Zinc forms in soils (Review of publications)

Zinc has no particular bearing phases in soils, and it forms very diverse compounds; this complicates zinc's identification by chemical fractionation. However, Zn-containing particles may be identified using synchrotron X-ray analysis. Franklinite, willemite, hemimorphite, and Zn-containing magnetite are found to be the main technogenic Zn-containing pollutants in the heavy fraction of the contaminated surface soil horizon. Among the secondary zinc compounds, Zn-containing trioctahedral structures and clay minerals (unidentifiable by chemical extraction), as well as zinc fixed by manganese oxides and iron hydroxides, predominate in the soil clay fraction. Being a chalcophile element, zinc precipitates in the form of sulfides and forms complexes with organic substances in organic soils and peats. The degree of affinity to chalcophile metals increases in the following sequence: O-, P-, N-, and S-containing functional groups of organic substances.