Experimental study of fly-ash migration by using magnetic method |
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| Authors: | Aleš Kapička Radka Kodešová Eduard Petrovský Zdeněk Hůlka Hana Grison Martin Kaška |
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| Institution: | (1) Pollution Ecology Research Laboratory, Centre of advanced study in Botany, Banaras Hindu University, Varanasi, 221005, India;(2) Centre for Environmental Science and Technology, Banaras Hindu University, Varanasi, 221005, India |
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| Abstract: | Several studies have shown that magnetic measurements can be used in assessing soil contamination due to atmospheric deposition
of pollutants. Reliable spatial mapping of magnetic susceptibility of soils assumes high temporal stability of deposited particles,
accumulated in top-soil horizons. One of the main methodological concerns is whether the migration of deposited anthropogenic
ferrimagnetic particles may bias the measured values. Measurements carried out on high-porosity (sandy) soils, or on soils
with a very variable water regime may yield inconsistent values of top-soil magnetic susceptibility as the indicator of contamination.
This study focuses on the laboratory examination of migration of fly ashes from a coal-burning power plant in sands of different
porosity and under a simulated rain regime. Columns of sand of different grain sizes, placed in plastic cylinders, were contaminated
on the surface by the fly ash. The vertical migration of magnetic particles was monitored using measurements of magnetic susceptibility
with an SM400 Kappameter. Calibration measurements in the water environment showed an erroneous performance and resulted in
the technical improvement of the used susceptibility meter (Model 2009). Our results show that the vertical distribution of
flyash particles deposited on fine sand is very stable even after repeated rain simulation. The peak value of magnetic susceptibility
is located in a stable position a few millimeters under the surface. Hence, standard top-soil magnetic mapping is in such
a case reliable and fully representative. Contrary to that, in case of coarse sand, the peak value of magnetic susceptibility
migrates by more than 10 cm. The results will be further used for numerical modeling of contaminant transport in porous media. |
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