Comparison of magnetic parameters of urban atmospheric particulate matter with pollution and meteorological data

Magnetic hysteresis parameters were measured for three sample sets of respirable atmospheric particulate matter collected in Munich, Germany, and were compared with pollution data and meteorological data using principal component analysis. The sample sets were collected at two urban locations by the filter method during August 1998-July 1999. The samples were measured in weekly batches, with the longest data set being 40 weeks. It was found that the magnetic hysteresis parameters generally had a stronger correlation with the meteorological data than with the pollution data. Correlations with the pollution data were found to be highly site dependent, that is, at one location there was a strong relationship between the magnetic parameters and vehicular derived combustion pollutants, but not at the other. The primary magnetic mineral was identified to be magnetite, in the grain size range 0.2-5 mum, which is small enough to be particularly dangerous to humans as the particles can be inhaled deeply into the lung. The grain size-dependent magnetic hysteresis parameters were strongly dependent on relative humidity. The concentration of magnetic particulate. matter was in the range of 0.3-0.6% by mass. As the amount of magnetic particulate matter did not always correlate significantly with the total particulate mass, the use of magnetic susceptibility as a rapid method of assessing the bulk magnetic content of atmospheric particulate matter could be misleading. (C) 2001 Elsevier Science Ltd. All rights reserved.