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Chirality has received progressive attention in the field of pesticides. Enantiomers of chiral pesticides have identical physicochemical properties but, commonly, they exhibit stereoselective response with chiral host systems and, therefore, enantioselectivity against the target pest. Despite this, approximately 30% of the pesticides in current use are formulated as mixtures of enantiomers or racemic mixtures. This has engendered new environmental problems, which demand exhaustive knowledge regarding the enantioselectivity of the processes that chiral pesticides may undergo in the soil environment. Changes in the enantiomer composition of chiral pesticides are caused mainly by biological interactions and, consequently, factors affecting the biodegradation of pesticides can also alter the enantioselectivity of the biotransformation of chiral pesticides in soils. Accordingly, soil parameters such as pH, redox conditions, texture, or agronomic practices have been reported to indirectly influence the final enantioselective behavior of these pesticides in soils, although there is limited knowledge in this regard. Hence, predicting the environmental behavior of chiral pesticides in soil turns challenging. This chapter summarizes the most recent enantioselective studies on chiral pesticide transfer and transformation processes in soils. Future research needs scientific foundations to establish under which agricultural and environmental conditions it is appropriate to replace racemic chiral pesticide mixtures with the biologically active purified enantiomers, the underlying mechanisms of enantioselective interactions, and the relationships between the soil microbial diversity and the biotransformation of chiral pesticides, which remain largely unknown. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG., Acknowledgements The authors received funding from the Spanish Ministry of Science and Innovation through projects AGL2017-82141-R, PID2019-109456RB-I00, PID2020-112563RBI00 and from Junta de Andalucía through project PY20-00746.

12 páginas.- 5 figuras.- 2 tablas.- 60 referencias.- The following are available online at https://www.mdpi.com/article/10.3390/agronomy11081593/s1.- (This article belongs to the Special Issue Allelochemicals: Effects on Seed Germination and Plant Growth), Based on the effects that allelochemicals can exert over organisms, their use as alternatives to synthetic pesticides has been proposed. To this aim, it is important to understand their behavior in soils as allelochemicals can readily dissipate by different routes. In this work, novel granules based on the commercial organoclay Cloisite® 10A were prepared as a new strategy for the possible application of S-carvone as a bioherbicide, overcoming its rapid dissipation in the environment. Batch release, degradation, mobility, and phytotoxicity tests in soil were performed. Until now, the phytotoxicity of organoclay-based formulations of S-carvone in soil has not been studied. The release of S-carvone in water from the granules occurred slowly. There were no differences in the persistence of the allelochemical after its application to soil as a free compound (readily available form) or supported on granules. However, the granulated formulation reduced and delayed the leaching of S-carvone, thus controlling its downward movement in soil columns, as compared to the free S-carvone. Bioassays revealed that S-carvone supported on granules reduced the germination and aerial biomass of Lactuca sativa L. to a greater extent than the free compound. Our results demonstrated that the prepared formulation of S-carvone, based on granules of the commercial organoclay Cloisite® 10A, could be used to control transport losses, such as leaching or volatilization, increasing the bioefficacy of the allelochemical. These findings could inspire further investigations for the preparation of novel formulations of monoterpenes as potential bioherbicides. View Full-Text, This work was financed by the Spanish Ministry of Science and Innovation (AEI grants PID2020-112563-I00 and AGL2017-82141-R) and Junta de Andalucía (grant PY20-00746), with EU FEDER-FSE funds

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)

9 páginas.-- 5 figuras.-- 3 tablas.-- 53 referecias.-- Supplementary data to this article can be found online at https://doi.org/10.1016/j.geoderma.2018.09.033, Knowledge of long-term pesticide behavior in biochar (BC) amended soil is still contradictory. In this work, we compared the sorption of three highly persistent and ionizable pesticides [two anionic (imazamox and picloram) and one weak base (terbuthylazine)] on both fresh and field-aged BC as well as on a soil amended with these biochars. The aging process was performed by burying the biochar at 10 cm in a silt loam soil [Upper Midwest USA (Wisconsin)] for six months. Field aged BC removed the three pesticides from solution to a higher extent (>85%) than the fresh BC (, This work has been financed by the Spanish Ministry of Economy and Competitiveness (MINECO Project AGL2016-77821-R ). B.G. gratefully acknowledges MINECO for her Juan de la Cierva-Incorporación postdoctoral contract (IJCI-2015-23309).

