Heteroaggregation with clay mineral particles (CMPs) is significant to the environmental application and fate of increasingly produced nanoparticulate zero-valent iron (nZVI). Co-settling, kinetic aggregation, calculation of the classical Derjaguin-Landau-Verwey-Overbeek interaction energy, and electron microscopic observation were carried out to investigate the interaction between nZVIs (three naked nZVIs of different sizes and one carboxymethyl cellulose (CMC) coated nZVI) and CMPs (kaolinite and montmorillonite). Under pH 6.5 and 9.5 conditions, Lewis acid-base interaction contributed to the attachment between nZVIs and CMPs, while electrostatic attraction was involved in nZVI-CMP attachment under pH 3.5. Compared with the heteroaggregates formed by nZVIs attaching to CMP edges and faces under pH 6.5 and 3.5 conditions, the heteroaggregates were smaller with nZVIs mainly connecting to CMP edges under pH 9.5. Small nZVI homoaggregates were bound to CMP edges at low nZVI concentrations (nZVI/CMP mass ratio at 0.015) with CMP concentrations of 330 mg L-1 and large nZVI-CMP heteroaggregates formed by nZVI bridging with increasing nZVI concentrations. The smallest nZVI exhibited the strongest heteroaggregation with CMPs; the CMC coating inhibited the interfacial interaction and heteroaggregation between nZVIs and CMPs; kaolinite had higher potential to interact with nZVIs under neutral conditions. These findings are helpful for understanding the interaction between nZVIs and minerals and of significance to environmental remediation using nZVIs. © 2019 The Royal Society of Chemistry.

Irrigation with treated wastewater (TWW) and application of biosolids introduce numerous pharmaceutical and personal care products (PPCPs) into agro-food systems. While the use of TWW and biosolids has many societal benefits, introduction of PPCPs in production agriculture poses potential food safety and human health risks. A comprehensive risk assessment and management scheme of PPCPs in agro-food systems is limited by multiple factors, not least the sheer number of investigated compounds and their diverse structures. Here we follow the fate of PPCPs in the water-soil-produce continuum by considering processes and variables that influence PPCP transfer and accumulation. By analyzing the steps in the soil-plant-human diet nexus, we propose a tiered framework as a path forward to prioritize PPCPs that could have a high potential for plant accumulation and thus pose greatest risk. This article examines research progress to date and current research challenges, highlighting the potential value of leveraging existing knowledge from decades of research on other chemicals such as pesticides. A process-driven scheme is outlined to derive a short list that may be used to refocus our future research efforts on PPCPs and other analogous emerging contaminants in agro-food systems. © 2019 American Chemical Society.

Carbamazepine (CBZ)is an anticonvulsant drug used for epilepsy and other disorders. Prescription of CBZ during pregnancy increases the risk for congenital malformations. CBZ is ubiquitous in effluents and persistent during wastewater treatment. Thus, it is re-introduced into agricultural ecosystems upon irrigation with reclaimed wastewater. People consuming produce irrigated with reclaimed wastewater were found to be exposed to CBZ. However, environmental concentrations of CBZ (μg L−1)are magnitudes lower than its therapeutic levels (μg ml−1), raising the question of whether and how environmental levels of CBZ affect embryonic development. The chick embryo is a powerful and highly sensitive amniotic model system that enables to assess environmental contaminants in the living organism. Since the chick embryonic development is highly similar to mammalians, yet, it develops in an egg, toxic effects can be directly analyzed in a well-controlled system without maternal influences. This research utilized the chick embryo to test whether CBZ is embryo-toxic by using morphological, cellular, molecular and imaging strategies. Three key embryonic stages were monitored: after blastulation (st.1HH), gastrulation/neurulation (st.8HH)and organogenesis (st.15HH). Here we demonstrate that environmental relevant concentrations of CBZ impair morphogenesis in a dose- and stage- dependent manner. Effects on gastrulation, neural tube closure, differentiation and proliferation were exhibited in early stages by exposing embryos to CBZ dose as low as 0.1 μg L−1. Quantification of developmental progression revealed a significant difference in the total score obtained by CBZ-treated embryos compared to controls (up to 5-fold difference, p < 0.05). Yet, defects were unnoticed as embryos passed gastrulation/neurulation. This study provides the first evidence for teratogenic effect of environmental-relevant concentrations of CBZ in amniotic embryos that impair early but not late stages of development. These findings call for in-depth risk analysis to ensure that the environmental presence of CBZ and other drugs is not causing irreversible ecological and public-health damages. © 2019

