Evaluation of laboratory and industrial meat and bone meal combustion residue as cadmium immobilizing material for remediation of polluted aqueous solutions: "chemical and ecotoxicological studies".

Meat and Bone Meals (MBM) combustion residues (ashes) are calcium and phosphate-rich materials. The aim of this work is to evaluate ashes efficiency for remediation of cadmium-contaminated aqueous solutions, and to assess the bioavailability of cadmium on Xenopus laevis larvae. In this study both industrial (MBM-BA) and laboratory (MBM-LA) ashes are compared regarding their efficiency. Kinetic investigations reveal that cadmium ions are quickly immobilized, with a maximum cadmium uptake at 57 mg Cd(2+)/g of ashes for MBM-LA, two times higher than metal uptake quantity of MBM-BA, in our experimental conditions. Chemical and X-ray diffraction analysis (XRD) reveal that Cd(2+) is mainly immobilized as Ca(10-x)Cd(x)(PO(4))(6)(OH)(2) by both ashes, whereas otavite, Cd(CO(3)), is also involved for MBM-LA in cadmium uptake. Otavite formation could be explained by the presence of carbonates in MBM-LA, as observed by IR. Genotoxicity of cadmium solution on Xenopus larvae is observed at 0.02, 0.2 and 2mg Cd(2+)/L. However addition of only 0.1g/L MBM-LA inhibits these effects for the above concentration values whereas Cd(2+) bioaccumulation in larvae's liver is similar for both experiments, with and without ashes.

Preliminary study of Lead (Pb) immobilization by meat and bone meal combustion residues (MBMCR) in soil: assessment of Pb toxicity (phytotoxicity and genotoxicity) using the tobacco model (Nicotiana tabacum var. xanthi Dulieu).

Lead (Pb) is a major chemical pollutant in the environment. The present investigation evaluates the possible use of Meat and Bone Meal Combustion Residues (MBMCR), to sequester Pb from the soil compartment using the heterozygous tobacco model (Nicotiana tabacum var. xanthi Dulieu) characterized by the a1+ /a1 a2+ /a2 system. The toxic potential of Pb-contaminations (50, 100, 1,000, 2,000 and 10,000 mg Pb kg(-1)) as Pb(NO3) in standard soil was investigated in lab conditions according to three endpoints: (i) acute toxicity of plants (mortality, height and surface area parameters), (ii) Pb-accumulation in roots, stems and leaves, and (iii) genetic effects as the expression of reversion in the leaf of plants. Moreover, chemical investigations of Pb interactions with soil were realized to complete the toxicity evaluation. The results demonstrated that: (i) MBMCR were not acutely toxic or genotoxic to tobacco plants, (ii) Pb is acutely toxic to tobacco plants at 10,000 mg Pb kg(-1) of soil, (ii) but is not genotoxic, and (iii) Pb-bioaccumulation is significant in leaves, stems and roots (from 1,000, 2,000, and 50 mg Pb kg(-1) of soil, respectively). In contrast, in the presence of MBMCR, the toxic impacts of Pb were inhibited and Pb-accumulation in tobacco plants was reduced. In complement, chemical analyses highlighted the high capacity of the standard soil to immobilize Pb. The results suggest that even if Pb is bioavailable from soils to plants, complex mechanisms could occur in plants protecting them from the toxic impact of Pb.

Evaluation of meat and bone meal combustion residue as lead immobilizing material for in situ remediation of polluted aqueous solutions and soils: "chemical and ecotoxicological studies".

As a result of bovine spongiform encephalopathy (BSE) crisis, meat and bone meal (MBM) production can no longer be used to feed cattle and must be safely disposed of or transformed. MBM specific incineration remains an alternative that could offer the opportunity to achieve both thermal valorization and solid waste recovery as ashes are calcium phosphate-rich material. The aim of this work is to evaluate ashes efficiency for in situ remediation of lead-contaminated aqueous solutions and soils, and to assess the bioavailability of lead using two biological models, amphibian Xenopus laevis larvae and Nicotiana tabaccum tobacco plant. With the amphibian model, no toxic or genotoxic effects of ashes are observed with concentrations from 0.1 to 5 g of ashes/L. If toxic and genotoxic effects of lead appear at concentration higher than 1 mg Pb/L (1 ppm), addition of only 100 mg of ashes/L neutralizes lead toxicity even with lead concentration up to 10 ppm. Chemical investigations (kinetics and X-ray diffraction (XRD) analysis) reveals that lead is quickly immobilized as pyromorphite [Pb10(PO4)6(OH)2] and lead carbonate dihydrate [PbCO(3).2H2O]. Tobacco experiments are realized on contaminated soils with 50, 100, 2000 and 10000 ppm of lead with and without ashes amendment (35.3g ashes/kg of soil). Tobacco measurements show that plant elongation is bigger in an ashes-amended soil contaminated with 10000 ppm of lead than on the reference soil alone. Tobacco model points out that ashes present two beneficial actions as they do not only neutralize lead toxicity but also act as a fertilizer.