Assisted attenuation of a soil contaminated by diuron using hydroxypropyl-β-cyclodextrin and organic amendments

7 páginas.-- 1 Grafico.-- 3 figuras.-- 2 tablas.-- 59 referenciasDiuron desorption and mineralisation were studied on an amended and artificially contaminated soil. The amendments used comprised two different composted organic residues i.e., sewage sludge (SS) mixed with pruning wastes, and urban solid residues (USR), and two different solutions (with inorganic salts as the micronutrients and hydroxypropyl-β-cyclodextrin (HPBCD)). After applying micronutrients to activate the soil flora, 15.5% mineralisation could be reached after 150 days, indicating that the soil has a potential capacity to mineralise the herbicide through biostimulation-assisted attenuation. Diuron mineralisation was also improved when HPBCD solutions were applied. Indeed, the extent of herbicide mineralisation reached 29.7% with this application. Moreover, both the lag phase and the half-life time (DT50) were reduced to 33 and 1778 days, respectively, relative to the application of just micronutrients (i.e., 39 and 6297 days, respectively). Organic amendments were also applied (i.e., USR and SS) on the contaminated soil: it was found that the diuron mineralisation rate was improved as the amendment concentration increased. The joint application of all treatments investigated at the best conditions tested was conducted to obtain the best diuron mineralisation results. The micronutrient amendment plus 4% USR or SS amendment plus HPBCD solution (10-fold diuron initially spiked) caused an extent of diuron mineralisation 33.2 or 46.5%, respectively.This work was supported by the Spanish Ministry of Science and Innovation (co-funded by the Fondo Europeo de Desarrollo Regional, FEDER) under the research project CTM2009-07335 and Junta de Andalucía (RNM 894).Peer reviewe

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

7 páginas.-- 3 figuras.-- 2 tablas.-- 52 referencias.-- Supplementary dataThe 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 β-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. © 2013 Elsevier Ltd. All rights reserved.The authors thank to Dr. J.R. Gallego from the Universidad de Oviedo for providing the contaminated soil sample. Support from projects CTM2006-04626 and CTM2009-07335, Spanish Ministry of Science and Innovation (co-funded by Fondo Europeo de Desarrollo Regional, FEDER), are greatly appreciated. M.A. Sánchez-Trujillo acknowledges a research contract from CSIC (JAEPre 0800763) cofinanced by Fondo Social Europeo (FSE).Peer Reviewe

Effects of soil characteristics on metribuzin dissipation using clay-gel-based formulations

Metribuzin (MTB) is a herbicide widely used for weed control in growing soybeans and other crops and has been identified in many parts of the world as a groundwater contaminant. To prepare controlled-release formulations (CRFs) of MTB, it was entrapped within a sepiolite-gel-based matrix with one of two proportions of clay/herbicide and used as either a gel or powder after freeze-drying. To determine how its persistence in soil is affected by formulation and soil type, MTB was applied as a CRF or commercial formulation (CM) to soils with different properties. MTB dissipation in all soils investigated was reduced when the herbicide was applied as CRFs, especially in the case of sandy soil and the freeze-dried formulations, with DT50 values of 57.5 and 104.1 days, respectively, versus 24.8 days for CM. A positive relationship between degradation rates, bioactivity, and soil pH was found. MTB adsorption-desorption studies on these soils were also performed, and no relationship between adsorption-desorption and the degradation rate of MTB was found, possibly because of the low adsorption capacity of the studied soils. MTB when applied as a CRF remains active longer than CM, avoiding the need to use more frequently herbicide applications.This work was supported by the Spanish Ministry of Education and Science (MEC) through Research Projects AGL 2005-00164, by Junta de Andaluc ́ıa (project P06-FQM-01909), and by AECID (project A/016047/08).Peer Reviewe

Novel system for reducing leaching of the herbicide metribuzin using clay-gel-based formulations

