Evolución y análisis filogenético de las comunidades microbianas desarrolladas como respuesta al aumento de los niveles de fenantreno en un suelo contaminado por PAHs

Trabajo presentado al citado Congreso que tuvo lugar del 21-24, de septiembre, 2009, en Almería, España.Las comunidades microbianas de los suelos contaminados con hidrocarburos aromáticos poli cíclicos (PAHs) presentan gran biodiversidad. Esta biodiversidad puede relacionarse con la respuesta a niveles elevados de PAHs. En este trabajo se presenta el estudio y la caracterización de las comunidades microbianas de un suelo contaminado principalmente con hidrocarburos aromáticos poli cíclicos (5LO), mediante técnicas basadas en ADN y técnicas de cultivo. Se ha estudiado la evolución de las comunidades como respuesta al aumento de la concentración de fenantreno.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

COVID-19 outbreaks in a transmission control scenario: challenges posed by social and leisure activities, and for workers in vulnerable conditions, Spain, early summer 2020

Severe acute respiratory syndrome coronavirus 2 community-wide transmission declined in Spain by early May 2020, being replaced by outbreaks and sporadic cases. From mid-June to 2 August, excluding single household outbreaks, 673 outbreaks were notified nationally, 551 active (>6,200 cases) at the time. More than half of these outbreaks and cases coincided with: (i) social (family/friends’ gatherings or leisure venues) and (ii) occupational (mainly involving workers in vulnerable conditions) settings. Control measures were accordingly applied

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

Formulaciones de liberación controlada de herbicidas mediante microencapsulación con etilcelulosa: obtención, caracterización y comportamiento en el sistema suelo-agua

Peer Reviewe

Adsorción-desorción de norflurazona en suelos con diferentes características fisico-químicas

43 páginas.-- 1 figura.-- 8 tablas.-- 40 referencias.-- Memoria del XXXIX Curso Internacional de Edafología y Biología Vegetal, 2002Directoras del trabajo: Morillo González Esmeralda y Maqueda Porras, CeliaCon objeto de incrementar la producción agrícola se ha trabajado intensamente en temas como la mejora genética, la integración de sistemas de riego y fertilizantes, mayor eficacia de los plaguicidas,etc. Actualmente el empleo de plaguicidas cada vez más efectivos y específicos da lugar a que su uso sea imprencible para incrementar el rendimiento en las cosechas. La selección del plaguicida se realiza en base a su especificidad frente al organismo que se quiere eliminar y a su concentración, la cual debe de ser óptima durante el tiempo necesario para alcanzar su objetivo. Posteriormente, el plaguicida debe de degradarse en compuestos que no sean tóxicos para el medio ambiente. Sin embargo, el uso de plaguicidas da lugar a una serie de consecuencias ambientales indeseables como son: la retención de los plaguicidas por los coloides del suelo, dando lugar a una contaminación potencial de los mismo; la contaminación de acuíferos y de aguas superficiales y la bioacumulación de estos compuestos en las cadenas tróficas. El norflurazona, es un herbicida, ampliamente utilizado en una gran variedad de tipos de cultivo a nivel mundial. En Andalucía por ejemplo, se ha utilizado con frecuencia en el cultivo de la fresa. Sin embargo, este herbicida presenta una serie de limitaciones en su uso debido a su baja solubilidad, su pobre velocidad de disolución y por otra parte, también presenta problemas de lixiviación en suelos con bajo contenido en materia orgánica y problemas de fotodegradación según el tipo de suelo y de su adsorción al mismo.Peer reviewe

Influence of soil characteristics and formulation on alachlor dissipation in soil

Alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] is one of the most commonly found herbicides in surface and groundwaters of the United States and Europe, and it contaminates these environments even when it is used according to the manufacturer's instructions for conventional formulations. To determine how its persistence in soil is affected by herbicide formulation and soil type, alachlor was applied to several soils in different formulations: technical grade (AT), a commercial formulation (CF), and different ethyl-cellulose microencapsulated formulations (MEFs). The results show that MEFs provided a prolonged release of the herbicide into the soil solution and protected against its dissipation in soil more than AT or the CF. The half-life in soil (f1/2) for the AT, CF, and MEFs was up to 2.7, 6.4, and 32.54 d, respectively. The lowest herbicide loss was observed in MEFs prepared using a lower stirring speed or a higher ethylcellulose viscosity during the microencapsulation process. As with AT and the CF, the microencapsulated alachlor persisted longer in the soils with low pH and high clay content. In the soil where alachlor showed the least persistence, MEFs reduced the herbicide loss by 54% compared with the CF. The use of MEFs extended the alachlor concentration in the soil, thereby avoiding the need for using high herbicide application rates and decreasing the risk of environmental contamination.Fátima Sopeña acknowledges an investigating contract from Junta de Andalucía. This work was supported by MEC (Spanish Ministry of Education and Science), Research Projects REN2003-01509 and AGL 2005-00164, and by Junta de Andalucía, Project P06-FQM-01909.Peer Reviewe

Controlled release formulations of herbicides based on micro-encapsulation

Annual worldwide losses to weeds are estimated to comprise approximately 10-15% of attainable production among principal food sources. Worldwide consumption of herbicides represents 47.5% of the 2 million tons of pesticide consumed each year. However, the heavy use of herbicides has given rise to serious environmental and public health problems. It is therefore important to develop new herbicide formulations that are highly effective, that are safer (for the worker and for the environment), and that involve a low cost/production ratio. In this sense, controlled release formulations of herbicides have become necessary in recent years, since they often increase herbicide efficacy at reduced doses. The present work reviews in detail the components of various types of herbicide formulations, with an emphasis on controlled release formulations and micro-encapsulation.The present work was financed by the Span- ish Ministry of Education and Science through the REN2003-01509 and AGL2005-00164 in- vestigation projects, by the Junta de Andalucía through an investigation contract (Resolution of May 12, 2006 by the General Secretariat of Uni- versities, Investigation and Technology), and by investigation Project P06-FQM-01909.Peer Reviewe

Ethylcellulose formulations for controlled release of the herbicide alachlor in a sandy soil

The development of controlled-release formulations of alachlor to diminish its leaching in sandy soils, avoiding groundwater contamination and maintaining its efficacy, was studied. For this purpose, ethylcellulose (EC) microencapsulated formulations (MEFs) of alachlor were prepared under different conditions and applied to soil columns to study their mobility. The results show that in all cases the release into water of alachlor from MEFs was retarded when compared with commercial formulation. Total leaching losses in soil columns were reduced to 59% from 98%. The mobility of alachlor from EC microspheres into soil columns has been greatly diminished in comparison with its current commercial formulation (CF), above all with increasing EC/herbicide ratios. Distribution of alachlor applied as MEFs at different depths in the soil was higher in the soil surface (66.3-81.3% of herbicide applied at the first 12 cm). In contrast, the residues from CF along the complete soil column were only 20.4%. From the results of bioassays, MEFs showed a higher efficacy than CF at 30 days after the treatment. The use of ME formulations could provide an advantage in minimizing the risk of groundwater contamination by alachlor and reducing the application rates, as a result of maintaining the desired concentration of the herbicide in the top soil layer, obtaining longer periods of weed control.This work was supported by MEC (Spanish Ministry of Education and Science) through Research Projects REN2003-01509 and AGL 2005-00164 and by Junta de Andalucía, Project P06-FQM-01909.Peer Reviewe