Home > Research > Publications & Outputs > Magnetic characterisation of London's airborne ...

Links

Text available via DOI:

View graph of relations

Magnetic characterisation of London's airborne nanoparticulate matter

Research output: Contribution to Journal/MagazineJournal articlepeer-review

E-pub ahead of print
Close
Article number119292
<mark>Journal publication date</mark>15/10/2022
<mark>Journal</mark>Atmospheric Environment
Volume287
Number of pages8
Publication StatusE-pub ahead of print
Early online date19/07/22
<mark>Original language</mark>English

Abstract

Iron-bearing particulate matter produced by vehicle emissions is known to be toxic. To better quantify potential health risks, we have conducted the first magnetic study of a time-series of London's inhalable particulate matter (<10 μm, PM 10), captured by three monitoring stations in central London (Marylebone Road, Earl's Court Road and Oxford Street) through 2010 and 2012. We conducted room-temperature analysis on all the samples, and a limited number of samples were analysed at both high and low temperatures. The high-temperature measurements identified magnetite as the dominant magnetic phase. The low-temperature measurements revealed high numbers of nanoparticles, which, assuming magnetite, are in the grain-size range 1–4 nm. It is estimated that as much as ∼40% of the total magnetic signal at 10 K is from particles <4 nm, that are magnetically ‘invisible’ at room-temperature and are being routinely under-estimated in room temperature-based magnetic studies. From the low-temperature measurements, the total concentration of magnetite was estimated at ∼7.5%, significantly higher than previously reported. The room-temperature magnetic data were compared with other pollution data, e.g., NO X and PM 10, and meteorological data. Mass-dependent terms like the saturation magnetisation were found to display a strong correlation with NO X and PM 10, indicating a common source for these pollutants, i.e., vehicle emissions. Magnetic coercivity measurements, which are independent of abundance, and provide information on grain-size, were consistent across all three sampling localities, again suggesting a major dominant source. Relatively small variations in coercivity were correlated with meteorological events, e.g., temperature and precipitation, suggesting preferential removal of larger airborne grains, i.e., >50 nm.