AGROCHEMICAL ASSESSMENT OF SOIL AND LEACHATE CONTAMINATION AT MUNICIPAL SOLID WASTE LANDFILLS AND THEIR ROLE IN FORMING ECOLOGICAL RISK FOR AGROCENOSES

Abstract

This study presents a comprehensive agrochemical assessment of soil and leachate contamination at operating municipal solid waste (MSW) landfills in the Akmola region of the Republic of Kazakhstan, aimed at identifying pollutant migration mechanisms and assessing ecological risks for agrosystems. The research is based on the analysis of composite soil and leachate samples collected from 15 MSW landfills and one control site. To conduct an integrated assessment of contamination, the total contamination index (Zc) and the geoaccumulation index (Igeo) were calculated using a local background level. Migration relationships within the “leachate–soil” system were analyzed using Pearson correlation coefficient and visualized through heat maps.

The results indicate that soil contamination in landfill impact zones is chronic and diffuse in nature, often occurring in a latent form without systematic exceedance of sanitary standards. Zinc was identified as the dominant contributor to total contamination, whereas cadmium forms a stable technogenic background, revealed by elevated Igeo values even at low concentrations in leachate. Localized accumulation of mercury and lead is characterized by increased ecological significance. Leachate analysis showed a high degree of mineralization and a predominance of poorly biodegradable organic compounds, which facilitate the migration of toxic elements. Correlation analysis confirmed the key role of leachate in the formation of secondary soil contamination, particularly for Cd, As, Pb, and K. The obtained results substantiate the necessity of applying integrated indices and a risk-oriented approach in the environmental assessment of MSW landfills and in monitoring the condition of agricultural landscapes.