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9 páginas.-- 8 figuras.-- 4 tablas.-- 63 referencias.-- Supplementary data to this article can be found online a https://doi.org/10.1016/j.scitotenv.2019.04.014., A local low value bentonite from Southern Spain (Raw Bentonite), previously decarbonated (Bent), was modified to improve its pesticide adsorption capacity with Fe 3+ , hexadecyltrimethylammonium (HDTMA) and the biopolymer chitosan (CH). Adsorption of pesticides on powdered samples showed that Fe 3+ and HDTMA were appropriate modifiers for this purpose. The modification was optimized by saturation with Fe 3+ (Bent-Fe) and hexadecyltrimethylammonium (Bent-HDTMA) and the obtained adsorbents were characterized by several physicochemical techniques (X-ray diffraction, thermogravimetric analysis, X-ray fluorescence, physisorption of N 2 ). Their adsorption capacity to remove three widely used pesticides in Andalusian crops (terbuthylazine, tebuconazole and MCPA) from water was assessed and compared with the commercial organoclay Cloisite® 10A (Clo10). The modified bentonites adsorbed the selected pesticides in a percentage ranging from 30 to 100%, whereas sorption on Clo10 ranged from 30 to 90%. For their possible use as filtering beds, Bent-HDTMA, Bent-Fe and Clo10 were granulated by using three different binders (colophony resin and carnauba and bee waxes) at three different mixing ratios and the water resistance and pesticide adsorption of the granules were measured. Results showed that the granulation process did not alter the pesticide adsorption capacity of the powdered modified bentonites, and both waxes granules (carnauba and bee wax) showed better behavior than resin granules. In this work, we succeeded in the preparation of granulated adsorbents derived from a low cost material with similar behavior against a high purity smectite (precursor of Cloisite® 10A). This raises an alternative for this waste material to be used in filter systems for removing pesticides from contaminated water. © 2019 Elsevier B.V., Grants P11-7400 and AGR-264 by Junta de Andalucía, Spanish Ministry of Science, Innovation and Universities (MICINN for Project AGL2016-77821-R) and Contract RECUPERA 2020 MINECO-CSIC. E.Durán acknowledges Junta de Andalucía for her postdoctoral contractand B. Gámiz MICINN for her Juan de la Cierva-Incorporación postdoc-toral contract (IJCI-2015-23309)

10 páginas.-- 8 figuras.-- 2 tablas.-- 45 referencias.-- Supplementary data to this article can be found online at https://doi.org/10.1016/j.clay.2018.10.014., A synthesized anionic clay (layered double hydroxide or LDH) and a commercial cationic organoclay (Cloisite 10A, Clo10A) were assayed as host nanocarriers for imazamox (Imz) herbicide. Imz-LDH complexes were obtained by direct synthesis (DS) and regeneration (RE), whereas Imz-Clo10A complexes were prepared by ground mixing (GM) and through methanol addition (weak [WC] and strong [SC] complexes). Characterization of the complexes showed that Imz was partially hosted in the interlayer structure of the resulting nanoherbicides, as anion or as neutral molecule, with some of the herbicide at the external surfaces, depending on the carrier and preparation. The nanoherbicides showed a total water release from 73 (Imz-LDH DS) to 98% (Imz-Clo10A GM) with an immediate release from 67 (Imz-LDH DS) to 93% (Imz-Clo10A GM), while technical Imz released instantaneously >98%. The herbicide maximum concentration in the leachates from Imz-treated soil columns decreased between 20 and 35% for nanoherbicides with respect to the technical Imz, and between 10 and 30% with respect to a commercial Imz formulation. Total herbicide soil leaching losses were reduced from 95 or 98%, for technical and commercial Imz, to 77–67% for nanoherbicides. Bioassays showed similar efficacy for nanoherbicides and commercial product. The diverse Imz-clay complexes are revealed as smart delivery systems for this systemic herbicide by decreasing Imz water pollution risk while maintaining efficacy, with the advantages of their soil compatible matrix and the possibility to be located at action point in the subsoil, This work was supported by Junta de Andalucía (Project P11-AGR-7400 ) and MINECO-CSIC (Project RECUPERA 2020 ), both co-financed by FEDER and FSE funds . Partial support by MINECO Projects AGL2014-51897-R and AGL2017-82141-R is also acknowledged. Prof Rachid Khatem thanks University of Mostaganem for Advanced Research Learning at Foreign Countries for supporting a stay at IRNAS-CSIC. Appendix A

