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Biomass reduction and arsenic transformation during composting of arsenic-rich hyperaccumulator Pteris vittata L
- Cao, Xinde, Ma, Lena, Shiralipour, Aziz, Harris, Willie
- Environmental science and pollution research international 2010 v.17 no.3 pp. 586-594
- Pteris vittata, X-radiation, X-ray diffraction, arsenic, biomass, composting, composts, energy, ferns and fern allies, high performance liquid chromatography, landfills, mass spectrometry, microorganisms, oxidation, phytoremediation, scanning electron microscopy, volatilization
- Background, aim, and scope Composting is being proposed as a pretreatment step before disposal of metal-rich biomass after phytoextraction process. This study determined the biomass reduction and arsenic transformation during composting As-rich biomass of hyperaccumulator Chinese brake fern (Pteris vittata L.). Materials and methods High-As fern biomass containing ∼4,600 mg As kg⁻¹ was composted for 120 days in a laboratory-scale composter under aerated condition. Solid As speciation was determined using X-ray diffraction (XRD) and scanning electron microscopy equipped with X-ray energy dispersive elemental spectroscopy (SEM-EDS), while liquid As speciation was evaluated by high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry. Results and discussion Composting reduced the fern biomass by 38%, comparable to 35% reduction of the low-As fern biomass containing ∼12 mg As kg⁻¹, indicating that the high As concentration in P. vittata had little detrimental effect on microorganisms involved in composting. Total As on a per composter basis and water-soluble As in composted biomass were lowered by 25% and 32%, respectively. Arsenic loss from the biomass resulted mainly from generation of compost leachate, with less from the As volatilization; whereas As immobilization was due to oxidation of As(III) to As(V), followed by precipitation of hoernesite [Mg₃(AsO₄)₂⋅8H₂O] which was evidenced by XRD and SEM-EDS analysis. Conclusions and perspectives Results from this study indicate that composting As-rich fern significantly reduced its biomass, As content, and water-soluble As. It seems that composting can be an effective step for treating As-rich biomass before disposal in landfill.