Nanohybrids of Mg/Al layered double hydroxide and long-chain (C18) unsaturated fatty acid anions: Structure and sorptive properties

10 páginas.-- 8 figuras.-- 1 tabla. 59 referencias.-- Appendix A. Supplementary data con 6 páginas (3 tablas y 2 figuras.-- Número espeical: Clay Science & Technology (XV International Clay Conference)Long-chain (C18) unsaturated fatty acid anions, elaidate (ELA), oleate (OLE), linoleate (LINO), and linolenate (LINOLEN), were intercalated into Mg/Al (3:1) layered double hydroxide (LDH) and the resultant organo-LDH nanohybrid materials were characterized and subsequently evaluated as sorbents of six pesticides (clopyralid, imazethapyr, diuron, atrazine, alachlor, and terbuthylazine). The effect of the degree (18:1, 18:2, 18:3) and type (cis/trans) of unsaturation in the fatty acid alkyl chain on both the structure and sorptive properties of the LDH-unsaturated fatty acid nanohybrids was determined. All fatty acid anions were readily intercalated into the LDH, yielding structures with basal spacing values ranging between 32 Å (LDH-LINOLEN) and 40 Å (LDHELA). The bend imposed by the cis geometry of the double bonds present in OLE, LINO and LINOLEN was identified as a major factor determining the arrangement of these anions in the LDH interlayer space. Intercalation of cis-unsaturated fatty acid anions led to less densely packed structures and reduced the interlayer distance of the resultant nanohybrid compared to the structures resulting from intercalation of the linear, trans-unsaturated elaidate anion. All organo-LDHs displayed higher affinity to uncharged pesticides as compared to unmodified LDH, but double bonds in the fatty acid alkyl chain, particularly when present in cis configuration, reduced the affinity of the organo-LDHs to all pesticides, presumably because they led to structures with reduced hydrophobicity as compared to those resulting from the incorporation of linear organic anions.This work has been financed by the Spanish Ministry of Economy and Competitiveness (MINECO Project AGL2011-23779) and Junta de Andalucía (JA Projects P07-AGR-03077 and P11-AGR-7400 and Research Group AGR-264), cofinanced with European FEDER-FSE funds (Operative Program 2007–2013). B. Gámiz thanks JA for a post-doctoral contract linked to the project P07-AGR-03077. M.A. Adelino thanks MINECO for her pre-doctoral FPI fellowship.Peer reviewe

Effect of exogenous carbon on movement of simazine and 2,4-D in soils. Soil Sci

ABSTRACT stimulate soil microbial activity, which could potentially lead to accelerated degradation, reducing the total Topp et al., 1996

Characterization of the phenolic ripening development of "BRS Vitoria" seedless table grapes using HPLC-DAD-ESI-MS/MS.

Determining the harvest date of table grapes is very important to achieve high-quality bunches with adequate soluble solids content, low titratable acidity, and high concentrations of polyphenols. Table grape consumption has increased worldwide due to its phenolic compound content and its beneficial effects on human health. Thus, this study aimed to characterize the phenolic ripening of ?BRS Vitoria? seedless table grapes at different ripening stages using HPLC?DAD?ESI-MS/MS. For this purpose, a trial was carried out during 2016 in a commercial vineyard of ?BRS Vitoria? seedless grape located in Marialva, state of Parana (Southern Brazil). Berry samples were assessed weekly, starting at v ́eraison until full ripeness. At each ripening stage, the berries were analyzed to determine their physicochemical characteristics and polyphenolic profile. It was observed that ?BRS Vitoria? grapes can be harvested approximately 28 days after v ́eraison, when the berries reach soluble solids content higher than 15◦Brix and low titratable acidity. The grapes presented a typical anthocyanin profile of hybrid grapes, composed of 3-glucoside and 3,5-diglucoside derivatives. In addition, pelargonidin traces were also observed, and this aglycone is rarely detected in grapes. The total anthocyanin concentration, as malvidin-3,5- diglucoside equivalents, is close to 596.9 mg k

