Magnetic properties are used throughout the world to measure the concentration of (ferri) magnetic minerals in soil, sediment and dust. These minerals in soil come from a variety of sources, including air-borne particulate pollution, parent rock and paedogenesis. Changes in the content of magnetic minerals, as well as their spatial and vertical distribution in soil profiles are caused by human activity. Magnetic minerals are distinguished by their affinity for other elements found in soil, such as heavy metal. As a result, magnetic susceptibility has been widely used as an approximation of heavy metal contamination in soil. The current study was conducted in a tropical deciduous forest in Central Uttar Pradesh, namely the kukrail reserve forest in Lucknow to assess heavy metal contamination levels caused by various anthropogenic activities and to confirm the utility of using MS surveying in these types of studies. The current study was conducted at two sites viz. agricultural area and forest area because these sites are the most contaminated ones. Significant correlation between heavy metal concentration and magnetic susceptibility with p<0.005 is noticed for Co, Cr, Pb, Zn, Cu and Fe of agricultural area. Similarly in forest area significant correlation exists between Cr, Ni, Pb and Zn.  The χLF values show a significant correlation with the concentration of heavy metals except for Cu and Cr in forest area and Pb and Zn in agricultural area. In comparison to the methodologies of chemical analysis, the χLF measurement techniques provide us with lower cost and less time consuming method for identification of possible soil pollution.

Pollution-tolerant lichens are recognized ecological indicators of air pollution in cities, which can also collect airborne anthropogenic particles in their tissues. Harmful (sub)micron-sized magnetites are a ubiquitous component of air particle pollution, adversely impacting human health. In this work, in situ magnetic susceptibility κᵢₛ of well-characterized ultrafine magnetite and lichen thalli were measured to quantify the amount of airborne magnetic particles (AMP) after calibration and to assess the lichen's decontamination over time. Up to 2850 magnetic measurements were carried out in twenty-nine transplanted lichens (collected in urban and clean areas) from winter 2020 to winter 2021. Before the transplants, their initial κᵢₛ values were 0.23–9.45 × 10⁻⁵ SI, representing AMP contents of 0.1–4.6 mg in lichen thalli. After lichens were transplanted to a shared site, the magnetic signals evidenced short-term increases and long-term decreases. After three, five and nine months, the AMP loss is more pronounced for transplanted lichens from polluted (e.g., AMP_5-months loss = 0.59 mg) than clean (= 0.08 mg) sites. Rainfall influenced the lichen's decontamination between seasons. In situ measurements and lichens offer a valued and time-saving methodology for biomonitoring harmful airborne particles simply and effectively.

Particulate air pollution in cities comprises a variety of harmful compounds, including fine iron rich particles, which can persist in the air for long time, increasing the adverse exposure of humans and living things to them. We studied street tree (among other species, Cordyline australis, Fraxinus excelsior and F. pensylvanica) barks as biological collectors of these ubiquitous airborne particles in cities. Properties were determined by the environmental magnetism method, inductively coupled plasma optical emission spectrometry and scanning electron microscopy, and analyzed by geostatistical methods. Trapped particles are characterized as low-coercivity (mean ± s.d. value of remanent coercivity Hcᵣ = 37.0 ± 2.4 mT) magnetite-like minerals produced by a common pollution source identified as traffic derived emissions. Most of these Fe rich particles are inhalable (PM₂.₅), as determined by the anhysteretic ratio χARM/χ (0.1–1 μm) and scanning electron microscopy (<1 μm), and host a variety of potentially toxic elements (Cr, Mo, Ni, and V). Contents of magnetic particles vary in the study area as observed by magnetic proxies for pollution, such as mass specific magnetic susceptibility χ (18.4–218 × 10⁻⁸ m³ kg⁻¹) and in situ magnetic susceptibility κᵢₛ (0.2–20.2 × 10⁻⁵ SI). The last parameter allows us doing in situ magnetic biomonitoring, being convenient because of species preservation, measurement time, and fast data processing for producing prediction maps of magnetic particle pollution.

