Main content area

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.