Acta Facultatis Ecologiae - Technická univerzita vo Zvolene

120PM 10 limit (10µm) can significantly affect humanhealth as they can easily be transported into deeperparts of the respiratory tract and accumulated inthe alveoli (LfU – Landesanstalt für Umweltschutz,1998). It is well known that due to their specificsurface, such particles are excellent absorbers andcarriers of pollutants such as heavy metals. Magneticmethods provide an inexpensive and quick diagnosticalternative to other techniques for (direct)analyzing pollutants and are extremely sensitive tomagnetic particles of the above mentioned grainsizes (Hoffmann et al,; 1998, Leven et al., 1998).Sediments and soils can act as natural storagefor many types of pollution. Magnetic proxies representpowerful means for routine screening anddetecting contamination due to heavy metals.Here, we report results of our investigationsfocused on pollution screening using magnetic susceptibilityon roadsides. The main aim of this studyis to test the applicability of the magnetic mappingmethod.ENVIRONMENTAL MAGNETISM– MAGNETO-SCREENINGOF POLLUTIONOverviewA description of the method of environmentalmagnetism including a few results demonstratingthe capabilities of this technique are presented below(more detailed reviews are found, e.g. in (Oldfield,1991; King and Chanell, 1991; Strzyszcz, 1993,Dearing, 1994; Heller and Evans, 1995; Verosub andRoberts, 1995; Reynolds and King, 1995; Petrovskýand Elwood, 1999).In environmental magnetism, magnetic propertiesof materials such as soils, sediments and dustsare investigated. Such measurements provide powerfultools for approaching environmental problemsof concern such as climate and environmentalchanges and, more recently, environmental pollution.The high sensitivity of magnetic measurementsallows the detection of very low quantitiesof magnetic material which often act as proxies forthe underlying environmental processes. Anthropogenicpollution can also have a strong magnetic signatureand magnetic techniques have proven to becapable of discriminating between different sourcesof pollution. Magnetic techniques have beenapplied successfully in studies of climate changes,soil erosion, analyzing of atmospheric (e.g. bydetecting high fly-ash) and pollution produced byhistorical or active mining and other anthropogenicactivities. The sensitivity of magnetic techniques issuited for rapid measuring of very small quantitiesof magnetic particles in bulk samples (in generalequivalent to ppb in chemical analyses). Magneticparameters are capable of discriminating the ferromagneticcomponent of atmospheric dust derivedfrom soil-sizes particles from different source areasas well as fly-ash from different industrial sources(e.g. Hunt et al,. 1984; Chester et al., 1984; Oldfieldand Robinson, 1985; Hunt, 1986).Although magnetic studies have been successfulin providing proxies for environmentalprocesses, the fact that many of the environmentalmagnetic results rely on bulk techniques meansthat only average magnetic parameters are obtainedfrom many measurements.MethodsThe principle of the method of environmentalmagnetism, namely of the magnetic-proxies techniquewhich is used in this study for the screeningand detection of pollution can be summarized asfollows:(1) All rocks, sediments and soils contain a certain,mostly accessory portion of ferri(o)magneticminerals.(2) These phases are: Fe-oxides (magnetite, Fe 3O 4,;maghemite, γ-Fe 2O 3;hematite, α-Fe 2O 3), Fe--hydroxides (goethite, a-FeOOH), Fe-sulfides(pyrrhotite, Fe 7S 8; greigite, Fe 3S 4) or similarphases.(3) In addition, aerosols and dust of anthropogenicorigin containing different ferri(o)magneticphases with Fe partly substituted by other cationslike Ni, Co, Cr, Ti, Al, Mg are depositedand accumulated in soils and sediments.(4) With the help of magnetic proxies such as susceptibility,potentially polluted areas can bemapped in the field (so-called magnetometry):2D-mapping.(5) Only the magnetic signal related to the secondaryferri(o)magnetic phases of anthropogenicorigin is of interest.(6) A series processes are known to result in an enhancementof the magnetic signal in soils or sediments(Maher, 1998). Therefore, the anthropogenicmagnetic signal must be discriminated