Natural formation of metal nanoparticles is an important pathway that will modify the fate, behavior, and biological availability of heavy metal ions in the environment. Most work has focused on the ability of natural organic matter (NOM) and extracellular polymeric substances (EPS) to convert metal ions into nanoparticles. However, plant roots, ubiquitous in soil and aquatic environments, may have a significant role in the formation of naturally occurring metal nanoparticles. This work demonstrates the importance of plant roots and associated exudates in mediating the transformation of Ag+ in the presence of sunlight. Using Ag+ as the starting material, transformation took place in three steps: 1) formation of AgCl microcubes (μAgCl) through complexation of Ag+ by plant-released chloride ions in root exudates; 2) stabilization of μAgCl by biomolecules in root exudates; 3) partial photoreduction of μAgCl to Ag(0) nanoparticles (nAg) facilitated by exudate biomolecules. Morphological and compositional changes were observed by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) on the particles from 0-24 h: Cubic AgCl microcrystals were converted into cauliflower-shaped core-shell structures with nAg clusters as the shell and μAgCl as the core. The quantification of Ag+, μAgCl and nAg species over time demonstrates that the transformation kinetics fit (R2 = 0.99) a second-order reaction (k = 1.11 mM-1 h-1). The discovery of plant root exudate-mediated phototransformation of Ag+ adds new knowledge to our understanding of Ag transformation in the plant root zone and will guide the assessment of both exposure and risk in the environment. © 2019 The Royal Society of Chemistry.

One of the most persistent pharmaceutical compounds commonly found in treated wastewater is lamotrigine (LTG). It has also been detected in soils and crops irrigated with treated wastewater. Here we focused on the ability of the white-rot edible mushroom Pleurotus ostreatus to remove and transform LTG in liquid cultures. At concentrations of environmental relevance (1 and 10 μg L−1) LTG was almost completely removed from the culture medium within 20 days. To elucidate the mechanism of LTG removal and transformation, we applied a physiological-based approach using inhibitors and a competing agent. These experiments were conducted at a higher concentration for metabolites detection. Based on identification of sulfur-containing metabolites and LTG N2-oxide and the effect of specific inhibitors, cytochrome P450 oxidation is suggested as one of the reaction mechanisms leading to LTG transformation. The variety and number of transformation products (i.e., conjugates) found in the current study were larger than reported in mammals. Moreover, known conjugates with glucuronide, glutathione, or cysteine/glycine, were not found in our system. Since the majority of the identified transformation products were conjugates of LTG, this study highlights the persistence of LTG as an organic pollutant in ecosystems exposed to wastewater. © 2019 Elsevier Ltd

