Experimental study of fly-ash migration by using magnetic method

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.

Investigation of polluted alluvial soils by magnetic susceptibility methods: a case study of the Litavka River

“…Prevailing sandy material in these profiles enables the downward movement of magnetic particles, thus only a smooth decrease and eventually almost stable magnetic signal in the whole profile was observed. Similar behaviour of magnetic grains in sandy material was reported by Kapička et al (2011).…”

Magnetic Investigations of Buried Palaeohearths Inside a Palaeolithic Cave (Lazaret, Nice, France)

“…Figure shows that the first fire had a limited impact on the surface MS, whereas the second fire significantly increased it at the centre of the fireplace. However, these previous surface MS measurements concern only the first centimetres of the experimental hearth (Lecoanet et al ., ; Kapièka et al ., ). The susceptibility values at low frequency for the sample taken from the hearth before fires (denoted BF) and from the upper millimetres after burning (AL) are 2.5 × 10 −6 m 3 kg −1 with χ fd cal = 11.4% and 20.4 × 10 −6 m 3 kg −1 for χ fd cal = 11.1%, respectively.…”

Regional Contamination of Moravia (South-Eastern Czech Republic): Temporal Shift of Pb and Zn Loading in Fluvial Sediments

“…A mechanical downward transport of very fine particulate contaminants in very coarse (mostly sandy) matrix has been suspected to cause too large depths of 137 Cs activity peaks in some overbank sediments, especially in levees (Ciszewski et al 2008;Nováková 2009). The downward transport of fly ash particles to sand column by infiltration of water has experimentally been verified by Kapička et al (2011). Actually, the depth profiles of 137 Cs are a useful tool to evaluate this phenomenon because, in coarse sediments, considerable activities of 137 Cs are found in considerable depths.…”