The Use of Biochar of High Growth Rate Plants to Agriculturally Remediate Heavy Metal Polluted Acidic Mine Wastes

Abstract

The chapter is meant to expose how a sound methodology can be instrumented to both, remediate acidic metal polluted mine wastes, taking advantage of the neutralizing power and high metal sorption affinity of biochar, and to utilize pyrolyzed material derived from high-rate growth plants (water hyacinth, Eichhornia crassipes Mart, and Eucalyptus, Eucalyptus globulus Labill), which have become of ecological relevance due to their unwanted proliferation over specific terrestrial, lacustrine or riverine environments. In addition, the proposal considers not only neutralizing the mine tailings and abating the toxic levels of specific heavy metals like Pb, Cd, Cu, Zn, etc., to fulfill the international and national standards and norms, but to conveniently combine biochar with widely used soil amendments to pass widely recognized biological tests of growth using heavy metal-sensitive plants. The approach addresses firstly: a) characterizing physiochemically mine tailings and biochar, in terms of their properties (metal speciation and contents, potential acidity and neutralization potential, chemical oxygen demand, heavy metal-biochar sorption-complexing affinities, among others), and secondly; b) creating a” fertile environment” by reconditioning, agriculturally, the heavy metal-polluted acidic mine waste to allow native vegetation, or other reforesting species, to regrow on the reclaimed site, based on the bioassay tests performances.

Heavy Metal Speciation, and the Evaluation and Remediation of Polluted Mine Wastes and Soils

“…Although there has been important progress in risk assessment strategies for soil metals, and research on methods to remediate Zn, Cd, and Pb polluted soils and sediments, by in situ treatments or by adding amendments (e.g., phosphates, compost, biochar, biosolids, lime-rich wood-ashes, etc. ), which reverse phytotoxicity of Zn and Pb risk [11,119], there is still a strong need to find sound methodologies to remediate HMpolluted mine wastes. The following sections will present examples of such methodologies to handle this type of HM-polluted terrestrial environment.…”

“…The proposal must then include the addition of ameliorating materials (lime, phosphates, compost, gypsum) that both, help to abate the HM-phytoavailable levels, while serving to neutralize the acidified metal-polluted site, and to mend the growing media, so that plant regrowth will not be impeded. Once these two aspects are guaranteed, results must, all in all, meet the requirements of national or international standards and norms and pass the chosen specific bioassay so that the site can be considered agrostabilized [9][10][11]. Other necessary physical and chemical characterization procedures shall include the total metal content, [M T ], original minerals identification, electrical conductivity, pH, HM-sorption-complexing affinities, etc.…”