9 págnas.- 6 figuras.- 3 tablas.- 57 referencias.- Supplementary material related to this article can be found, in the online version, at doi:https://doi.org/10.1016/j.jece.2020.104623, A low cost bentonite was modified with Fe3+ and hexadecyltrimethylammonium (HDTMA) cations and subsequently optimized to be used in small-scale water filter systems. Two types of formulations were assessed: immobilization of modified clays on anthracite particles and their extrusion as pellets using the natural binders, colophony resin and carnauba and bee waxes. The innovation of this work was to assess which clay formulation showed better performance for the adsorption of the pesticides MCPA, tebuconazole and terbuthylazine in a pilot or pre-commercial water filter system. A commercial organoclay (Cloisite 10A (R)) and activated carbon were also assayed for comparison purposes. The characterization studies showed that the disintegration in water of the formulated clay adsorbents behaved better when formulated with carnauba wax as binder. The adsorption study was performed in a semi-pilot system by treating 40 L of contaminated water with pesticides in a closed circuit for 24 h at 0.8 bar where the formulated clays were placed in a fixed bed configuration with anthracite particles. Pesticide removal varied depending on the type of formulation, the highest removal efficiency (90-100 %) was reached for the immobilized HDTMA-clay on anthracite particles, which showed better pore distribution according to scanning electron microscopy. The values were similar to those rendered by the commercial Cloisite10A (R) and activated carbon. The outcomes from this work suggested the convenience of using the new formulated adsorbents based on low-cost raw materials in water purification systems, which may open economic possibilities and employment opportunities for rural areas., This work has been financed by The Regional Government Junta de Andalucía (Excelencia Project, MOTRIZ type, P11-AGR-7400) and the Spanish Government through the Ministry of Economy and Competitiveness (Project RECUPERA 2020) both co-financed with EU FEDER funds. A research contract to Zoitech Lab S.L is also acknowledged. Additionally, the authors acknowledge Mr. Manuel Fernández-Márquez (fellowship Programme Emplea@Joven, Junta de Andalucía, FEDER-FSA funds) his contribution to the experimental work.

7 páginas.-- 4 figuras.-- 3 tablas.-- 31 referencias.-- Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.scitotenv.2016.06.126, Occurrences of surface water contamination by herbicides in areas where olive orchards are established reveal a need to understand soil processes affecting herbicide fate at field scale for this popular Mediterranean crop. A monitoring study with two herbicides (terbuthylazine and oxyfluorfen) in the first 2 cm of soil, runoff waters, and sediments, was carried out after under natural rainfall conditions following winter herbicide application. At the end of the 107 day field experiment, no residues of the soil applied terbuthylazine were recovered, whereas 42% of the oxyfluorfen applied remained in the top soil. Very low levels of both herbicides were measured in runoff waters; however, concentrations were slightly higher for terbuthylazine (0.53% of applied) than for oxyfluorfen (0.03% of applied), relating to their respective water solubilities. Congruent with soil residue data, 38.15% of the applied oxyfluorfen was found in runoff-sediment, compared to only 0.46% for terbuthylazine. Accordingly, the herbicide soil distribution coefficients measured within runoff field tanks was much greater for oxyfluorfen (Kd = 3098) than for terbuthylazine (Kd = 1.57). The herbicide oxyfluorfen is co-transported with sediment in runoff, remaining trapped and/or adsorbed to soil particle aggregates, due in part to its low water solubility. In contrast, terbuthylazine soil dissipation may be associated more so with leaching processes, favored by its high water solubility, low sorption, and slow degradation. By comparing these two herbicides, our results reaffirm the importance of herbicide physico-chemical properties in dictating their behavior in soil and also suggest that herbicides with low solubility, as seen in the case oxyfluorfen, remain susceptible to offsite transport associated with sediments., The financial and partial support through the projects P11-AGR-7400, AGR-264, and P08-AGR-03925 (all of them by PAIDI-Junta de Andalucia), Recupera2020 (Hito2.2.2.), and AGL2012-40128-C03-01 (by the National Government), all of them co-financed by FEDER funds (PO 2007-13 and 2014-20) and RESEL (Spanish Ministry of Agriculture, Food and Environment) are gratefully acknowledged.

