Analysis on contaminant migration through vertical barrier walls in a landfill in China |
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Authors: | Wen-Jie Zhang Qing-Wen Qiu |
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Institution: | (1) Department of Civil Engineering, Shanghai University, 200072 Shanghai, China |
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Abstract: | Vertical barrier walls are often constructed to prevent contamination of ground water and soils by landfill leachate. The
leachate water levels in landfills in southern China are generally high. Contaminants in such landfills may migrate through
the vertical barrier walls and give rise to environmental problems. Qizishan landfill in Suzhou, China was taken as an example
to investigate contaminant migration through the vertical barrier walls. Advection, diffusive and adsorption processes were
considered in the analysis. Influences of permeability and depth of the barrier wall on contaminant migration were analyzed.
The results show that it will be 13.5 years before breakthrough at 0.1% of the source concentration and 20.5 years before
breakthrough at 10% of the source concentration. By and large, the contaminant has not passed through the barrier wall at
present, and the contaminated zone is mainly located in the sandy clay layer near the earth dam, which is validated by testing
on sampled soils. Hydraulic conductivity and depth of the barrier wall are critical to contaminant migration. Special attention
need to be paid on them when building such a barrier wall. If bottom of the barrier wall is keyed into the aquitard and the
hydraulic conductivity reaches 10−9 m/s, the time before breakthrough will be long enough to allow stabilization of the landfill. Pollution of the surroundings
will be avoided, and therefore the requirement for contaminant control will be attained. |
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