Ecological and biological assessment of the state of soils and vegetation cover of the closed municipal solid waste landfill in Kokshetau

Abstract

The ecological state of a closed municipal solid waste (MSW) landfill in Kokshetau, operated from 1960 to 2017 and lacking engineered protective systems, was assessed with a focus on heavy metal contamination and its effects on vegetation. Soil analysis revealed substantial exceedances of maximum permissible concentrations (MPCs) and background concentrations. Maximum concentrations reached 4230 mg/kg for Zn, 870 mg/kg for Cu, 299 mg/kg for Pb, 58 mg/kg for As, and 145 mg/kg for Ni, exceeding MPCs by 42.3, 15.8, 9.3, 29.0, and 3.6 times, respectively. Compared with background concentrations, these values were 48.1, 8.5, 19.9, 4.1, and 3.2 times higher, respectively. A pronounced radial contamination gradient was identified, with maximum concentrations in the central zone and a gradual decrease toward the periphery. However, even peripheral areas showed elevated concentrations relative to background levels, indicating persistent anthropogenic impact despite landfill closure. The geo-accumulation index (Igeo) classified the central soils as strongly to extremely contaminated, particularly with respect to Zn and Pb, while the phytotoxicity index (FTI) indicated a high level of phytotoxicity. Geobotanical analysis revealed substantial transformation of the vegetation, which was dominated by herbaceous and short-lived species, with annual species accounting for 49% of the recorded flora. The preva-lence of Asteraceae, Poaceae, Brassicaceae, and Chenopodiaceae is consistent with adaptation to chemically stressed environments. The dominance of Bassia scoparia suggests its potential as a bioindicator of technogenically disturbed soils. Overall, the landfill represents a long-term anthropogenically transformed ecosystem requiring integrated environmental monitoring and reclamation measures.