The purpose of this pilot study was to test spider webs as a fast tool for magnetic biomonitoring of air pollution. The study involved the investigation of webs made by four types of spiders: Pholcus phalangioides (Pholcidae), Eratigena atrica and Agelena labirynthica (Agelenidae) and Linyphia triangularis (Linyphiidae). These webs were obtained from outdoor and indoor study sites. Compared to the clean reference webs, an increase was observed in the values of magnetic susceptibility in the webs sampled from both indoor and outdoor sites, which indicates contamination by anthropogenically produced pollution particles that contain ferrimagnetic iron minerals. This pilot study has demonstrated that spider webs are able to capture particulate matter in a manner that is equivalent to flora-based bioindicators applied to date (such as mosses, lichens, leaves). They also have additional advantages; for example, they can be generated in isolated clean habitats, and exposure can be monitored in indoor and outdoor locations, at any height and for any period of time. Moreover, webs are ubiquitous in an anthropogenic, heavily polluted environment, and they can be exposed throughout the year. As spider webs accumulate pollutants to which humans are exposed, they become a reliable source of information about the quality of the environment. Therefore, spider webs are recommended for magnetic biomonitoring of airborne pollution and for the assessment of the environment because they are non-destructive, low-cost, sensitive and efficient.

Children in urban environments are exposed to potential harmful elements (PHEs) through variable exposure media. Playing activities in outdoor playgrounds have been considered of high concern due to children's exposure to sand-bound PHEs through unintentional or intentional sand ingestion. Furthermore, the affinity of magnetic particles with dust-bound PHEs in playgrounds has been reported. In this study, playground sands (PG sands) from public playgrounds in the city of Thessaloniki, N. Greece were sampled and the levels, the contamination degree, oral bioaccessibility and exposure assessment of PHEs were evaluated. In addition, low-cost and fast magnetic measurements (i.e. mass specific magnetic susceptibility, χₗf) were explored as potential pollution and health risk proxies. Mineralogically, siliceous PG sands dominated, while morphologically angular magnetic particles and Fe-rich “spherules” of anthropogenic origin were revealed and verified by enhanced χₗf values. The average total elemental contents exhibited a descending order of Mn > Ba > Cr > Zn > Ni > Pb > Cu > Co > As > Sn > Bi > Cd, however only Cd, Bi, Pb, Cr, As and Zn were presented anthropogenically enhanced. Notable increase on PHEs levels and finer sand fractions were observed with continuous sand use. Anthropogenically derived elements (i.e. Cd and Pb with high Igₑₒ values) exhibited higher bioaccessible fractions in PG sands and considered easily soluble in gastric fluids through ingestion. However, increased risks were found for specific PHEs (especially Pb) only in a worst case exposure scenario of an intentional sand ingestion (pica disorder). Statistical analysis results revealed a linkage of anthropogenic components with sand-bound magnetic particles. Moreover, the recorded high affinity of Pb contents (in an enhanced magnetized sub-set of PG sands) and bioaccessible Cd fractions with χₗf provide a preliminary indication on the successful applicability of low-cost and fast magnetic measurements in high impacted playground environments.

Soil magnetic susceptibility (MS) is an important parameter in pollution studies owing to its relationship with atmospheric deposition, and the concomitance of technogenic magnetic particles (TMPs) with potentially toxic elements (PTEs), Fe and Mn. In this study, we performed a detailed soil study under tree canopies for a forest area with high historical TMP-bearing industrial dust deposition. The technogenic sources of magnetic signals in topsoil were analyzed via scanning electron microscope electron dispersive spectroscopy (SEM/EDS), while the minor role of geogenic sources was obtained from soil profile analysis. To our knowledge, this is the first study to show soil TMP distribution in three dimensional (3D) space. In addition, using the data from 275 soil cores and 8250 individual measurements, 3D maps of MS for four tree species were plotted. There is a noticeable difference between coniferous (spruce and pine) and deciduous (beech and oak) species regarding depth of maximum concentration of magnetic particles in the topsoil. For beech and oak, maximum MS values were measured at 3 cm depth; pine and spruce, maximum MS values were measured at 5 cm depth. However, no significant differences were found among tree species in terms of mean MS or PTE contents. This suggests that there is little different among tree species in terms of dust capture over their life span. Significant correlations between MS and other parameters (PTEs and organic matter contents) present new possibilities for spatial 3D analysis of topsoil horizons.

