The impact of contamination from a municipal solid waste landfill (Zagreb, Croatia) on underlying soil

The present study was conducted on the main landfill of the city of Zagreb which contains about 5 million tons of waste disposed of directly onto highly permeable alluvial sediments. The investigations were aimed at assessing the impact of contamination from the landfill on underlying soil and comprised the determination of a broad spectrum of inorganic and organic constituents in the samples (size fractions <2 mm) of solid waste, soil and aquifer sediments. Both the total content of various contaminants as well as their part which is readily leachable with water were determined in the examined samples. Compound classes identified in the landfill can be classified into the two main categories: (1) markers of biological waste and of its microbial transformation (ammonia, dissolved organic carbon, short-chain aliphatic acids, phenols, derivatives of abietic acid) and (2) markers of anthropogenic waste (toxic metals, hydrocarbons, chlorinated hydrocarbons, surfactant-derived compounds, phthalates, pharmaceutical chemicals). The complex assemblages of contaminants were shown to change dramatically during the transport from the solid waste through unsaturated zone of the soil to aquifer sediments. It was shown that, in addition to the vertical infiltration of leachate from the solid waste, the hydrological regime of groundwater has also a strong impact on the contaminant distribution in soils below the landfill.