8 páginas.-- 4 figuras.-- 2 tablas.-- 50 referencias.-- Supplementary data to this article can be found online at https://doi.org/10.1016/j.geoderma.2018.02.005., he use of monoterpenes as agrochemicals has been proposed, but the behavior of this family of compounds once they reach the soil environment has not been completely examined. In this work, we investigated the sorption of the two optical isomers of the monoterpene carvone, R-carvone and S-carvone, on different soils and model sorbents, as well as their dissipation in selected soils. Sorption was a non-enantioselective process; from racemic initial solutions, R-carvone was sorbed to the same extent as S-carvone. Correlations with soil properties indicated that organic matter was the most important component determining the sorption of carvone on the soils. Accordingly, higher sorption of carvone enantiomers was measured on organic model sorbent (humic acid, Kd = 28 L kg−1) compared to mineral model sorbents (kaolinite, illite, montmorillonite, ferrihydrite, Kd < 6.3 L kg−1). Desorption from the soils was hysteretic, most likely because of the rapid degradation of the enantiomers in the soils. Dissipation of carvone in soils was microbial mediated and enantioselective, with S-carvone being degraded faster than R-carvone. The individual enantiomer dissipation rates and enantioselectivity depended on soil characteristics, such as pH. The findings of this study constitute a base for the understanding of the fate of monoterpenes in soils and for further investigations on their applicability as environmentally friendly agrochemicals, This work has been financed by the Spanish Ministry of Economy, Industry and Competitiveness (MINEICO Project AGL2017-82141-R ) and Junta de Andalucía (JA Project P11-AGR-7400 ), co-financed with European FEDER-FSE funds. The authors thank I. Pavlovic for supplying the commercial humic acid sample and G. Facenda for her technical assistance. B.G. also thanks MINEICO for her Juan de la Cierva-Incorporación postdoctoral contract (IJCI-2015-23309). Appendix A

10 páginas.-- 6 figuras.-- 2 tablas.-- 56 referencias.-- The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jafc.6b03668, The potential use of allelopathic and signaling compounds as environmentally friendly agrochemicals is a subject of increasing interest, but the fate of these compounds once they reach the soil environment is poorly understood. This work studied how the sorption, persistence, and leaching of the two enantiomers of the phytohormone abscisic acid (ABA) in agricultural soil was affected by the amendments of two organoclays (SA-HDTMA and Cloi10) and a biochar derived from apple wood (BC). In conventional 24-h batch sorption experiments, higher affinity toward ABA enantiomers was displayed by SA-HDTMA followed by Cloi10 and then BC. Desorption could be ascertained only in BC, where ABA enantiomers presented difficulties to be desorbed. Dissipation of ABA in the soil was enantioselective with S-ABA being degraded more quickly than R-ABA, and followed the order unamended > Cloi10-amended > BC-amended > SA-HDTMA-amended soil for both enantiomers. Sorption determined during the incubation experiment indicated some loss of sorption capacity with time in organoclay-amended soil and increasing sorption in BC-amended soil, suggesting surface sorption mechanisms for organoclays and slow (potentially pore filling) kinetics in BC-amended soil. The leaching of ABA enantiomers was delayed after amendment of soil to an extent that depended on the amendment sorption capacity, and it was almost completely suppressed by addition of BC due to its irreversible sorption. Organoclays and BC affected differently the final behavior and enantioselectivity of ABA in soil as a consequence of dissimilar sorption capacities and alterations in sorption with time, which will affect the plant and microbial availability of endogenous and exogenous ABA in the rhizosphere., This work has been financed by the Spanish Ministry of Economy and Competitiveness (MINECO Project AGL2014- 51897-R), EU FACCE-JPI (Designchar4food Project), and Junta de Andalucıa (P011-AGR-7400 and Research Group ́ AGR-264), cofinanced with European FEDER funds. The use of trade, firm, or corporation names in this paper is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture, the Agricultural Research Service, or the Instituto de Recursos Naturales y Agrobiologıa de Sevilla ́ (IRNAS-CSIC) of any product or service to the exclusion of others that may be suitable

