Novel nonylphenol-degrading bacterial strains isolated from sewage sludge: Application in bioremediation of sludge.

Nonylphenol (NP) is an anthropogenic pollutant frequently found in sewage sludge due to the insufficient degrading effectiveness of conventional WWTPs and has attracted attention as an endocrine disruptor. The aim of this study was to isolate specific NP-degrading bacteria from sewage sludge to be used in the degradation of this contaminant through bioaugmentation processes in aqueous solution and sewage sludge. Up to eight different bacterial strains were isolated, six of them not previously described as NP degraders. Bacillus safensis CN12 presented the best NP degradation in solution, and glucose used as an external carbon source increased its effect, reaching DT50 degradation values (time to decline to half the initial concentration of the pollutant) of only 0.9 days and a complete degradation in <7 days. Four NP metabolites were identified throughout the biodegradation process, showing higher toxicity than the parent contaminant. In sewage sludge suspensions, the endogenous microbiota was capable of partially degrading NP, but a part remained adsorbed as bound residue. Bioaugmentation was used for the first time to remove NP from sewage sludge to obtain more environmentally friendly biosolids. However, B. safensis CN12 was not able to degrade NP due to its high adsorption on sludge, but the use of a cyclodextrin (HPBCD) as availability enhancer allowed us to extract NP and degrade it in solution. The addition of glucose as an external carbon source gave the best results since the metabolism of the sludge microbiota was activated, and HPBCD was able to remove NP from sewage sludge to the solution to be degraded by B. safensis CN12. These results indicate that B. safensis CN12 can be used to degrade NP in water and sewage sludge, but the method must be improved using consortia of B. safensis CN12 with other bacterial strains able to degrade the toxic metabolites produced.

Bioremediation of a trifluralin contaminated soil using bioaugmentation with novel isolated bacterial strains and cyclodextrin.

Trifluralin (TFL) is a highly persistent with a strong adsorption capacity on soil particles herbicide. This study was to isolate microbial consortia and bacterial strains from a soil with a historical application of pesticides to evaluate their potential to degrade TFL in soil. Different bioremediation techniques were considered for increasing the effectiveness of TFL degradation in soil. These techniques consisted of: i) biostimulation, using a nutrients solution (NS); ii) bioaugmentation, using a natural microbial consortium (NMC), seven individual bacterial strains isolated from NMC, and an artificial bacterial consortium formed by the seven TFL-degrading bacterial strains (ABC); iii) bioavailability enhancement, using a biodegradable compound, a randomly methylated cyclodextrin, RAMEB. Biostimulation using NS leads up to 34 % of soil TFL biodegraded after 100 d. When the contaminated soil was inoculated with NMC or ABC consortia, TFL loss increased up to 62 % and 74 %, respectively, with DT50 values (required time for the pollutant concentration to decline to half of its initial value) of 5.9 and 11 d. In the case of soil inoculation with the isolated individual bacterial strains, the extent of TFL biodegradation ranged widely from 2.3 % to 55 %. The most efficient bacterial strain was Arthrobacter aurescens CTFL7 which had not been previously described in the literature as a TFL-degrading bacterium. Bioaugmentation with CTFL7 bacterium was also tested in the presence of RAMEB, provoking a drastic increase in herbicide biodegradation up to 88 %, achieving a DT50 of only 19 d. Cyclodextrins had never been tested before for enhancement of TFL biodegradation. An ecotoxicity assay was performed to confirm that the proposed bioremediation techniques were also capable to reduce toxicity. A Microtox® test showed that after application A. aurescens CTF7 and A. aurescens CTF7 + RAMEB, the TFL-contaminated soil, which initially presented acute toxicity, became non-toxic at the end of the biodegradation experiments.

Dissipation of a mix of priority PAHs in soils by using availability enhancers. Effect of aging and pollutant interactions.

