Mobility indexes of Cu, Pb, and Zn in soil ecosystems with various levels of metal contamination (in Poland)

The aim of the study was to investigate and compare the soils of three groups of grassland ecosystems with varying degrees of heavy metal (Cu, Pb, and Zn) pollution as well as estimating of mobility on the basis of calculated mobility indexes (MI) expressed as a percentage of the EDTA-extracted forms of metals in their total content. A total of 55 surface soil samples were collected from various areas of Poland: urban soils, rural soils, and soils along communication routes. Heavy metal concentrations were determined in solutions after wet mineralization (using a mixture of acids) by atomic absorption spectrometry (AAS) with flame atomization. To isolate the mobile forms of metals in soils, a one-step extraction method was used with 0.05-M EDTA solution. The ranges of Cu, Pb, and Zn concentrations in soils were varied, respectively: 6.7–47.6, 61.1–563.9, and 86.4–644.5 mg·kg(−1) (A); 5.7–39.8, 13.56–45.71, and 16.3–119.6 mg·kg(−1) (B); and 1.0–195.8, 19.2–310.2, and 27.4–894.1 mg·kg(−1) (C). The average values of mobility indexes of Cu, Pb, and Zn were at the level of 40.9, 33.5, and 22.2% (A); 23.2, 27.1, and 25.9% (B); and 37.5, 34.3, and 30.7% (C). Studies have shown that metals derived from anthropogenic sources are characterized by greater mobility compared to metals of natural origin (lithological associated with the ground). The inclusion of metal mobility indices in the environmental monitoring strategy may minimize errors in assessing the actual risk associated with the potential uptake of these metals by plants and incorporation into circulation.