9 páginas.-- 5 figruas.-- 3 tablas.-- 54 referencias.-- The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jafc.7b00458, Biochar (BC), solid biomass subjected to pyrolysis, can alter the fate of pesticides in soil. We investigated the effect of soil amendment with several biochars on the efficacy of two herbicides, clomazone (CMZ) and bispyribac sodium (BYP). To this aim, we evaluated CMZ and BYP sorption, persistence, and leaching in biochar-amended soil. Sorption of CMZ and BYP was greater in soil amended with BC produced at high temperature (700 °C). Significant sorption of the neutral CMZ herbicide also occurred in amended soil with BC prepared at low temperature (350 and 500 °C). For both herbicides, desorption possessed higher hysteretic behavior in soil amended with BC made at 700 °C (pyrolysis temperature). Dissipation of CMZ was enhanced after addition of BCs to soil, but no correlation between persistence and sorption was observed. Persistence of BYP was up to 3 times greater when BC made at 700 °C was added to soil. All BCs suppressed the leaching of CMZ and BYP as compared to the unamended soil. Amendment with 700 °C BC inhibited the action of CMZ against weeds, but 350 and 500 °C BCs had no such effect when added to soil. BYP activity was similar to that exhibited by unamended soil after the addition of 700 °C BC. From these results, biochar amendments can be a successful strategy to reduce the environmental impact of CMZ and BYP in soil. However, the phytotoxicity of soil-applied herbicides will depend on BC sorption characteristics and the pesticide's chemical properties, as well as the pesticide application timing (e.g., pre- or postemergence). According to our results, proper biochar screening with intended pesticides in light of the application mode (pre- or postemergence) is required prior to use to ensure adequate efficacy., This work has been financed by the Spanish Ministry of Economy and Competitiveness (MINECO Project AGL2013- 48446-C3-1-R and AGL2016-77821-R), EU FACCE-JPI (Designchar4food Project), and Junta de Andalucía (P011-AGR-7400 and Research Group AGR-264), cofinanced with European FEDER funds.

We studied the interaction between the naturally occurring polycation spermine (SPERM) and Na-exchanged SWy-2 Wyoming montmorillonite (Na-SWy-2 Mt) and between spermine-exchanged montmorillonite (Mt-SPERM) and the herbicide fluometuron. Mt-SPERM with spermine contents ranging between 0 and 1.2 times the cation exchange capacity (CEC) of Na-SWy-2 were studied by XRD, FTIR and TGA analysis. Spermine was intercalated stoichiometrically into Na-SWy-2 up to the CEC of the clay mineral, resulting in basal spacing of 1.29nm. TGA analysis indicated that intercalation of spermine into Na-SWy-2 increased the thermal stability of the organic cations and affected the dehydroxylation temperature of the clay mineral. FTIR measurements of Mt-SPERM samples showed the involvement of NH and CH groups of spermine in the interaction with the clay mineral. The intensity of the spermine NH and CH deformation vibrations increased linearly with the amount of spermine incorporated into Na-SWy-2 up to an amount close to the CEC of the montmorillonite. Structural modeling suggested that the arrangement of spermine cations formed a horizontal monolayer within the interlayer space of SWy-2 with strong interaction between the NH 3 + and NH 2 +-groups of spermine and the montmorillonite surface oxygen atoms. Mt-SPERM showed pronounced affinity for the herbicide fluometuron.

Biochar, the solid residual remaining after the thermochemical transformation of biomass for carbon sequestration, has been proposed to be used as a soil amendment, because of its agronomic benefits. The effect of amending soil with six biochars made from different feedstocks on the sorption and leaching of fluometuron and 4-chloro-2-methylphenoxyacetic acid (MCPA) was compared to the effect of other sorbents: an activated carbon, a Ca-rich Arizona montmorillonite modified with hexadecyltrimethylammonium organic cation (SA-HDTMA), and an agricultural organic residue from olive oil production (OOW). Soil was amended at 2% (w/w), and studies were performed following a batch equilibration procedure. Sorption of both herbicides increased in all amended soils, but decreased in soil amended with a biochar produced from macadamia nut shells made with fast pyrolysis. Lower leaching of the herbicides was observed in the soils amended with the biochars with higher surface areas BC5 and BC6 and the organoclay (OCl). Despite the increase in herbicide sorption in soils amended with two hardwood biochars (BC1 and BC3) and OOW, leaching of fluometuron and MCPA was enhanced with the addition of these amendments as compared to the unamended soil. The increased leaching is due to some amendments' soluble organic compounds, which compete or associate with herbicide molecules, enhancing their soil mobility. Thus, the results indicate that not all biochar amendments will increase sorption and decrease leaching of fluometuron and MCPA. Furthermore, the amount and composition of the organic carbon (OC) content of the amendment, especially the soluble part (DOC), can play an important role in the sorption and leaching of these herbicides.