A remediation strategy using three non-toxic availability enhancers (two cyclodextrins and a rhamnolipid biosurfactant) was applied to various soils artificially contaminated with a mix of Polycyclic Aromatic Hydrocarbons (PAHs) considered priority pollutants at two levels of contamination: only with 7 low molecular weight PAHs (LMW PAHs, 5 with 3-ring and 2 with 4-ring - fluoranthene and pyrene) or with 14 PAHs (from 3 to 6 rings). Natural attenuation of PAHs in all soils showed degradation capacity for the LMW PAHs, with a final content of LMW PAHs <5% of their initial concentration. Conversely, the rest of PAHs (high molecular weight PAHs, HMW) remained in the soils (61% - 83.5%), indicating abiotic dissipation of HMW PAHs due to formation of non-extractable residues in soils. The influence of the presence of HMW PAHs on the degradation of the 7 LMW PAHs was also tested, showing a general decrease in the time to obtain 50% dissipation (DT50), statistically significant for acenaphthene, acenaphthylene and fluorene. Availability enhancers showed different effects on PAHs dissipation. 2-hydroxypropyl-ß-cyclodextrin (HP) decreased DT50 of some of the lighter PAHs, whereas the rhamnolipid (RL) caused a slight DT50 increase due to its initial toxicity on native soil microorganisms, but showing later high degradation rate for LMW PAHs. On the contrary, randomly methylated-ß-cyclodextrin (RAMEB) slowed down PAHs degradation due to its high adsorption onto soil surface, blocking the desorption of PAHs from the soils. The high number of experimental factors not studied simultaneously before (soil type, co-contamination, availability enhancers and incubation time) allowed to conduct a statistical analysis which supported the conclusions reached. Principal Component Analysis separated the studied PAHs in 3 groups, in relation with their molecular weight and Kow. The first principal component was related with LMW PAHs, and separate the inefficient RAMEB from the other availability enhancers.

Soil bioremediation by cyclodextrins. A review.

Remediation of soils contaminated by organic pollutants has become an urgent necessity worldwide. A wide variety of techniques have been developed but many of them are associated with drawbacks (complexity, high costs, environmental risks, etc.). Bioremediation, the use of living organisms to remediate polluted sites, is an alternative approach considered a cost-effective and more environmentally friendly technique, but the low bioavailability of the organic pollutants in soils is its main limitation. Cyclodextrins have been proposed as a ́greener alternative to organic solvents or synthetic surfactants for increasing organics bioavailability in soils. Cyclodextrins can form inclusion complexes with hydrophobic pollutants increasing their aqueous solubility and enhancing their bioremediation in soils. This review gives an overview on the use of cyclodextrins for this purpose, highlighting the advantages and disadvantages and perspectives of this technology for future research. The effect of those cyclodextrins more commonly used is analyzed, particularly hydroxypropyl-ß-cyclodextrin (HPBCD) and randomly methylated-ß-cyclodextrin (RAMEB), as well as some of the more common contaminants treated (almost 80% are industrial chemicals and the rest are pesticides) and the bioremediation strategies used (by microorganisms and/or phytoremediation). The review also provides a critical view on knowledge gaps and limitations of this technology which must be overcome to bring it for field-scale application.

QSAR/QSPR models based on quantum chemistry for risk assessment of pesticides according to current European legislation.

In Europe, agencies and official organizations involved in the pesticide control such as the EFSA, ECHA, JRC and ECETOC or even the OECD are pointing out that the software tools based on quantitative structure relationship models, i.e. QSAR and QSPR, have a huge potential to improve the pesticide risk assessment process. In this sense, these non-animal test methods can promote the competitiveness of agriculture in this region: the consumer safety is increased with them due to the possibility of perform an overall better risk assessment of the degradation products and metabolites from pesticides. However, the use of theses computational-based (in silico) tools must be much more systematised and harmonised, improving their validation and including case studies to test them. To open databases, incorporating critical data in an orderly manner for building the models, becomes also necessary. Moreover, quantum chemistry through the Density Functional Theory should be promoted as tool for calculation of quantum descriptors, especially for the study of similar compounds with the same carbon skeleton but differing substitution patterns, e.g. isomers.

Natural and assisted dissipation of polycyclic aromatic hydrocarbons in a long-term co-contaminated soil with creosote and potentially toxic elements.