13 páginas.- 5 figuras.- 2 tablas.- 74 referencias.- The online version contains supplementary material available at https://doi.org/10.1007/s00374-021-01556-2., The sorption of the allelochemical scopoletin (7-hydroxy-6-methoxycoumarin) was studied in eight agricultural soils and different model sorbents. We also determined its degradation in selected soils and related sorption and degradation results to the expression of scopoletin phytotoxicity in soil towards two model plant species, Eruca vesicaria and Hordeum vulgaris. Scopoletin was sorbed to a greater extent in acid soils than in alkaline soils. Correlations with soil properties indicated that the soil pH and fine (silt/clay) fraction played a primary role in the sorption of scopoletin by soils. Weak interactions controlled its sorption in acid soils, whereas stronger interactions, probably with mineral clay constituents, became more relevant in alkaline clay soils. Dissipation of scopoletin in the soils was microbial-mediated and occurred more slowly in acid than alkaline soils. As a result, the phytotoxic activity of scopoletin was expressed in acid but not in alkaline soil. The results point to the influence that soil properties are expected to exert on the expression of the phytotoxicity of scopoletin in natural and agricultural ecosystems. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature., This work was supported by the Spanish Ministry of Science, Innovation, and Universities (MCIU/AEI) with FEDER-FSE funds (grant AGL2017-82141-R). J.A. Galán-Pérez also thanks MCIU/AEI for a pre-doctoral contract (grant PRE2018-083293) linked to project AGL2017-82141-R.

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.

11 páginas.- 9 figuras.- 55 referencias.-Supplementary data to this article can be found online at https://doi. org/10.1016/j.buildenv.2020.107214, Mortars containing biocidal chemicals are widely applied as they show resistance to microbiological growth, thus preventing the aging of heritage materials. However, factors such as ultraviolet radiation, the weather etc. could greatly affect the biocidal activity of the active principles in mortars. The aim of this study was to optimize the preparation of several complexes of the biocide carbendazim (CBZ) with clays: natural Wyoming montmorillonite SWy-1 and two commercial organoclays, Cloisite® 10 and Cloisite® 20, and to test their antimicrobial activity for their potential application in restoration mortars. The optimized material here proposed would minimize the amount of active principle needed avoiding its leaching and consequently reducing its environmental impact with a maximum heritage compatibility. Prepared organoclay-CBZ adsorption complexes were inoculated with microorganisms (algae and fungus) to assess the antimicrobial activity. In this sense, one of the CL20-CBZ adsorption complexes which showed the best algicidal and fungicidal activity was used to prepare the antimicrobial mortar, and subsequently compared to those with pure CBZ as an antimicrobial additive. Furthermore, the mortars specimens were subjected to a standardized leaching test to check the effectiveness of the antimicrobial activity. After the leaching tests, the antimicrobial action of mortar containing only CBZ was lower compared to CL20-CBZ which had a good antimicrobial effect. We can conclude from these results that the heritage lime mortars could be easily prepared and have good efficiency against microbial contamination., Spanish government (MINECO), (RTC-2015-3916-6) and Junta de Andalucía government (PAI Groups FQM-214 and FQM-175) financed this work. A. Pastor acknowledges a contract (FPU16/05041) from the Ministerio de Educación, Cultura y Deporte (MECD) to research at the University of Córdoba (Spain). The authors also acknowledge the support of Grupo Puma S.L.

6 páginas.- 1 figura,- 1 tabla.- 23 referencias.- Data for this article are available at doi:10.5061/dryad.70rxwdbwd, Bicyclopyrone is an herbicide that is marketed for the control of herbicide‐resistant weeds. However, there is a lack of extensive data on its sorption and factors that control its sorption in the soil system. In this study, we evaluated a series of 25 different soils, with a variety of properties to determine if an empirical relationship could be developed to predict the sorption coefficient for bicyclopyrone. Overall, there were no statistically significant relationships observed with organic carbon, cation exchange capacity, or clay content. There was a moderate negative correlation with soil pH (R = −.61). Additionally, Freundlich isotherm analysis suggests that the partitioning coefficient (KD) value could adequately characterize the sorption behavior for the range of soils evaluated here.

10 páginas, 4 figuras, 5 tablas y 63 referencias, BACKGROUND Allelochemicals can act as biopesticides or enhance the action of synthetic pesticides. In this work, we assessed the bioavailability of the allelochemical coumarin in soils amended with fresh or field-aged biochars (BCs). The fresh BC from oak wood (Fresh BC) was prepared at 550 degrees C and was buried for aging in two different places: in a sandy loam soil in Spain for 15 months (Aged BC_1) and a sandy loam soil in USA for six months (Aged BC_2). RESULTS Sorption experiments showed that all BCs were able to increase the affinity of soil towards coumarin, with the distribution coefficient following the order: unamended soil < Aged BC_2-amended soil < Aged BC_1-amended soil < Fresh BC-amended soil. All biochars ensure greater persistence of coumarin and the effect was more pronounced at high chemical dose (10 mg kg(-1)). Conversely, leaching studies in soil columns revealed that BCs were able to maintain coumarin within the first 5 cm of top-soil with total amount extracted ranging between 17% and 22% for BC-amended soil and, This work was nanced by the Spanish Ministry of Science, Innovation and Universities (MICINN Project AGL2016-77821-R and PID2019-109456RB-I00). The USDA is an equal opportunity employe

