Assessment of heavy metal contamination of soils by leachate from Kiteezi landfill.

Abstract

Landfills like Kiteezi pose significant environmental and public health risks due to heavy metal (HM) leaching from solid waste (SW). This study assessed HM levels in SW by age (week old, month old, year old), four leachate samples, and 67 soil samples from eight locations and a control at Kiteezi landfill. Samples were collected from June to October 2023 and analysed using AAS and ICP-MS. The SW contained Pb, Cu, Cr, and Cd concentrations of 373.2 ± 74.5, 214.3 ± 46.3, 208.3 ± 161.8, and 25.2 ± 4.0 mg/kg, respectively, with highest levels in month-old waste. Mercury was undetectable (<0.001 mg/kg). Leachate contained Cu, Pb, Cr, and Cd levels of 51.5 ± 86.9, 1.0 ± 0.4, 2.4 ± 2.4, and 0.8 ± 0.6 mg/L, respectively, non-compliant with the NEMA discharge standards. Mercury was also undetectable in the leachate (<0.001mg/L). The Hydrological Evaluation of Landfill Performance model estimated a leachate generation rate of 437 ± 59.1 m³/day, 42% of the field-observed 1033 ± 252.8 m³/day, largely attributed to potential inclusion of surface runoff from adjacent areas and the continual blockage and opening of leachate channels from collapsed waste, which could have significantly increased field value. Soil HM concentrations reached 123.9 ± 77.2, 39.7 ± 22.7, 36.7 ± 30.2 and 11.7 ± 8.5 mg/kg for Pb, Cr, Cu and Cd respectively, with no detectable levels of Hg. HM levels exceeded South African standards but met Tanzanian limits, except for Cd, hence the need for Ugandan based standards. Lead (Pb) and Cr contamination in soil was classified as “high,” posing serious health risks as HMs degrade soil quality and harm microbial communities. With potential impacts on aquatic life and human health risks (such as cancer, heart disease, infertility, birth defects), public awareness and soil remediation are critical to protecting environmental and public health.