Rapid industrialization leads to the introduction of dyes and nanoparticles (NPs) into the environment posing threats to water quality and aquatic organisms. The highly reactive NPs are known to interact with dyes to form stable NPs-dye complexes. Herein, we report the adsorptive interactions of two inorganic NPs, Ag-Ag2S and CeO2 with cationic methylene blue. Experiments were also performed with NPs coated with 2 types of dissolved organic matter. The maximal adsorption capacities for methylene blue with Ag-Ag2S and CeO2 were calculated to be 16.64 and 5.35 mg g−1, respectively. The obtained adsorption capacities are attributed to electrostatic interactions (attractive/repulsive) between the NPs and the dyes and also the van der Waals force of interaction between the dye molecules. DOM coatings on the NPs significantly reduced the adsorption of dyes (maximum adsorption capacities for methylene blue with DOM coated Ag-Ag2S and CeO2 were reduced by ˜40% and ˜61%, respectively; the more hydrophobic DOM coating on the NPs resulted in reduction of adsorption capacity by ˜54 and ˜70%, respectively). Our results suggest that the DOM coatings alter the arrangements of the NPs in the dye solution, creating the active surface sites less accessible for adsorption. Furthermore, the reduction of the adsorption efficiency for the NPs toward dyes with simultaneously addition of DOM is probably due to blockage of the active surface sites by the DOM molecules and the competition between the dye and the DOM.

Copper oxide nanoparticles (CuO NPs), as an antimicrobial nanomaterial, have found many applications in agriculture. Ubiquitous and complex root exudates (RE) in the plant root zone motivates the determination of how specific components of RE interact with CuO NPs. This work aims to reveal the role of maize (Zea mays L.)-derived RE and their components on the aggregation and dissolution of CuO NPs in the rhizosphere. We observed that RE significantly inhibited the aggregation of CuO NPs regardless of ionic strength and electrolyte type. In the presence of RE, the CCC of CuO NPs in NaCl shifted from 30 to 125 mM and the value in CaCl2 shifted from 4 to 20 mM. Furthermore, this inhibition was correlated with molecular weight (MW) of RE fractions. Higher MW fraction (>10 kDa) reduced the aggregation most. We also discovered that RE significantly promoted the dissolution of CuO NPs and lower MW fraction (<3 kDa) RE mainly contributed to this process. Additionally, phytotoxicity of CuO NPs in the presence of RE and different fractions of RE was evaluated. The addition of 20 mg/L RE reduced the seedlings growth rate to 1.89% after 7 days exposure to 25 mg/L CuO NPs, which were significantly lower than the control group (4.82%). Notably, Cu accumulation in plant root tissues was significantly enhanced by 20 mg/L RE. This study provides useful insights into the interactions between RE and CuO NPs, which is of significance for the safe use of CuO NPs-based antimicrobial products in agricultural production.

Similar to soils, soilless media are composed of three phases: solid, aqueous, and gaseous. The substantial differences between the former and the latter are related to the solid phase composition and associated texture and structure. While the solid phase of soils is mostly minerals, it is a mixture of minerals and organic matter for soilless culture, resulting in substantial differences in their physical and hydraulic properties. The physical and hydraulic properties of soil have been intensively studied, both experimentally and theoretically, the application and implementation of these knowledge and methods to soilless substrates is limited. This chapter aims to close the gaps in physics and hydraulic characterization and application between mineral soils and soilless media by applying terminology, methods, and approaches that are commonly used for the former to the latter. The current version of this Chapter extents the topic of particle wettability and its effect on the physical properties of soilless media. Although research on sales-media wettability and its effect on water retention and flow in the media has only recently initiated, its relevance is essential owing to the high organic matter content of these media and the relationship between the two.

Secondary treated wastewater, a commonly used water resource in agriculture in (semi-)arid areas, often contains salts, sodium, and organic matter which may affect soil structure and hydraulic properties. The main objective of this study was to jointly analyse the effects of long-term irrigation with treated wastewater on physicochemical soil characteristics, soil structure, and soil water dynamics in undisturbed soils. X-ray microtomography was used to determine changes in macro-porosity (> 19 μm), pore size distribution, and pore connectivity of a sandy clay loam and a loamy sand. Differences in the pore network among soils irrigated with treated wastewater, fresh water that replaced treated wastewater, and non-irrigated control plots could be explained by changes in textural composition, soil physicochemical parameters, and hydraulic properties. In this study we showed that irrigation led to the development of a connected macro-pore network, independent of the studied water quality. The leaching of silt and clay particles in the sandy soil due to treated wastewater irrigation resulted in an increase of pores < 130 μm. While this change in texture reduced water retention, the unsaturated hydraulic conductivity was diminished by physicochemical alteration, i.e. induced water repellency and clay mineral swelling. Overall, the fine textured sandy clay loam was much more resistant to soil alteration by treated wastewater irrigation than the loamy sand.

