Magnetic mapping air pollution Tandil city (Arg) using the lichen Parmotrema pilosum as biomonitor

What is it about?

The lichen Parmotrema pilosum is sensitive to pollution and it can live accumulating airborne pollutants for long time, such characteristic allows its use as biomonitor for environmental mapping in urban areas when this epiphytic specie is available. In this work, we investigated the use of such passive collector and magnetic techniques to monitor the air pollution in Tandil, a city located in Buenos Aires province with approximately 125,000 inhabitants, 60,000 vehicles and various metallurgical factories inside the urban area. The sampling strategy was carried out following a random stratified design and measuring magnetic susceptibility, magnetic hysteresis loops, anhysteretic and isothermal remanent magnetization and thermomagnetic studies to determine the magnetic properties of airborne particles accumulated on lichen 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) produced by metallurgical factories and by gaseous/solid vehicle emissions. The magnetic mineralogy shows the predominance of pseudo-single domain magnetite-like mineral and the magnetic grain size estimations indicate the presence of fine particles (<0.1 μm) in sites with low vehicular traffic or less polluted, while sites more affected by pollution (high vehicular traffic and metallurgical industries) are characterized by coarser magnetic grain size particles, between 0.1 and 5 μm. Mass-specific magnetic susceptibility was represented in a 2-D contour map to observe in detail the distribution of magnetic particles in this urban area, giving high values (up to 1161.2 × 10−8 m3 kg−1) that are indicative of areas with high pollution loading.

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Why is it important?

In this contribution, the urban area of Tandil city was studied in detail using the lichen Parmotrema pilosum to monitor the air quality. Taking into account results obtained by Chaparro et al. (2013), where a pilot study was presented in order to evaluate the usefulness of different lichen species for studying anthropogenic pollution in urban areas, the aim of this work focuses on: 1) a detailed sampling strategy based on a random stratified design that included about 660 blocks in the city; 2) the choice and use of magnetic parameters as tools for environmental monitoring; 3) the determination of more impacted areas through concentration dependent magnetic parameters; and 4) the identification of the pollution sources from magnetic grain size dependent parameters.

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