The impact of heavy metal contamination on soil quality and plant nutrition. Sustainable management of moderate contaminated agricultural and urban soils, using low cost materials and promoting circular economy

Abstract

A three-year experiment was conducted over six different soils, from northern and central Greece. The soils samples derived from both rural and urban environments, and they were moderately contaminated with heavy metals (Cu, Cd, Pb, Zn). Experiments were carried out by adding crop residues of wheat straw, cultivated in the plain of Thessaly, in the soil samples. Preliminary experiments were carried out to find the optimal mixing ratio of straw with soils, as well as the cut size, the temperature and humidity of the straw before its incorporation. The addition of wheat straw caused significant changes in the visual, physical, chemical, nutritional and microbiological quality indices of the soils studied. The indices related to the fertility and nutritional capacity of the soil samples were, in most cases, significantly improved, enhancing the soil health. Furthermore, the use of the straw reduced the availability of toxic metals, increasing, on the other hand, the availability of trace elements. Although the use of straw for improving soil properties has been known since ancient times, its use for polluted soil remediation is a matter of concern. A significant number of environmental and economic problems could be addressed if the principles of the circular economy were taken into account by decision-makers. Wheat straw, could be a key factor for soil health improvement, increasing its fertility and limiting the risks of toxic pollutants.