Use of organosmectites to reduce leaching losses of acidic herbicides

The modification of smectitic clays with organic cations via cation-exchange reactions produces sorbents with an increased sorption capacity for organic compounds such as acidic herbicides. These organoclays (OCIs) could be used as carriers in controlled release formulations of herbicides to decrease their contamination potential. Various OCIs and two acidic herbicides (bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4 (3H) one 2,2-dioxide] and dicamba [2-methoxy-3,6-dichlorobenzoic acid]) were selected and herbicide-OCI complexes were prepared by either sorbing the herbicides on the OCI from solution or by dry mixing of both components. Those preparations were assayed as controlled-release formulations under static (water solution) and dynamic (soil column leaching) conditions. Herbicide release in closed (static) systems was fast and reached a maximum concentration after 10 to 20 h. The total herbicide released ranged from 20 to 100% of the active ingredient initially incorporated in the complex depending on the sorption capacity of the OCI for the herbicide and the strength of herbicide-OCI interaction (aging time). Complexes releasing <50% of the herbicide, corresponding to the most sorptive OCIs, may not be appropriated for weed control. Total leaching losses in soil columns were reduced from 94% for free technical bentazone to 55 to 90% for bentazone-OCI complexes, and from 100% for technical dicamba to 50 to 100% for dicamba-OCI complexes. Maximum concentrations in the leaching profiles of the herbicide-OCI complexes were much smaller than for the technical compounds. Bioassays of dicamba-OCI complexes as preemergence herbicide showed the same efficiency as the technical compound. These results suggest OCIs as possible carriers in controlled release formulations for very mobile and persistent acidic herbicides, thereby decreasing their potential for surface and ground water contamination.This work has been partially supported by the CICYT proj- ect AMB96-0445-C02-01 and by the Research Group RNM124 of Junta de Andalucía.Peer Reviewe

Cambios en la adsorción/biodisponibilidad de dos fungicidas con el tiempo de residencia en el suelo

4 páginas, 2 figuras, 3 tablas, 18 referencias. El libro de resúmenes consta de 414 páginas.[ES]: Se han determinado los cambios en la distribución fase adsorbida/fase en solución del suelo de los fungicidas metalaxyl y triciclazol con el tiempo de residencia en el suelo. Tres suelos de diferentes características físico-químicas se trataron con los fungicidas y se incubaron 30 días a 20 0C y humedad del 40 % de la capacidad máxima de retención de agua del suelo. Los coeficientes de distribución Kd para triciclazol fueron mayores que para metalaxil en los tres suelos, y para ambos fungicidas fueron mayores en los suelos con alto contenido en materia orgánica y/o arcilla. Con el tiempo de residencia en el suelo, los coeficientes Kd de metalaxyl tan sólo aumentaron en el caso del suelo de mayor contenido en materia orgánica, mientras que en el caso de triciclazol los valores de Kd aumentaron en el caso del suelo de mayor contenido en materia orgánica y en el suelo de mayor contenido en arcilla y bajo contenido en materia orgánica.[EN]: The present study was conducted to determine the changes in distribution between sorbed and solution phases of the fungicides metalaxyl and tricyclazole with incubation time. Three different soils were selected for this study, treated with the fungicides, and incubated for 30 days at 20 ºC and soil moisture content equivalent to 40 % of soil water holding capacity. Distribution coefficients Kd for tricyclazole were higher than for metalaxyl in the three soils considered, and as in the case of metalaxyl increased with organic matter and/or clay content of the soil. With aging, Kd for metalaxyl only increased in the case of the soil of higher organic matter content, whereas in the case of tricyclazole Kd values increased with incubation time in the soil of highest organic matter content and in a soil with very high clay content and low organic matter content.Este trabajo ha sido financiado con el proyecto AGL 2001-1554 del Ministerio de Ciencia y Tecnologia y RNM 124 de la Junta de Andalucía. M.C. Fernandes agradece a la Fundación de Ciencia y Tecnología de Portugal por su beca predoctoral BFRH/BD/721/2000 del Programa POCTI.Peer reviewe

Triadimefon interactions with organoclays and organohydrotalcites

8 pages, 5 figures, 3 tables, 42 references.We determined the ability of several organoclays (octadecylam- monium- and hexadecyltrimethylammonium-exchanged montmoril- lonite) and organohydrotalcites (dodecylsulfate- and dodecylbenzene- sulfonate-exchanged hydrotalcite) to sorb the uncharged pesticide triadimefon [1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1- yl)-2-butanone] to test the potential use of these sorbents for decon- tamination purposes and as slow release formulations of the pesticide. Interlayered organoclays and organohydrotalcites were at least six times more sorptive than the untreated minerals. Triadimefon sorption was higher on paraffin-like sorbents (organohydrotalcites and or- ganoclays prepared from high-charge Arizona montmorillonite) than on bilayered sorbents (organoclays prepared from low-charge Wyo- ming montmorillonite). The nature and amount of organic ion in the interlayer also influenced triadimefon desorption from the different sorbents. Desorption and spectroscopic studies suggested, in general, weak hydrophobic interactions between triadimefon and the inter- layer organic phase of the organoclays and organohydrotalcites. How- ever, hydrogen bonding between the carbonyl group of triadimefon and the monosubstituted amino group of octadecylammonium- exchanged organoclays reinforced the strength of the interaction and resulted in reduced desorption from these sorbents. Selecting the interlayer ion appeared, therefore, as a good strategy to control the sorptivity and desorption of the sorbed pesticide for organoclays and organohydrotalcites. The results showed that organoclays and organo- hydrotalcites may find application as sorbents of pesticides similar to triadimefon.This work has been partially supported by the CICYT project AMB96-0445-CO2-01 and by the Research Group 124 of Junta de Andalucía. Rafael Celis also thanks the financial support from the Spanish Ministry of Education and Culture.Peer reviewe

