Temporal Interpretation of Environmental Pollution around Landfill Site Using Core of Bottom Sediments from Pond

There is little environmental monitoring data or documentation of the materials being disposaled at the many old landfill sites existing in Japan. We tried to clarify the level of temporary environmental impact in and around a landfill by measuring the concentration of heavy metals within various sediments. The site for this case study was at the uppermost stream of an alluvial valley plain in the eastern part of Boso Peninsula. No liner exists in the landfill and a pond lies about 100 m downstream from the site. Concentration trends were analyzed for heavy metals such as Pb, Cu, Zn, and Cs-137 found in the bottom sediments of the pond. As a result, the temporal changes of the environmental pollution were clarified in accordance with land use around the site. In addition, to collect reference data, the study also measured concentration of heavy metals in the drilled cores of the landfill and surface soil samples between the landfill and the pond, as well as bottom sediments from another pond and the surface soil surrounding the landfill. Water quality of the groundwater and the two ponds was also analyzed. The trend for heavy metal concentrations in the bottom sediments is a very useful indicator for interpreting environmental changes in and around the landfill.