An enhanced bioremediation strategy was applied to an industrial soil co-contaminated with Polycyclic Aromatic Hydrocarbons (PAHs) and Potentially Toxic Elements (PTEs). Hydroxypropyl-ß-cyclodextrin (HPBCD) and a natural mixture of two rhamnolipids (RL) were added to increase PAHs bioavailability, and combined with a microbial consortium (MC) to biodegrade soil PAHs. Bioavailability of only six PAHs (3-, 4-ring PAHs) increased when using HPBCD, with a maximum increase about 2.8-fold higher. The highest dose of HPBCD (5%) enhanced PAH degradation, with the best results for 4-ring PAHs with treatments of HPBCD + MC (up to 48% degradation for pyrene and 43% for fluoranthene), whereas dissipation for 5-ring PAHs was very low and for 6-ring was negligible. The use of RL increased the bioavailability of 13 of the 16 PAHs studied, reaching up to 60-fold higher values for phenanthrene or 18-fold higher for acenaphtene. RL addition did not show degradation improvement in any situation, and even inhibited the scarce degradation observed in the control treatment. The high increase in availability of both PAHs and mainly PTEs when using RL as amendment could make them toxic for microorganisms. In fact, Microtox Acute Toxicity test using Aliivibrio fischeri and the absence of colony forming units (CFUs) of indigenous bacteria demonstrated the extremely high levels of toxicity in RL treated soil.

Combined use of microbial consortia isolated from different agricultural soils and cyclodextrin as a bioremediation technique for herbicide contaminated soils.

The phenylurea herbicide diuron is persistent in soil, water and groundwater and is considered to be a highly toxic molecule. The principal product of its biodegradation, 3,4-dichloroaniline, exhibits greater toxicity than diuron and is persistent in the environment. Five diuron degrading microbial consortia (C1C5), isolated from different agricultural soils, were investigated for diuron mineralization activity. The C2 consortium was able to mineralize 81.6% of the diuron in solution, while consortium C3 was only able to mineralize 22.9%. Isolated consortia were also tested in soil slurries and in all cases, except consortium C4, DT50 (the time required for the diuron concentration to decline to half of its initial value) was drastically reduced, from 700 days (non-inoculated control) to 546, 351, and 171 days for the consortia C5, C2, and C1, respectively. In order to test the effectiveness of the isolated consortium C1 in a more realistic scenario, soil diuron mineralization assays were performed under static conditions (40% of the soil water-holding capacity). A significant enhancement of diuron mineralization was observed after C1 inoculation, with 23.2% of the herbicide being mineralized in comparison to 13.1% for the control experiment. Hydroxypropyl-ß-cyclodextrin, a biodegradable organic enhancer of pollutant bioavailability, used in combination with C1 bioaugmentation in static conditions, resulted in a significant decrease in the DT50 (214 days; 881 days, control experiment). To the best of our knowledge, this is the first report of the use of soil-isolated microbial consortia in combination with cyclodextrins proposed as a bioremediation technique for pesticide contaminated soils.

Behaviour of glyphosate in a reservoir and the surrounding agricultural soils.

Glyphosate (GPS) is an herbicide currently used on olive crops in Spain, and can be transported to the nearby reservoirs currently used for human consumption. The purpose of this work was to study the behaviour and environmental fate of GPS in water and sediments of the Vibora Reservoir, its tributary river, and the surrounding agricultural soils to assess the risk of water pollution of this reservoir. The adsorption of GPS by different matrices was as follows: heading of the reservoir sediment (Cabecera)>tail sediment (Cola)>soils>Vibora sediment. The highest amount of oxides (especially Fe oxides) was observed in sediments from Cabecera and Cola whereas the lowest values were recorded on Vibora sediment. Results indicate that the highest GPS adsorption is due to the amorphous oxides and the edge sites of the clay minerals. Glyphosate adsorption increased with decreasing pH from 8 to 7. The desorption percentage of GPS from the four soils studied ranged only from 0.40 to 1.22%. Desorption was almost irreversible for Cabecera and Cola sediments, with values between 0 and 1.1%. Conversely, Vibora sediment presented about 20% desorption, probably due to its coarse texture and lower levels of amorphous oxides. Hockey-stick first-order kinetics was the best descriptor for water glyphosate dissipation at the Cabecera and Cola locations, and simple first-order kinetic for the water from the tributary Vibora River. The half-lives (DT50) were between 6.3 and 11.0days. The rapid degradation of GPS in surface waters and its practically irreversible sorption on these soils and sediments implies that GPS use in similar agricultural areas is of very low environmental risk. This manuscript also outlines the importance of the presence of photo-sensitizers in waters in the degradation routes of GPS in reservoirs.

