MAGNETIC SUSCEPTIBILITY AND ELECTRIC CONDUCTIVITY AS A PROXY OF SOIL HEAVY METAL POLUTION FROM MINING AND METALLURGICAL AREAS

The mining and metallurgical wastes are an important source of arsenic and heavy metals, which are prone to eolian dispersion and water erosion, causing in this way the pollution of surrounding soils. In order to determine the spatial delineation of these wastes and the mapping of contaminated soils is necessary to realize routinely geochemical studies that are rather time consuming, laborious in terms of sample preparation, and expensive. Therefore, any other method, although approximate, but yielding fast information can be helpful as indicator for better targeting and selection of sampling sites for subsequent routinely geochemical studies.

We selected two areas from Mexico to evaluate the use of magnetic susceptibility (MS) and electrical conductivity (EC) as an alternative tool for mapping the spatial distribution of arsenic and heavy metals in mining and metallurgical wastes and polluted soils. The MS, EC and total concentration of potentially toxic elements (PTE) as As, Cd, Pb and Fe were determinate on 237 samples of wastes and soils from the two studied areas.

Analysis of studied wastes yielded the highest values of MS, EC and total concentrations of PTE, which confirm that they are a potential source of contamination in the areas adjacent to it. Also, the results indicate that in soils nearest to the wastes were determined high values of SM, EC and total concentrations of PTE, which decrease with distance from the wastes.

The analysis of results shows a straight correlation between the SM, EC and concentration of PTE in the two studied areas. Linear regression was also tried for the pollution index (PI) and SM and EC. The PI gives an assessment of the overall toxicity status for a sample, and it is a result of the contribution of several contaminants (As, Cd and Pb). There is a significant linear correlation between PI and SM for mining area (r = 0.82) and metallurgical area (r = 0.92). However, we only found a strong linear correlation between PI and EC for mining area (r = 0.81) but not for metallurgical area (r = 0.25).

This finding suggests that the simple, rapid and non-destructive magnetic and electrical conductivity measurements can be used as an indicator for the arsenic and heavy metal contamination and proxies for the measurement of these contaminant contents in mining and metallurgical areas.