The recognition of treated wastewater (TWW) as an alternative water resource is expanding in areas with a shortage of freshwater (FW). While many studies have been devoted to the effects of long-term irrigation with TWW on soil wettability and spatial flow variations in the soil profile, much less attention has been given to the spatial distribution of soil water repellency in the soil surface layer. This is the objective of the current study. Undisturbed soil samples (5 cm thick) were taken at 15-cm intervals parallel to a drip lateral in two adjacent plots of a commercial citrus orchard in central Israel. Each soil sample was sectioned into five consecutive 1-cm layers for which soil water repellency was determined by water drop penetration time method, and soil organic matter by loss-on-ignition method. Geostatistics and multivariate empirical mode decomposition were used to investigate the overall and scale-specific spatial variation of soil water repellency and its dependence on dripper intervals along the lateral. A high degree of soil water repellency with strong spatial variation was found in the surface soil after 4–6 years of TWW irrigation. Weak to moderate spatial dependence of soil water repellency with maximum autocorrelation distance of around 30 cm was discovered by geostatistical analysis. The spatial distribution of soil water repellency was considered to be greatly affected by the location of the drippers, being higher between adjacent drippers and lower underneath them. This soil water repellency distribution is presumed to result from ongoing lateral displacement of the amphiphilic substances in the TWW toward the outer edge of the wetted plume periphery. Multivariate empirical mode decomposition of the overall spatial variation of soil water repellency yielded three scale-specific variations with corresponding characteristic scales of 30 cm, 110 cm and 200 cm. Most of the soil water repellency variation was separated into the 30 cm and 110 cm spatial scales, which were correlated to processes related to the drippers and trees. Replacing TWW with FW for the reclamation of water-repellent soils partially alleviated the intensity of TWW irrigation-induced soil water repellency. Moreover, an inconsistency between the hot spots of water-repellency development between adjacent drippers and the areas that are effectively ameliorated by FW irrigation below the drippers could be developed and affect the spatial distribution of flow pattern in an a priori unpredictable way.

The improvement of crop productivity under abiotic stress is one of the biggest challenges faced by the agricultural scientific community. Despite extensive research, the research-to-commercial transfer rate of abiotic stress-resistant crops remains very low. This is mainly due to the complexity of genotype◻×◻environment interactions and in particular, the ability to quantify the dynamic plant physiological response profile to a dynamic environment.Most existing phenotyping facilities collect information using robotics and automated image acquisition and analysis. However, their ability to directly measure the physiological properties of the whole plant is limited. We demonstrate a high-throughput functional phenotyping system (HFPS) that enables comparing plants’ dynamic responses to different ambient conditions in dynamic environments due to its direct and simultaneous measurement of yield-related physiological traits of plants under several treatments. The system is designed as one-to-one (1:1) plant–[sensors+controller] units, i.e., each individual plant has its own personalized sensor, controller and irrigation valves that enable (i) monitoring water-relation kinetics of each plant–environment response throughout the plant’s life cycle with high spatiotemporal resolution, (ii) a truly randomized experimental design due to multiple independent treatment scenarios for every plant, and (iii) reduction of artificial ambient perturbations due to the immobility of the plants or other objects. In addition, we propose two new resilience-quantifying-related traits that can also be phenotyped using the HFPS: transpiration recovery rate and night water reabsorption.We use the HFPS to screen the effects of two commercial biostimulants (a seaweed extract—ICL-SW, and a metabolite formula—ICL-NewFo1) on Capsicum annuum under different irrigation regimes. Biostimulants are considered an alternative approach to improving crop productivity. However, their complex mode of action necessitates cost-effective pre-field phenotyping. The combination of two types of treatment (biostimulants and drought) enabled us to evaluate the precision and resolution of the system in investigating the effect of biostimulants on drought tolerance. We analyze and discuss plant behavior at different stages, and assess the penalty and trade-off between productivity and survivability. In this test case, we suggest a protocol for the screening of biostimulants’ physiological mechanisms of action.