Advanced technologies for the remediation of pesticide-contaminated soils.

The occurrence of pesticides in soil has become a highly significant environmental problem, which has been increased by the vast use of pesticides worldwide and the absence of remediation technologies that have been tested at full-scale. The aim of this review is to give an overview on technologies really studied and/or developed during the last years for remediation of soils contaminated by pesticides. Depending on the nature of the decontamination process, these techniques have been included into three categories: containment-immobilization, separation or destruction. The review includes some considerations about the status of emerging technologies as well as their advantages, limitations, and pesticides treated. In most cases, emerging technologies, such as those based on oxidation-reduction or bioremediation, may be incorporated into existing technologies to improve their performance or overcome limitations. Research and development actions are still needed for emerging technologies to bring them for full-scale implementation.

Bioremediation of diuron contaminated soils by a novel degrading microbial consortium.

Diuron is a biologically active pollutant present in soil, water and sediments. It is persistent in soil, water and groundwater and slightly toxic to mammals and birds as well as moderately toxic to aquatic invertebrates. Its principal product of biodegradation, 3,4-dichloroaniline, exhibits a higher toxicity than diuron and is also persistent in the environment. On this basis, the objective of the study was to determine the potential capacity of a proposed novel diuron-degrading microbial consortium (DMC) for achieving not only diuron degradation, but its mineralisation both in solution as well as in soils with different properties. The consortium was tested in a soil solution where diuron was the only carbon source, and more than 98.8% of the diuron initially added was mineralised after only a few days. The consortium was composed of three diuron-degrading strains, Arthrobacter sulfonivorans, Variovorax soli and Advenella sp. JRO, the latter had been isolated in our laboratory from a highly contaminated industrial site. This work shows for the first time the potential capacity of a member of the genus Advenella to remediate pesticide-contaminated soils. However, neither of the three strains separately achieved mineralisation (ring-14C) of diuron in a mineral medium (MSM) with a trace nutrient solution (NS); combined in pairs, they mineralised 40% of diuron in solution, but the most relevant result was obtained in the presence of the three-member consortium, where complete diuron mineralisation was achieved after only a few days. In the presence of the investigated soils in suspension, the capacity of the consortium to mineralise diuron was evaluated, achieving mineralisation of a wide range of herbicides from 22.9 to 69.0%.

Natural attenuation of fluorene and pyrene in contaminated soils and assisted with hydroxypropyl-ß-cyclodextrin. Effect of co-contamination.

The objectives of this study were to investigate the mutual effect of the PAHs fluorene and pyrene on their respective biodegradation and dissipation processes in an agricultural soil, and to determine the effect of hydroxypropyl-ß-cyclodextrin (HPBCD), used to increase the bioavailability of PAHs, on such processes. Fluorene dissipation was primarily due to abiotic processes, although a small contribution from biodegradation was also observed. Therefore, fluorene dissipation did not increase with HPBCD and its presence did not significantly alter the dehydrogenase activity. In contrast to fluorene, pyrene dissipation depended primarily on biotic factors, with endogenous soil microorganisms capable of degrading pyrene, with large increases in dehydrogenase activity. HPBCD increased biodegradation rate of pyrene. The co-contamination of soil with both PAHs did not affect fluorene evolution, but significantly inhibited pyrene biodegradation. The different abilities of soil bacterial consortia to catabolize these PAHs are discussed. Additionally, the possibility that the abiotic loss of fluorene through volatilization had a significant effect on the microbial community biodegradation of both fluorene and pyrene is examined.