8 páginas.-- 4 figuras.-- 6 tablas.-- 70 referencias.-- Appendix A. Supplementary data ( 1 figura), © 2014 Elsevier B.V. Biochars, from different organic residues, are increasingly proposed as soil amendments for their agronomic and environmental benefits. A systematic detection method that correlates biochar properties to their abilities to adsorb organic compounds is still lacking. Seven biochars obtained after pyrolysis at different temperatures and from different feedstock (alperujo compost, rice hull, and woody debris), were characterized and tested to reveal potential remedial forms for pesticide capture in flooded soils. Biochar properties were determined by nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy, specific surface area (SSA) assessment and scanning electron microscopy. In addition, dissolved organic matter (DOM) from these biochars was extracted and quantified in order to evaluate the effect on pesticide sorption. The biochars from alperujo compost presented very high affinity to the fungicide tricyclazole (55.9, 83.5, and 90.3% for B1, B4, and B5, respectively). This affinity was positively correlated with the pyrolysis temperature, the pH, the increased SSA of the biochars, and the enhanced aromaticity. Sorptive capacities were negatively related to DOM contents. The amendment with a mixture of compost and biochar endows the alluvial soil with high sorptive properties (from Kfads(soil)=9.26 to Kfads(mixture)=17.89) without impeding the slow release of tricyclazole., This research was supported by the Ministry of Economy and Competitiveness (AGL2010-21421 and AGL2013-48446-C3-1-R) and the Autonomous Government of Andalusia (PAIDI AGR-264). The projects were co-financed with European funds (FEDER-FSE PO2007-13). Manuel García-Jaramillo thanks MEC/FECYT for a doctoral fellowship through AGL2010-21421-CO2-01 project of MICINN. Further, we would like to thank to the Analytical Service of the IRNAS (CSIC) and to the Center of Research Technology and Innovation of the University of Seville (CITIUS) for their technical assistance.

New designs of pesticide formulations based on organoclays are receiving increasing attention in reducing offsite movement of pesticides in the environment and in prolonging the efficacy of soil-applied pesticides. In the present article, we report the results of laboratory and field experiments conducted to evaluate the influence of the saturating cation, the sorbent:herbicide ratio, and the type of preparation on the controlled release properties of organoclay-based formulations of the herbicide hexazinone. Two organoclays with different affinities for hexazinone (hexadecyltrimethylammonium-exchanged Arizona montmorillonite, HDTMA-SA, and phenyltrimethylammonium-exchanged Arizona montmorillonite, PTMA-SA), two herbicide loadings (10% and 20% AI), and three types of preparation were assayed. Laboratory experiments showed that hexazinone formulations based on HDTMA-SA displayed slow-release properties in water, retarded herbicide leaching through soil columns, and maintained a herbicidal efficacy similar to that of the currently available commercial hexazinone formulation (wettable powder). In contrast, PTMA-SA formulations released the herbicide instantaneously and did not display slow-release properties. High organoclay-herbicide ratios and the use of organic solvent made the interaction between HDTMA-SA and the herbicide more intimate and reduced the release rate of hexazinone, suggesting that a range of release and leaching behaviours can be achieved by selecting the type of preparation and the herbicide loading in the formulations. A field experiment confirmed the usefulness of HDTMA-SA formulations of hexazinone to reduce herbicide leaching while maintaining weed-control efficacy.

The effect of organic amendments (OA) on imidacloprid sorption and dissipation in soil was investigated. A sandy soil was treated at a rate of 10% w/w with three OA: one liquid (Liquid Fertiormont,...

