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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 wereaimed 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 unsaturatedzone 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. (c) 1998 IAWQ. Published by Elsevier Science Ltd. [ABSTRACT FROM AUTHOR]

The environmental impact of the main landfill of the city of Zagreb (Croatia), which contains about 5 million tons of waste, on the adjacent groundwater was studied. The waste is disposed of directly onto the highly permeable alluvial sediments, only few kilometres upstream of a large protected groundwater zone. Systematic monitoring was performed in the framework of a major project aimed to assess strategies for remediation of the landfill. Results obtained in 6 sampling campaigns during 1995--96 were used to determine the redox zones in the leachate plume and to describe horizontal and vertical distributions ofselected contaminants. A relatively narrow non-continuous iron-reducing zone was found along the edge of the landfill in the prevailing directions of the groundwater flow. Even after a distance of 1200 m the redox conditions in the aquifer still remained anaerobic (nitrate-reducing), while a permanently aerobic zone was present only upstream from the landfill. The horizontal distribution of the contaminants was highly dependant on the hydrological regime, but the preferential direction of spreading was toward the protected groundwater zone. Moreover, it was shown that this aquifer section is polluted not only in the surface layer but across its whole vertical profile (as deep as 60 m). (c) 1998 IAWQ. Published by Elsevier Science Ltd. [ABSTRACT FROM AUTHOR]