8 páginas.- 6 figuras.- 4 tablas.- referencias.- Supplementary data to this article can be found online at https://doi. org/10.1016/j.jenvman.2021.114102., We assessed the effect of three organic amendments and two organo-clays on sorption, persistence, and phytotoxicity of scopoletin, an allelochemical compound with potential as bioherbicide, in a Mediterranean alkaline soil. The aim was to elucidate whether the phytotoxicity of scopoletin could be expressed better in amended than unamended soil. The three organic amendments were fresh solid olive-mill waste (OMW), composted solid olive-mill waste (OMWc), and biochar (BC) prepared from OMWc. The two organo-clays were a commercial organo-montmorillonite (Cloi10) and lab-synthesized oleate-modified hydrotalcite (HT-OLE). The amendments enhanced sorption of scopoletin by the soil consistently with their individual affinities for the allelochemical: Cloi10 ≫ OMW > BC > OMWc > HT-OLE. The soil persistence of scopoletin increased significantly because of the addition of Cloi10, OMW, and BC. This increase was attributed to a combination of sorption, which protected the allelochemical from rapid biodegradation, and microbial activity changes. Although the inhibitory effect produced by the amendments themselves obscured the phytotoxicity of scopoletin to Lactuca sativa L. in soil treated with OMW and Cloi10, applying scopoletin to BC-amended soil led to a marked reduction in root length and aerial biomass of the emerged seedlings even though BC alone did not negatively affect these parameters. This inhibitory effect of scopoletin in BC-amended soil was in contrast to the negligible effect exerted by the allelochemical when applied to unamended soil. The results show that soils treated with suitable amendments, such as BC, might provide a scenario in which the herbicidal properties of 7-hydroxycoumarins could be better expressed., This work was financed by the Spanish Ministry of Science and Innovation (MCIN/AEI grant PID2020-112563RB-I00) and Junta de Andalucía (JA grant P20-00746), with EU FEDER funds. J.A. Galán-Pérez also thanks MCIN/AEI for a pre-doctoral contract (grant PRE2018-083293) linked to project AGL2017-82141-R and cofinanced with FSE funds.

Addition of biomass chars (biochar) to soil reportedly suppresses emissions of nitrous oxide (N2O), a potent greenhouse and ozone-depleting gas, but the causes and endurance of the effect are unclear. To determine whether adsorption may play a role, adsorption isotherms of N2O were constructed at 273 K on outgassed samples of anoxically-prepared wood-derived chars (300–700 °C) and on a subset briefly reheated in air at 400 °C. Sorption by the chars was greater and more reversible than sorption by soils or soil mineral phases. Adsorption by chars increased with pyrolysis temperature and upon post-pyrolysis air oxidation. The Langmuir maximum capacity correlates well with the CO2-determined (but not N2-B.E.T.-determined) surface area. At environmentally realistic partial pressures in soil, N2O adsorption correlates with CO2 adsorption, and is found to predominate in the micropores (

BACKGROUND Biochar, a carbon-rich product of biomass pyrolysis, could limit glyphosate transport in soil and remediate contaminated water. The present study investigates the sorption/desorption behavior of glyphosate on biochars prepared from different hardwoods at temperatures ranging from 350 to 900 °C to elucidate fundamental mechanisms. RESULTS Glyphosate (1 mg L−1) sorption on biochars increased with pyrolysis temperature and was highest on 900 °C biochars; however, total sorption was low on a mass basis (

10 páginas.- 6 figuras.- 5 tablas.- 57 referencias.- The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jafc.9b02618, In this study, we assessed the sorption, dissipation, and leaching of the herbicide mesotrione in soil amended with fresh and field-aged biochars, when added to the soil. The aging process was performed by burying the fresh biochar at 10 cm depth in three soils located in different points across the USA [Wisconsin (ABC_WI), Idaho (ABC_ID), and South Carolina (ABC_SC)] for six months. ABC_ID and ABC_SC slightly increased the sorption of mesotrione in soils, whereas ABC_WI removed greater amounts of herbicide from the solution. This was attributed to differences in water-soluble components and metal content of this aged biochar. Consequently, the persistence of the herbicide in the amended soils with fresh biochar and ABC_ID and ABC_SC were similar to that in unamended soils, while ABC_WI slightly increased mesotrione half-life. Differences between treatments were detected in leaching studies although no direct relationship with the dissipation batch studies was observed. Mesotrione leaching could not be detected in soil columns amended with ABC_WI and was high for the rest of treatments. The outcomes from this work demonstrate that temporal variability of biochar sorption capacities due to soil exposure can occur altering mesotrione’s behavior in biochar-amended soils., This work was financed by the Spanish Ministry of Science, Innovation and Universities (MICINN Project AGL2016-77821-R). B.G. thanks MICINN for her Juan de la Cierva Incorporacion postdoctoral contract (IJCI-2015-23309).

11 páginas.- 5 figuras.- 2 tablas.- 60 referencias.- Supplementary information accompanies this paper at https://doi.org/10.1038/s41598-019-46031-z, Coumarins represent an important family of allelochemicals with fungicidal, bactericidal, insecticidal, nematicidal, and herbicidal properties. Like for other allelochemicals, the short persistence of coumarins in soils can reduce their biological activity and hamper their application as environmentally friendly agrochemicals. We evaluated the sorption of the coumarin umbelliferone by eight soils and six sorbent materials, and then selected two nanoengineered sorbents, hexadecyltrimethylammonium-modified Arizona montmorillonite (SA-HDTMA) and olive-mill waste biochar (BC), to assess the effect of their addition to two distinct soils on umbelliferone sorption, persistence, and leaching. Umbelliferone was sorbed to a greater extent by the acid soils (A1-A2, Kd > 4.0 L kg−1) than by the alkaline soils (B1-B6, Kd, Tis work was fnanced by the Spanish Ministry of Economy, Industry and Competitiveness (MINEICO Project AGL2017-82141-R) with FEDER-FSE funds. Te authors thank G. Facenda for technical help. B.G. also thanks MINEICO for her Juan de la Cierva-Incorporación postdoctoral contract (IJCI-2015-23309).