Three organic cations with a natural origin (L-carnitine, L-cystine dimethyl ester, and thiamine) were introduced at different loadings in the interlayer of a low-charge montmorillonite, and the performance of the modified clays as adsorbents of the herbicide simazine was investigated using batch adsorption-desorption experiments. The organic cations were selected on the basis of their natural origin and the presence of diverse functional groups in their structures, which was expected to influence simazine adsorption. Elemental analysis and spectroscopy results demonstrated the presence of the organic cations in the modified montmorillonites and their entrance in the clay mineral interlayers. Batch adsorption results showed that modification with thiamine (Kf = 96-138), cystine dimethyl ester (Kf = 400-753), and especially carnitine (Kf > 10 000) enhanced the adsorption of simazine by montmorillonite (Kf = 28-47). It appeared that the specific interlayer microenvironment provided by the functional groups of each organic cation was an important factor controlling the adsorption efficiency of the modified clays. For carnitine and cystine dimethyl ester, the increase in simazine adsorption was considerably greater than that observed after montmorillonite modification with >classical> alkylammonium cations, such as phenyltrimethylammonium or hexadecyltrimethylammonium. This illustrated how modification of smectitic clay minerals with natural organic cations containing appropriate functional groups can be a useful strategyto improve the performance of organoclays for the removal of specific organic pollutants from the environment.

The sorption capacity and possible mechanisms of sorption of two new sulfonylaminocarbonyltriazolinone herbicides, methyl 2-[[[(4,5-dihydro-4-methyl-5-oxo-3-propoxy-1 H -1,2,4-triazol-1-yl)carbonyl]amino]sulfonyl]benzoate (MKH 6561) and (4,5-dihydro-3-methoxy-4-methyl-5-oxo- N -[[2-(trifluoromethoxy)phenyl]sulfonyl]-1 H -1,2,4-triazole-1-carboxamide) (MKH 6562), and their potential metabolites, 2,4-dihydro-4-methyl-5-propoxy-3 H -1,2,4-triazol-3-one (triazole) and 2-trifluoromethoxybenzenesulfonamide (phenylsulfonamide) on octadecyl (C18) and dioctadecyldimethylammonium (DOD) saturated and Fe 3+ and Na + saturated smectites has been investigated. Sorption of MKH 6561 on inorganic clays and C18 organoclays was much higher than for MKH 6562, but was similar on DOD saturated clays. For C18 saturated clays, sorption of both parent compounds increased with decreasing layer charge of the organosmectite. Sorption of triazole metabolite, which was much lower than for its parent compound MKH 6561, was higher on in...

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.

Certain soil management practices can affect the enantioselective behavior of chiral pesticide enantiomers in agricultural soils. In this work, laboratory experiments were conducted to study the effects of olive-mill waste (OMW) addition to a Mediterranean agricultural soil on the enantioselectivity of sorption, degradation, and leaching processes of the chiral fungicide metalaxyl. Sorption-desorption isotherms indicated that the sorption of metalaxyl enantiomers by unamended and OMW-amended soil (2% w/w) was non-enantioselective and that OMW addition had little effect on the extent of sorption of metalaxyl enantiomers by the soil. Soil incubation experiments revealed that the degradation of metalaxyl in unamended soil was highly enantioselective, with R-metalaxyl being degraded faster (t1/2=12 days) than S-metalaxyl (t1/2=39 days). OMW addition to the soil increased the half-life of the biologically-active R-metalaxyl enantiomer from 12 to 28 days, and decreased the half-life of the non-active S-metalaxyl enantiomer from 39 to 33 days. Consequently, the enantioselectivity of metalaxyl degradation in the soil was greatly reduced upon OMW addition. Column leaching data were consistent with batch sorption and incubation results, showing similar retardation of S- and R-metalaxyl in unamended and OMW-amended soil and enantioselective leaching of the fungicide only in unamended soil. The results have important implications regarding the biological efficacy and environmental impact of the fungicide when applied as a mixture of enantiomers or racemate to OMW-treated soils.

This chapter focuses on applications of nanotechnology in the field of agriculture. The first part deals with nanoformulations of agrochemicals for applying pesticides and fertilizers to crops. Three types of nanomaterials are considered: organic polymers, inorganic compounds, and hybrid materials (nanocomposites). This is followed by a brief discussion of the potential for developing nanodevices for the genetic manipulation of plants. Finally, the application of nanosensors in crop production for the identification of diseases, residues of agrochemicals, and specific characteristics is discussed.

