RP12 Application of Spatially Explicit Techniques in Ecological Risk Assessment
Thursday, 17 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(HID-1117-805200) Investigation of the vertical toxicity distribution of solid waste landfill sites by boring core samples.

Nakayama, H¹, Shoji, R¹, Mitani, T¹, Ishii, H¹, Abe, M², Asakura, H², Yamada, M², ¹ Tokyo Natinal College of Technology, Hachioji, Tokyo, Japan² National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan

ABSTRACT- A field investigation by boring core samples was carried out at three waste landfill sites containing municipal solid wastes and incineration residue. From the core samples collected by boring, the vertical distribution of toxicity and physicochemical parameters (pH, electrical conductivity, ignition loss, etc.) were traced in each waste layers. To evaluate the toxicity of the core samples, three difference bioassays, in vitro cytotoxicity test by using human hepatoblastoma cell (HepG2) lines, algal growth inhibition test, the Microtox test and genotoxicity test (umu test), were conducted on the leaching test samples prepared from the bored core sampled from the three landfill sites. The results of the toxicity tests showed significant differences in sensitivity among the three bioassays. While no toxicity was observed in the Microtox test, significant toxicities in the bored core samples were observed within the concentration range tested by the growth inhibition test and the cytotoxicity test, (12.5-100g/L) and (0.1-100g/L), respectively. In Japan, a certain thickness of the intermediate cover soil layer should be placed between the waste layers in waste landfill site. The toxicities of these soil layers were also observed. The toxic chemicals such as heavy metals leached from the waste layers could be accumulated in the lower soil layer. Therefore, the intermediate cover soil layer has a function to prevent toxic chemicals into the putflowing leachate. Particularly, the toxicity of soil layer was mainly found at soil layers just below waste incinerator ash layers. The vertical distribution of the toxicity-predominant chemicals depended upon the amount of toxic chemicals in waste, modification of toxicity during waste degradation process and the vertical migration and deposition of these contaminants to specific layers. The chemical analysis and bioassays can present key information on the fate of toxic chemicals in landfill.

Key words: Boring Core Sample, Leaching Test, Vertical Distribution of Toxicity, Waste Landfill Site