Magnetic mapping of air pollution in Tandil city (Argentina) using the lichen Parmotrema pilosum as biomonitor

Özet

The lichen Parmotrema pilosum is sensitive to pollution and it can live accumulating airborne pollutantsfor long time, such characteristic allows its use as biomonitor for environmental mapping in urban areaswhen this epiphytic specie is available. In this work, we investigated the use of such passive collector andmagnetic techniques to monitor the air pollution in Tandil, a city located in Buenos Aires province withapproximately 125,000 inhabitants, 60,000 vehicles and various metallurgical factories inside the urbanarea. The sampling strategy was carried out following a random stratified design and measuring magneticsusceptibility, magnetic hysteresis loops, anhysteretic and isothermal remanent magnetization andthermomagnetic studies to determine the magnetic properties of airborne particles accumulated onlichen samples. Scanning electron microscopy observations show particles with different morphologies(individual particles, spherules and aggregates) and composition (Fe, Al, Ni, Cr, Ti, Cu, K and Br) producedby metallurgical factories and by gaseous/solid vehicle emissions. The magnetic mineralogy shows thepredominance of pseudo-single domain magnetite-like mineral and the magnetic grain size estimationsindicate the presence of fine particles (<0.1 mm) in sites with low vehicular traffic or less polluted, whilesites more affected by pollution (high vehicular traffic and metallurgical industries) are characterized bycoarser magnetic grain size particles, between 0.1 and 5 mm. Mass-specific magnetic susceptibility wasrepresented in a 2-D contour map to observe in detail the distribution of magnetic particles in this urbanarea, giving high values (up to 1161.2 108 m3 kg1) that are indicative of areas with high pollutionloading.