Biochar Amendment for Reducing Leachability of Nitro Explosives and Metals from Contaminated Soils and Mine Tailings

Abstract

The mobility and bioavailability of nitro explosives (2,4-dinitrotoluene [DNT], 2,4,6-trinitrotoluene [TNT], and hexahydro-1,3,5-trinitro-1,3,5-triazine [RDX]) in biochar-amended soils and toxic metals (As, Cd, Cu, Pb, and Zn) in biochar-amended mine tailings were investigated via various types of leaching procedures in laboratory-scale batch experiments. The results from the toxicity characteristic leaching procedure (TCLP) and hydroxypropyl-β-cyclodextrin (HPCD) extraction showed that approximately 55 to 95% of the explosives were released from the contaminated soils and would thus be considered as mobile. With the addition of biochar, the extracted concentrations of explosives were reduced to less than 10% of the initial concentrations after 10 d. According to the results from a Korean waste leaching method, the TCLP method, and diethylenetriaminepentaacetic acid (DTPA) extraction, adding biochar to mine tailings reduced the extractability and bioavailability of metals. The chemical forms of the metals, types of extractants, pH, and curing period strongly affected the extractability of metals from mine tailings. The results suggest that biochar is a promising immobilizer of explosives and metals in contaminated soils and mine tailings under limited conditions.

Mechanisms of arsenic assimilation by plants and countermeasures to attenuate its accumulation in crops other than rice

“…The impact of the organic matter addition is also affected by the type of crop; Madeira et al (2012) found that the addition of an olive-mill waste compost to a highly contaminated soil significantly reduced the As concentrations in tomato fruit while the levels of the pollutant in parsley shoot were not affected at all as compared to the non-amended counterpart. Among other organic-based amendments, biochar has been shown to reduce the bioavailability of metal (loid)s (Oh and Yoon, 2016;Ippolito et al, 2017) and to enable successful revegetation of contaminated areas (Park et al, 2011). Biochar is the byproduct of a variety of thermochemical processes, including slow or fast pyrolysis, torrefaction, hydrothermal carbonization, and gasification; it can be obtained from several wastes, such as crop residues, weeds, wood sawdust, litter, and municipal solid waste.…”

Abandoned metalliferous mines: ecological impacts and potential approaches for reclamation

“…Fellet et al (2011) proposed that biochar could be used as potential amendment for the reclamation of abandoned dumping sites of mining areas. Very recently, Oh and Yoon (2016) also reported that soils near the abandoned mines can be reclaimed through biochar amendment owing to the potential of the biochar to reduce the leachability of toxic contaminants such as nitro explosives and metals from the mine tailings. Also, the review by Brown and Chaney (2016) highlights the possible use of combination of mixtures, typically consisting of a material with high metal binding capacity (cyclone ashes, municipal biosolids or materials rich in Al, Fe or Mn oxides), materials to adjust pH (sugar beet lime, dolomitic limestone, cement kiln dust), and an organic residue to provide better soil structure and nutrients (compost, animal manures, municipal solid waste) for the successful reclamation of abandoned mine impacted sites.…”