The identification of preferential flow generation and the tracking of their pathways in agricultural soils are challenging tasks, in particular while keeping the soil profile undisturbed. The noninvasive electrical resistivity tomography (ERT) method seems, a priori, to be an ideal tool for these purposes, but the simultaneous dependence of soil electrical resistivity (ER) on soil moisture content and salt concentration poses a problem when high-salinity water is involved. The dependence of these variables is expressed, for example, by Archie’s law. Irrigation with brackish or treated wastewater are two such complicated cases. The latter has been found to render soils water-repellent with inherent flow in preferential pathways. A method that resolves this complication is developed and applied for in-situ-measured ERT data. This method combines a model that simulates the preferential ER(t) as a series of interconnected well-mixed units (WMUs) with frequent ERT scans during soil wetting and subsequent drying. Following validation by comparison of its output to simulations using the Richards equation for flow and convection-dispersion equation for transport, the WMU model was used to simulate scenarios of simultaneous variations in moisture content, salinity, and ER(t) in a well-mixed soil volume (unit). The characteristic patterns acquired by these simulations were compared with in-situ measured ER(z,t) to determine whether the observed preferential ER pathways coincide with preferential flow or salinity pathways, or both. From the eight sections in the profile where this analysis was made for, five exhibit preferential flow, characterized by fast wetting front propagation that includes by-passing of a certain soil volume, while the wetting front velocity in the other three was moderate. We, therefore, concluded, based on the water content/salinity effect on ER, that the measured preferential ER pathways coincide with preferential flow pathways. Salinity has, for the current case, a minor, if any, effect on the ER spatial variation. Therefore, ERT is an advantageous mean of mapping of preferential flow pathways in the soil profile, and the method developed herein can be used for studying the water distribution in the soil profile. Particular irrigation design and management can be then used to ease the negative effects of preferential flow pathways on soil water availability to plant roots and the enhanced leaching of agrochemical below the active root zone.

Alternative transportation fuels (ATFs) can reduce air pollution. However, the influence of conventional fuels—diesel and gasoline, and particularly ATFs on photochemical air pollution is not well-characterized, limiting assessments of ATFs and air quality. This is mainly due to frequent use of lumped chemical mechanisms by related atmospheric modeling. Here we hypothesized that applying a chemical mechanism that is specifically developed according to both emission fractions and photochemical ozone creation potential of volatile organic compounds (VOCs) is key to gaining reliable insights into the impact of transportation fuels on photochemistry. We used a heterogeneous chemical mechanism with 927 reactions and relatively detailed emission inventories to specifically meet the requirements for reliable simulation of the effect of exhaust emissions from vehicles fueled by selected model fuels—diesel, gasoline, and mixtures of 15% gasoline with 85% ethanol (E85) or 85% methanol (M85)—on photochemistry. These dispersion-box model simulations revealed a strong influence of atmospheric background balance between VOCs and nitrogen oxides (NOX = [NO] + [NO2]) on the impact of exhaust emissions on photochemistry, with higher tendency toward ozone (O3) formation or destruction for more VOC-limited or NOX-limited conditions, respectively. Accordingly, higher [NOX]/[VOC] exhaust emission, such as from diesel and M85, resulted in lower O3, not only locally but also downwind of the emission. This offers a new perspective and measure for transportation fuel assessment. Rapid conversion of O3 to hydroxyl and hydroperoxyl radicals downwind of the exhaust emission indicates the importance of simulating the impact of road transportation on photochemistry at high spatial and temporal resolution. Peroxyacetyl nitrate formation was more sensitive to VOC emission under VOC-limited conditions than to NOX emission under NOX-limited conditions. Secondary formaldehyde dominated over primary emitted formaldehyde several minutes after emission. These findings should be verified using a 3D modeling study under varying meteorological conditions.

