Heavy metals geochemical baseline in topsoil on local scale : a case study in misrata, libya

Abstract EN

In May 2022, fifty-two topsoil samples (0 to 20 cm) were collected from the Tummina agricultural area in Misrata, situated in the northwestern region of the Libyan Sahel.

We analyzed the collected samples for (Fe, Al, Mn, Co, Zn, Cr, Pb, Cu, Ni, Cd, and As) through the XRF technique.

Aiming to : Set the most proper normalizing element for this area, develop a local geochemical baseline (GBL) using four methods (cumulative frequency curve, iteration removal, reference metal normalization, and box-whisker plot), and compare the outcome to the upper continental crust composition and data from other continental-scale soil surveys.

This investigation is the first to propose baseline values for a region in Libya.

The result demonstrated that, out of two viable reference elements (Fe and Al), Al is the best reference element for the normalizing method.

The mean local GBL values obtained from the four procedures of (Mn, Co, Zn, Cr, Pb, Cu, Ni, Cd, and As) were (64.12, 6.61, 8.53, 4.81, 9.5, 8.73, 5.59, 1.98, and 1.74 mg/kg), respectively.

The estimated local GBL levels of (Co, Zn, Cr, Pb, Cu, Ni, and As) were significantly lower than the upper crust's (UCC) and the Earth's crust's (ECS) values for sedimentary rocks, which are often employed in screening contaminated soil.

At the same time, Cd baseline levels were more significant in comparison.

Hence, using the global background as a benchmark may result in underestimation or overstate of toxic elements pollution in soil, thus misrepresenting the risk heavy metals pose to human and environmental health.

We propose such studies for the country's various geological regions to overcome the shortcomings of using global or world soil geochemical reference values.