La endarterectomía carotídea debe persistir como la técnica de elección para la mayoría de los pacientes con estenosis carotídea en la era endovascular / Carotid endarectomy must remain the technique of choice for the majority of patients with carotid stenosis in the endovascular era

El cambio en el paradigma de tratamiento en la cirugía vascular se ha producido gracias al desarrollo de las técnicas endovasculares, que se han ido posicionado como alternativa de tratamiento respecto a técnicas quirúrgicas tradicionales en múltiples sectores de nuestra especialidad. Pero el sector carotídeo supone una excepción a este hecho, ya que los resultados de las técnicas mínimamente invasivas aún no han conseguido igualar a los de la técnica quirúrgica tradicional, la endarterectomía carotídea. El objetivo de este artículo de opinión es el de defender la adopción de la endarterectomía carotídea quirúrgica como la técnica de elección para el tratamiento de la estenosis carotídea frente al stent carotídeo, mediante una revisión no sistemática de la literatura, de los ensayos clínicos de mayor impacto y de las principales recomendaciones de guías clínicas internacionales

The paradigm of treatment in vascular surgery is changing, due to the huge advances in endovascular techniques, as well as in the new endovascular skills of the next generations of vascular surgeons. Minimal invasive techniques are becoming the first line of treatment in many vascular sectors, but this assumption is still very controversial in carotid bifurcation disease, where the results of angioplasty plus stenting strategy are not as good at it seems when this technique is compared with carotid endarterectomy. The aim of this paper is to justify the adoption of the carotid endarterectomy as the first line treatment for carotid bifurcation disease in the endovascular era. This is based on a non-systematic review of the literature, the analisis of the main randomized controlled trials published, and the guidelines of the most relevant scientific committees

Effect of contact time and the use of hydroxypropyl-ß-cyclodextrin in the removal of fluorene and fluoranthene from contaminated soils.

Sorption-desorption experiments of fluorene (FLU) and fluoranthene (FLT) in soils were carried out and correlated to their removal from aged contaminated soils using aqueous solutions in the absence and in the presence of hydroxypropyl-ß-cyclodextrin (HPBCD) as the extraction agent. FLU became more resistant to extraction in aged contaminated soils due to its initial adsorption onto the mineral and amorphous soil organic matter (SOM) domains, sites of lower binding energy from which, due to its small size, it could spread towards the condensed SOM as the contact time increased. Therefore, FLU will not be easily desorbed from aged contaminated soils due to physical entrapment mechanisms, even when using HPBCD as extractant, presenting FLU low risks to the environment. On the contrary, FLT was extracted from aged soils in the presence of HPBCD in solutions to a much greater extent than in its absence. Due to its more hydrophobic character FLT sorption in soils was relatively quicker, remaining more or less fixed on hydrophobic sites of the organic matter (OM) with different energies, and therefore the amount of FLT extracted was almost constant for different ageing times. During extraction experiments, the influence of the OM quality of the soils was also highlighted because an inverse proportionality between OM content of soil and extractability of sorbed FLT was observed. It was concluded that soils with lower OM content that had more diagenetically processed OM could block the extraction of FLT more effectively than soils with higher OM content that are less humified. This indicates the need to use not only adsorption-desorption data in contaminant fate and transport models, but also extraction studies in aged contaminated soils and other complementary analytical approaches when assessing soil contamination-related risks.

Comparative effects of several cyclodextrins on the extraction of PAHs from an aged contaminated soil.

The objective of the present study was to characterise the polycyclic aromatic hydrocarbons (PAHs) content of an aged contaminated soil and to propose remediation techniques using cyclodextrins (CDs). Four CDs solutions were tested as soil decontamination tool and proved more efficient in extracting PAHs than when an aqueous solution was used; especially two chemically modified CDs resulted in higher extraction percentages than natural ß-CD. The highest extraction percentages were obtained for 3-ring PAHs, because of the appropriate size and shape of these compounds relative to those of the hydrophobic cavities of the CDs studied. A detailed mechanistic interpretation of the chemical modification of CDs on the extraction of the different PAHs has been performed, and connected with the role that the different hydrophobicities of the PAHs play in the extraction behaviour observed for the 16 PAHs, limiting their accessibility and the remaining risk of those PAHs not extractable by CDs.

Comparison of the reliability and validity of four contemporary risk stratification schemes to predict thromboembolism in non-anticoagulated patients with atrial fibrillation.

