Magnetic biomonitoring of airborne particles using lichen transplants over controlled exposure periods

Abstract

Lichens are able to retain airborne pollution-derived particles in their thalli for a long time, and therefore, their use in assessing atmospheric pollution may be suitable and beneficial. In this study, we transplanted species of Parmotrema pilosum in bags and exposed them to atmospheric pollutants at different sites over the course of 1 year. The exposed lichen retained anthropogenic ferrimagnetic Fe oxides that were identified and characterized by environmental magnetism methods, X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The ubiquitous magnetite, released by metallurgical factories and vehicular sources, had small grain sizes (< 0.1-1 μm) falling in the range of harmful particulate matter PM 2.5 and PM 1.0. According to the anhysteretic ratios (χ ARM /χ, ARM/SIRM), magnetic grain size tends to increase (ratios decrease) over time. Concentration-dependent magnetic parameters evidenced the cumulative presence of anthropogenic magnetite-like particles which reached high values during the study period, increasing from an initial mass-specific magnetic susceptibility χ value (mean ± S.D.) of 24.1 ± 5.0 × 10 −8 m 3 kg −1 to higher values up to 51.2 ± 23.0 × 10 −8 m 3 kg −1. Joint analysis of meteorological data and magnetic susceptibility indicated a magnetic enhancement (χ/χ initial) during the austral winter season when mean temperatures were lower; moreover, relative decreases in χ values after rainy periods are observed. This simple and low-cost methodology allowed us to study, in controlled exposure periods of 1-11 months, the ability of transplanted lichens to retain fine and ultrafine airborne particles that may have impacts on human health.

Magnetic Emissions from Brake Wear are the Major Source of Airborne Particulate Matter Bioaccumulated by Lichens Exposed in Milan (Italy)

“…Bags of Parmotrema pilosum exposed to atmospheric pollutants over the course of 1 year increased from an initial mass-specific magnetic susceptibility value (mean ± S.D.) of 24.1 ± 5.0 × 10 −8 m 3 kg −1 to higher values up to 51.2 ± 23.0 × 10 −8 m 3 kg −1 [48]. This dataset included three sites, two at metallurgical factories, and one influenced by vehicular emissions, where values increased by 100%.…”

The effect of Covid-19 lockdown on airborne particulate matter in Rome, Italy: A magnetic point of view

“…Rock magnetism was extensively used also for biomonitoring airborne pollution using tree leaves, barks, mosses and lichens, being efficient PM receptors; for a review, see Hofman et al (2017) , thereinafter, Winkler et al (2019) , Marié at al. (2020) : the magnetic properties of PM filters and bioaccumulators depend on the concentration and the grain-size of magnetite-like minerals accumulated on the samples, with the magnetic susceptibility being the fastest and most used parameter ( Kapper et al, 2020 ).…”

Magnetic Biomonitoring Using Native Lichens: Spatial Distribution of Traffic-Derived Particles

“…Such decrease, and hence partial loss of magnetic particles, may be explained by results concluded for transplanted P. pilosum as well. Recently, Marié et al (2020) found decreases of 5-28% in χ after rainy month periods.…”

“…Magnetic biomonitoring studies have taken advantage of this fact and that magnetic properties of accumulated particles are suitable proxies for pollution, which allow identifying adversely impacted zones within study areas. From the 2010s (Jordanova et al 2010;Salo et al 2012;Chaparro et al 2013;Kodnik et al 2017;Marié et al 2018), three methodologies have been defined for lichens in magnetic biomonitoring, that is, (1) the lichen native species collection; (2) the lichen transplant technique; and (3) "in situ magnetic biomonitoring" or biomonitoring using in situ measurements of magnetic susceptibility, as detailed in Marié et al (2018Marié et al ( , 2020. These methodologies allow us to assess particle pollution; however, differences between them arise from (a) the choice of exposure time for PM collection (weeks, months, years), (b) the possibility of determining the initial conditions of exposure, (c) the preservation species, and (d) the use of available native species to record air pollution over the lichen's life.…”