AbstractA reliable forecast of potential evapotranspiration (ET0) is key to precise irrigation scheduling toward reducing water and agrochemical use while optimizing crop yield. In this study, we examine the benefits of using the Weather Research and Forecasting (WRF) Model for ET0 and precipitation forecasts with simulations at a 3-km grid spatial resolution and an hourly temporal resolution output over Israel. The simulated parameters needed to calculate ET0 using the Penman?Monteith (PM) approach, as well as calculated ET0 and precipitation, were compared to observations from a network of meteorological stations. WRF forecasts of all PM meteorological parameters, except wind speed Ws, were significantly sensitive to seasonality and synoptic conditions, whereas forecasts of Ws consistently showed high bias associated with strong local effects, leading to high bias in the evaluated PM?ET0. Local Ws bias correction using observations on days preceding the forecast and interpolation of the resulting PM?ET0 to other locations led to significant improvement in ET0 forecasts over the investigated area. By using this hybrid forecast approach (WRFBC) that combines WRF numerical simulations with statistical bias corrections, daily ET0 forecast bias was reduced from an annual mean of 13% with WRF to 3% with WRFBC, while maintaining a high model?observation correlation. WRF was successful in predicting precipitation events on a daily event basis for all four forecast lead days. Considering the benefit of the hybrid approach for forecasting ET0, the WRF Model was found to be a high-potential tool for improving crop irrigation management.AbstractA reliable forecast of potential evapotranspiration (ET0) is key to precise irrigation scheduling toward reducing water and agrochemical use while optimizing crop yield. In this study, we examine the benefits of using the Weather Research and Forecasting (WRF) Model for ET0 and precipitation forecasts with simulations at a 3-km grid spatial resolution and an hourly temporal resolution output over Israel. The simulated parameters needed to calculate ET0 using the Penman?Monteith (PM) approach, as well as calculated ET0 and precipitation, were compared to observations from a network of meteorological stations. WRF forecasts of all PM meteorological parameters, except wind speed Ws, were significantly sensitive to seasonality and synoptic conditions, whereas forecasts of Ws consistently showed high bias associated with strong local effects, leading to high bias in the evaluated PM?ET0. Local Ws bias correction using observations on days preceding the forecast and interpolation of the resulting PM?ET0 to other locations led to significant improvement in ET0 forecasts over the investigated area. By using this hybrid forecast approach (WRFBC) that combines WRF numerical simulations with statistical bias corrections, daily ET0 forecast bias was reduced from an annual mean of 13% with WRF to 3% with WRFBC, while maintaining a high model?observation correlation. WRF was successful in predicting precipitation events on a daily event basis for all four forecast lead days. Considering the benefit of the hybrid approach for forecasting ET0, the WRF Model was found to be a high-potential tool for improving crop irrigation management.

