Characterization and geochemistry of technogenic magnetic particles (TMPs) in contaminated industrial soils: Assessing health risk via ingestion

- Magnetic susceptibility (χlf) depended on the content of TMPs.
- A dominant iron spinel phase was detected in TMPs.
- Potentially harmful elements (PHEs) were preferentially enriched in the TMPs.
- Significant fractions (> 50%) of Pb and Zn occur in bioaccessible forms in the TMPs.
- Hazard Quotient (HQ) values were significantly higher than safe level (= 1).

The objective of this study was the detailed characterization of “technogenic” magnetic particles (TMPs) separated from contaminated industrial soils. Moreover, non-carcinogenic health risk posed by “technogenic” metals Pb and Zn via the ingestion exposure pathway was carried out. Volume magnetic susceptibility (κ) was measured directly in the field around a chemical industry in Sindos industrial area, Northern Greece. Representative soil samples were collected from the sites where elevated κ values were recorded. Mass specific magnetic susceptibility (χlf) depended on the content of TMPs and ranged from 52.6 × 10− 8 m3 kg− 1 to 821.2 × 10− 8 m3 kg− 1 with the maximum values detected in the immediate vicinity of the industrial unit where the most contaminated soils were also identified. Mineralogically the TMPs exhibited a dominant iron spinel phase, while other iron-bearing phases such as hematite and lepidocrocite were detected. Morphologically, Fe-rich spherules and irregular-shaped particles were the most commonly observed particles in TMPs, revealing various Fe contents often associated with elevated heavy metal contents. TMPs exhibited significantly higher concentrations of trace elements compared to non-magnetic fractions (NMFs) indicating that potentially harmful elements (PHEs) are preferentially enriched in the TMPs. Furthermore, for the first time, a health risk assessment study for the incidental soil magnetic fractions (MFs) ingestion of the “technogenic” metals Pb and Zn was carried out based on U.S. Environmental Protection Agency (U.S.E.P.A.) guidelines, incorporating oral bioaccessibility measurements using the BARGE Unified Bioaccessibility Method (UBM). Significant fractions (> 50%) of Pb and Zn occur in bioaccessible forms in the TMPs and both children and adults are experiencing potential health risk since determined HQs values were significantly higher than safe level (= 1).