Accumulation, contamination, health and ecological risk assessment of heavy metals in landfill soil: Case study of Shiraz city in the Middle East

Abstract Population concentration in metropolitan areas generates and disposes of substantial quantities of waste with varying compositions. Transporting this waste to landfills produces leachate, which causes harmful heavy metal pollution. In this study, seven soil sampling stations were established at Shiraz Engineering Landfill, with five additional stations near residential areas. Sampling occurred during low and high rainfall seasons. The Aqua Regia method determined heavy metal concentrations. The share of these heavy metals in landfill soil was as follows: 42.20% for Ni, 29.06% for Cr, 17.42% for Cu, 7.24% for Co, 3.95% for As, and only 0.13% for Cd metal. The average pollution load index in the analyzed soils was 2.58 and it showed the High level of pollution of these soils. The ecological risk index for residential areas and most landfill locations (excluding the recycling plant) fell within the low pollution category. The results of the non-carcinogenic risk assessment indicated that the hazard index (HI) for all heavy metals in the soil samples of the study area was 0.3933 for children and 0.0854 for adults. These values suggest that workers at the landfill site and children and adults residing near the site are not exposed to short-term risks associated with heavy metals. The chronic and long-term carcinogenic risk (TCR) for the studied heavy metals in the landfill soil exceeded the threshold of 1×10⁻⁴ for both adults and children, indicating an unacceptable and dangerous risk to human health. For soil samples from residential areas, the TCR value for children was 1.30×10⁻⁴, indicating the risk of carcinogenesis specifically for children.