8 páginas.-- 4 figuras.-- 2 tablas.--50 referencias.-- The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jafc.8b05692., This study investigates the changes in sorption/desorption, dissipation, and leaching of the two enantiomeric forms of the allelochemical carvone, R-carvone and S-carvone, after amending an agricultural soil sample with two nanoengineered sorbents: biochar (BC) and organoclay (OCl). The sorption of carvone enantiomers was nonenantioselective and similarly improved by the addition of OCl and BC to the soil. However, OCl-amended soil showed reversible sorption, whereas BC-amended soil displayed sorption-desorption hysteresis. Dissipation of carvone enantiomers was enantioselective. Both amendments increased the half-life of the enantiomers in the soil. This effect was more pronounced for BC-amended soil and for S-carvone. Leaching of R- and S-carvone through soil columns was scarce in unamended soil (, This work was financed by the Spanish Ministry of Science, Innovation and Universities (MICINN Project AGL2017-82141-R). B.G. would like to thank MICINN for her Juan de la Cierva-Incorporación postdoctoral contract (IJCI-2015- 23309).

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

16 páginas.-- 6 figuras.-- 2 tablas.-- 50 referencias, The activity of allelochemicals in agroecosystems is highly dependent on their soil persistence. The aim of this work was to establish a link between the soil persistence of salicylic acid (SA) and its bioactivity, to better understand the mechanisms of allelochemical-mediated soil-plant interactions. Incubation and bioassay experiments were conducted for this purpose. The addition of HgCl2 and decreasing temperature to 4 °C increased the persistence of SA in soil. Since these treatments greatly decreased the soil respiration, they probably slowed the SA dissipation by reducing the soil microbial activity. To a lesser extent, soil humidity and soil pH also influenced the SA dissipation rate. Exogenous olive-mill organic waste (ALP) increased the soil respiration, but interestingly, delayed the degradation of SA, presumably because ALP acted as an alternative source of C for soil microorganisms. The phytotoxicity of SA towards Eruca vesicaria in soil increased by the addition of ALP. Applied to soil at 0.5%, ALP reduced the SA dose for 50% Eruca vesicaria aerial biomass inhibition to 40%. Our results show how certain agronomic practices, such as the application of agri-industrial biosolids, could be used to modulate the persistence of allelochemicals in the rhizosphere and control their biological functions in soils. © 2018, This work was supported by the Spanish Ministry of Economy, Industry and Competitiveness (MINEICO grants AGL2014-51897-R and AGL2017-82141-R), with FEDER-FSE funds. B.G. grateful acknowledges MINEICO for her Juan de la Cierva-Incorporación postdoctoral contract (IJCI-2015-23309).

BACKGROUND Soil incubation and column leaching experiments were conducted to address the question of whether the type of formulation (unsupported versus clay supported) and repeated applications of the chiral fungicide (RS)-metalaxyl affected the enantioselectivity of its dissipation and leaching in a slightly alkaline, loamy sand agricultural soil. RESULTS Regardless of the type of formulation and the number of fungicide applications, the R-enantiomer of metalaxyl was degraded faster than the S-enantiomer, but the individual degradation rates of R- and S-metalaxyl were highly affected by the different application regimes assayed (t1/2 = 2–104 days). Repeated applications accelerated the degradation of the biologically active R-metalaxyl enantiomer, whereas they led to slower degradation of the non-active S-metalaxyl enantiomer. The type of formulation had less influence on the dissipation rates of the enantiomers. For all formulations tested, soil column leachates became increasingly enriched in S-enantiomer as the number of fungicide applications was increased, and application of metalaxyl to soil columns as clay-based formulations reduced the leaching of both enantiomers. CONCLUSION Pesticide application conditions can greatly influence the enantioselective dissipation of chiral pesticides in soil, and hence are expected to exert a great impact on both the biological efficacy and the environmental chiral signatures of pesticides applied as mixtures of enantiomers or racemates to agricultural soils. © 2014 Society of Chemical Industry

