Ecotoxicological assessment of soils polluted with legacy waste in Kerala using the earthworm Perionyx excavatus and terrestrial plants for effective management of legacy waste dumpsites.

The Municipal Solid Waste (MSW) dumpsite in Brahmapuram, Kerala, India, experienced a massive fire incident that burned continuously for 12 days, releasing hazardous smoke and toxic emissions into the nearby areas. The ecological impact, particularly on the terrestrial toxicity of the legacy site resulting from the fire incident, was not thoroughly investigated. The study focuses on the physicochemical properties of MSW soil collected after the fire incident and its effects on Perionyx excavatus and plants using Ecotoxicological tests. The results showed the presence of microplastics such as linear low-density polyethylene, low-density polyethylene, high-density polyethylene, polypropylene, and polyethylene terephthalate in the MSW soil. The observation of metals like Ni, Co, Zn, Cr, Pb, and Hg in the legacy waste soil indicates the presence of contamination from both waste dumping and industrial sources. The highest bioaccumulation in earthworms from the MSW soil was Hg. No mortality of earthworms was observed in the acute toxicity test. In the chronic toxicity test, a higher number of cocoons and juveniles was observed in MSW soil. The histopathological analysis showed increased mucus secretion in the epidermal layer after 14 days, mild hyperplasia and fusion of villi in the intestinal epithelium after 28 days of exposure to MSW soil. The plant growth test with the MSW soil showed a significant increase in the root length of the pea, presumably due to the high nutrient content of the soil outweighing the effects of contaminants. Although there were no toxic effects observed in earthworms and plants exposed to the MSW dumpsite soil based on the acute/chronic toxicity studies, use of soil for agricultural/infrastructure purposes should be undertaken with caution, considering the bioaccumulation of contaminants in earthworms and possible leachates to plant parts.