Environmental availability of trace metals in a fired brick elaborated from a marine dredged sediment.

Each year, hundreds of millions of tons of sediments are dredged around the world. Alternatively to sea or land disposal, the reuse of these sediments as raw material in various civil engineering applications is developing. In this context, the French SEDIBRIC project (valorisation de SEDIments en BRIQues et tuiles) aims to replace, in the preparation of clay-fired bricks, a part of natural clays by harbor dredged sediments. The present study focuses on the fate of some potentially toxic elements (Cd, Cr, Cu, Ni, Pb, and Zn) that are initially present in the sediments. A fired brick is elaborated exclusively from one dredged sediment, after a desalination step. The total content of each element of interest is evaluated by ICP-AES, after a microwave-assisted acid (aqua regia) digestion, in the raw sediment and in the brick. Then, single extractions (H2O, HCl, or EDTA as reactant) and one sequential extraction procedure (according to Leleyter and Probst, Int J Environ Anal Chem 73(2): 109-128 1999) are applied to the raw sediment and to the brick, in order to assess the environmental availability of the elements of interest. For Cu, Ni, Pb, and Zn, the results obtained with the various extractions procedures applied are consistent and confirm that the firing process induces their stabilization in the brick. The availability however increases for Cr and remains unchanged for Cd.

Use of soil fungi in the biosorption of three trace metals (Cd, Cu, Pb): promising candidates for treatment technology?

Trace metal contamination is a widespread and complex environmental problem. Because fungi are capable of growing in adverse environments, several fungal species could have an interesting potential in remediation technologies for metal contaminated environments. This study proposes to test the ability to tolerate and biosorb three trace metals (Cd, Cu and Pb) of 28 fungal isolates collected from different soils. First, a tolerance assay in agar medium was performed. Each isolate was grown in the presence of Cd, Cu, and Pb at different concentrations. Then, we exposed each soil fungus to 50 mg L-1 of Cd, Cu, or Pb during 3 days in liquid medium. Parameters such as biomass production, pH, and biosorption were evaluated. The results showed that responses to metal exposure are very diverse even with fungi isolated from the same soil sample, or belonging to the same genera. Several isolates could be considered as good metal biosorbents and could be used in future mycoremediation studies. Among the 28 fungi tested, Absidia cylindrospora biosorbed more than 45% of Cd and Pb, Chaetomium atrobrunneum biosorbed more than 45% of Cd, Cu, Pb, and Coprinellus micaceus biosorbed 100% of Pb.

Comparison of tolerance and biosorption of three trace metals (Cd, Cu, Pb) by the soil fungus Absidia cylindrospora.

Trace metals cause deterioration of the soil and constitute a major concern for the environment and human health. Bioremediation could be an effective solution for the rectification of contaminated soils. Fungi could play an important role in biodegradation because of the morphology of their mycelium (highly reactive and extensive biological surface) and its physiology (high tolerance to many stresses, production of enzymes and secondary metabolites). Fungi can effectively biosequestrate, or biotransform many organic and inorganic contaminants into a non-bioavailable form. This experiment was designed to evaluate the tolerance and the biosorption abilities of the fungus Absidia cylindrospora against three trace metals: Cadmium (Cd), Copper (Cu), and Lead (Pb). Firstly, the tolerance of the strain was evaluated on metal-enriched malt extract agar (MEA). Secondly, the strain was exposed to trace metals, in a liquid malt extract medium. After 3 or 7 days of exposure, the quantities of absorbed and adsorbed metals were measured with Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Biomass production and pH evolution were also evaluated during the test. Our experiment revealed differences between the three metals. In agar medium, Cd and Pb were better tolerated than Cu. In liquid medium, Cd and Pb were mostly absorbed whereas Cu was mostly adsorbed. A. cylindrospora biosorbed 14% of Cu, 59% of Pb and 68% of Cd when exposed for 3 days at 50 mg L-1.

Cr in dredged marine sediments: Anthropogenic enrichment, bioavailability and potential adverse effects.

This study focuses on chromium detected in 13 harbor sediments dredged across the English Channel. The total concentrations of Cr range from 5 to 61mgkg-1, which reveal no or low enrichment for 12 of the 13 samples, according the enrichment factor (EF) calculations. Sequential extraction procedure was applied to determine the mineralogical speciation of Cr, in order to assess its potential (re)mobilization to the aquatic environment. Cr is mainly associated to the residual fraction, then distributed in the oxydizable and reducible fractions. The possible relationships between the enrichment, mobility and possible biological effects (according calculation of Adverse Effect Index (AEI)) suggests possible toxicity incidence even for moderate enrichment. A link is observed with the oxydizable fraction (r=0.8 and r=0.5 respectively for EF and AEI).