Traffic-derived magnetite pollution in soils along a highway on the Tibetan Plateau

Abstract

Anthropogenic magnetite nanoparticles have been identified to be present in the human brain and circulatory system, which are potentially linked with the incidence of neurodegenerative and cardiovascular diseases. Specifically, magnetite nanoparticles originating from exhaust emissions and brake wear are an important hazardous species in particulate matter. Here, we investigated the occurrence, spatial characteristics, and chemical fingerprints of traffic-derived magnetite particles in the roadside soils of a national highway on the Tibetan Plateau, which is a less polluted region and provides a unique scenario to estimate the magnetite pollution from traffic sources. We report the high magnetite levels (mean concentration 2.05 ± 1.50 mg g⁻¹ within a distance of 10 m from the road) and the spatial patterns of magnetite particles in the roadside soils. We found that most of the magnetite particles were less than 150 nm in particle size and that the concentration was highly dependent on the distance away from the roadside and on the surrounding anthropogenic activities. Furthermore, we identified the sources of magnetite particles by morphological characterization and multi-element fingerprints, which verified their main origins from traffic (especially from wear particles) rather than natural sources. Our findings reflect the impact of anthropogenic activities on the Tibetan Plateau and, more importantly, demonstrate that anthropogenic magnetite pollution from traffic emission is an important risk factor for near-road residents.