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 figuras.-- 2 tablas.-- 56 referencias.-- Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.geoderma.2017.01.024., Sorption, persistence, and leaching of the enantiomers of the herbicide imazaquin, S-imazaquin and R-imazaquin, in two soils under different application regimes were studied. Imazaquin dissipation was evaluated after a single application of the racemic herbicide and the pure enantiomers, and after a repeated application of the racemic herbicide. The effects of adding two olive-mill wastes (ALP and ALPc), biochar (BC), and organoclay (SA-HDTMA) on sorption, dissipation, and leaching of imazaquin enantiomers applied as racemic herbicide to the soils was also evaluated. For all treatments, sorption, dissipation, and leaching of imazaquin in the soils were either non-enantioselective or scarcely enantioselective. No interconversion of R-imazaquin to S-imazaquin or vice-versa was observed in the experiments with the pure isomers. Addition of ALP, ALPc, or BC did not enhance the negligible sorption of imazaquin enantiomers by the soils, but accelerated their dissipation. Addition of SA-HDTMA increased sorption of both enantiomers and delayed their dissipation and leaching. The results illustrate how agricultural practices can impact the behavior of imazaquin enantiomers in soils and support the suitability of replacing currently used racemic formulations of imazaquin with formulations based on the single biologically-active (R) enantiomer to reduce the environmental impact of this chiral pesticide., This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO grants AGL2011-23779 and AGL2014-51897-R) and Junta de Andalucía (JA Research Group AGR-264), co-financed with FEDER-FSE funds. The authors thank L. Cox for kindly supplying samples of ALP and ALPc. R. López-Cabeza also thanks MINECO for a pre-doctoral fellowship (grant BES-2012-059945).

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.

Improving the existing knowledge on the enantioselectivity of processes affecting chiral pesticide enantiomers in the environment is necessary to maximize the efficacy and minimize the environmental impact caused by the use of pesticides with chiral properties. In this work, the enantioselectivity of the sorption, degradation, and leaching processes of the chiral fungicide metalaxyl in three slightly alkaline, agricultural soils from southern Spain was studied. Batch sorption experiments indicated that the sorption of racemic-metalaxyl on soils, their clay (< 2 οm) fractions, and a number of model sorbents simulating naturally-occurring soil colloidal particles was non-enantioselective; the S-enantiomer was sorbed to the same extent as the R-enantiomer on all soil materials. Soil incubation experiments revealed that the R-enantiomer of metalaxyl was degraded faster than the S-enantiomer in all three soils, but the extent and enantioselectivity of metalaxyl degradation was soil-dependent, occurring more slowly and with less enantioselectivity in the fine-textured soil (soil 1) than in the coarse-textured soils (soils 2 and 3). For soils 2 and 3, S- and R-metalaxyl dissipation data were very well described by single first-order kinetics, whereas for soil 1 dissipation data were better fitted by two coupled first-order equations. It is suggested that sorption and entrapment of metalaxyl enantiomers in the abundant small-size pores of soil 1 (i.e., pore radius < 100 nm) could have resulted in a fraction of the fungicide of reduced bioavailability, and consequently, protected from enantioselective degradation. Metalaxyl leaching through soil columns was also enantioselective; the concentration of S-metalaxyl in all leachates collected was greater than that of R-metalaxyl. Despite being non-enantioselective, sorption influenced the enantioselectivity of metalaxyl leaching, as it determined the residence time of the fungicide within the soil column, and consequently, the extent and enantioselectivity of its degradation during leaching.

10 páginas.-- 4 figuras.-- 3 tablas.-- referencias.-- Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.agee.2016.05.017, Laboratory and field experiments were conducted to assess how the addition of oleate-modified hydrotalcite (clay) and biochar (BC) to an agricultural soil affected the sorption, leaching, persistence, and enantiomeric composition of soil residues of two chiral fungicides, tebuconazole and metalaxyl. Laboratory experiments showed that the sorption of both fungicides ranked as follows: unamended soil < BC-amended soil < clay-amended soil. The addition of clay at a rate of 1% increased metalaxyl soil sorption coefficient (Kd) from 0.34 to 3.14 L kg−1 and that of tebuconazole from 2.4 to 47.4 L kg−1. In our experimental set-up, field plots were either unamended or amended with clay (2 t ha−1) or BC (4 t ha−1), and subsequently treated with a mixture of tebuconazole and metalaxyl at 3 and 6 kg ha−1, respectively. The leaching, persistence, and enantiomer composition of fungicides residues were monitored by sampling at different soil depths (0–5, 5–10, 10–20 cm) for 98 days. No significant changes in the scarce mobility and long persistence of tebuconazole upon amending the soil with clay or BC were observed. In contrast, sorption to clay and BC particles reduced the leaching and degradation of metalaxyl and the clay increased its persistence in the topsoil compared to the unamended soil. The enantioselective analysis of tebuconazole and metalaxyl soil residues indicated that tebuconazole remained mostly racemic along the experiment, whereas for metalaxyl the concentration of S-enantiomer was greater than the concentration of R-enantiomer, more so at longer experimental times and deeper horizons. Nevertheless, for the top 0–5 cm soil layer metalaxyl remained more racemic in clay- and BC-amended soil than in unamended soil. Our results show that addition of amendments with high sorptive capacities can be beneficial in reducing leaching and degradation losses of chiral pesticide enantiomers from the topsoil, and that sorption by the amendments can influence the final enantiomeric composition of pesticide residues., This work was financed by the Spanish Ministry of Economy and Competitiveness (MINECO Projects AGL2011-23779, AGL2013-48446-C3-1-R and AGL2014-51897-R) and Junta de Andalucía (JA Research Group AGR-264), with FEDER-FSE funds. R. López-Cabeza thanks MINECO for a pre-doctoral fellowship linked to the Project AGL2011-23779 (Grant BES-2012-059945). The authors also thank P. Franco (Chiral Technologies Europe) and I. Girón (IRNAS) for their technical assistance