Between 9 March and 18 May 2020, strict lockdown measures were adopted in Italy for containing the COVID-19 pandemic: in Rome, despite vehicular traffic on average was more than halved, it was not observed a evident decrease of the airborne particulate matter (PM) concentrations, as assessed by air quality data. In this study, daily PM₁₀ filters were collected from selected automated stations operated in Rome by the regional network of air quality monitoring: their magnetic properties – including magnetic susceptibility, hysteresis parameters and FORC (first order reversal curves) diagrams - were compared during and after the lockdown, for outlining the impact of the COVID-19 measures on airborne particulate matter. In urban traffic sites, the PM₁₀ concentrations did not significantly change after the end of the lockdown, when vehicular traffic promptly returned to its usual levels; conversely, the average volume and mass magnetic susceptibilities approximately doubled, and the linear correlation between volume magnetic susceptibility and PM₁₀ concentration became significant, pointing out the link between PM₁₀ concentrations and the increasing levels of traffic-related magnetic emissions. Magnetite-like minerals, attributed to non-exhaust brakes emissions, dominated the magnetic fraction of PM₁₀ near urban traffic sites, with natural magnetic components emerging in background sites and during exogenous dusts atmospheric events. Magnetic susceptibility constituted a fast and sensitive proxy of vehicular particulate emissions: the magnetic properties can play a relevant role in the source apportionment of PM₁₀, especially when unsignificant variations in its concentration levels may mask important changes in the traffic-related magnetic fraction. As a further hint, increasing attention should be drawn to the reduction of brake wear emissions, that are overcoming by far fuel exhausts as the main particulate pollutant in traffic contexts.

This study explored the suitability of available lichen species as air pollution biomonitors and assessed their potential for magnetic monitoring in cities. Several lichens on tree bark were collected in urban and industrial sites from Tandil city, as well as control sites. The results showed that magnetite-like minerals were the main magnetic carriers in all sites and samples. However, the concentration varied between clean and polluted sites. In addition, magnetic-grain size-distribution showed clear differences between sites. Observations by scanning electron microscopy showed different particles in a variety of shapes and grain sizes; moreover, the presence of iron oxides and several toxic elements was detected by energy dispersive spectroscopy analysis. Although eleven lichen species were identified that appeared suitable for use as air-pollution monitors, three of them, Parmotrema pilosum, Punctelia hipoleucites and Dirinaria picta, occurred more frequently in the area, thus constituting appropriate species for future monitoring in the study area.

Lakes and lake sediments are significant components of the global carbon (C) cycle, and may store very large amounts of organic matter. Carbon sequestration in lakes is subject to substantial temporal and spatial variation and may be strongly affected by human activities. Here, we report accumulation rates (AR) of organic C (OC), total nitrogen (TN) and total phosphorous (TP), and investigate their responses to anthropogenic impact over the past 150 years by analyzing 62 sediment cores from 11 shallow lakes in the Songnen Plain, northeast China. From the center of each of the lakes, we selected one master core for age determination by ²¹⁰Pb and ¹³⁷Cs radioisotopes. The contents of OC, TN, TP, dry bulk density and mass specific magnetic susceptibility were then determined for all cores. The regional OCAR, TNAR and TPAR up-scaling from the multiple cores yielded mean values of 51.63 ± 15.13, 2.50 ± 0.98, and 0.90 ± 0.21 g m⁻² yr⁻¹, respectively. Nutrient AR in the studied lakes increased by a factor of approximately 2 × from the middle 19th century to the 1950s, and approximately 5 × after the 1950s. Elemental ratios show that the increase in OCAR is mainly the result of C autogenesis from the growth of aquatic plants stimulated by agricultural intensification, including increased chemical fertilizer application and farmland expansion. Significantly enhanced nutrient burial by these lakes after the 1950s resulted from increased anthropogenic impacts in northeast China. More sustainable agricultural practises, including a decrease in P fertilizer use, would result in a lowering of OCAR, TNAR and TPAR in the future.

Magnetic properties of road dusts from 26 urban sites in Bulgaria are studied. Temporal variations of magnetic susceptibility (χ) during eighteen months monitoring account for approximately 1/3rd of the mean annual values. Analysis of heavy metal contents and magnetic parameters for the fraction d < 63 μm reveal significant correlations (p < 0.05) between χ and Fe, Mn and PLI index. The highest negative correlation (R2 = −0.84) is observed between the ratio ARM/χ and Pb content. It suggests that Pb is related to brake/tyre wear emissions, releasing larger particles and higher Pb during slow driving – braking. Bulk χ values of road dusts per city show significant correlation with population size and mean annual NO2 concentration on a log-normal scale. The results demonstrate the applicability of magnetic measurements of road dusts for estimation of mean NO2 levels at high spatial density, which is important for pollution modelling and health risk assessment.