Magnetic techniques applied to study the accumulation times period of urban/industrial dust in lichens

ANA M. SINITO; DEBORA C. MARIÉ; MARCOS A.E. CHAPARRO

Praga

Congreso; 26th IUGG General Assembly 2015; 2015

IUGG

This study assesses the accumulation time period of urban/industrial dust in the lichen Parmotrema Pillosum, using different magnetic parameters. The study was carried out in Tandil City (37º19.5?S; 59º08.3?W), Argentina. We selected a control (without or with low pollution load) site for collecting lichens to transplant. Such lichens were prepared and transplanted in various selected sites inside the urban area. These sites are affected by different pollutant emission sources (vehicle traffic and metallurgical factories). Twelve samples for each site were prepared and simultaneously transplanted in order to make monthly collections.Magnetic susceptibility (X), anhysteretic and isothermal magnetizations (ARM, IRM) were measured. Also, associated parameters were used, such as kFD%, XARM, HCR, S-ratio, SIRM/X and kARM/k. In addition, deposited particles onto the lichen surface were observed by scanning electron microscopy (SEM) and analyzed by x-ray energy dispersive spectroscopy (EDS).The analysis of the set of parameters indicates the predominance of ferromagnetic minerals, like (titano)magnetite. The King´s plot indicates a majority of fine magnetic grains (less than 0.1 um).There is a general trend of increase for parameters related to magnetic concentration, though a slight decrease is observed after rainy periods, apparently due to a washing effect of surface particles. The magnetic grain size dependent parameters decrease with time while magnetic concentration increases, suggesting that higher magnetic concentrations are associated with the accumulation of coarser magnetic grains.SEM and EDS indicate higher Fe content and the presence of spherules produced by industrial activity near the collection sites.