The use of nano-materials as a stabilizing agent in soils has a significant role, particularly in improving their mechanical properties. This study investigates the impact of stabilization using nano-materials, specifically nano-cement, on natural and contaminated clays. A series of laboratory tests, including Atterberg limits, compaction, unconfined compressive strength, permeability, and consolidation, are conducted to evaluate the soil properties. Various percentages of nano-cement (0 %, 0.5 %, 1 %, 1.5 %, and 2 %) are added to two sample groups; one prepared with water and the other with leachate. Based on the results of Atterberg limits tests, adding 2 % nano-cement to natural clay increases the liquid limit by 8.6 % and decreases the plasticity index by 16 %. These values diminish to 8.3 % and 13 % for contaminated clay. Furthermore, according to the compaction test results, increasing nano-cement content by up to 2 % leads to a reduction in maximum dry density by about 11.5 % and an increase in optimum moisture content by about 15.9 %. However, these values change to 5.77 % and 32.25 % for contaminated clay. The results indicate that increasing nano-cement content generally improves the strength and stiffness of the soil while reducing its permeability. On the other hand, contamination of the soil leads to a reduction in strength and stiffness, while permeability increases. Based on the Field Emission Scanning Electron Microscopy (FESEM) analysis, the incorporation of nano-cement improved the microstructure by decreasing pore spaces and enhancing bonding between particles. While chemical complexity of leachate negatively affects nano-cement dispersion, which leads to increased particle aggregation.

Leachate is a highly complex waste with high toxicological potential that poses a significant threat to the terrestrial environment. Determining leachate physicochemical parameters and identifying xenobiotics alone is, however, not enough to determine the real environmental impacts. In this context, the use of terrestrial model organisms has been highlighted as a tool in ecotoxicological leachate assessments and as a guiding principle in risk assessments. In this context, this review aimed to present the most current state of knowledge concerning leachate toxicity and the bioassays employed in this evaluation concerning terrestrial plants and animals. To this end, a literature search on leachate effects on terrestrial organisms was carried out using ten search terms, in 32 different combinations, at the Web of Science and Scopus databases. A total of 74 eligible articles were selected. The retrieved studies analyzed 42 different plant and animal species and employed nine endpoints, namely phytotoxicity, genotoxicity, bioaccumulation, antioxidant system, cytotoxicity, reproduction, physiological changes, behavior and lethality. A frequent association of toxic leachate effects with metals was observed, mainly Pb, Cd, Cr, Mg, Zn and Cr, which can cause antioxidant system alterations and cytoand genotoxicity. These elements have also been associated to reproductive effects in earthworms and mice. Specifically concerning plants, most of the retrieved studies employed Allium cepa in toxicity assays, reporting phytotoxic effects frequently associated to metals and soil parameter changes. Animal studies, on the other hand, mostly employed mice and evaluated genotoxicity and antioxidant system effects. Even with the description of toxic leachate effects in both plants and animals, a lack of knowledge is still noted concerning reproductive, physiological, cytotoxic, and behavioral effects in terrestrial species. We, thus, suggest that further studies be carried out on other animals, advancing our understanding on potential environmental leachate effects, also allowing for human health risk assessments.