Spatial variations of heavy metal contamination and associated risks around an unplanned landfill site in India

The study highlights the impact of unplanned landfill site on quality of groundwater, soil, and plants. The site selected is the Bhalaswa landfill site located in the urbanized region of Delhi, India. The associated potential ecological and human health risks to the population residing within the catchment area of the landfill site were evaluated. The order of abundance of heavy metals (measured using atomic absorption spectrometer) in the soil was found to be Fe > Cu > Cd > Ag, with Cu and Cd exceeding the WHO (World Health Organization)-recommended limits. Translocation factor (Root_metal/Shoot_metal) for Cd in P. juliflora plant (most dominant species in the region) at the landfill site was found to be the highest. The groundwater at the landfill site, 500 m, and 1000 m distance were found to exceed the WHO recommendation limits for Cd by 14.2%, 7.1%, and 1.4%, respectively. The estimated ecological risk index (E_r) indicated a high level of contamination particularly by Cu (E_r = 90.63) and Cd (E_r = 180). Children were found to be at higher risk by ingestion of Cd contaminated water (target hazard quotient = 5.1 > 1, indicating highest risk due to noncarcinogenic effects) followed by Ag (1.5) and Cu (1.4). The strong positive correlation of Cd between various ecological compartments with distance (Spearman rho's correlation > 0.75, 99% confidence level test) implied its high mobility and easy dispersion capacity towards the residential colony around the landfill, thereby indicating high associated ecological and human health risks. To conclude, there is a need to maintain a setback distance greater than 500 m from the landfill site in order to reduce the ecological as well as health risks associated with the landfill. The findings of this study provides a brief glimpse of the scenario of heavy metal pollution around such unplanned landfill sites and aids in taking remedial steps.