BACKGROUND: The risk of thromboembolic (TE) complications in atrial fibrillation (AF) patients is not homogeneous. Risk schemes can help target anticoagulant therapy for patients at highest risk of TE complications. OBJECTIVES: To test the predictive ability of 4 risk schemes: The Framingham, the 8th ACCP, the ACC/AHA/ESC 2006, and the CHA2DS2-VASc. METHODS: 186 patients with non-valvular AF and off anticoagulant therapy were included. All subjects who experienced a stroke, transient ischemic attack, or peripheral embolism were identified. Each schema was divided into low, intermediate, and high-risk categories. Discrimination was assessed via the c-statistic. RESULTS: We identified 10 TE events that occurred during 668 person-years off anticoagulation therapy. All risk schemes had fair discriminating ability (c-statistic ranged from 0.59 [for CHA2DS2-VASc] to 0.73 [for Framingham]). The proportion of patients assigned to individual risk categories varied widely across schemes. CHA2DS2-VASc categorized the fewest patients into low and intermediate-risk categories, whereas the Framingham schema assigned the highest patients into low-risk strata. There were no TE events in the low and intermediate-risk categories using CHA2DS2-VASc, whereas the most schemes assigned patients into intermediate-risk category had a event rate ranging from 2.5 (ACC/AHA/ESC and 8th ACCP schemes) to 6% (Framingham). The negative predictive value of TE events was of 100% for the no high-risk patients using CHA2DS2-VASc. CONCLUSIONS: Compared to ACC/AHA/ESC, 8th ACCP, and Framingham, CHA2DS2-VASc risk stratification schema may be better in discriminating between patients at a low and intermediate risk of TE complications.

Alternativa quirúrgica de recurso en pacientes con AAA sintomático, sin indicación técnica de exclusión endovascualar y elevado riesgo quirúrgico / Surgical alternative in high risk patients with AAA and anatomical limitations for evar

INTRODUCCIÓN. El aumento de expectativa de vida da lugar a que, actualmente, se presenten pacientes con AAA sintomáticos (fisurados o no) sin indicación anatómica de endoprótesis estándar y con elevado riesgo quirúrgico en la cirugía abierta convencional, que demandan tratamiento porque no se resignan a esperar la muerte por rotura aneurismática. Se le ofrece como alternativa, reactualizando una técnica antigua, la revascularización extraanatómica y la resección aneurismática. Nuestro objetivo es analizar los resultados obtenidos con esta actitud terapéutica. MATERIAL Y MÉTODO. Fueron tratados 7 pacientes con edad media de 78,8 años y AAA sintomático ( uno con rotura posterior contenida) de 5,2 cm a 8 cm. de diámetro. Todos tenían patología cardiorrespiratoria severa y riesgo anestésico ASA III-IV. En todos se practicó bypass axilobifemoral y resección aneurismática. RESULTADOS. El resultado fue satisfactorio en todos los pacientes con un seguimiento entre 1 y 15 años. Como complicaciones en el post-operatorio inmediato se registró neumonía en un caso y perforación intestinal en otro, resueltos satisfactoriamente. A los ocho años de seguimiento se registró un éxitus por neoplasia pulmonar. CONCLUSIONES. A la vista de los resultados obtenidos, nos parece que la derivación axilobifemoral y resección aneurismática puede ser una alternativa terapéutica útil para los pacientes con AAA sintomático sin indicación anatómica de endoprótesis estándar y elevado riesgo quirúrgico convencional que demandan tratamiento, aunque creemos también que debe indicarse de una manera individualizada, reforzándonos en la idea de que no hay técnicas obsoletas sino indicaciones inoportunas (AU)

INTRODUCTION. The increase in life expectancy leads to a higher number of symptomatic patients with AAA with anatomical limitations for EVAR and high surgical risk in conventional open surgery, seeking treatment because they are not resigned to wait death from aneurysm rupture. An alternative is offered , reviving an old technique, extra-anatomic revascularization and aneurysm resection. Our goal is to analyze the results obtained with this therapeutic approach. MATERIALS AND METHODS. We treated 7 patients with a mean age of 78.8 years and symptomatic AAA (one with subsequent contained rupture) of 5.2 cm to 8 cm. in diameter. All had severe cardiorespiratory disease and anesthetic risk ASA III-IV. An axilobifemoral bypass and aneurysm resection was performed in all the cases. RESULT. The result was satisfactory in all patients with follow up between 1 and 15 years. As complications in the immediate postoperative: A pneumonia occurred in one case and a intestinal perforation in other case, satisfactorily resolved. After eight years of follow up there was one death by lung cancer. CONCLUSIONS. In view of these results, we believe that the axilobifemoral bypass and aneurysmal resection may be a useful therapeutic option for patients with symptomatic AAA with anatomical limitations for standard EVAR and high surgical risk , but we also believe that it should be a tailored treatment for each patient, reinforcing the idea that there is not outdated techniques only inopportune indications (AU)

Delignification of Miscanthus x Giganteus by the Milox process.

