Assessment of phytotoxicity in soil-like material recovered from landfill mining of legacy waste in open dumpsites

Biomining, or landfill mining, involves the excavation, processing and engineered disposal of legacy waste from unscientifically created landfills/dumpsites to reclaim valuable land and facilitates to recover resources. However, unrestricted reuse of recovered materials may cause adverse environmental impacts. Soil-Like Material (SLM) constitutes the major fraction of the biomined residues; hence, to achieve the major objective of Biomining, the reusability of SLM must be assessed. This study evaluates the potential of biomined SLM from Ariyamangalam dumpyard, Tiruchirappalli, for reuse as a soil amendment or bio-fertiliser. The phytotoxicity of SLM was assessed with the Seed Germination Test (SGT) using White mustard (<i>Sinapis alba</i> L.) seeds. The SGT was performed for five consecutive months and compared with the control red soil. The SGT was also performed in different combinations of SLM with red soil to obtain the suitable combination for disposal. The heavy metal accumulation in different bodily elements in plants were identified using bio-concentration factor and metal accumulation ratio. Results from the phytotoxicity assessment reveal that the SLM 40 (mixture of 40% SLM and 60% red soil) is optimal, which exhibits the highest germination index of 212%, relative seed germination of 132%, relative root elongation of 160%, and relatively lower heavy metal accumulations. The widespread application of SLM from the study area to agricultural land has proved to be a viable alternative for the reutilisation of residual resources with high-nutrient content and organic matter, making it favourable for growing non-edible plants.