Interactions of acidic herbicides bentazon and dicamba with organoclays

We determined the sorption mechanism of the acidic herbicides bentazon [3-(1-methylethyl)-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] and dicamba (3,6-dichloro-2-methoxybenzoic acid) on two organoclays, octadecylammonium (ODA)- and hexadecyltrimethylammonium (HDTMA)-exchanged Arizona montmorillonite (SAz-1), as part of a study to determine their potential use assorbent materials for ionizable organic pollutants. To determine the mechanisms involved in the sorption process, herbicide-organoclay complexes were characterized by x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). In general, the d001 values of SAz-HDTMA and SAz-ODA organoclays expanded after herbicide saturation, indicating interlayer sorption of the herbicide. Also, FTIR spectroscopic studies suggested weak Hydrophobic interactions between these herbicides and the interlayer organic phase of the organoclays. However, H bonding between these herbicides and the monosubstituted amino group in SAz-ODA reinforced the strength of the hydrophobic interactions resulting in nonreadily reversible sorption on that organoclay. These results suggest that organoclays can be used to remove this type of pollutants from water or soils.This work has been partially financed by Spanish CICYT through Project AMB 96-0445-CO2-01 by the Predoctoral Fellowship of PFPI of the Spanish MEC. This research was done by M.J. Carrizosa in the USDA-ARS Laboratory at the Department of Soil Water and Climate, University of Minnesota, and at IRNAS-CSIC laboratory.Peer Reviewe

Organic amendments affecting sorption, leaching and dissipation of fungicides in soils

Metalaxyl and tricyclazole are two fungicides widely used in Spain in vineyard and rice crops respectively. In this study an investigation has been made of the effect of three organic amendments [two commercial amendments, solid fertiormont (SF) and liquid fertiormont (LF), and a residue from the olive oil production industry, alperujo (OW)] on fungicide fate in soils. Changes in soil porosity on amendment were studied by mercury intrusion porosimetry, sorption-desorption studies were performed by the batch equilibration method, dissipation of metalaxyl and tricyclazole in the soil was studied at -33 kPa moisture content and 20°C and leaching was studied in hand-packed soil columns. Amendments with SF and LF reduced soil porosity, while OW increased porosity through an increase in pore volume in the highest range studied. Tricyclazole sorbed to soils to a much higher extent than metalaxyl. With some exceptions, sorption of both fungicides increased on amendment, especially in the case of SF-amended soils, which rendered the highest Koc values. In soils amended with the liquid amendment LF, sorption either remained unaffected or decreased, and this decrease was much higher in the case of metalaxyl and a soil with 70% clay. In this clay soil, amendment with OW, of very high soluble organic matter content, also decreased metalaxyl sorption. Tricyclazole is more persistent in soil than metalaxyl, and both fungicides were found to be more persistent in amended soils than in unamended soils. Leaching of metalaxyl and tricyclazole in soil columns was inversely related to sorption capacity. The low recoveries of tricyclazole in leachates and in soil columns when compared with metalaxyl, a less persistent fungicide, were attributed to diffusion into micropores and to increase in sorption with residence time in the soil, both processes favoured by the low mobility of tricyclazole.Peer Reviewe

Heavy metal adsorption by montmorillonites modified with natural organic cations

Agricultural and industrial pollution release large amounts of heavy metals into the atmosphere, surface water, soil, and plants. The protection and restoration of soils and water contaminated with heavy metals generate a great need to develop efficient adsorbents for these pollutants. This study reports the adsorption of Pb(II) and Hg(II) by two reference montmorillonites, Wyoming (SWy-2) and Arizona (SAz-1), that were pretreated with various natural organic cations containing different functional groups (L-carnitine, L-cysteine ethyl ester, L-cystine dimethyl ester, and thiamine cations) and with synthetic, nonfunctionalized organic cations (hexadecyltrimethylammonium [HDTMA] and phenyltrimethylammonium [PTMA] cations). Most of the organoclays adsorbed less Pb(II) than the untreated montmorillonites, with the exception of the L-carnitine-treated montmorillonites. The carboxyl functional group on L-carnitine was apparently effective for complexing Pb. In contrast, Hg(II) adsorption was greatly increased by several of the organic cation pretreatments. Sulfur-containing organic functional groups enhanced Hg(II) adsorption. The synthetic organic cations PTMA and HDTMA suppressed adsorption of Pb(II) and Hg(II) because these organic cations competed with the metals for adsorption sites on the day surfaces and lack organic functional groups capable of interacting with the heavy metals. These findings are consistent with prior understanding of organic functional group-metal complexation reactions but go further by demonstrating that organoclays can be selectively functionalized with natural organic cations to enhance their affinity for heavy metals.This work was partially supported by the MCYT Project REN2001-1700-CO2-01/TECNO and by Junta de Andalucía through Research Group RNM124. M.C-G. gratefully acknowledges the Spanish Ministry of Education and Culture for her F.P.U. fellowship.Peer Reviewe