Abstract
BackgroundEnvironmental magnetism, focusing on ferrimagnetic iron oxides, provides useful additional information on pollution of different environments. Magnetic methods have been applied to studies of atmospheric dust, namely PM10 (particulate matter smaller than 10 µm) in, e.g., industrial or urban areas. Until now, positive correlation was reported between concentration of iron oxides (expressed in terms of either magnetic susceptibility, saturation remanent or saturation induced magnetization) and concentration of PM10 or smaller. Purpose of this study was to verify the relationship between iron oxides and PM at monitoring site close to source of emissions rich in iron oxides during period of smoggy conditions.ResultsWe examined 24-h PM10 and PM1 samples, collected during 10 days of smoggy winter period at a site close to steel plant, which represents a significant source of atmospheric emissions in industrial region of Northern Moravia (Czech Republic), known for generally high degree of air pollution. Magnetic hysteresis loops were measured to obtain parameters reflecting the concentration and grain-size distribution of iron oxides. Our data show unexpected negative correlation between saturation magnetization (concentration of ferrimagnetic iron oxides) and both PM1 and PM10 concentrations, to the best of our knowledge the trend not being reported yet.ConclusionsOur finding may seemingly disqualify magnetic methods as useful proxy in air pollution studies. However, we suggest that this is an exceptional case, specific to this region and monitoring site, as well as to synoptic conditions during the smoggy period. Although the significant dust emissions are presumably rich in iron oxides, the overall air quality at the monitoring site is determined by the general environment, controlled by many other sources of different character in the region, and by the specific climatic conditions. Thus, the steel plant, presumably emitting dust rich in ferrimagnetic iron oxides, dominates the deposited dust at the nearby monitoring site only during few days of suitable weather (namely wind speed and direction).
Highlights
Environmental magnetism, focusing on ferrimagnetic iron oxides, provides useful additional information on pollution of different environments
Magnetite as the dominant magnetic mineral was identified in particulate matter 10 μm or less in diameter (PM10) collected at sites with different level of air pollution by Petrovsky et al [3]
It is obvious that except for one specimen (G148, day period towards the end of the sampling), the PM10 concentrations determined by the automatic monitoring system exceeded the allowed limit for daily average of 50 μg/m3 [47]
Summary
Environmental magnetism, focusing on ferrimagnetic iron oxides, provides useful additional information on pollution of different environments. Petrovský et al Environ Sci Eur (2020) 32:134 used to study magnetic properties of, e.g., sediments, soils, atmospheric dust and its biocarriers (tree leaves and needles, lichens, mosses), mainly to establish the correlation between magnetite (and/or maghemite) and environmentally significant parameters, such as concentration of heavy metals or particulate matter of specific size (PM10), and to assess the environmental stress reflected by the presence of these minerals. Magnetic measurements of different carriers of atmospherically deposited dust particles have unambiguously several advantages: very high sensitivity in terms of concentration of ferrimagnetic iron oxides, non-destructive character, ability to investigate short-term (daily samples) as well as long-term deposition (months to years), and/or possibility to be applied in remote places without any infrastructure and electricity (transplanted lichens and moss bags). It seems clear that saturation magnetization (either remanent or induced) is more sensitive and reliable magnetic parameter compared to magnetic susceptibility, the use of the latter one as a rapid method of assessing the bulk magnetic content of atmospheric particulate matter could be misleading
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