SOILS, SEC 5 • SOIL AND LANDSCAPE ECOLOGY • RESEARCH ARTICLE Effects of natural zeolites on ryegrass growth and bioavailability of Cd, Ni, Pb, and Zn in an Albanian contaminated soil Marco Contin 1 & Liri Miho 2 & Elisa Pellegrini 1 & Fran Gjoka 2 & Enkeleda Shkurta 2 Received: 15 December 2018 /Accepted: 24 May 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Purpose The use of eco-friendly and cost-effective adsorbent materials in the remediation of soils contaminated by potentially toxic elements (PTE) is a sustainable way of reducing the transfer of these elements into the food chain. However, an evaluation of the potential of natural zeolites to immobilize toxic elements in contaminated soils was required to enable their efficient use. Materials and methods The effect of natural zeolite (Stilbite-Stellerite) from the Munella area (Northern Albania), added at rates ranging from 1.25 to 10 % w/w on a contaminated soil was investigated in a greenhouse pot experiment with ryegrass (Lolium multiflorum L.) and by selective extractions. PTE availability for plants was assessed either as their accumulation in plant tissue or by DTPA-extraction. Oral bio-accessibility was estimated by the in vitro PBET method and the mobility and consequent potential risk of leaching by the USEPA TLCP method. The effect of zeolites on soil properties (pH, electrical conductivity-EC, organic C, and total N) was also investigated. A five steps sequential extraction procedure (SEP) was applied to investigate the immobilization mechanism. Results and discussion The addition of 2.5% w/w of natural zeolites caused a significant decrease of PTE mobility, but to observe a significant reduction of DTPA-extractable metals, it was necessary to reach 10% addition rate. In contrast, plant growth showed a gradual increase with addition rate and a corresponding decrease of concentration of PTE in plant tissue. Correlation between DTPA-extractable PTE and their concentration in both root and shoot plant tissue was rather poor. Human hazard due to soil ingestion (PBET method) changed only for Cu and Zn in the gastric phase with 1.25 and 5% addition rate respectively, whereas decreased for Cu and Zn at 5% rate in the Intestinal phase. The results of SEP support the hypothesis that the main mechanism involved in metals fixation are as follows: (1) insolubilization by pH rise, (2) adsorption on Fe/Mn oxides (3) increase of cation exchange retention, (4) organic complexation. Conclusions The results of this work suggest that the addition of natural zeolites from the Munella area (AL) is a sustainable practice to reduce the environmental impact of PTE contaminated soils, but an assessment on the longevity of their immobili- zation need to be evaluated in the long-term perspectives. Keywords Contaminated soil . Natural zeolite . Plant availability . Potentially toxic elements . Soil remediation 1 Introduction The use of soils contaminated with heavy metals for agricul- tural purposes poses a great threat to human health, as metals can be transferred and accumulated in the human body through the whole food chain (Singh 2010). Some studies in Albania have identified high levels of heavy metals in soils near industrial sites, in agricultural soils where agrochemicals and polluted irrigation water have been intensively applied, and in soils naturally contaminated with these metals (Gjoka et al. 2002, 2007, 2011a; Kasa et al. 2014). However, indus- trial hotspots pose the highest ecological risk due to the higher pollution level and the frequent accumulation of more than one pollutant. Their number in the country accounts to 14 Responsible editor: Claudio Bini Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11368-019-02359-7) contains supplementary material, which is available to authorized users. * Marco Contin marco.contin@uniud.it 1 Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, Udine, Italy 2 Agricultural University of Tirana, Kodër Kamëz, Tirana, Albania Journal of Soils and Sediments https://doi.org/10.1007/s11368-019-02359-7