Replacement of natural inorganic cations of clay minerals with organic cations has been proposed as a strategy to improve the adsorptive capacity of clay minerals for organic compounds, including pesticides. The organic cations most commonly used for this purpose have been quaternary ammonium ions containing alkyl or aryl chains without specific functional groups. In this work, we evaluated the ability of two bentonites (SWy-2 and SAz-1) exchanged with four natural organic cations containing diverse functional groups (L-carnitine, L-cysteine ethyl ester, L-cystine dimethyl ester, and thiamine) as adsorbents of pesticides varying in their chemical structures (simazine, hexazinone, triadimefon, alachlor, carbaryl, and imazethapyr). For comparison purposes, the adsorptive properties of two >classical> organobentonites, hexadecyltrimethylammonium- and phenyltrimethylammonium- exchanged bentonites, were also determined. Most organobentonites displayed higher affinity for the pesticides than the untreated bentonites, but the improvement in adsorption capacity varied depending on the characteristics of the pesticide and the interlayer organic cation. Triadimefon, carbaryl, and imazethapyr displayed the highest affinity for carnitine (Kf = 229-2377)-, thiamine (Kf = 83-354)-, and cystine (Kf = 96-100)-treated bentonites, respectively, whereas alachlor was adsorbed similarly by all organobentonites. In general, pesticide adsorption-desorption hysteresis was greater for adsorbents with the highest adsorption capacities. The results demonstrate that selective modification of smectitic clay minerals with natural organic cations containing appropriate functional groups can be a useful strategy to improve their performance for the removal of specific pesticides from the environment.

The effect of aging in the soil of three organic amendments (OAs), one liquid (LF) and two solid ones (SF and AL), has been investigated and related to changes in soil adsorption of metalaxyl and tricyclazole. LF and AL have very high dissolved organic carbon (DOC) contents with low humification index values, whereas SF has a low DOC content but the highest amounts of highly humified material. All OAs increased the adsorption of tricyclazole, whereas adsorption of metalaxyl decreased in soils amended with LF and AL, due to competition with DOC for mineral adsorption sites. With aging, DOC from SF amended soils is not significantly affected and neither is adsorption behavior. On the contrary, the great reduction of DOC from LF and AL with aging has been shown to affect adsorption of metalaxyl and tricyclazole, and this effect is dependent on the pesticide, the nature of the DOC, and the type of soil, in particular its clay mineralogy.

The risk of ground water contamination resulting from rapid leaching of highly soluble pesticides can be minimized through the application of the pesticide adsorbed on a matrix or carrier, which limits the amount of pesticide immediately available for undesirable losses. The use of natural materials for this purpose is of special interest in terms of economy and sustainability. In this work the adsorption of the herbicide hexazinone by two montmorillonites saturated with various inorganic and organic cations was determined and the ability of the two clays displaying the highest adsorption capacities [Fe3+-saturated Wyoming montmorillonite, (Fe-SW) and hexadecyltrimethylammonium-saturated Arizona montmorillonite (HDTMA-SA)] to act as carriers for slow release of hexazinone and to reduce herbicide leaching losses was evaluated. Hexazinone formulations based on Fe-SW and HDTMASA displayed slow release properties in water and soil/water suspensions, reduced herbicide leaching in soil columns, and maintained herbicidal activity, as compared with the currently available commercial hexazinone formulation (wettable powder). Loosely bound hexazinone-HDTMASA formulations, which led to the slowest breakthrough of hexazinone in soil columns along with the greatest amounts of herbicide released from the clay particles, displayed the most interesting characteristics for their use as slow release formulations and to prevent ground water contamination.

Two phyllosilicates of high permanent charge and expandable (swelling) structure, montmorillonites, and two silicates of low permanent charge and nonexpandable structure, kaolinite (phyllosilicate) and sepiolite (fibrous silicate), were used as sorbents to elucidate the capacity and mechanism of adsorption of monobutyltin (MBT) species, as related to the presence and dynamics of MBT in sediments and participate matter. Adsorption kinetics and isotherms, desorption measurements, and studies of organotin-clay complexes by X-ray diffraction and FTIR spectroscopy indicated that the MBT adsorption process is a cationic exchange on these clay minerals, besides an additional adsorption of neutral (MBT)C13 attracted by the lipophilic moiety of the first MBTn+ adsorbed. The expandable (swelling) minerals showed much higher adsorption capacity because MBT adsorbed in their interlayer spaces where MBTn+ species, besides (MBT)Cl3, make >aggregates> or >clusters> that propelled some montmorillonite layers from 14 to 22 A. The results show the important role of clay minerals in the presence and dynamics of MBT in sediments as bound residues. The use of montmorillonite as a filter for MBT-contaminated waters is also suggested.