Abstract
This study assesses the extent of heavy metal contamination in the soil of the Eskişehir landfill drainage area in northwest Türkiye, where long-term waste accumulation and leachate pose potential environmental risks. Two boreholes were drilled to a depth of 30 meters downstream of the landfill site, and soil samples were collected during both wet (May) and dry (September) seasons in 2021. Concentrations of manganese, iron, cobalt, nickel, copper, arsenic, cadmium, lead, zinc, chromium, and mercury were determined together with pH values. Pollution indices, such as the contamination factor, pollution load index, and geoaccumulation index, were used to evaluate contamination levels. To support the geochemical results, geophysical surveys including electrical resistivity tomography, self-potential, and resistance measurements were carried out. Although measured heavy metal concentrations stayed below the legal thresholds set by national soil regulations, the calculated indices indicated localised contamination, particularly for cobalt, nickel, and chromium, which showed high levels during the wet season and remained elevated for chromium during the dry season. The pollution load index suggested a generally low overall pollution risk. Geophysical measurements did not reveal significant subsurface contamination-related anomalies. These findings demonstrate that heavy metal accumulation in the landfill drainage area is both seasonally variable and spatially localised. Periodic monitoring combining geochemical and geophysical approaches is recommended to manage and mitigate long-term risks in such waste storage environments.