Qualité du sol — Lignes directrices pour le diagnostic de la pollution du sol par des éléments toxiques en utilisant la magnétométrie

This document specifies methods for the measurements of magnetic susceptibility of soils (κ) as an indicator of potential soil pollution/contamination with trace elements associated with technogenic magnetic particles (TMPs) and describes related procedures, protocols and guidelines to be applied as a screening geophysical method of determination of soil pollution with trace elements. The results of measurements are used for preparing the maps of magnetic susceptibility of soils in the area of interest. From these maps, the areas of elevated and high magnetic susceptibility indicating high trace element total pollution load are discriminated for further identification of pollutants by geochemical methods.

This document is applicable to screening all TMPs-related anthropogenic emission sources including long-range transport of airborne elements, of which TMPs are carriers and indicators. Such emission sources comprise the majority of high-temperature industrial processes, where iron is present in any mineralogical form in raw materials, additives or fuels, is transformed into ferrimagnetic iron oxides (e.g. fossil solid and liquid fuels combustion, metallurgy, cement and ceramics industry, coke production, industrial waste landfills, land transport). This document is not applicable to screening anthropogenic emissions not associated with TMPs, e.g. organic pollutants or emissions from agricultural sources.

NOTE 1 Copper, zinc and other non-ferrous metal ores also contain iron (in many sulfides) as this element is abundant in almost all environments. During smelting, the iron occurring in sulfides is transformed into ferrimagnetic oxides (TMPs). However, in such cases, the proportion of TMPs and related PTEs is usually less than at coal combustion or iron metallurgy, for example, and not all PTEs are physically associated and transported by TMPs. Non-airborne elements are deposited in the close proximity of the emission source, while TMPs can be used in these cases as indicators of airborne elements and of the spatial distribution of the total element deposition from a smelter in the area.

In rare cases, some soils are developed on bedrock exhibiting geogenically high magnetism, which can cause false-positive results. This influence can, however, be easily indicated by measurements of magnetic susceptibility along soil profiles. This method is not applicable when the bedrock exhibits extremely high magnetic signals.

NOTE 2 Such cases are rare.