Górka-Kostrubiec, Tomasz Werner, Sylwia Dytłow, Iga Szczepaniak- Wnuk, Maria Jeleńska, Aneta Hanc-Kuczkowska

A thermomagnetic study was performed to identify the magnetic mineralogy of urban dust (indoor dust, outdoor dust, street dust, and dust from cabin air cars filters) collected from different environments. Temperature dependence of magnetic susceptibility (T) and induced magnetization M(T) were measured in the range of 30–700 °C and 30–800 °C, respectively. The presence of a “tail” in the heating curve of (T) between 600 °C and 700 °C is very often interpreted in the literature as evidence for the presence of hematite. However, the thermomagnetic curve of M(T) measured in the wider temperature range of up to 800 °C revealed that the Curie temperature of ~760 °C is typical of metallic iron. The presence of Fe-rich elongated shaving-like magnetic particles was confirmed by scanning electron microscopy observations. In various types of urban dust, the presence of metallic Fe can be due to traffic-related pollution as the concentration of elemental iron correlates with the key heavy metals Cu, Pb, Ba, Mn, Cr, and Zn, emitted by motor vehicles.

Keywords: Magnetic methods, Anthropogenic magnetic particles, Metallic iron, Traffic related heavy metals

Proscience vol. 5

Pp 46-51

DOI:10.14644/dust.2018.008