Metribuzin is an herbicide widely used for weed control that has been identified as a groundwater pollutant. It contaminates the environment even when it is used according to the manufacturer's instructions. To reduce herbicide leaching and increase weed control, new controlled release formulations were developed by entrapping metribuzin within a sepiolite-gel-based matrix using two clay/herbicide proportions (0.5/0.2 and 1/0.2) (loaded at 28.6 and 16.7% a.i.) as a gel (G28, G16) or as a powder after freeze-drying (LF28, LF16). The release of metribuzin from the control released formulations into water was retarded, when compared with commercial formulation (CF) except in the case of G28. The mobility of metribuzin from control released formulations into soil columns of sandy soil was greatly diminished in comparison with CF. Most of the metribuzin applied as control released formulations (G16, LF28 and LF16) was found at a depth of 0-8 cm depth. In contrast, residues from CF and G28 along the column were almost negligible. Bioassays from these control released formulations showed high efficacy at 0-12 cm depth. The use of these novel formulations could minimize the risk of groundwater contamination while maintaining weed control for a longer period.Peer Reviewe

Decontamination of polycyclic aromatic hydrocarbons and nonylphenol from sewage sludge using hydroxypropyl-β-cyclodextrin and evaluation of the toxicity of leachates

11 páginas.-- 2 tablas.-- 3 figuras.-- 61 referenciasA decontamination technique based in cyclodextrin extraction has been developed to eliminate nonylphenol (NP) and 16 polycyclic aromatic hydrocarbons (PAHs; the US Environmental Protection Agency priority pollutants list) from sewage sludge. In a first step, PAHs and NP were characterised in six sludges to determine contamination levels according to limit values proposed by the European Union Sludge Directive draft. There were few variations in the total PAHs content with levels of 1.88 to 3.05 mg kg-1. Three-ring PAHs predominated, but fluoranthene and pyrene were also present. None of the sludge exceeded the PAHs limit proposed by the European Union's draft Directive. On the contrary, NP content in four of the six sludges was over the recommended limits of 50 mg kg-1 for NP ethoxylates. With the aim of obtaining NP values below the concentration limits proposed to use the sewage sludge as agricultural amendments, a preliminary study using hydroxypropyl-β-cyclodextrin (HPBCD) extractions as a decontamination technique was carried out. About 90 % of NP content was removed with only one extraction with HPBCD, whereas after three sequential extractions using an aqueous solution without HPBCD, the NP extraction percentage was less than 1 %. Simultaneously, PAHs extraction percentages obtained with HPBCD were also much higher than when aqueous solution was used, especially in the case of two- and three-ring PAHs. Finally, the potential environmental hazard of HPBCD leachates to aquatic organisms (Daphnia magna) was tested. These results indicate that the treatment of sewage sludge with cyclodextrin could allow their safe use as fertiliser in agriculture. © 2013 Springer-Verlag Berlin Heidelberg.Support from projects CTM2006-04626 and CTM2009-07335, Spanish Ministry of Science and Innovation (cofunded by Fondo Europeo de Desarrollo Regional, FEDER), are greatly appreciated. M.A. Sánchez-Trujillo acknowledges a research contract from Consejo Superior de Investigaciones Científicas (CSIC, JAEPre 0800763) cofinanced by Fondo Social Europeo (FSE).Peer Reviewe

Time-dependent sorption of norflurazon in four different soils: Use of β-cyclodextrin solutions for remediation of pesticide-contaminated soils

High pesticide concentrations in soil from spills or discharges can result in point-source contamination of ground and surface waters. Cost-effective technologies are needed for on-site treatment that meet clean-up goals and restore soil function. Remediation is particularly challenging when a mixture of pesticides is present. β-Cyclodextrins (BCD) solutions are employed to enhance the aqueous solubility of a hydrophobic organic compound. The interaction of norflurazon (NFL) with BCD yielded the formation of inclusion complexes at a 1:1 stoichiometric ratio in solution. The change of the sorption parameter Kd as affected by the time, and desorption studies of NFL previously adsorbed on four different soils with different characteristics have been performed in the presence of 0.01 M BCD or 0.01 M Ca(NO3)2 acting as extractant solutions. NFL sorption increased with the residence time in soil, making it more resistant to be desorbed. Likewise, leaching experiments were performed in packed soil columns eluting initially with distilled water, with the aim to simulate the herbicide drainflow losses because of rainfall, approaching to a more realistic environment, and later with 0.01 M BCD solutions to extract the residual NFL bound. The results showed that removal efficiencies of the different flushing systems were significantly influenced by their affinity and selectivity for the contaminants in the soil matrix as well as BCD adsorption on soils, since this could act like a bridge between pesticide molecule and soil particles increasing the stay of NFL in soil. These results are further information to be in condition to predict the potential effect of the BCD solutions on soil chemical decontamination in the field situation assessing the likelihood for bioremediation of a pesticide contaminated-soil, since the increasing in hydrosolubility of the contaminants means the first step before microorganism uptaken.Peer Reviewe

