Enrique Eymar

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.

Combination of biochar amendment and mycoremediation for polycyclic aromatic hydrocarbons immobilization and biodegradation in creosote-contaminated soil

Soils impregnated with creosote contain high concentrations of polycyclic aromatic hydrocarbons (PAH). To bioremediate these soils and avoid PAH spread, different bioremediation strategies were tested, based on natural attenuation, biochar application, wheat straw biostimulation, Pleurotus ostreatus mycoremediation, and the novel sequential application of biochar for 21 days and P. ostreatus 21 days more. Soil was sampled after 21 and 42 days after the remediation application. The efficiency and effectiveness of each remediation treatment were assessed according to PAH degradation and immobilization, fungal and bacterial development, soil eco-toxicity and legal considerations. Natural attenuation and biochar treatments did not achieve adequate PAH removal and soil eco-toxicity reduction. Biostimulation showed the highest bacterial development but low PAH degradation rate. Mycoremediation achieved the best PAH degradation rate and the lowest bioavailable fraction and soil eco-toxicity. This bioremediation strategy achieved PAH concentrations below Spanish legislation for contaminated soils (RD 9/2005). Sequential application of biochar and P. ostreatus was the second treatment most effective for PAH biodegradation and immobilization. However, the activity of P. ostreatus was increased by previous biochar application and PAH degradation efficiency was increased. Therefore, the combined strategy for PAH degradation have high potential to increase remediation efficiency.

Implications of polluted soil biostimulation and bioaugmentation with spent mushroom substrate (Agaricus bisporus) on the microbial community and polycyclic aromatic hydrocarbons biodegradation

Different applications of spent Agaricus bisporus substrate (SAS), a widespread agro-industrial waste, were investigated with respect to the remediation of a historically polluted soil with Polycyclic Aromatic Hydrocarbons (PAH). In one treatment, the waste was sterilized (SSAS) prior to its application in order to assess its ability to biostimulate, as an organic amendment, the resident soil microbiota and ensuing contaminant degradation. For the other treatments, two bioaugmentation approaches were investigated; the first involved the use of the waste itself and thus implied the application of A. bisporus and the inherent microbiota of the waste. In the second treatment, SAS was sterilized and inoculated again with the fungus to assess its ability to act as a fungal carrier. All these treatments were compared with natural attenuation in terms of their impact on soil heterotrophic and PAH-degrading bacteria, fungal growth, biodiversity of soil microbiota and ability to affect PAH bioavailability and ensuing degradation and detoxification. Results clearly showed that historically PAH contaminated soil was not amenable to natural attenuation. Conversely, the addition of sterilized spent A. bisporus substrate to the soil stimulated resident soil bacteria with ensuing high removals of 3-ring PAH. Both augmentation treatments were more effective in removing highly condensed PAH, some of which known to possess a significant carcinogenic activity. Regardless of the mode of application, the present results strongly support the adequacy of SAS for environmental remediation purposes and open the way to an attractive recycling option of this waste.

Effect of activated charcoal and 6-benzyladenine on in vitro nitrogen uptake by Lagerstroemia indica

A sterile hydroponic culture system suitable for studying nitrogen (N) uptake ofLagerstroemia indica L.in vitro was developed. Four different treatments were assayed: with and without activated charcoal (AC and NAC, respectively), with and without 50 μM of 6-benzyladenine (+BA and −BA, respectively). Medium pH, electrical conductivity (EC), NO3− and NH4+ concentrations were measured weekly. At the end of the culture, propagules were sampled and SPAD indices, and shoot and root fresh weights were determined. Explants grown in media with activated charcoal were able to take up both NO3− and NH4+, although NH4+ uptake was lower. Subsequently the pH of the media was maintained between 5.5–6.0. In treatments with no addition of activated charcoal, NH4+ uptake was preferential and the pH dropped to 3.1. Explants in these conditions were unable to raise the pH by taking up NO3−, especially when root morphogenesis was inhibited by addition of BA. Supply of this PGR produced root growth inhibition, which was almost complete in the treatment without activated charcoal. This component significantly reduced the inhibitory effect of 50 μM BA on root growth.

Bioremediation of multi-polluted soil by spent mushroom (Agaricus bisporus) substrate: Polycyclic aromatic hydrocarbons degradation and Pb availability

This study investigates the effect of three spent Agaricus bisporus substrate (SAS) application methods on bioremediation of soil multi-polluted with Pb and PAH from close to a shooting range with respect natural attenuation (SM). The remediation treatments involve (i) use of sterilized SAS to biostimulate the inherent soil microbiota (SSAS) and two bioaugmentation possibilities (ii) its use without previous treatment to inoculate A. bisporus and inherent microbiota (SAS) or (iii) SAS sterilization and further A. bisporus re-inoculation (Abisp). The efficiency of each bioremediation microcosm was evaluated by: fungal activity, heterotrophic and PAH-degrading bacterial population, PAH removal, Pb mobility and soil eco-toxicity. Biostimulation of the native soil microbiology (SSAS) achieved similar levels of PAH biodegradation as SM and poor soil detoxification. Bioaugmented microcosms produced higher PAH removal and eco-toxicity reduction via different routes. SAS increased the PAH-degrading bacterial population, but lowered fungal activity. Abisp was a good inoculum carrier for A. bisporus exhibiting high levels of ligninolytic activity, the total and PAH-degrading bacteria population increased with incubation time. The three SAS applications produced slight Pb mobilization (<0.3%). SAS sterilization and further A. bisporus re-inoculation (Abisp) proved the best application method to remove PAH, mainly BaP, and detoxify the multi-polluted soil.

