ASSESSMENT OF GROUNDWATER CONTAMINATION IN THE VICINITY OF A MUNICIPAL SOLID-WASTE LANDFILL (ZAGREB, CROATIA)

The environmental impact of the main landfill of the city of Zagreb (C roatia), which contains about 5 million tons of waste, on the adjacent groundwater was studied. The waste is disposed of directly onto the h ighly 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 rem ediation of the landfill. Results obtained in 6 sampling campaigns dur ing 1995-96 were used to determine the redox zones in the leachate plu me and to describe horizontal and vertical distributions of selected c ontaminants. 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 condit ions in the aquifer still remained anaerobic (nitrate-reducing), while a permanently aerobic zone was present only upstream from the landfil l. The horizontal distribution of the contaminants was highly dependan t on the hydrological regime, but the preferential direction of spread ing was toward the protected groundwater zone. Moreover, it was shown that this aquifer section is polluted not only in the surface layer bu t across its whole vertical profile las deep as 60 m). (C) 1998 IAWQ. Published by Elsevier Science Ltd.