Comportamiento del herbicida norflurazona en el sistema suelo-agua. Obtención, caracterización y aplicación de complejos de inclusión norflurazona-ciclodextrina

181 páginas.Peer reviewe

Aplicación del complejo de inclusión β-CD-Norflurazona para la descontaminación de suelos

87 páginas.-- 11 figuras.-- 10 tablas.-- 137 referencias Memoria del XXXIX Curso Internacional de Edafología y Biología Vegetal, 2002Directoras del trabajo: Morillo González, Esmeralda y Maqueda Porras, CeliaLa FAO/OMS define el ténnino plaguicida como cualquier sustancia o mezcla de ellas utilizada para prevenir o controlar plantas o animales indeseables e incluso aquellas otras destinadas a utilizarse como regulador del crecimiento de la planta, defoliante o desecante. Según su naturaleza química, los plaguicidas pueden agruparse en varias clases, pudiéndose clasificar como (Ware,1983; García y Remanz, 1987): l.-Insecticidas y acaricidas: *Organoclorados: endosulfan, DDT, dicofol, lindano. *Organofosforados: paratión, fenitrotión, dimetoato, metidation, malation, triclorfon. *Organosulfurados: tetradifon, clorfeson *Carbamatos: cabaril, aldicarb, metiocarb, pirimicarb, metomilo, butocarboxim, cabofurano. *Otros grupos: fonnamidinas (amitraz), dinitrofenoles (dinocap), tiocianatos orgánicos (lethane), organoestánnicos (fenbutestan), compuestos de flúor (fluoruro sódico), insecticidas naturales (piretrinas, nicotina), piretroides sintéticos (cipennetrina), compuestos inorgánicos (azufre, arseniatos). 2.-Rerbicidas: *Inorgánicos: sulfamato amónico, boratos. *Orgánicos: Aceites derivados del petróleo, derivados organoarsenicales (DSMA), áciodos fenoxialifáticos (2,4-D, MCPA), amidas sustituidas (propanil), nitroanilinas (triflularin), ureas sustituidas (diuron, linuron), carbamatos (profam), tiocabamatos (EPTC), triazinas, triazoles, derivados de la piridina, uracilos sustituidos (atrazina, simazina, amitrol, bromacilo), ácidos alifáticos (dalapon), ácidos aril alifáticos (dicamba), derivados fenólicos (PCP), bipiridilos (diquat, paraquat). 3.-Fungicidas: *Inorgánicos: azufre, cobre, mercurio. *Orgánicos: ditiocarbamatos (maneb, zineb), tiazoles (etridiazol), triazinas (anílazina), aromáticos sustituidos (RCB, dicloran), dicarboxiamidas (captan, folpet), dinitrofenoles (dinocap), quinonas, organoestánnico. 4.-0tros: *Nematicidas *Rodenticidas *Relicidas *Desinfectantes del suelo El producto activo plaguicida es obtenido por la industria química con un grado de pureza variable. Este producto, llamado técnicamente, puro no es apto para uso agrícola, por lo que debe acondicionarse antes en una "formulación". Esta contiene la materia activa o producto puro más o menos diluido en un soporte sólido o en un disolvente líquido y sustancias auxiliares que mejoran su acción (coadyuvantes). Estas formulaciones pueden aplicarse de forma directa o dispersas en agua. Las interacciones que tiene lugar entre las moléculas del plaguicida y las fracciones coloidales del suelo están influenciadas considerablemente por la humedad, temperatura, pR, contenido en minerales y contenido en materia orgánica del suelo. A su vez, también están relacionadas con las características de los componentes orgánicos en cuanto a solubilidad en agua, polaridad, tamaño molecular y características químicas. De acuerdo con esto el grado de adsorción de un plaguicida por el suelo depende de la naturaleza de la fracción coloidal y de la estructura química del compuesto. En general, los plaguicidas son compuestos orgánicos con propiedades tóxicas. Por eso es necesario saber qué tipo de interacción existe entre estos compuestos y los suelos, así como con sus constituyentePeer reviewe

Use of clay/β-cyclodextrin formulations to obtain a slow release of a hydrophobic herbicide