Dry deposition of ozone (O3) to vegetation is an important removal pathway for tropospheric O3, while O3 uptake through plant stomata negatively affects vegetation and leads to climate change. Both processes are controlled by vegetation characteristics and ambient conditions via complex mechanisms. Recent studies have revealed that these processes can be fundamentally impacted by coastal effects, and by dry and warm conditions in ways that have not been fully characterized, largely due to lack of measurements under such conditions. Hence, we hypothesized that measuring dry deposition of O3 to vegetation along a sharp spatial climate gradient, and at different distances from the coast, can offer new insights into the characterization of these effects on O3 deposition to vegetation and stomatal uptake, providing important information for afforestation management and for climate and air-quality model improvement. To address these hypotheses, several measurement campaigns were performed at different sites, including pine, oak, and mixed Mediterranean forests, at distances of 20–59 km from the Eastern Mediterranean coast, under semiarid, Mediterranean and humid Mediterranean climate conditions. The eddy covariance technique was used to quantify vertical O3 flux (Ftot) and its partitioning to stomatal flux (Fst) and non-stomatal flux (Fns). Whereas Fst tended to peak around noon under humid Mediterranean and Mediterranean conditions in summer, it was strongly limited by drought under semiarid conditions from spring to early winter, with minimum average Fst/Ftot of 8–11% during the summer. Fns in the area was predominantly controlled by relative humidity (RH), whereas increasing Fns with RH for RH < 70% indicated enhancement of Fns by aerosols, via surface wetness stimulation. At night, efficient turbulence due to sea and land breezes, together with increased RH, resulted in strong enhancement of Ftot. Extreme dry surface events, some induced by dry intrusion from the upper troposphere, resulted in positive Fns events.

Abstract Wetting and drying affects soil structure and pesticide migration, which both may lead to land degradation. The effect on soil structure has been mainly addressed by classical methods at the macroaggregate scale, and the effect on herbicide leaching has not been thoroughly addressed. We aimed to characterize the effects of wetting and drying on soil microstructure, aggregate packing and stability, and subsequent effect on pesticide mobility in three agricultural soils. We developed advanced methods to quantitatively describe soil microstructure changes, induced by wetting and drying. Changes in soil packing, observed by micro-CT, indicate that large aggregates in a Clay soil disintegrate, whereas particles from a Sandy Loam form larger aggregates. To reflect these changes in terms of soil stability, we developed an aggregate durability index, based on changes in soil particle-size distribution measured by laser granulometry. For a Clay soil, the index decreased from 17.0% to 1.7%, indicating soil disaggregation upon wetting and drying. Whereas for a Sandy Clay Loam soil, the index increased from 0.4% to 2.6%, indicating formation of more durable aggregates, explained in terms of cementation by CaCO3. As expected, wetting and drying did not alter a Loamy Sand soil structure. The adverse effects of wetting and drying on soil structure correspond with the trends of atrazine mobility. As atrazine is trapped within the Clay soil aggregates, disaggregation leads to a 35% enhancement in pesticide mobility, whereas stabilization of a Sandy Clay Loam aggregates reduced atrazine leaching by 23%. Finally, wetting and drying directly affects the soil microstructure, which has an immense indirect effect on pollutant mobility, with both potentially leading to land degradation.

Polycation conformation upon adsorption to a negatively charged surface can be modulated by its charge density. At high charge density monomers directly interact with the surface in a ‘trains’ conformation and as charge density decreases a high degree of monomers dangle into solution in a ‘loops and tails’ conformation. In this study, the conformations of polycations upon adsorption to montmorillonite, as a function of polycation charge (20, 50 and 100% of the monomers, denoted as P-Q20, P-Q50 and P-Q100) were characterized and in accordance with their conformation, the adsorption of non-ionic and anionic molecules by the composite was tested. As expected, the adsorption of the nonionic pharmaceuticals increased to a composite with a ‘loops and tails’ conformation, due to both conformation and chemical properties. On the other hand, the anionic molecules, gemfibrozil and diclofenac, preferably adsorbed to composites with higher charge density (Q50 or Q100 composites). However, they showed different tendency toward the composites, i.e. higher adsorption of diclofenac by Q100 composite vs. higher adsorption of gemfibrozil by Q50 composite. To elucidate the differences in adsorption between these two pharmaceuticals, density functional theory calculations were employed. Both gemfibrozil and diclofenac were found to be better stabilized by methyl pyridinium sites (prevail in Q100 composite). The preferable adsorption of gemfibrozil by Q50 composite was explained by the presence of ‘loops and tails’ conformation enabling additional adsorption sites and diverse monomer-target molecule orientations.