7 páginas.-- 3 figuras.-- 3 tablas.-- 52 referencias.-- Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.geoderma.2016.01.024, Little is known about the enantioselectivity of the processes that determine the efficacy and environmental fate of natural compounds with potential to be used as environmentally-friendly agrochemicals. We conducted incubation and column leaching experiments to examine the extent and enantioselectivity of the sorption, persistence, and leaching of (RS)-abscisic acid (ABA) in three agricultural soils. Sorption of ABA enantiomers was a non-enantioselective process that occurred only in the soil with pH close to the pKa (4.8) of ABA enantiomers, but not in the two other (alkaline) soils. The degradation of (RS)-ABA was enantioselective for the three soils tested. (S)-ABA, the naturally-occurring enantiomer, was always degraded faster (DT50 < 4 days), compared to (R)-ABA (DT50 > 8 days). The movement of ABA enantiomers through the soil profile was enantioselective with column leachates being enriched in (R)-ABA enantiomer. Leaching was delayed in the soil that displayed sorption for both enantiomers. The results showed that the behavior of ABA enantiomers in soil was enantioselective and that the final fate of (R)-ABA and (S)-ABA depended on the soil type and appeared to be affected by their sorption on soil. The longer persistence of (R)-ABA should be considered when assessing the possibility of using this enantiomer or formulations containing enantiomer mixtures of ABA for crop management., This work has been financed by the Spanish Ministry of Economy and Competitiveness (MINECO Project AGL2014-51897-R) and Junta de Andalucía (Research Group AGR-264). The authors thank G. Facenda and P. Velarde (IRNAS, CSIC) and P. Franco (Chiral Technologies Europe) for technical assistance.

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.

9 páginas, 7 figuras, 3 tablas, 43 referencias.-- cmartin@irnase.csic.es, Research on organoclays as sorbents of pesticides has shown the usefulness of these materials both as soil amendments and as pesticide supports, to prolong the effi cacy and reduce the environmental impact of soil-applied pesticides. Organoclays can also be formed in situ by direct modifi cation of smectiterich soil clays through treatment with appropriate organic cations. In this work, laboratory experiments were conducted to investigate the effect of the addition to soil of a natural organic cation, spermine, on sorption (batch equilibration procedure), persistence (incubation experiments), and leaching (column experiments) of the herbicide fl uometuron. Four soils differing in their clay contents and mineralogy were used. A sevenfold increase in the fl uometuron sorption distribution coeffi cient, K d, by the presence of spermine was observed for a clay soil rich in smectites (Soil 1), whereas the effect on fl uometuron sorption was negligible for a soil with similar clay texture but lacking smectites (Soil 4) and for a loamy sand soil with very low content in smectites (Soil 3). A sandy loam soil (Soil 2) with moderate smectite content had an intermediate behavior. The increase in fl uometuron sorption was thus related to the smectite content of the soils, strongly indicating that reaction of spermine with soil smectites formed in situ an organoclay complex with high affi nity for fl uometuron. The simultaneous application of fl uometuron and spermine to the smectite-rich soil retarded the leaching of the herbicide but, at the same time, increased the total amount of fl uometuron leached from 25 to 52%. This was attributed to the fact that spermine, apart from increasing sorption, also prolonged the persistence of fl uometuron in the smectite-rich soil. In contrast, the presence of spermine had no effect on the leaching pattern of fl uometuron in the clay soil lacking smectites. The results indicated that the application of suitable organic cations to smectitic soils can be a useful strategy to control pesticide retention and persistence in the soil environment., This work has been financed by the Spanish Ministry of Science and Innovation (Project AGL2008-04031-C02-01) and Junta de Andalucía (Project P07-AGR- 03077 and Research Group AGR-264), and cofinanced with FEDER-FSE funds.

8 páginas.-- 4 figuras.-- 4 tablas.-- referencias.-- Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.envpol.2016.03.052., Although enantioselective sorption to soil particles has been proposed as a mechanism that can potentially influence the availability of individual chiral pesticide enantiomers in the environment, environmental fate studies generally overlook this possibility and assume that only biotic processes can be enantioselective, whereas abiotic processes, such as sorption, are non-enantioselective. In this work, we present direct evidence for the effect of the enantioselective sorption of a chiral pesticide in a natural soil on the availability of the single pesticide enantiomers for transport. Batch sorption experiments, with direct determination of the sorbed amounts, combined with column leaching tests confirmed previous observations that from non-racemic aqueous solutions the sorption of the chiral fungicide metalaxyl on the soil appeared to be enantioselective, and further demonstrated that the enantiomer that was sorbed to a greater extent (R-metalaxyl, Kd = 1.73 L/kg) exhibited retarded leaching compared to its optical isomer (S-metalaxyl, Kd = 1.15 L/kg). Interconversion and degradation of the pesticide enantiomers, which are potential experimental artifacts that can lead to erroneous estimates of sorption and its enantioselectivity, were discarded as possible causes of the observed enantioselective behavior. The results presented here may have very important implications for a correct assessment of the environmental fate of chiral pesticides that are incorporated into the environment as non-racemic mixtures, and also of aged chiral pesticide residues that have been transformed from racemic to non-racemic by biologically-mediated processes. © 2016 Elsevier Ltd. All rights reserved., This work was financed by the Spanish Ministry of Economy and Competitiveness (MINECO Project AGL2014-51897-R) and Junta de Andalucía (Research Group AGR-264), with European FEDER funds (Operative Program 2014–2020).