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.

Nitrogen Fertilization Using Hydroponic Cultures to Fertigate Ornamental Shrubs

ABSTRACT The total nitrogen (N) concentration and nitrate/ammonium ratio (NO3 −/NH4 +) in nutrient solutions were optimized in sand cultures and in 15N experiments for laurustinus (Viburnum tinus), tobir (Pittosporum tobira), and strawberry tree (Arbutus unedoL.) under controlled conditions during three growing cycles. Results from the 15N experiment suggest that Arbutus unedo and, to a minor extent, Pittosporum could regulate the N-NH4 + absorption independently of the external concentration and reduce the toxic effects of N-NH4 +. For Viburnum tinus plants, however, higher external N-NH4 + concentration increased root N-NH4 + and, therefore, could have toxic effects. The optimal N concentration in nutrient solutions and in nitrate-only nutrition would be close to 4.6 mmolc L−1 for Viburnum tinus and close to 5.8 mmolc L−1 for Pittosporum tobira, with a 70/30 (%) NO3 −/NH4 + ratio. For Arbutus unedoL., a total N concentration higher than 9 mmolc L −1 is suggested, with a 70/30 NO 3 −/NH 4 + ratio. Plant-tissue reference levels were obtained for their use for nutritional diagnosis of ornamental shrubs.

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.

Methodology for Polycyclic Aromatic Hydrocarbons Extraction from Either Fresh or Dry Spent Mushroom Compost and Quantification by High-Performance Liquid Chromatography–Photodiode Array Detection

Polycyclic aromatic hydrocarbons (PAH) are a family of compounds classified as persistent organic pollutants, which are hazardous for environmental and human health. White rot fungi are organisms that are able to remediate PAH from polluted soils. Spent mushroom compost (SMC) is employed for soil bioremediation and environmental research. In this study, four solvents [acetone/dichloromethane (CH2Cl2) 1:1 mixture; acetone/hexane 1:1 mixture; methanol, and acetone], which are among those already used for PAH solvents, were chosen to be combined with two extraction procedures (ultrasound and orbital shaking). All extracted PAH were quantified by high-performance liquid chromatography (HPLC)–photodiode array detection (PDA). Certified soil CRM141, containing 16 PAH included in the U.S. Environmental Protection Agency priority list, was used for methodology validation. The orbital shaking procedure was selected because all detected and quantified PAH were within the CRM141 prediction interval, and there was less variability for all checked solvents than in the ultrasonic procedure. Once the orbital shaking methodology was selected, fluorene, phenanthrene, anthracene, and pyrene standards were added to fresh (60% moisture content) and dry SMC. The orbital shaking procedure was carried out over 24 h to avoid PAH degradation, and 1 month later to provide PAH interaction with solid matrix in this period of time. The PAH orbital shaking extraction over dry SMC showed large recovery percentages for all tested solvents. The PAH extracted from fresh SMC showed biodegradation after 24 h. Acetone/CH2Cl2 (1:1), methanol, and acetone solvents employed over fresh SMC recovered less than solvents over dry SMC. Acetone/hexane (1:1) recovered more than 80% and did not show any decrease in recovery over fresh SMC. Results indicate that it is not necessary to include a drying step prior to PAH extraction if the acetone/hexane (1:1) solvent mixture is employed. The recommended methodology for PAH extraction includes orbital shaking of fresh compost with acetone/hexane (1:1) solvent mixture and quantification by HPLC-PDA.

Estimation of Leaf, Root, and Sap Nitrogen Status using the SPAD‐502 Chlorophyll Meter for Ornamental Shrubs

Abstract The SPAD‐502 chlorophyll meter was evaluated as a rapid tool to predict plant nitrogen (N) concentration. The SPAD‐502 index utility, as a comparative tool with respect to N nutritional status, was evaluated for Laurustine (Viburnum tinus L.), tobir (Pittosporum tobira Thumb.), and strawberry tree (Arbutus unedo L.). The effect of sampling time on the SPAD‐502 index measures was also evaluated. Two sand culture experiments evaluating 1, 3, 5, and 7 mmolc · L−1 of total N concentration in nutrient solution and 70/30, 50/50, 40/60, and 30/70% nitrate/ammonium (NO3 −/NH4 +) ratios were applied. In a media experiment, with similar conditions and fertilization, the accuracy of the SPAD‐502 regression data was evaluated. Leaf, root, and sap samples were taken in the middle and at the end of each experiment. Regression equations were established among leaf N, root N, of sap N analyzed concentrations and SPAD values with regard to global, as well as specific, data within each sampling time. Regression coefficients (b) among leaf N and SPAD were highly significant (P<0.05) for practically all sampling times. However, liner regression equations were different in all treatments among all the sampling dates. Determination coefficients (R2), in some cases, show that the SPAD‐502 index is not an adequate method for leaf, root, or sap N concentration fir Viburnum tinus L. and Pittosporum tobira Thumb. or for root or sap for Arbutus unedo L. in these experimental conditions. Nonetheless, the SPAD‐502 index could be a useful tool for relative comparison purposes and field operational nutrient management. However, the SPAD‐502 leaf greenness meter is a relatively good tool for leaf N and nutritional diagnosis for Arbutus unedo L. within the 38–66 SPAD‐502 index range.