Environmental aspects of organic and inorganic amendments – implications for sustainable soil remediation

Szimona Zarzsevszkij

Disertační práce

Abstract:

In this work, various organic and inorganic amendments were tested under different environmental conditions to elucidate on their suitability as soil remediation agents. For sustainability and circularity reasons, waste materials were tested along with commercially available or synthesized products. While the use of sorbents for metal(loid) immobilization has been shown a promising approach to heavily polluted areas, the complexity of factors that influence remedial efficiency requires comprehensive assessment of the amendments prior to their full-scale application. Therefore, firstly, the effects of soil moisture manipulation on metal(loid) immobilization by nanoscale zero-valent iron (nZVI), biochar (BC), and BC composites (nZVI-BC and Fe/FeS-BC) were assessed by a laboratory soil incubation experiment. The amendments were applied in organic-rich and mineral layers of a mine soil and incubated under 100 and 50 % soil water holding capacity to imitate flooding and common field conditions. Secondly, the effects of soil properties on the immobilization potential of (in)organic waste-derived amendments were evaluated in soils with different types and levels of metal(loid) contamination. The amendments were applied either alone or combined. Finally, since composting was shown to mitigate the adverse effects of sewage sludge application to soil, the third experiment involved field application of composted sewage sludges to a degraded soil impacted by coal mining. Traditional single and sequential soil extractions and leaching tests were employed including ones developed specifically for waste-materials. The diffusive gradients in thin films (DGT) technique was applied to get a better estimate of real in-situ metal(loid) availability. Solid phase investigations of the incubated amendments and metal(loid) sorption were done by microscopic analyses. Geochemical modelling was used to predict solid/liquid speciation and solubility controlling phases of the metal(loid)s under the studied environmental conditions. The overall results showed that (i) soil moisture content and redox potential, (ii) soil properties including pH, organic and mineral contents, and metal(loid) type and concentration, and (iii) the characteristics of the applied amendments significantly influenced the immobilization potential of the tested materials. Nevertheless, the iron-based amendments generally exhibited close to 100% immobilizing efficiency towards the target metal(loids) (As, Cd, Co, Cr, Cu, Ni, Pb, Sb, Zn), although metal(loid) availability was also increased in some cases. Yet, solid phase analyses confirmed metal(loid) associations with iron phases, several of which were predicted as solubility controlling phases. Contrary, the organic amendments had poor performance, and even increased metal(loid) availability in many cases, which, however, was overcome by combining them with iron-based amendments. The results of the field experiment revealed a seasonal trend in metal(loid) availability during 2.5 years after the land application of composted sewage sludge, with the interactions between organic matter and metal(loid)s as main driving forces, which are influenced by both abiotic and biotic factors. In summary, the work presented here confirms that soil remediation by chemical immobilization of metal(loid)s is feasible, but complex and challenging task that requires further research especially in soils polluted by multiple risk elements, and under real and long-term conditions.

Keywords

Metal(loid)s, Risk elements, Immobilization, Biosolids, Waste materials, Leaching, Environmental availability and mobility

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 27. 10. 2024

Obhajoba závěrečné práce

• Vedoucí: doc. Mgr. Martina Vítková, Ph.D.
• Oponent: Petr Drahota, externi, Edgar Hiller, externi, Barbora Doušová, externi

Česká zemědělská univerzita v Praze

Fakulta životního prostředí

Doktorský studijní program / obor:
Landscape Engineering / Environmental Modelling