9 páginas.-- 6 figuras.-- 43 referencias.-- Appendix A. Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.jhazmat.2015.07.059, Mechanisms governing the enantioselectivity of the processes that determine the behavior of chiral pol-lutants in the environment need to be better understood. Understanding these mechanisms should helpimprove predictions of the hazards and risks chiral compounds can pose to people and the environment.We report the results of batch sorption experiments indicating that the sorption of the chiral fungicidemetalaxyl on soil from non-racemic initial solutions was enantioselective. While from a racemic initialsolution the two enantiomers of metalaxyl were sorbed on the soil to the same extent, increasing the frac-tion of R-enantiomer in the initial solution led to enhanced sorption of this enantiomer and to reducedsorption of the S-enantiomer. Considering the shape of the sorption isotherms (S-type) and the sorp-tion behavior of model sorbents, we attributed this effect to molecular interactions between metalaxylenantiomer species at the sorbed state, where R-R metalaxyl interactions appeared to be more favor-able than R–S metalaxyl interactions. We discuss important environmental implications of the proposedmechanism, such as those related to the fact that the biological degradation of metalaxyl is known to bean enantioselective process that can yield non-racemic residues in soils shortly after application of thefungicide as a racemic mixture., This work has been financed by the Spanish Ministry ofEconomy and Competitiveness (MINECO Projects AGL2011-23779and AGL2014-51897-R) and Junta de Andalucía (Research GroupAGR-264), cofinanced with European FEDER-FSE funds (OperativeProgram 2007-2013). The authors thank M.J. Calderón, M.I. Cardo,and R. López-Cabeza (IRNAS-CSIC) and P. Franco (Chiral Technolo-gies Europe) for technical assistance.

8 páginas.--7 figuras.-- 1 tablas.-- 66 referencias.-- Data Supplementary data associated with this article can befound, in the online version, at http://dx.doi.org/10.1016/j.apsusc.2015.01.179., © 2015 Elsevier B.V. All rights reserved. The goal of this work was to prepare and characterize a novel functional material by the modification of SAz-1 montmorillonite with the cationic polymer hexadimethrine (SA-HEXAD), and to explore the potential use of this nanocomposite as a pesticide adsorbent. Comparative preparation and characterization with the well-known hexadecyltrimethylammonium-modified SAz-1 montmorillonite (SA-HDTMA) was also assessed. The characterization was performed by elemental analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), physisorption of N2, scanning electron microscopy (SEM) and Z potential measurements. The characterization and adsorption experiments showed that the extent of pesticide adsorption was markedly subjected to the structure and features of the surface of each organo-clay and also to the nature of the considered pesticide. SA-HEXAD displayed a high affinity for anionic pesticides which, presumably, were adsorbed by electrostatic attraction on positively-charged ammonium groups of the polymer not directly interacting with the clay. In contrast, SA-HDTMA displayed great adsorption of both uncharged and anionic pesticides with predominance of hydrophobic interactions. This work provided information about the surface properties of a new organic-inorganic nanohybrid material, SA-HEXAD, and its potential as an adsorbent for the removal of anionic organic pollutants from aqueous solutions., This work has been financed by the Spanish Ministry of Economy and Competitiveness (Grant AGL2011-23779) and Junta de Andalucía (Grants P07-AGR-03077 and P11-AGR-7400). B. Gámiz also thanks Junta de Andalucía for her postdoc-contract linked to Project P07-AGR-03077.

