Estudio preliminar de las propiedades magnéticas de hojas de árboles y polvo urbano en la ciudad de Bilbao

Abstract

This paper presents preliminary results of an environmental magnetism study carried out in the city of Bilbao. Magnetic properties of leaves from two types of trees (Tilia tomentosa and Acer negundo) and urban dust have been measured. Sampling was conducted during one week in late September 2011 and a total of 52 sites were sampled which include streets with different traffic intensity, parks and squares. The following experiments have been performed in all samples: magnetic susceptibility at low frequency (χ), isothermal remanent magnetization (IRM) acquisition curves, backfield and hysteresis curves. Thermomagnetic curves were also carried out on urban dust samples. These analyses show differences in magnetic behaviour between leaf and dust samples. The magnetic signal is dominated by ferrimagnetic minerals and magnetite is the predominant magnetic mineral of dust samples. Urban dust samples show a more heterogeneous magnetic composition and their ferromagnetic mineral concentration is much higher than in the case of leaf samples. Furthermore, in some dust samples the presence of hematite has been observed. This behaviour of urban dust may indicate the different origin of magnetic particles, which is not only linked to traffic, but also to industrial activity.