Magnetic signature of daily sampled urban atmospheric particles

Abstract

The magnetic signature of two sets of daily-sampled particulate matter (PM) collected in Munich, Germany, were examined and compared to variations in other pollution data and meteorological data using principal component analysis. The magnetic signature arising from the magnetic minerals in the PM, was examined using a fast and highly sensitive magnetic remanence measurement. The longest data set studied was 160 days, significantly longer than that of similar magnetic PM studies improving the statistical robustness. It was found that the variations in the mass dependent magnetic parameters displayed a complicated relationship governed by both the meteorological conditions and the PM loading rate, whereas mineralogy/grain-size dependent magnetic parameters displayed little variation. A six-fold increase in the number of vehicles passing the sampling locations only doubled the magnetic remanence of the samples, suggesting that the measured magnetic signature is in addition strongly influenced by dispersion rates. At both localities the saturation isothermal remanent magnetisation (SIRM) was found to be strongly correlated with the PM mass, and it is suggested that measuring SIRM as a proxy for PM monitoring is a viable alternative to magnetic susceptibility when the samples are magnetically too weak. The signal was found to be dominated by magnetite-like grains less than 100 nm in diameter which is thought to be derived primarily from vehicles. Such small grains are known to be particularly dangerous to humans. There was also evidence to suggest from magnetic stability parameters that the magnetite-like grains were covered with an oxidised rim. The concentration of magnetic particulate matter was in the range of 0.3-0.5% by mass.

Plants and Atmospheric Aerosols

“…Measurement of magnetic susceptibility or saturation isothermal remanent magnetization (SIRM) is a relatively new method to determine foliar-deposited aerosols in urban vegetation (Hofman et al 2014;Kardel et al 2011;Matzka and Maher 1999;Sant'Ovaia et al 2012;Urbat et al 2004). This technique has demonstrated that metallic PM 2.5 from road and rail traffic, including fuel combustion, brake abrasion, and corrosion, is deposited to leaves and may become embedded in them (Hofman et al 2014;Muxworthy et al 2003;Urbat et al 2004). SIRM of urban tree leaves has proven to be a good estimator of trafficderived aerosol (Kardel et al 2011;Maher et al 2013;Rai 2013).…”

Using urban man-made ponds to reconstruct a 150-year history of air pollution in northwest England

“…Magnetic susceptibility (v) indicates the concentration of ferrimagnetic grains within a sample and is a suitable proxy for PM 10 concentration (Muxworthy et al 2003). A Bartington (Oxford, England) MS2B dual-frequency susceptibility sensor, connected to a MS2 susceptibility meter, was used according to Dearing (1999).…”

Lead isotope composition and host phases in airborne particulate matter from Budapest, Hungary

“…Iron impurities are often found in combustibles and can convert to iron oxides, such as magnetite or hematite, depending of the burning conditions (Muxworthy et al 2003), but they can also be related to the presence of ferrocene as a fuel additive (Braun et al 2006). That is why several studies have revealed large concentrations of iron in anthropogenic particulate matter (generally between 5 and 15%) and magnetite was identified as the dominant magnetic phase of Fe-rich particles (e.g.…”