Miscanthus x giganteus stalks were subjected to delignification with formic acid-hydrogen peroxide-water in two stages. A face-centered experimental design was used to study the effects of different variables (formic acid and hydrogen peroxide concentrations, time and temperature) on yield, lignin content and viscosity of pulps on the first stage. Fitting equations described satisfactorily the system behaviour and showed that hydrogen peroxide concentration and temperature were the most influencing variables. A set of independent variables (90% formic acid, 1.5% hydrogen peroxide, 60 min, and 67 degrees Celsius) produced a pulp with low lignin content (kappa 17.2) and high viscosity (899 cm(3)/g), in the first stage. For the second stage a treatment time of 30 min was the more suitable, producing good quality pulps (kappa number 4.6, viscosity 788 cm(3)/g). Phenolic hydroxyl and carboxyl group contents were higher lignins from the first stage.

The kinetics of sorption by retarded diffusion into soil aggregate pores.

This study investigates time-dependent sorption of pesticides in soil aggregates. We tested if the sorption kinetics of pesticides in soil aggregates can be described by modeling diffusion into aggregates for a range of soils and pesticides. Our hypothesis is that the rate of sorption is negatively related to sorption strength due to retardated diffusion. Natural aggregates of 3-5 mm diameter were separated from three soils: a clay, a silty clay loam, and a clay loam. The aggregates were stabilized with alginate gel, and adsorption of azoxystrobin, chlorotoluron, and atrazine was measured in batch experiments with eight equilibration times up to 28 days. Equilibrium sorption appeared to be reached within the 28-day period for each pesticide. An intra-aggregate diffusion model was employed to describe the increase of sorption with time. The model describes diffusion of the dissolved pesticides through the pore space inside the aggregates and sorption on internal surfaces. Sorption could be described by pore diffusion into the aggregates with diffusion coefficients between 0.5 x 10(-10) and 1.5 x 10(-10) m(2) s(-1). The model fits support the theory that pore diffusion is the rate-limiting process for sorption of pesticides in aggregates, although the diffusion coefficients were a factor 3-10 smaller than the theoretical diffusion coefficient for diffusion in water. Comparing the results from the different pesticide-soil combinations showed that the extent of nonequilibrium increased with increasing sorption strength. This confirmed that sorption takes longer to reach equilibrium for pesticides and soils with stronger sorption. The differences between the different pesticides and soils were fully accounted for in the model by stronger retardation of the more strongly sorbed pesticides. The results imply that diffusion into aggregates may be the major time-limiting process for sorption of pesticides in structured soils. Commonly performed sorption experiments with sieved soil fail to account for this process.

Miscanthus x giganteus extractives: a source of valuable phenolic compounds and sterols.

The chemical composition of the lipophilic extracts of bark and core, of the Miscanthus x giganteus stalk, was studied by gas chromatography-mass spectrometry (GC-MS). Aromatic compounds, sterols, and fatty acids, followed by long-chain fatty alcohols, were the major families of components present in the M. x giganteus stalk. Aromatic compounds are more abundant in the M. x giganteus bark (521 mg/kg of bark), with vanillic acid, vanillin, and p-hydroxybenzaldehyde as the major compounds of this family. In the M. x giganteus core, sterols represent about 949 mg/kg of dry core with beta-sitosterol, 7-oxo-beta-sitosterol, stigmasterol, and campesterol as the major components. The detection of small amounts of esters in the GC-MS analysis with short columns explains the small increase in the abundance of the identified families after alkaline hydrolysis. The high content of valuable sterols and aromatic compounds in M. x giganteus and, particularly, in the core, which is considered a residue in most applications, can open new perspectives for the integrated upgrading of this grass within the biorefinery perspective.