Reclamation of degraded soils: Analysis of selected parameters after organic/inorganic modifications

Degraded soils are unable to perform key functions and, thus, it is very important to develop effective reclamation methods. To restore utility or natural values to degraded ecosystems, various compounds are applied. In this study, the impacts of additives of various origin and composition on Polish (Eutric Cambisol) and Bulgarian (Epicalcic Chernozem) soils were compared. The main goal of the study was to make a comprehensive assessment of the validity of using popular soil additives in a real context. Physicochemical and hydrophysical parameters including pH, variable surface charge, porosity, specific surface area, wettability, sorption capacity relative to trace metals, and water retention of soils were taken into account. Surface charge and porosity of soils were determined using potentiometric titration and nitrogen adsorption/desorption method, respectively. Wettability was measured by sessile-drop method, whereas water retention, using different matric potentials (pF curves). Sorption study on trace metals included isotherm and kinetics determination as well as experimental data modeling. The most positive effect on soil surface charge, porosity, wettability, and cadmium (Cd) sorption was observed for synthetic zeolite, zeolite-carbon composite, and vermicompost. This effect was noted only for Polish soil characterized by poor porosity, low content of organic carbon, and moderately acidic reaction. For eroded Bulgarian soil, the condition of which was definitely better, the impact of modifiers was not spectacular. Among tested amendments, only divergan increased water retention properties of both examined soils significantly. Zeolite, zeolite-carbon composite, and vermicompost can be apply for degraded soils of low organic carbon content, poor porosity, and moderately acidic pH to improve their physicochemical parameters and sorption ability toward trace metals. Divergan should be used to improve water retention of degraded soils during their reclamation.