Purification of polluted water with spent mushroom (Agaricus bisporus) substrate: from agricultural waste to biosorbent of phenanthrene, Cd and Pb.

The present research was aimed to (i) report the recycling of spent A. bisporus substrate (SAS) to remove heavy metals (Cd and Pb) and phenanthrene (Phe) from polluted water and (ii) assess the possibility to use the treated water for irrigation. Batch experiments were carried out to assess, firstly, the effect of interaction time between pollutants with SAS and, secondly, the pH of the polluted water. Then a biofilter was designed by using pressurized glass columns. Chemical parameters such as pH, electrical conductivity and content of Pb, Cd, Phe, nutrients (NPK) and Cl- were determined. Equilibrium for contaminants was quickly reached (1-2 h). The pH of the polluted water was the key factor for pollutants' adsorption. The polluted water's pH was increased after biofilter interaction. Phe was not detected in any fraction. Pb and Cd sorption rates were higher than 99%. The pollutant concentrations were within the permitted range to be used for agriculture purposes. Purified water showed significant concentrations of NPK, indicating its potential use as fertilizer. The SAS shows potential to be used as Phe, Pb and Cd biosorbent and the resulting treated water can be used for irrigation according to pollutant contents and agronomical evaluation.

Cadmium and lead bioavailability and their effects on polycyclic aromatic hydrocarbons biodegradation by spent mushroom substrate.

Bioremediation of mixed metal-organic soil pollution constitutes a difficult task in different ecosystems all around the world. The aims of this work are to determine the capacity of two spent mushroom substrates (Agaricus bisporus and Pleurotus ostreatus) to immobilize Cd and Pb, to assess the effect of these metals on laccase activity, and to determine the potential of spent A. bisporus substrate to biodegrade four polycyclic aromatic hydrocarbons (PAH): fluorene, phenanthrene, anthracene, and pyrene, when those toxic heavy metals Cd and Pb are present. According to adsorption isotherms, spent P. ostreatus and A. bisporus substrates showed a high Pb and Cd adsorption capacity. Pb and Cd interactions with crude laccase enzyme extracts from spent P. ostreatus and A. bisporus substrates showed Cd and Pb enzyme inhibition; however, laccase activity of A. bisporus presented lower inhibition. Spent A. bisporus substrate polluted with PAH and Cd or Pb was able to biodegrade PAH, although both metals decrease the biodegradation rate. Spent A. bisporus substrate contained a microbiological consortium able to oxidize PAH with high ionization potential. Cd and Pb were immobilized during the bioremediation process by spent A. bisporus substrate. Consequently, spent A. bisporus substrate was adequate as a multi-polluted soil bioremediator.

Effect of citric acid on metals mobility in pruning wastes and biosolids compost and metals uptake in Atriplex halimus and Rosmarinus officinalis.

To assess metal mobility in pruning waste and biosolids compost (pH 6.9 and total concentration of metals in milligram per kilogram of Cd 1.9, Cu 132, Fe 8,513, Mn 192, Pb 81, and Zn 313), shrubs species Atriplex halimus and Rosmarinus officinalis were transplanted in this substrate and irrigated with citric acid (4 g L(-1), pH 2.9) and nutrient solution daily for 60 days. Citric acid significantly increased the concentrations of soluble Mn and Fe in the nutrient substrate solution measured by suction probes, while other metals did not vary in concentration (Cu and Zn) or were not observed at detectable levels (Cd and Pb). In plants, citric acid significantly increased the concentrations of Cu (2.7 ± 0.1-3.3 ± 0.1 mg kg(-1)), Fe (49.2 ± 5.2-76.8 ± 6.8 mg kg(-1)), and Mn (7.2 ± 1.1-11.4 ± 0.7 mg kg(-1)) in leaves of R. officinalis, whereas the concentration of only Mn (25.4 ± 0.3-42.2 ± 2.9 mg kg(-1)) was increased in A. halimus. Increasing Fe and Mn solubility by citric acid addition indicates the possibility of using it to improve plant nutrition. The mobility of metals in this substrate was influenced for the concentration of the metal, the degree of humification of organic matter and its high Fe content.

Influence of chemical and mineralogical properties of organic amendments on the selection of an adequate analytical procedure for trace elements determination.

Six digestion procedures were tested to improve extraction methods for determination of trace elements in various organic amendments with high inorganic fractions. These procedures were tested in terms of pH, CaCO(3), organic matter, elemental analysis, BCR sequential extraction and X-ray diffraction analysis. Aqua regia extraction (ISO 11466), total digestion HF-HNO(3)-HClO(4) and four microwave-assisted digestions (i.e., HNO(3), HCl-HNO(3), HNO(3)-HF and HCl-HNO(3)-HF) were used. The effect of acid mixtures on microwave-assisted digestion of mineral fractions was assessed by Si and Al analysis and X-ray diffraction in the solid residues obtained. Microwave HF acid mixtures obtained highest trace element recoveries for all tested metals except Al. CaF(2) and CaAlF(5) precipitates were also detected using X-ray diffraction in the residues after microwave digestions with HF acid mixtures of amendments with high calcium content. A decision flowchart was suggested to determine the best acid mixture according to the amendment and the metals to be analyzed.

Phytoextraction of cadmium by four Mediterranean shrub species.

The possibility of remediating contaminated soils though the use of high biomass-generating, native plant species capable of removing heavy metals is receiving increased attention. The cadmium (Cd) accumulation capacities of the native Mediterranean, perennial shrubs Atriplex halimus, Phyllirea angustifolia, Rhamnus alaternus and Rosmarinus officinalis were tested by growing transplanted specimens in a pine bark compost substrate (pH 5.6) contaminated with 100 mg Cd kg(-1). After 70 days, only R. alaternus showed reduced growth. The increase in biomass seen in all the test species enhanced the phytoextraction of Cd. However, the species behaved as metal excluders, except for the halophyte A. halimus, which behaved as an indicator plant. In this species the leaf Cd concentration reached 35 mg Cd kg(-1), with the shoot responsible for some 86% of total Cd accumulation. Atriplex halimus showed the highest bioconcentration factor (BCF) (0.36) and leaf Cd transport index (1.68); consequently, this species showed the highest Cd phytoextraction capacity.

Chemical characterization and evaluation of composts as organic amendments for immobilizing cadmium.

The ability of three composted materials to immobilize cadmium (Cd) was examined in order to assess their potential for recovering soils contaminated with this metal. Composted pine bark (PB) pH 5.6, spent mushroom compost (SM) pH 8.0, and composted pruning waste+biosolids (BS) pH 6.9 (containing 81%, 75% and 47% total organic matter, respectively) were characterized. FT-IR and CP-MAS (13)C NMR spectroscopy indicated the BS and SM to have a higher percentage of aliphatic and carboxyl groups than PB. The composts were artificially contaminated with Cd (80 and 200 mg kg(-1)) and, after 4 weeks incubation, subjected to sequential extraction. In column leaching experiments, the total Cd leached from the composts exposed to both Cd treatments was similar, but much less leached from the BS (0.2%) than the PB (4.0%) or SM (0.7%). The greater capacity of BS to immobilize Cd was attributed to the greater humification of its organic matter and higher content of inorganic components, particularly Fe.