title: Impacts of natural weathering on the transformation/neoformation processes in landfilled MSWI bottom ash: a geoenvironmental perspective.
abstract: Natural weathering processes are significant mechanisms that noticeably affect the fundamental nature of incineration ash residues. To provide a greater understanding of these processes, a MSWI (mono)landfill site in the north east of the US was selected as the target for systematic investigation of the natural weathering of bottom ash residues. Samples of various ages were collected from locations A (1 yr), B (10 yrs), C (13-14 yrs) and D (20 yrs) of the landfill in 2009. We investigated the phase transformation of the collected bottom ash particles, neoformation processes as well as the behavior and distribution of certain heavy metals (Cu, Pb, Zn, Ni, and Cr) in the neoformed phases using optical microscopy, SEM-EDX, and bulk examinations.
  
  
  RESULTS
  at the preliminary stage, the waste metallic particles (Al, Fe, and Cu) and unstable minerals such as lime, portlandite, ettringite and hydrocalumite convert to oxide and hydroxide (hydrate) phases, calcite, alumina gel and gypsum. At the intermediate stage, the decomposition of melt products including magnetite spinels and metallic inclusions is triggered due to the partial dissolution of the melt glass. At the longer time horizon it is possible to track the breakdown of the glass phase, the extensive formation of calcite and anhydrite, Al-hydrates and more stable Fe-hydrates all through the older ash deposits. Among the dominant secondary phases, we propose the following order based on their direct metal uptake capacity: Fe-hydrates>Al-hydrates>>calcite. Calcite was found to be the least effective phase for the direct sorption of heavy metals. Based on overall findings, a model is proposed that demonstrates the general trend of ash weathering in the landfill.
authors.affiliation: Department of Urban and Environmental Engineering, Faculty of Engineering, Kyushu University, 916, West 3, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan. amir@doc.kyushu-u.ac.jp
authors.forename: Amirhomayoun
authors.initials: A
authors.lastname: Saffarzadeh
authors.forename: Takayuki
authors.initials: T
authors.lastname: Shimaoka
authors.forename: Yunmei
authors.initials: Y
authors.lastname: Wei
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Gardner
authors.forename: Craig N
authors.initials: CN
authors.lastname: Musselman
mesh_terms: D002947:Cities; D017745:Incineration; D019216:Metals, Heavy / Q000032:analysis; D008855:Microscopy, Electron, Scanning; D009513:New Hampshire; D012037:Refuse Disposal / Q000379:methods*; D013052:Spectrometry, X-Ray Emission; D014866:Waste Products / Q000032:analysis*; D014961:X-Ray Diffraction
chemical_list: D019216:Metals, Heavy; D014866:Waste Products