Is biomagnetic leaf monitoring still an effective method for monitoring the heavy metal pollution of atmospheric particulate matter in clean cities?

The development of a reasonable method for predicting heavy metal (HM) pollution in atmospheric particulate matter (PM) remains challenging. This paper presents an elution-filtration method to collect PM from the surface of Osmanthus fragrans in a very clean area (Guiyang, China). The aim is to assess biomagnetic leaf monitoring as a simple and rapid method whether or not can be used to evaluate HM pollution in clean cities. For this purpose, the magnetic parameters and the concentration of selected HMs in PM samples were determined to investigate the relationships between magnetic properties and the concentration of HMs in deposited atmospheric PM. The results showed that the magnetic minerals in PM samples were mainly low coercivity ferrimagnetic minerals, with a small amount of high coercivity magnetic minerals. The types of magnetic minerals were generally single, and the magnetic domain state was pseudo-single domain (PSD). There was a significant correlation between magnetic parameters and the HM concentrations in PM. Low-field magnetic susceptibility (χ) could be used as an ideal proxy for determining anthropogenic HM pollution. Traffic emissions were the main atmospheric pollution source in urban Guiyang. Due to the incomplete traffic network and large traffic flow, traffic congestion (TC) often occurred at road intersections in the northwest and southwest corners of the city, resulting in the highest concentration of magnetic minerals and the most severe PM pollution. In order to ameliorate the pollution levels of atmospheric PM and safeguard public health, it is highly recommended that municipal authorities prioritize urban planning and traffic management. Specifically, measures should be taken to alleviate stop-and-go traffic and mitigate air pollution.