Magnetic biomonitoring: towards a standardization of the operational and measurement protocols
(1) Istituto Nazionale di Geofisica e Vulcanologia, 00143 Rome, Italy (2) Department of Life Sciences, University of Siena, 53100 Siena, Italy
During the last twenty years, rock magnetism methodologies have been applied to trees (leaves, bark, wood), mosses, lichens, insects and human tissues for air pollution biomonitoring purposes. Magnetic measurements are now evolving towards very sophisticated and sensitive measurements such as First Order Reversal Curves (FORC) that, on the one hand, may give extremely accurate information for the characterization and the identification of airborne particulate matter (PM) sources but, on the other hand, are partly qualitative, not validated, and may appear very specialistic. Furthermore, magnetic biomonitoring should reach a true multidisciplinary level, in which the chemical and physical properties are investigated and interpreted under a biological and environmental perspective, including a rigorous statistical approach. Here, we present the basic principles behind magnetic biomonitoring and the main laboratory methodologies involved in the determination of the parameters that are useful for outlining the abundance, the composition and the grain-size of the magnetic fraction of PM. The best practices for sample acquisition and treatment as well as the theoretical and technical aspects behind the determination of the concentration-dependent magnetic parameters (magnetic susceptibility, saturation and remanent magnetizations) will be argued, along with the role of various qualitative diagrams (Day plot, King’s plot, FORC diagrams) for recognizing the grain-size of the particles according to their magnetic domain state. The discussion will take into account the wide range of available magnetic instruments, spanning from cheap (2k€) portable magnetic susceptibility-meters, to expensive (200k€) vibrating sample magnetometers. The aim is to identify standardized parameters and protocols that can be successfully inter-calibrated among different labs, promoting the production of validated, reproducible and comparable data.
Keywords: magnetic properties, hysteresis loops, PM, metals, magnetometers, intercalibraton
