海成粘土の透水係数および鉛の吸着特性に及ぼす塩類の影響

概要

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In recent years incinerated municipal solid waste has been disposed in landfill sites near coastal area in Japan where underlying marine clay deposits are expected to serve as a natural clay barrier. In this study marine clay is examined for the effects of salt on permeability and the sorption of lead using column leaching tests with deionized water, sea water and bottom ash leachate spiked with 100mg/L lead as permeants, and then selective sequential extraction (SSE) was employed to assess the retention mechanism of lead onto marine clay. The hydraulic conductivity of column clay was 2.5 to 7 times higher for the sea water and the ash leachate than for the deionized water. Lead concentration in the effluent was less than 6mg/L throughout the column leaching test with the deionized water, whereas it exceeded Pb concentration in influent below one pore volume leaching for the sea water. Lead in pore water accumulated in the top layer of the column soil for the deionized water whereas it was distributed throughout depth for the sea water and ash leachate. The SSE indicated that carbonate, exchangeable and hydroxides phases are predominant for Pb retention.
2009-02-27