In situ distributions and characteristics of heavy metals in full-scale landfill layers
Resource
Journal of Hazardous Materials 137 (3): 1385-1394
Journal
Journal of Hazardous Materials
Journal Volume
137
Journal Issue
3
Pages
1385-1394
Date Issued
2006
Date
2006
Author(s)
Abstract
The leachate from methanogenic landfill normally contains low concentrations of heavy metals. Little samples had ever been collected from the full-scale landfill piles owing to technical difficulty for well drilling. We drilled two wells in Hangzhou Tianziling landfill, 20 m and 32 m in depth each, and collected solid samples of waste age of 1-4 years from both wells. The total amounts, the sequentially extracted amounts, and the chemical binding forms of heavy metals of the samples collected at different depths were measured. With the correlation between leachate production amount and the yearly rainfall amount, the leached ratio of the heavy metals were estimated only 0.13%, 1.8%, 0.15%, and 0.19% of Cu, Cd, Pb, and Zn, respectively. The heavy metals amounts in the main compositions of MSW, like glass, food waste, paper, coal cinders, were measured using fresh MSW samples. Afterward, the contents of heavy metals initially landfilled were estimated. A positive correlation was noted between the measured and the estimated initial contents of heavy metals, indicating that the low migration of heavy metals in landfill layers. However, among the metals investigated, Zn has shown better mobility inside landfill layers. Acid volatile sulfide (AVS) and the simultaneously extracted metals (SEM) were measured for all collected samples with optimal reaction conditions identified to yield nearly perfect sulfide recovery as follows: 100 g wet samples, 80 mL min-1 N2 flow rate, reaction time of 150 min. The SEM/AVS ratios ranged 25-45, indicating that the AVS was insufficient to immobilize the SEM. Sequential extraction using six-fraction scheme revealed that the sum of exchangeable and the avid soluble fractions of heavy metals follow: Zn > Cd > Cu, Ni, Pb > Cr. The insoluble fraction of heavy metals in MSW was high, for instance, over 80% for Cr and Pb high insoluble fractions of heavy metals in the landfilled MSW and the sorption capability of the methanogenic landfill layers should be responsible to the low concentrations of heavy metals found in leachate. © 2006 Elsevier B.V. All rights reserved.
Subjects
Chemical speciation; Heavy metals; Landfill; Mobilization; Municipal solid waste
Other Subjects
Chemical speciation; Methanogenic landfill; Municipal solid waste; Sequential extraction; Concentration (process); Heavy metals; Methanogens; Scanning electron microscopy; Solid wastes; Well drilling; Land fill; cadmium; chromium; coal; copper; glass; heavy metal; lead; nickel; zinc; Concentration (process); Heavy metals; Land fill; Methanogens; Scanning electron microscopy; Solid wastes; Well drilling; chemical binding; drilling; heavy metal; landfill; leachate; leaching; sampling; well; adsorption; article; correlation analysis; flow rate; food; landfill; leaching; metal extraction; municipal solid waste; paper; pollution transport; reaction time; scanning electron microscopy; transport kinetics; Metals, Heavy; Nitrogen; Soil; Time Factors; Asia; China; Eurasia; Far East; Hangzhou; Tianjin; Zhejiang
Type
journal article
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