9 páginas.-- 3 figuras.-- 31 referencias.-- Supporting Information: characteristics of the three multiwalled CNTs; selected physicochemical properties of sorbates; Freundlich model fits to sorption and competitive sorption data of monaromatics by CNTs; adsorption kinetics of BA, DNP, and NB onto C−CNT at pH 7 and adsorption kinetics of MBPh, MBA, and PTA onto C−CNT at pH 6; comparison of sorption isotherms of a given adsobate on hydroxylated (H−), carboxylated (C−), and graphitized (G−)CNTs at pH 7.0; zeta potential measurements for the three CNTs; pH records of the NB adsorption on CNTs at initial pH 7.0; titration curves of the three CNTs from pH 3−12; consumption of OH− as a function of pH for the three CNTs from the titration curves; sorbed concentration of NB on three CNTs as function of sorbed competitor concentration at pH 7.0 and displacement efficiency (DE %) of BA or DNP as function of sorbed competitor concentration; sorbed concentration of MBPh on C−CNT as function of amount sorbed of competitors, MBA and PTA at pH 4 and pH 6 at fixed initial concentration of MBPh of 0.2 Mm; and solution pH change versus moles BA−/DNP− adsorbed for (A, C, E) H−CNT and (B, D, F) C−CNT without or with cosolute. This material is available free of charge via the Internet at http://pubs.acs.org, We recently proposed that weak acids (AH) adsorb to partially oxidized carbonaceous materials in part by forming strong hydrogen bonds with acidic surface groups, depicted by (A···H···O-surf)-, known as negative charge-assisted hydrogen bonds, (-)CAHBs. Here we use competition experiments to show that sorption of AH on carbon nanotubes (CNTs) can be described conceptually by a dual specific/nonspecific domain model, where one domain involves (-)CAHB sites that can become saturated. The trends observed in single-solute adsorption, including the stoichiometric release of hydroxide upon sorption of carboxyate or phenolate anions, were consistent with trends in the previous studies and pointed to the formation of (-)CAHB. 3,4-Dinitrophenolate formed (-)CAHBs more efficiently than did 2,6-dichloro-4-nitrophenolate because of alleviation of steric hindrance to approach by the ortho chlorines. Competition against a (-)CAHB-capable target compound was greater when the competitor was also (-)CAHB-capable than when it was not (e.g., benzoate as target vs 3,4-dinitrophenolate or nitrobenzene as competitor; mono-n-butyl phthalate as target vs methyl benzoate or p-tolyl acetate as competitor). Experiments also revealed competition between the nitroaromatic species for π-π electron donor-acceptor sites. The findings will contribute to a better understanding of the adsorption mechanism of ionizable compounds on carbonaceous materials., (NSF) (CBET 1235459) and U.S. Department of Agriculture National Institute of Food and Agriculture (USDA NIFA) (MAS00475). B.G. thanks Junta de Andalucia for a postdoctoral contract linked to the project P07-AGR-03077

Soil incubation and column leaching experiments were conducted to address the question of whether the type of formulation (unsupported versus clay supported) and repeated applications of the chiral fungicide (RS)-metalaxyl affected the enantioselectivity of its dissipation and leaching in a slightly alkaline, loamy sand agricultural soil.Regardless of the type of formulation and the number of fungicide applications, the R-enantiomer of metalaxyl was degraded faster than the S-enantiomer, but the individual degradation rates of R- and S-metalaxyl were highly affected by the different application regimes assayed (t1/2 = 2-104 days). Repeated applications accelerated the degradation of the biologically active R-metalaxyl enantiomer, whereas they led to slower degradation of the non-active S-metalaxyl enantiomer. The type of formulation had less influence on the dissipation rates of the enantiomers. For all formulations tested, soil column leachates became increasingly enriched in S-enantiomer as the number of fungicide applications was increased, and application of metalaxyl to soil columns as clay-based formulations reduced the leaching of both enantiomers.Pesticide application conditions can greatly influence the enantioselective dissipation of chiral pesticides in soil, and hence are expected to exert a great impact on both the biological efficacy and the environmental chiral signatures of pesticides applied as mixtures of enantiomers or racemates to agricultural soils.

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.

Laboratory and field experiments were conducted to evaluate the effect of olive-mill waste (OMW) addition to a Mediterranean olive grove soil on sorption, persistence, and mobility of two herbicides which are simultaneously applied for weed control in olive groves: terbuthylazine (TA) and fluometuron (FM). Laboratory batch sorption experiments showed that OMW addition to the soil at rates of 5 and 10% (w/w) greatly enhanced the sorption of both herbicides, thus suggesting that amendment with OMW could be useful to enhance the retention and reduce the mobility of FM and TA in the soil. Incubation experiments showed that OMW increased the persistence of FM and had little effect on the long persistence of TA in the soil studied. A demonstration field experiment was also conducted in field plots with a slope of about 5%, either unamended or amended with OMW at a rate of 10 kg m¿2, and then treated with a commercial formulation containing a mixture of TA and FM. Extraction of field soil samples, taken from different soil depths (0¿5, 5¿10, 10¿20, and 20¿30 cm) at different times after herbicide application, showed that both TA and FM moved deeper in unamended soil than in OMW-amended soil, and that OMW addition affected the persistence of FM in the toplayer, increasing its half-life from 24 to 58 days, while having little effect on the persistence of TA. Thus, data obtained under real field conditions were consistent with those obtained under controlled laboratory conditions. Preliminary herbicide runoff data indicated that the total herbicide runoff losses were also reduced upon OMW addition. Addition of OMW could be beneficial in reducing the mobility of TA and FM in olive grove soils, and also in increasing the persistence of FM in soils where this herbicide could be rapidly degraded., This work has been financed by Junta de Andalucía (Project P07-AGR-03077 and Research Group AGR-264) and the Spanish Ministry of Science and Innovation (Projects AGL2008-04031-C02-01 and AGL2010-21421-C02-01), cofinanced with European FEDER-FSE funds (OP 2007–2013). B. Gámiz thanks Junta de Andalucía for her FPI fellowship, cofinanced with European FSE funds.