The study aimed to prepare slow release formulations of the hydrophobic herbicide norflurazon (4-chloro-5-methyl-amino-2-(α,α,α)- trifluoro-m-tolypyridazin-3-(2H)-one) based on a standard montmorillonite, a pillared montmorillonite and an organo-montmorillonite. For this purpose, a β-cyclodextrin-norflurazon solution was used, due to its ability to form an inclusion complex which yields an increase in norflurazon solubility in water (up to 5 times). The amount of herbicide adsorbed on the standard montmorillonite was directly proportional to the herbicide concentration in solution, obtaining an herbicide adsorption 5 times higher when β-cyclodextrin-norflurazon solutions were used. The organo-clay was prepared modifying the surface of montmorillonite from hydrophilic to hydrophobic preadsorbing an organic cation (phenyltrimethylamonium), at a loading yielded the highest affinity of adsorption for norflurazon. Pillared clay used was an alumina pillared montmorillonite which showed a similar affinity by norflurazon adsorption than the untreated montmorillonite. Water release experiments were also performed in order to test the slow release capacity of the different matrices selected in this study. Pillared montmorillonite formulations showed a similar norflurazon release profile compared with the untreated montmorillonite. Likewise, release profiles of the pillared clay with two different herbicide loadings were obtained revealing the influence of the herbicide loading on the release rate from the formulations. The release profile corresponding to the organo-clay sample showed the slowest release rate, reaching only a 24% of the herbicide loaded released after 3 days of experiment. The results of this study indicate that the use of selectively-modified clays could are useful for the preparation of herbicide slow release formulations, where the increase of the hydrophilic character of the montmorillonite using an organic cation is a critical property when slow release formulations of herbicide want to be prepared. The use of these formulations can be advantageous, because they can minimize the risk of groundwater contamination and permit herbicide use reduced rates, maintaining the desired concentrations of herbicide in the topsoil layer for longer periods of weed control.This work was conducted with the financial support of the Spanish Ministry of Education and Science, Research proyect AGL-2005-00164, and Junta de Andalucía, Project P06-FQM-1909.Peer Reviewe

Adsorption and degradation of four acidic herbicides in soils from southern Spain

8 pages, 3 figures, 6 tables, 35 references.BACKGROUND: Pesticide degradation and adsorption in soils are key processes determining whether pesticide use will have any impact on environmental quality. Pesticide degradation in soil generally results in a reduction in toxicity, but some pesticides have breakdown products that are more toxic than the parent compound. Adsorption to soil particles ensures that herbicide is retained in the place where its biological activity is expressed and also determines potential for transportation away from the site of action. Degradation and adsorption are complex processes, and shortcomings in understanding them still restrict the ability to predict the fate and behaviour of ionisable pesticides. This paper reports the sorption and degradation behaviour of four acidic pesticides in five soils from southern Spain. Results are used to investigate the influence of soil and pesticide properties on adsorption and degradation as well as the potential link between the two processes. RESULTS: Adsorption and degradation of four acidic pesticides were measured in four soils from Spain characterised by small organic matter (OM) contents (0.3-1.0%) and varying clay contents (3-66%). In general, sorption increased in the order dicamba < metsulfuron-methyl < 2,4-D < flupyrsulfuron-methyl-sodium. Both OM and clay content were found to be important in determining adsorption, but relative differences in clay content between soils were much larger than those in OM content, and therefore clay content was the main property determining the extent of herbicide adsorption for these soils. pH was negatively correlated with adsorption for all compounds apart from metsulfuron-methyl. A clear positive correlation was observed for degradation rate with clay and OM content (P < 0.01), and a negative correlation was observed with pH (P < 0.01). The exception was metsulfuron-methyl, for which degradation was found to be significantly correlated only with soil bioactivity (P < 0.05). CONCLUSIONS: Both OM and clay content were found to be important in determining adsorption, but relative differences in clay content between soils were much larger than those in OM content, and therefore clay content was the main property determining the extent of herbicide adsorption for soils of this type. pH was negatively correlated with adsorption for all compounds apart from metsulfuron-methyl. The contrasting behaviour shown for these four acidic pesticides indicates that chemical degradation in soil is more difficult to predict than adsorption. Most of the variables measured were interrelated, and different behaviours were observed even for compounds from the same chemical class and with similar structures.This work was conducted with the financial support of the Spanish Ministry of Education and Science.Peer Reviewe